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Boletín de la Sociedad Geológica Mexicana

versión impresa ISSN 1405-3322

Bol. Soc. Geol. Mex vol.72 no.3 Ciudad de México dic. 2020  Epub 11-Oct-2021

https://doi.org/10.18268/bsgm2020v72n3a110 

Articles

The Miocene Tatatila-Las Minas IOCG skarn deposits (Veracruz) as a result of adakitic magmatism in the Trans-Mexican Volcanic Belt

Los depósitos de tipo skarn IOCG miocénicos de Tatatila-Las Minas (Veracruz) como resultado del magmatismo adakítico de la Faja Volcánica Trans-Mexicana

Edith Fuentes-Guzmán1  2  3 

Eduardo González-Partida4 

Antoni Camprubí1  3  * 

Geovanny Hernández-Avilés2 

Janet Gabites5 

Alexander Iriondo4  6 

Giovanni Ruggieri7 

Margarita López-Martínez8 

1Instituto de Geología, Universidad Nacional Autónoma de México. Ciudad Universitaria, 04510 Coyoacán, CDMX, México.

2Programa de Posgrado en Ciencias de la Tierra, Universidad Nacional Autónoma de México. Ciudad Universitaria, 04510 Coyoacán, CDMX,/ Boulevard Juriquilla 3001, 76230 Juriquilla, Querétaro, Mexico.

3Laboratorio Nacional de Geoquímica y Mineralogía (LANGEM). Universidad Nacional Autónoma de México. Ciudad Universitaria, 04510 Coyoacán, CDMX, Mexico.

4Centro de Geociencias, Universidad Nacional Autónoma de México, Boulevard Juriquilla 3001, 76230 Juriquilla, Querétaro, Mexico.

5Pacific Centre for Isotopic and Geochemical Research, Department of Earth, Ocean and Atmospheric Sciences, University of British Columbia; Earth Sciences Building, 2207 Main Mall, Vancouver, V6T 1Z4, British Columbia, Canada.

6Department of Geosciences, University of Arizona. 1040 E 4th Street, 85721, Tucson, Arizona, USA.

7Istituto di Geoscienze e Georisorse, Consiglio Nazionale delle Ricerche. Via G. Moruzzi 1, 56124 Pisa, Italy.

8Centro de Investigación Científica y Estudios Superiores de Ensenada. Carretera Tijuana-Ensenada km. 107, 22860 Ensenada, Baja California, Mexico.


Abstract

The Cu- and Au-rich Tatatila-Las Minas IOCG skarn deposits in Veracruz (central-east Mexico) are circumscribed to the earliest stages of the Trans-Mexican Volcanic Belt (TMVB) and stand for a metallogenic province directly linked to its tectonomagmatic dynamics. This is the first well-documented case for such metallogenic province. These deposits were formed as skarns between rocks of the Mesozoic carbonate series and Miocene intermediate to acid hypabyssal rocks. New U-Pb zircon and 40Ar/39Ar ages provide evidence for four epochs of magmatic activity in the area: (1) early Permian (Artinskian), in association with the Paleozoic basement, (2) late Oligocene to early Miocene suite of pre-TMVB intrusive rocks, (3) middle to late Miocene suite of early TMVB-related intrusive rocks, and (4) Pliocene intrusive and extrusive rocks of the TMVB, possibly associated with the Los Humeros post-caldera stage. The obtained ages range between 24.60 ± 1.10 and 19.04 ± 0.69 Ma for stage 2, and between 16.34 ± 0.20 and 13.92 ± 0.22 Ma for stage 3. Stage 2 corresponds to a magmatic stage unheard of in the area, until this study. Only stage 3 rocks are associated with the IOCG skarn mineralization, with retrograde stages dated at 12.44 ± 0.09 (chromian muscovite, phyllic association) and 12.18 ± 0.21 Ma (zircon, potassic association). Therefore, the ages of stage-3 intrusive rocks are interpreted to date the formation of the prograde skarn associations (mostly ~15.4 to <14 Ma). The petrogenetic affinity of stage-2 and stage-3 rocks is about the same-the main difference has to do with higher Y and Yb contents in stage-3 rocks (although no affinity with within-plate granites was found), which is suggestive of an interaction of their parental magmas with alkaline magmas that most likely belong to the conterminous and contemporaneous Eastern Mexico Alkaline Province. Petrological indicators (elemental and isotopic) in Cenozoic rocks consistently point to intermediate to acid, metaluminous, I- and S-type rocks that were emplaced in a subduction-related continental arc, within the medium- to high-potassium calc-alkaline series, with high-silica adakitic signatures due associated to deep-sourced magmas that underwent crustal contamination to some degree. The various possible sources for the magmas with adakitic signature in this context can be narrowed down to two of them that are not mutually exclusive: adakitic derived from subducted slab melting and melting-assimilation-storage-homogenization (MASH)-derived adakites. Both sources are, in principle, capable of generating magmas that would eventually produce magmatic-hydrothermal mineralizing systems with an associated variety of ore deposit types, including IOCG. Also, both possible sources for adakites are compatible with the renewed steepening of the subducted slab after a period of flat subduction, for the earliest stage in the evolution of the TMVB.

Keywords: IOCG; adakites; Miocene; Trans-Mexican Volcanic Belt; skarn; magmatic-hydrothermal; iron oxides

Resumen

Los skarns IOCG ricos en Cu y Au de Tatatila-Las Minas en Veracruz (centro-oriente de México) están circunscritos a los estadíos más tempranos de la Faja Volcánica Transmexicana (FVTM) e indican directamente la existencia de una provincia metalogenética vinculada a su dinámica tectonomagmática. Este es el primer caso bien documentado para dicha provincia metalogenética. Estos depósitos se formaron como skarns entre rocas de la secuencia carbonatada del Mesozoico y rocas hipabisales indermedias a ácidas del Mioceno. Los nuevos fechamientos U-Pb en zircón y 40Ar/39Ar evidencian la existencia de cuatro épocas de actividad magmática en el área: (1) en el Pérmico temprano (Artinskiano), en asociación con el basamento paleozoico de las secuencias del Mesozoico, (2) un conjunto de intrusivos pre-FVTM entre del Oligoceno tardío y el Mioceno temprano, (3) un conjunto de intrusivos del Mioceno medio y tardío asociados a la FVTM, y (4) rocas intrusivas extrusivas del Plioceno de la FVTM, posiblemente asociadas a los depósitos del estadio post-caldera de Los Humeros. Las edades obtenidas varían entre 24.60 ± 1.10 y 19.04 ± 0.69 Ma para el estadío 2, y entre 16.34 ± 0.20 y 13.92 ± 0.22 Ma para el estadío 3. El estadío 2 corresponde a una etapa magmática hasta el presente estudio desconocida en el área. Sólo las rocas del estadío 3 están asociadas a las mineralizaciones de skarn IOCG, cuyas etapas retrógradas han sido fechadas en 12.44 ± 0.09 (moscovita crómica, asociación fílica) y 12.18 ± 0.21 Ma (zircón, asociación potásica). Por tanto, las edades de las rocas intrusivas del estadío 3 se interpretan como parte de las asociaciones de skarn prógrado (mayormente, de ~15.4 a <14 Ma). La afinidad petrogenética de las rocas correspondientes a los estadíos 2 y 3 es prácticamente la misma-su principal diferencia estriba los contenidos más altos de Y e Yb en rocas del estadío 3 (aunque no se encontró afinidad alguna con granitos de intraplaca), lo cual sugiere la interacción de sus magmas primigenios con magmas alcalinos que posiblemente pertenecieron a la contigua y contemporánea Provincia Alcalina Oriental Mexicana. Los indicadores petrogenéticos (elementales e isotópicos) en las rocas del Cenozoico apuntan consistentemente a rocas intermedias a ácidas, metalumínicas, de tipo I y S, emplazadas en un arco continental debido a subducción y pertenecen a las series calci-alcalinas de potasio medio a alto, con (mayormente) firmas de adakitas altas en sílice debidas a un origen profundo de magmas que experimentaron cierto grado de contaminación cortical. La diversidad de posibles orígenes para las fimas adakíticas en este contexto pueden reducirse a sólo dos de ellas, que no son mutuamente exclusivas: adakitas derivadas de la fusión de la placa subducida y adakitas derivadas de procesos tipo fusión-asimilación-almacenamiento-homogeneización (MASH, por sus siglas en inglés). Ambas fuentes, en principio, poseen la capacidad de generar magmas que eventualmente pudieran producir sistemas mineralizantes magmático-hidrotermales con una cierta variedad de tipos de depósitos minerales asociados, incluyendo depósitos IOCG. Además, ambas posibles fuentes de adakitas son compatibles con la reverticalización de la placa subducida tras un periodo de subducción plana para el estadío más temprano en la evolución de la FVTM.

Palabras clave: IOCG; adakitas; Mioceno; Faja Volcánica Transmexicana; skarn; magmático-hidrotermal; óxidos de hierro

1. Introduction

Recent assessment has shown that the metallogenic potential of the mid-Miocene to Holocene Trans-Mexican Volcanic Belt (TMVB) and the potential of Miocene to Holocene ore deposits in Mexico are greater than previously believed (Camprubí, 2009, 2013; Clark and Fitch, 2009; Poliquin, 2009; Jansen et al., 2017; Camprubí et al., 2019, 2020; Fuentes-Guzmán et al., 2020). The metallogeny of Miocene to Holocene epochs in Mexico is, in fact, distributed across several regions, namely (1) the southernmost part of the Sierra Madre Occidental, in association with its last ignimbritic flare-up, (2) the Trans-Mexican Volcanic Belt (TMVB), (3) the southern part of the Eastern Mexico Alkaline Province (EMAP) and northern Chiapas, (4) the easternmost part of the Sierra Madre del Sur (in Oaxaca), and (5) the Gulf of California. As (a) the easternmost ending of the TMVB coincides with the N-S geographic distribution of the EMAP, (b) the metallogeny of the TMVB is still poorly understood, and (c) there is a wide variety of types of ore deposits across the EMAP-including, skarns, metalliferous porphyries, epithermal deposits, IOCG deposits and carbonatites-, the identification of whether an ore deposit in such a region is geologically associated with the TMVB or the EMAP is not a straightforward task.

The Tatatila-Las Minas district in Veracruz State is located precisely in the region in which the TMVB and the EMAP overlap geographically, in the Palma Sola area. The ore deposits in the Tatatila-Las Minas have a magmatic-hydrothermal origin and are essentially Cu-Au iron oxide skarns, part of the IOCG “clan”, and epithermal deposits (Camprubí, 2013). Therefore, in order to investigate the origin of these deposits, the first necessary step would be to elucidate their genetic affinity with either magmatic province. Camprubí (2013) deduced a plausible age of ~11 Ma and some affinity with alkaline magmatism for the deposits in the Tatatila-Las Minas district, based on Negendank et al. (1985) and Ferrari et al. (2005a), which linked the Palma Sola massif with the EMAP. However, the middle Miocene to Recent alkaline and calc-alkaline volcanism of the Palma Sola area was ascribed to the TMVB, and to the subduction along the Pacific trench, as in Besch et al. (1988), Gómez-Tuena et al. (2003), and Orozco-Esquivel et al. (2007). The relevance of the EMAP, besides its petrotectonic affinity, as a major metallogenic province was already stressed by Camprubí (2009, 2013). However, the age of magmatism with which these ore deposits were plausibly associated corresponds well to the middle and late Miocene arc at the beginning of the TMVB (~19 to 10 Ma; Gómez-Tuena et al., 2005, 2007).

In summary, we may use as a starting hypothesis the fact that neither the EMAP nor the TMVB are implausible magmatic provinces to have produced the parental magmatism to the Tatatila-Las Minas deposits. The implications for regional mineral exploration that may arise from either possibility are very different, nonetheless. In this paper, we analyze the petrologic affinity of the hypabyssal intrusive bodies with which the formation of the IOCG deposits of the Tatatila-Las Minas district is associated. This will enable a discrimination between the ascription of these deposits to the metallogeny of the TMVB or the EMAP. The proximal-to-source character of these magmatic-hydrothermal deposits (i.e., iron skarns) allows to soundly elucidate the linkage between the magmatism and the hydrothermal activity that generated the deposits. In addition, this paper contributes to a long-standing program that aims to the geochronological characterization of Mexican mineral deposits and the geologic events with which they are genetically associated (Camprubí et al., 2015, 2016a, 2016b, 2017, 2018, 2019, 2020; Farfán-Panamá et al., 2015; Martínez-Reyes et al., 2015; González-Jiménez et al., 2017a, 2017b; Enríquez et al., 2018; Fuentes Guzmán et al., 2020) to better constrain the metallogenic evolution of Mexico, as documented by Camprubí (2009, 2013, 2017).

2. Geological setting

The Tatatila-Las Minas mining district is located in the central-eastern part of the state of Veracruz (Figure 1) within the Palma Sola massif. It is characterized by the intrusion of Neogene stocks. Stock compositions are described to vary between gabbro and granodiorite, with dominantly monzodioritic to dioritic compositions, and intruded middle Jurassic, red beds and lower Cretaceous carbonate rocks. The latter rocks are part of the continental to marine sequences of the Sierra Madre Oriental that were deformed during the orogenic pulses of the Mexican Fold-and-Thrust Belt between the late Cretaceous and the Paleocene (Centeno-García, 2017; Fitz-Díaz et al., 2018; and references therein). The Middle Jurassic red bed sequence in the area correlates with the Cahuasas Formation, and is overlain by carbonates and lutites of the Pimienta (Tithonian-Barriasian) and Orizaba (Albian-Cenomanian) formations. The host carbonate series in the study area consists essentially of platform carbonates that correspond to the Orizaba Formation (Ortuño-Arzate et al., 2005). The Lower Cretaceous sequence unconformably overlies Permo-Triassic schists intruded by granitic rocks. The latter can be mistaken for Neogene intrusive bodies with similar compositions, as the thick vegetation cover commonly hinders their visualization and the identification of the lithologic contacts; both groups of intrusive rocks come in contact by faulting in the northernmost termination of the mineralized area (Figure 1). The Mesozoic sedimentation was controlled by the horst-and-graben configuration that resulted from the opening of the Gulf of Mexico during the breakup of Pangea (Martini and Ortega-Gutiérrez, 2018), thus developing simultaneously shallow platforms and relatively deep open-sea facies, hence the Córdoba platform (Ortuño-Arzate et al., 2005) on which the upper Jurassic and Lower Cretaceous sedimentary units developed.

Figure 1 Geological map of the Tatatila-Las Minas mining district, east of the Palma Sola massif. Adapted from Servicio Geológico Mexicano (2007, 2010). Purple circles denote the location of samples on which this study is based, with indication of the obtained ages. 

Neogene intrusive bodies generated typical skarn associations, with prograde mineralization by contact metamorphism (Ca silicate-rich) that was followed by retrograde IOCG-type hydrothermal stages of mineralization (Figure 2). Such intrusive bodies made up a NE-SW striking ~20 km long and ~10 km wide intrusive ensemble whose composition varies from gabbro to granodiorite, with dominantly monzodioritic to dioritic compositions (see below) with phaneritic textures. These rocks typically contain hornblende, biotite, pyroxenes, apatite and zircon this two as accessory mineral (Figure 3). Some andesite dykes, up to 30 m long and ~2 m thick crosscut the intrusive ensemble and predate the mineralization. A sequence of andesitic, basaltic and dacitic hypabyssal, this with porphyritic texture include plagioclase phenocrysts and volcanic rocks postdates the mineralization and the emplacement of the associated intrusive rocks, and comprises a variety of deposits, including volcanic conglomerates, tuffs, ash-fall and pyroclastic deposits. Such rocks are interpreted as distal Pliocene deposits associated with the post-caldera deposits of Los Humeros caldera (Carrasco-Nuñez et al., 2018; Dorantes-Castro, 2016; Sarabia-Jacinto, 2017). Ages for the Palma Sola area to the east of the Tatatila-Las Minas area were 14.6 ± 0.3 (U-Pb, zircon) and 11 ± 0.87 Ma (K-Ar, biotite), were reported by Poliquin (2009) and Murillo-Muñetón and Torres-Vargas (1987), respectively. These correspond to the ensemble of hypabyssal and volcanic rocks that allowed Camprubí (2013) to deduce a tentative age of ~11 Ma for these ore deposits, which is also constrained by the formation of capping volcanic rocks between 9 and 6.6 Ma. Contact metamorphism and mineralization of the fresh carbonate rocks can be observed in the conspicuous formation of marble in a 300 to 400 m wide zone that shows an outward decreasing degree of recrystallization. Skarn associations are distributed in the classic zonation from endoskarn to exoskarn. Endoskarns consist of grossular-andradite, clinopyroxene, and quartz in prograde associations, and magnetite, chalcopyrite, bornite, and native gold in retrograde associations (Figure 2). Exoskarns consist of wollastonite, clinopyroxene, potassium feldspar, quartz, epidote, and chromian muscovite (“fuchsite”; Figure 2).

Figure 2 Selected aspects of the IOCG skarn mineralization at the Tatatila-Las Minas deposits showing both prograde (garnet and tourmaline) and retrograde (actinolite and fuchsite) associations. (A) Hand specimen showing a garnet-rich prograde association followed by an actinolite- and fuchsite-rich retrograde association in the Santa Cruz mine. (B) Photomicrography of a garnet and tourmaline prograde association followed by an actinolite and fuchsite retrograde association; transmitted light, crossed polars; same sample as in A. Fuchsite separates from A and B were dated by argon geochronometry in this study. (C) Hand specimen of prograde patchy to partially banded magnetite ore; El Dorado mine. (D) Hand specimen of banded exoskarn magnetite- and chalcopyrite-rich retrograde ore, with martitized magnetite; El Dorado mine. Key: Amp = amphibole-group minerals (actinolite), Cal = calcite, Ccp = chalcopyrite, Ep = epidote, Fuch = chromian muscovite or “fuchsite”, Grt = garnet-group minerals (grossular-andradite), Hm = hematite, Mag = magnetite, Mc = malachite, Py = pyrite, Tur = tourmaline. 

Figure 3 Photomicrographs of representative hypabyssal bodies, unaffected by hydrothermal alteration, associated with IOCG skarn mineralization in the Tatatila-Las Minas district. (A) Quartz-monzodiorite showing euhedral apatite crystals within plagioclase phenocrysts, Santa Cruz mine; transmitted light, crossed polars. (B) Quartz-monzodiorite showing myrmekitic intergrowths, surrounded by hornblende and plagioclase phenocrysts, La Virgen mine; transmitted light, crossed polars. (C) Quartz-monzodiorite showing hornblende phenocrysts, Santa Cruz mine; transmitted light, crossed polars. (D) Quartz-monzodiorite showing euhedral zircon crystals within potassium feldspar, Santa Cruz mine; transmitted light, crossed polars. (E) Monzodiorite showing hornblende intergrown with magnetite, Carbonera mine; plane-polarized transmitted light. (F) Monzodiorite showing euhedral hornblende, biotite and apatite crystals within a plagioclase-potassium feldspar assemblage, Carbonera mine; plane-polarized transmitted light. (G) Monzogranite showing rock-forming biotite crystals, same sample as in F, Rancho La Virgen; transmitted light, crossed polars. (H) Monzogranite showing late biotite crystals intergrown with magnetite, Rancho La Virgen; plane-polarized transmitted light. Key: Ap = apatite, Bt = biotite, Fp = potassium feldspar, Hb = hornblende, Mt = magnetite, Pl = plagioclase, Qz = quartz, Zr = zircon. 

Mining activity in the study area can be dated back to pre-colonial epochs, when the native population of Chiconquiaco obtained gold that was mainly destined to fulfill the contributions imposed upon them by their Aztec overlords. Formal mining by the Spaniards can be dated back to at least 1680, when the exploitation of large high-grade gold and silver bonazas has been documented (Castro-Mora et al., 1994). Mining and exploration have remained intermittently active in the area ever since (Viniegra, 1965; Castro-Mora et al., 1994; Servicio Geológico Mexicano, 2007). By 1996, the exploration endeavors carried out by International Northair, in association with Battle Mountain Gold Co., allowed location of relevant Au-Cu-Fe resources in a broad area. In 2006, Bell Resources Corp. took over the property in the Las Minas area and subsequently assigned the mining rights to Chesapeake Gold Corp.

The formation of this Au-Cu-Fe rich area is generally acknowledged to belong to an IOCG model with overimposed late epithermal veins (Servicio Geológico Mexicano, 2007; Camprubí, 2009, 2013; Dorantes-Castro, 2016; Castro-Mora et al., 2016; Sarabia-Jacinto, 2017). The metal grades in the deposit range between 1 and 39.3 ppm Au, between 4.11 and 127 ppm Ag, and between 0.64 and 11.7% Cu; inferred reserves are 719000 Oz Au equiv., and indicated reserves are 304000 Oz Au equiv. (Castro-Mora et al., 2016).

3. Methodology

Representative samples from the Neogene intrusive ensemble were collected in the Tatatila-Las Minas mineralized area (47 samples; purple circles in Figure 1) in order to characterize the petrologic affinity and age of skarn-generating intrusive bodies, as well as the age of hydrothermal activity itself. The ages of intrusions are considered as representative of the age of prograde mineralization in IOCG skarns, and hydrothermal assemblages correspond to retrograde stages of these deposits. The representativeness of such samples with regard to the formation (or postdating) of mineralized bodies was determined on the basis of their distribution, their possible association with mineralized bodies, and the types of rocks thereby represented, after thorough cartography and sampling. All the analyzed samples were examined by means of petrographic studies in order to ensure that no alteration would cause any disturbances to the geochemical or geochronological analyses.

Elemental analyses were carried out on 15 g aliquots from samples at a 200 mesh. The two dated samples from retrograde hydrothermal associations are chromian muscovite, which correspond to high-temperature phyllic assemblages from the Las Minas area, and zircon within pervasive potassic alteration assemblages from the Tatatila area.

Multi-elemental geochemical analyses of host rocks were carried out by means of X-ray fluorescence (XRF) with a Rigaku Primus II equipment available at the Laboratorio Nacional de Geoquímica y Mineralogía (LANGEM) in accordance with the procedure described by Lozano-Santa Cruz et al. (1995); results are presented in Table 1. Trace and rare-earth elements (REE) were analyzed by means of inductively coupled plasma quadrupole mass spectrometery (Q-ICP-MS) with a Termo ICap Qc equipment, coupled to a collision/reaction cell (He, N2, NH3 and O2) in order to minimize spectral interference, the procedure described by Mori et al. (2007), at the Laboratorio de Estudios Isotópicos (LEI) of the Centro de Geociencias (CGeo-UNAM). The obtained data are presented in Table 2. For Sr, Nd and Pb isotopic analyses, a Thermo Fisher Neptune Plus mass spectrometer available at the CGeo-UNAM. Sample preparation and measurement procedures for Sr-Nd-Pb isotopic analyses are described in Gómez-Tuena et al. (2003) for LDEO. 87Sr/86Sr ratios obtained in both labs were normalized to 86Sr/88Sr = 0.1194 and corrected to a NBS-987 standard ratio of 87Sr/86Sr = 0.710230, and 143Nd/144Nd ratios were normalized to 146Nd/144Nd = 0.72190 and corrected to a La Jolla standard value of 143Nd/144Nd=0.511860. At LDEO, Sr and Nd were measured by dynamic multicollection, with each analysis consisting of ~120 isotopic ratios. Sr ratios were measured using tungsten filaments and a TaCl4 activator solution (Birck, 1986). Nd isotopes were measured as NdO+. During five separate analysis intervals the measured values of the NBS-987 standard were 87Sr/86Sr = 0.710245 ± 0.000016 (2σ, n = 4); 0.710271 ± 0.000014 (2σ, n = 6); 0.710274 ± 0.000016 (2σ, n=18); 0.710310 ± 0.000013 (2σ, n = 5); 0.710261 ± 0.000012 (2σ, n = 10). The measured 143Nd/144Nd ratio of the La Jolla standard at LDEO was 0.511836 ± 0.000013 (2σ, n = 15), as of Todt et al. (1996), according to the procedure described by Mori et al. (2007), obtained data are presented in Table 3.

Table 1 Major elements in host intrusive rocks to the Tatatila-Las Minas IOCG deposits. All values in wt.%. Asterisks (*) correspond to analyses in Dorantes-Castro (2016)

UTM coordinates Rock SiO2 TiO2 Al2O3 Fe2O3(t) MnO MgO CaO Na2O K2O P2O5 LOI Total
E N
TMG-1 699173 2176551 Gabbro 43.89 0.81 17.94 13.66 0.22 8.92 13.02 1.30 0.19 0.04 1.12 99.60
TMG-2 698856 2176474 Diorite 61.33 0.75 17.09 5.32 0.07 2.31 4.78 3.95 4.20 0.20 0.75 99.58
TMG-3 698516 2176325 Quartz monzodiorite 62.14 0.71 17.06 5.41 0.07 2.49 4.53 4.10 3.30 0.19 1.79 99.56
TMG-4 697820 2176599 Quartz monzodiorite 58.22 0.78 17.87 6.81 0.11 3.23 5.85 3.93 2.96 0.23 0.71 99.60
TMG-5 697764 2176999 Monzodiorite 58.63 0.85 17.35 6.81 0.12 3.03 5.72 3.97 3.28 0.23 0.68 99.60
TMG-6 696871 2177577 Quartz monzodiorite 61.78 0.71 17.05 5.46 0.10 2.39 4.32 3.82 4.19 0.19 0.49 99.60
TMG-7 692733 2179299 Quartz diorite 59.29 0.60 16.53 6.15 0.13 4.40 7.10 3.68 1.92 0.19 0.71 99.58
TMG-8 692919 2179241 Diorite 48.99 0.73 15.64 9.98 0.17 9.21 12.27 2.24 0.64 0.13 1.17 99.60
TMG-9 692782 2178838 Diorite 52.39 0.85 19.26 9.48 0.15 4.07 8.50 3.93 1.02 0.35 0.95 99.50
TMG-10 701856 2183672 Diorite 55.09 1.47 17.04 7.86 0.14 3.87 7.57 4.13 2.42 0.41 0.19 99.50
TMG-11 701275 2182995 Monzodiorite 62.15 0.90 16.83 5.13 0.10 2.42 4.02 4.60 3.58 0.27 0.54 99.28
TMG-12 701201 2183034 Monzonite 63.44 0.88 16.16 4.60 0.11 2.03 3.50 4.51 4.55 0.22 0.03 99.59
TMG-13 700794 2183290 Quartz diorite 59.34 1.00 15.69 6.09 0.17 5.08 4.72 3.76 3.82 0.35 2.31 99.58
TMG-14 699639 2181985 Monzonite 55.79 1.05 14.15 5.82 0.10 4.60 10.97 3.47 3.46 0.60 0.46 99.55
TMG-15 699490 2180296 Sienite 59.34 0.61 20.94 4.23 0.05 1.69 4.52 4.92 3.36 0.33 1.29 99.60
TMG-16 698062 2181248 Quartz monzonite 55.76 1.18 17.36 8.87 0.17 4.14 7.11 3.10 2.00 0.31 0.04 99.58
TMG-17 698283 2181931 Monzodiorite 57.89 1.16 17.38 6.62 0.12 3.51 6.11 4.12 2.75 0.34 0.67 99.55
TMG-18 698504 2182345 Monzogranite 71.60 0.25 15.89 1.13 0.02 0.36 1.95 3.64 5.09 0.07 0.72 99.60
TMG-19 694715 2179684 Diorite 63.04 0.82 16.39 4.86 0.11 2.26 4.67 4.22 3.39 0.23 0.75 99.59
TMG-20 696828 2180239 Quartz monzonite 63.02 0.52 18.26 4.66 0.07 1.74 5.24 4.71 1.51 0.27 0.79 99.61
TMG-21 696325 2179917 Diorite 52.79 1.47 19.06 8.42 0.15 3.73 7.90 4.27 1.80 0.42 1.41 99.62
TMG-22 695717 2179384 Granite 77.60 0.09 14.83 0.42 0.00 0.31 1.02 2.78 2.91 0.04 1.63 99.61
TMG-23 694397 2177628 Diorite 60.88 0.54 15.82 6.07 0.13 4.41 6.16 3.97 1.88 0.13 0.95 99.59
TMG-24 694207 2177867 Quartz diorite 55.59 0.79 19.02 7.76 0.14 3.14 8.17 3.75 1.39 0.25 0.47 99.59
TMG-26 692818 2176784 Diorite 58.33 0.92 18.96 6.01 0.10 2.40 6.50 4.17 2.23 0.38 0.52 99.58
TMG-23 B 694397 2177628 Diorite 52.36 1.37 18.46 7.94 0.14 3.93 6.67 4.34 1.63 0.39 2.38 99.61
TMG-1 2a 699173 2176551 Gabbro 43.27 0.79 17.69 13.34 0.21 8.80 12.86 1.30 1.87 0.37 1.12 99.60
RV-2 694740 2179098 Granodiorite 66.55 0.44 17.38 2.95 0.03 0.89 4.22 4.88 1.83 0.16 0.57 99.90
RV-3 694688 2179102 Gabbro 47.00 0.95 15.66 10.86 0.14 10.61 9.47 1.89 2.35 0.20 0.84 99.97
BQ-1 694445 2178202 Granite 65.36 0.48 17.94 2.72 0.03 1.06 4.01 5.01 2.06 0.17 1.04 99.86
CR-1 6946662 2179718 Gabbro-diorite 52.00 0.85 16.65 8.79 0.15 6.67 8.44 3.17 1.19 0.25 1.04 99.96
SC-2 b 1 694317 2177448 Diorite 61.46 0.53 17.10 5.30 0.08 2.43 5.20 4.28 2.10 0.19 1.24 99.92
SC-2 b 2 694317 2177448 Diorite 61.78 0.52 16.79 5.12 0.09 2.32 5.30 4.17 2.25 0.19 0.19 99.91
SC-2 b 3 694317 2177448 Diorite 60.65 0.53 16.58 5.89 0.10 2.77 5.37 4.39 2.32 0.21 1.13 99.92
LS-6 696153 2179805 Gabbro-diorite 54.06 1.32 18.07 8.60 0.14 3.97 8.14 3.52 1.50 0.31 0.36 100.00
Es-3 698250 2181451 Gabbro-diorite 51.68 1.21 18.04 8.75 0.16 5.10 8.83 3.77 1.05 0.32 1.09 99.99
Ag-2 699636 2180877 Monzodiorite 59.70 0.76 16.78 6.43 0.09 2.94 5.34 3.72 3.45 0.22 0.58 99.99
LS-4 697074 2180612 Granodiorite 64.27 0.47 18.58 3.81 0.10 1.09 4.39 3.93 2.50 0.22 0.64 99.99
CR-6 693182 2179054 Gabbro-diorite 52.84 0.90 18.13 9.12 0.14 4.64 8.49 3.39 1.29 0.28 0.78 99.99
SC-3 694347 2177616 Diorite 57.52 0.76 18.06 7.40 0.12 2.55 7.43 3.61 1.60 0.26 0.70 99.99
LV-1 701870 2184419 Monzodiorite 56.29 1.15 18.15 7.23 0.13 3.29 6.70 4.03 2.31 0.35 0.15 100.00
CR-5 694325 2179704 Gabbro-diorite 53.49 0.92 17.21 8.28 0.15 4.73 8.12 3.48 1.97 0.24 1.42 100.00
LV-2 702091 2184527 Monzodiorite 56.67 1.16 17.64 7.38 0.13 3.38 6.76 3.80 2.55 0.34 0.19 100.00
LS-3 696389 2080049 Monzodiorite 56.88 1.09 18.09 7.37 0.13 2.94 6.33 3.76 2.39 0.34 0.68 100.00
Ag-5 699561 2181458 Gabbro 51.74 1.16 16.83 7.95 0.07 6.17 9.68 3.49 2.02 0.27 0.62 100.00
Es-2 698330 2181972 Monzodiorite 57.42 1.16 17.22 7.03 0.12 3.49 6.30 3.76 2.83 0.35 0.32 100.00
1TJBQ* Diorite 58.74 0.38 16.96 6.61 0.14 2.81 8.09 5.08 0.38 0.15 0.61 99.22
538* Gabbro 48.29 0.94 15.68 7.58 0.14 4.24 9.59 2.51 1.60 0.22 9.1 99.06
33* Monzodiorite 54.57 1.14 16.14 6.59 0.14 5.21 9.57 3.72 2.13 0.34 0.34 99.17
529* Granodiorite 66.94 0.42 16.95 2.60 0.029 1.22 3.89 4.66 2.00 0.17 0.96 99.55

Key: LOI = loss on ignition.

Table 2 Trace elements in host intrusive rocks to the Tatatila-Las Minas IOCG deposits. All values in ppm unless otherwide noted. Asterisks (*) correspond to analyses in Dorantes-Castro (2016)

Sample Li Be P (wt.%) Sc Ti V Cr Co Ni Cu Zn Ga Rb Sr Y Zr Nb Mo Sn Sb Cs
TMG-1 10.41 0.48 0.04 19.77 0.85 336.71 109.71 46.43 63.59 9.98 94.35 20.53 5.25 731.84 10.7 32.39 1.16 0.34 0.53 0.05 2.63
TMG-2 18.39 2.01 0.2 10.62 0.72 106.68 24.75 12.03 13.19 25.61 31.25 18.77 116.18 368.41 29.54 408.71 15.69 2.6 1.39 0.15 5.6
TMG-3 14.42 2.06 0.19 9.67 0.65 102.97 32.98 10.81 15.39 17.67 31.95 19.07 84.49 383.55 27 299.28 12.43 0.83 1.67 0.18 3.78
TMG-4 20.78 1.8 0.23 10.68 0.75 145.4 46.61 17.02 24.86 65.46 54.42 19.8 73.54 485.78 24.52 235.53 11.03 1.02 1.29 0.14 3.39
TMG-5 15.65 1.96 0.24 12.4 0.8 143.79 25.73 16.48 15.02 57.07 53.66 19.97 102.15 412.51 28.5 237 14.78 2.35 1.81 0.15 4.02
TMG-6 21.71 2.22 0.19 8.82 0.7 106.15 27.58 14.17 15.98 59.79 54 18.99 149.19 344.29 49.66 304.06 18.62 0.58 1.87 0.24 8.77
TMG-7 4.66 1.09 0.18 14.39 0.57 144.73 147.41 17.73 45.05 16.3 45.61 17.25 30.52 524.35 16.86 110.45 5.36 0.91 0.81 0.05 0.29
TMG-8 2.85 0.73 0.12 35.53 0.69 222.77 438.99 40.15 125.95 44.98 62.08 16.53 13.63 513.94 17.18 82.24 2.73 1.12 0.62 0.1 2.61
TMG-9 2.8 1.04 0.34 12.12 0.78 210.81 29.58 19.41 13.33 12.13 51.5 21.53 18.84 761.65 20.99 102.43 5.77 0.36 0.79 0.1 0.49
TMG-10 12.25 2.06 0.43 19.45 1.47 175.3 38.49 20.68 19.64 72.53 80.69 21.06 44.03 626.13 30.65 246.34 22.97 1.63 1.87 0.05 2.44
TMG-11 21.63 2.69 0.27 12.46 0.83 106.97 22.99 11.77 12.35 25.98 56.51 20.58 82.95 419.99 25.43 371.97 20.68 0.68 1.85 0.33 5.09
TMG-12 10.97 2.63 0.22 12.29 0.79 100.45 25.74 9.92 10.76 42.84 62.44 19.65 108 351.48 24.65 425.83 20.55 0.82 1.83 0.13 4.2
TMG-13 24.95 2.64 0.35 18.79 0.89 139.84 160.33 20.25 66.75 39.44 83.06 19.23 95.24 727.7 23.69 263.88 11.23 0.4 1.52 0.38 1.07
TMG-14 9.64 3.2 0.59 17.16 0.96 171.71 131.04 19.67 32.34 94.74 64.38 20.52 54.81 1124.33 34.36 413.32 17.21 1.09 2.35 0.16 1.69
TMG-15 22.67 3.09 0.33 9.65 0.57 118.47 13.32 6.14 18.4 47.05 34.44 23.15 69.27 792.45 9.84 256.89 4.19 0.27 0.56 0.13 6.76
TMG-16 14.2 1.41 0.31 21.06 1.16 191.06 17.87 14.09 4.49 6.91 89.43 20.55 59.36 496.28 36.74 159.13 10.47 0.78 1.48 0.58 5.26
TMG-17 10.17 2.25 0.35 12.62 1.13 147.96 48.94 14.88 20.4 53.18 57.11 20.62 59.19 536.61 25.91 322.84 19.02 2.85 1.55 0.36 2.74
TMG-18 8.03 1.11 0.07 1.41 0.23 11.74 2.97 1.3 0.13 0.64 20.65 14.82 79.79 338.12 8.54 168.55 5.49 0.32 0.54 0.18 5.67
TMG-19 8.15 2.13 0.23 14.76 0.79 101.29 18.97 10.77 6.77 23.39 80.37 18.99 73.33 466.29 20.39 260.61 16.56 1.14 1.19 0.18 1.64
TMG-20 4.58 2.01 0.27 5.61 0.47 77.35 8.37 8.3 2.9 33.81 30.72 20.66 36.48 845.42 17.22 149.11 8.53 0.48 1.56 0.26 1.35
TMG-21 7.46 1.63 0.42 15.65 1.38 240.87 13.21 19.85 17.12 63.18 69.19 23 25.03 717.8 24.29 172.85 11.56 0.89 1.12 0.12 1.14
TMG-22 3.83 1.16 0.03 - 0.08 6.41 2.03 - - - 11.2 12.54 79.74 55.65 7.49 70.92 10.26 0.16 0.6 0.32 6.61
TMG-23 10.45 1.62 0.37 14.93 1.29 208.09 18.75 20.12 14.32 58.4 72.76 22.34 28.14 644.22 22.53 186.92 14.65 1.77 1.24 0.62 2.47
TMG-24 7.03 1.21 0.24 13.74 0.75 161.35 6.21 15.59 4.54 12.66 62.2 20.69 31.34 563.93 21.65 20.08 5.58 1.03 0.78 0.08 0.88
TMG-26 9.65 1.94 0.37 8.11 0.9 120.98 11.78 12.2 9.27 34.38 65.37 21.6 33.51 731.53 21.16 239.47 11.07 0.67 1.14 0.08 1.26
AG-2 13.67 2.05 0.22 12.99 0.73 122.8 133.6 14.6 27.98 38.45 43.63 18.83 107.72 395.48 27.55 207.93 13.89 4.23 1.8 0.17 5.1
AG-5 27.01 1.3 0.26 26.37 1.12 235.84 128.56 15.77 25.51 8.3 26.28 19.92 53 898.63 20 154.15 7.18 1.44 0.7 0.45 3.34
CR-6 2.94 1.07 0.27 19.11 0.86 220.45 108.01 18.67 26.28 11.84 51.3 19.33 20.19 633.39 20.93 130.93 6.98 1.03 0.85 0.28 0.28
ES-2 7.49 2.19 0.35 13.71 1.11 154.96 128.08 17.57 23.35 77.23 64.48 20.46 71.91 556.29 24.13 327.13 17 10.1 1.61 0.26 5.95
ES-3 9.2 1.43 0.32 21.69 1.21 223.94 110.03 24.5 30.73 42.77 80.77 21.46 19.7 620.53 23.53 153.09 9.46 1.34 1.04 0.23 1.03
LS-3 8.01 1.88 0.34 10.41 1.07 168.94 56.1 16.3 6.62 74.84 76.16 21.62 36.53 748.69 21.75 220.73 11.42 1.53 1.28 0.28 1.77
LS-4 12.8 1.97 0.22 5.13 0.46 44.52 100.47 4.73 6.29 9.2 57.71 19.12 75.95 416.9 20.22 266.6 8.92 3.72 1.3 0.11 4.22
LV-1 16.15 2.05 0.35 12.32 1.16 160.92 70.38 16.6 14.9 43.69 73.91 21.6 49.93 591.43 24.45 313.51 17.07 2.47 1.54 0.08 3.45
SC-2 b 1 10.28 1.55 0.2 8.8 0.53 106.97 178.66 13.91 22.59 34.97 37.89 18.21 57.47 468.02 16.89 251.57 7.71 3.12 0.78 0.24 2.28
SC-3 9.46 1.35 0.26 8.75 0.74 140.78 93.78 11.91 4.93 13.42 40.99 19.97 31.25 500.22 27.9 244.55 8.75 2.38 1.09 0.09 0.7
LS-6 5 1.6 0.31 17.23 1.32 226.21 78.98 21.84 19.6 45.06 78.92 21.08 29.3 504.79 22.88 116.97 10.54 1.23 1.26 0.16 3.12
LV-2 15.18 2.2 0.35 13.27 1.15 176.32 80.44 18.11 15.98 74.96 76.69 21.35 59.5 586.07 25.62 290.33 17.29 4.23 2.09 0.19 5.36
CR-5 13.47 2.75 0.06 1.61 0.23 15.9 6.91 2.02 2.5 1.88 31.6 15.14 77.21 123.28 9.67 114.46 18.26 0.24 2.22 0.12 1.36
RV-3     1.89                   45.95 66.24 14.45 10.5 18.53 1.05 0.41 14.67 98.31
SC-2-B3     2.13                   39.32 58.31 12.42 5.37 52.35 4.98 0.49 0.81 25.48
CR-1     2.59                   18.63 101.88 16.56 10.97 30.82 1.41 0.34 0.97 4.31
SC-2-B1     1.84                   23.48 49.83 7.8 3.74 43.12 3.23 0.33 1.6 12.41
SC-2-B2     2.15                   12.27 93.14 6.37 4.59 48.28 4.4 0.42 -3.86 -26.9
AG-2     -                   46.43 54.47 17.55 53.73 56.48 4.6 1.05 1.08 27.15
AG-5     -                   22.85 123.78 12.74 39.83 29.19 1.57 0.41 2.81 17.75
CR-6     -                   8.7 87.24 13.33 33.83 28.39 1.12 0.49 1.75 1.5
ES-2     -                   31 76.62 15.37 84.53 69.11 10.98 0.93 1.65 31.66
ES-3     -                   8.49 85.47 14.99 39.56 38.47 1.45 0.61 1.41 5.48
LS-3     -                   15.75 103.13 13.86 57.04 46.43 1.66 0.74 1.77 9.4
LS-4     -                   32.74 57.42 12.88 68.89 36.26 4.04 0.76 0.68 22.46
LV-1     -                   21.52 81.46 15.57 81.01 69.38 2.69 0.89 0.48 18.34
SC-3     -                   13.47 68.9 17.77 63.19 35.59 2.59 0.63 0.54 3.74
LS-6     -                   12.63 69.53 14.57 30.22 42.85 1.34 0.73 1.01 16.58
LV-2     -                   25.65 80.73 16.32 75.02 70.28 4.6 1.21 1.2 28.5
CR-5     -                   33.28 16.98 6.16 29.58 74.23 0.26 1.29 0.74 7.25
33*     -                     598.15 43.42 43.86 11.27 1.51 1.46 0.23 0.55
1TIJBQ*     -                     615.63 1197 23.77 6.12 4.12 3.23 0.32 0.68
529*     -                     734.4 3.86 5.93 5.67 2.14 0.63 0.16 1.41
538*     -                     640.89 20.42 169.66 8.03 1.26 1.04 0.14 8.76
Sample Ba La Ce Pr Nd Sm Eu Tb Gd Dy Ho Er Yb Lu Hf Ta W Tl Pb Th U B Tm
TMG-1 89.31 4.81 12.29 1.59 7.69 2.11 0.67 0.33 2.19 2 0.41 1.05 0.98 0.15 0.92 0.08 0.07 0.08 3.5 0.33 0.21    
TMG-2 692.36 28.5 59.17 7.69 29.47 6.18 1.29 0.85 5.66 4.98 1.02 2.91 3.02 0.46 10.02 0.99 0.66 0.7 8.36 21.6 4.68    
TMG-3 690.67 27.28 54.61 7.2 27.38 5.72 1.3 0.79 5.22 4.58 0.92 2.65 2.69 0.41 7.48 0.84 0.76 0.58 8.52 17.62 3.61    
TMG-4 628.1 29.72 59.39 7.27 26.77 5.32 1.3 0.71 4.85 4.06 0.82 2.34 2.33 0.35 5.87 0.71 0.37 0.48 13.26 11.62 2.62    
TMG-5 708.86 30.3 60.74 8.04 30.67 6.41 1.39 0.87 5.8 5 0.99 2.81 2.81 0.42 6.21 0.93 0.73 0.67 10.46 18.05 2.63    
TMG-6 735.52 32.27 56.3 8.4 32.99 7.68 1.58 1.31 8.17 8.73 1.89 5.66 6.65 1.13 7.77 1.28 0.76 0.86 12.14 20.65 4.45    
TMG-7 499.87 15.34 26.95 3.5 14.34 3.09 0.93 0.45 3.01 2.68 0.56 1.59 1.61 0.25 2.77 0.38 0.25 0.11 5.23 5.5 0.79    
TMG-8 205.84 10.92 21.44 2.97 13.4 3.35 1.05 0.51 3.36 3.12 0.62 1.67 1.54 0.23 2.08 0.16 0.14 0.11 3 1.23 0.38    
TMG-9 406.33 18.82 40.09 5.24 21.26 4.6 1.37 0.63 4.34 3.77 0.75 2.04 1.98 0.3 2.61 0.29 0.17 0.1 3.15 2.33 0.58    
TMG-10 689.26 35.72 77.57 10.03 39.54 8.29 2.03 1.03 7.21 5.66 1.08 2.97 2.72 0.4 5.47 1.34 0.34 0.3 11.2 9.12 2.53    
TMG-11 572.79 41.44 81.94 10.48 38.18 7.29 1.48 0.86 6.14 4.54 0.86 2.4 2.23 0.33 8.58 1.39 0.73 0.74 13.84 21.32 4.85    
TMG-12 701.13 40.56 82.5 10.28 37.47 7.1 1.43 0.84 5.92 4.48 0.86 2.44 2.33 0.35 10.07 1.36 0.42 0.76 20.51 21.48 6.26    
TMG-13 1067.1 51.04 103.69 12.69 51.18 10.01 2.38 0.99 7.77 4.62 0.82 2.23 1.92 0.28 6.57 0.73 0.34 1.25 10.11 19.85 5.31    
TMG-14 1351.37 91.44 198.89 23.31 89.81 20.16 4.18 1.77 14.79 7.46 1.21 3.21 2.47 0.35 10.19 1.1 0.32 0.35 16.6 35.51 8.67    
TMG-15 796.79 8.51 16.16 2.25 9.35 1.98 0.73 0.28 1.9 1.6 0.34 0.95 1.03 0.18 5.98 0.11 0.97 0.67 10.33 7.43 1.63    
TMG-16 546.99 24.49 56.34 7.66 31.59 7.22 1.66 1.07 7.03 6.63 1.29 3.67 3.46 0.51 4.06 0.65 0.72 0.6 12.16 7.38 1.39    
TMG-17 723.95 37.54 74.16 9.77 37.57 7.47 1.8 0.9 6.39 4.81 0.91 2.52 2.34 0.35 7.53 1.19 0.46 0.64 12.57 12.13 3.39    
TMG-18 2387.17 50.34 91.28 9.25 31.36 3.86 1.63 0.35 2.8 1.35 0.28 0.85 0.84 0.14 4.37 0.33 0.33 0.69 11.22 13.96 1.2    
TMG-19 734.89 33.82 61.68 7.92 29.11 5.49 1.4 0.68 4.75 3.73 0.72 2.06 2.03 0.31 6.25 1.15 1.54 0.63 24.12 16.54 3.89    
TMG-20 808.02 15.07 27.79 3.67 15.52 3.23 0.97 0.44 2.98 2.66 0.55 1.54 1.68 0.26 3.63 0.6 0.63 0.4 11.67 2.66 2.49    
TMG-21 583.71 30.74 63.69 8.85 35.68 7.37 2.05 0.87 6.33 4.58 0.87 2.39 2.12 0.31 4.13 0.68 0.22 0.25 8.05 6.24 1.75    
TMG-22 518.65 8.67 17.53 1.59 5.71 0.98 0.29 0.16 1 0.98 0.23 0.66 0.78 0.13 2.24 0.85 0.37 1.09 8.38 1.36 0.89    
TMG-23 503.48 24.25 46.53 7.27 29.82 6.49 1.82 0.8 5.7 4.28 0.81 2.23 2 0.29 4.44 0.85 0.36 0.36 6.26 4.82 1.36    
TMG-24 411.36 17.98 37.94 4.83 19.95 4.41 1.33 0.63 4.09 3.65 0.74 2.07 2.02 0.3 0.78 0.33 0.22 0.17 3.73 3.01 0.65    
TMG-26 660.1 33.47 59.21 8.71 32.97 6.22 1.72 0.73 5.25 3.83 0.75 2.11 2.07 0.31 5.66 0.68 0.23 0.33 10.92 9.26 2.37    
AG-2 649.99 25.5 53.23 7.1 27.56 5.99 1.25 0.82 5.46 4.8 0.95 2.69 2.65 0.4 5.31 0.86 0.74 0.75 10.09 17.07 4.49 8.19  
AG-5 471.36 15.67 32.39 4.54 20.42 5.08 1.29 0.66 4.67 3.73 0.71 1.91 1.74 0.26 3.89 0.4 0.12 0.56 4.54 5.54 1.13 3.66  
CR-6 391.33 16.96 36.8 4.86 20.16 4.47 1.28 0.62 4.2 3.72 0.75 2.08 2.05 0.31 3.2 0.39 0.35 0.14 3.95 2.31 0.57 3  
ES-2 725.3 36.21 72.89 9.25 35.1 7.02 1.79 0.83 5.96 4.47 0.85 2.35 2.2 0.33 7.45 1.04 1.23 0.64 15.55 13.67 3.97 4.85  
ES-3 317.06 20.11 44.17 5.91 24.61 5.52 1.6 0.74 5.07 4.28 0.84 2.32 2.18 0.32 3.53 0.53 0.24 0.25 15.02 3.18 0.99 5.04  
LS-3 545.55 29.06 60.47 8.04 31.67 6.55 1.74 0.77 5.55 4.08 0.77 2.11 1.93 0.29 5.3 0.69 0.3 0.34 11.87 9.44 2.83 3.56  
LS-4 606.24 13.09 25.42 3.18 12.7 2.96 1.35 0.51 2.97 3.38 0.71 2.06 2.24 0.34 6 0.86 0.71 0.71 20.19 3.97 2.4 6.27  
LV-1 670.19 34.38 63.88 9.11 35.11 7.1 1.79 0.85 6.08 4.55 0.87 2.38 2.18 0.33 6.73 0.97 0.34 0.46 11.44 9.34 2.91 3.7  
SC-2 b 1 732.89 21.54 37.86 4.57 16.95 3.33 0.99 0.46 3.1 2.67 0.55 1.55 1.62 0.26 5.58 0.53 6.59 0.32 11.05 8.07 1.65 2.65  
SC-3 434.39 19.65 40.63 5.87 24.07 5.4 1.4 0.78 5.12 4.72 0.96 2.73 2.76 0.42 5.63 0.52 0.42 0.16 4.4 5.33 1.24 3.51  
LS-6 337.69 17.97 40.82 5.59 23.56 5.4 1.57 0.76 5.09 4.51 0.9 2.48 2.36 0.35 2.56 0.65 0.31 0.28 8.99 3.98 2.03 4.58  
LV-2 558.92 33.04 66.95 9.03 35.12 7.23 1.7 0.88 6.18 4.76 0.91 2.5 2.33 0.35 6.86 1.06 0.73 0.49 13.19 11.78 3.77 4.14  
CR-5 368.05 19.71 35.73 3.96 13.47 2.42 0.48 0.3 2.04 1.6 0.32 0.91 1.01 0.16 3.47 1.96 0.19 0.49 12.93 9.68 3.53 5.07  
RV-3 111.82 61.83 51 49.19 43.86 32.71 25.17 20.47 23.47 17.31 15.63 14.5 12.2 12.08 17.06 35.08 42.02   2.08 82.13 87.64   12.79
SC-2-B3 297.65 125.42 67.37 59.23 44.73 29.71 21.89 17.88 22.13 14.85 13.73 13.4 12.82 13.31 9.79 92.44 146.71   4.25 471.59 230.2   12.6
CR-1 167.89 83.39 65.46 57.15 50.7 37.12 27.38 23.12 26.58 19.73 18.14 17.09 15.2 15.54 19.88 47.5 61.72   1.45 94.35 59.66   15.52
SC-2-B1 332.11 75.4 29.29 42.17 33.22 20.97 16.89 12.88 15.27 10.85 10.27 10.09 9.64 10.16 7.3 72.34 175   4.96 144.16 95.9   9.42
SC-2-B2 433.45 91.48 50.73 50.66 39.97 23.94 19.36 12.12 16.61 8.97 7.84 7.61 7.08 7.48 8.4 73.83 198.92   4.57 145.47 93.43   6.88
AG-2 269.71 107.61 86.98 74.79 59.01 39.16 21.53 21.82 26.56 18.9 16.87 16.23 15.57 15.56 49.85 61.08 7.82   4.09 588.76 561.31   0
AG-5 195.59 66.1 52.92 47.74 43.72 33.24 22.28 17.67 22.75 14.7 12.62 11.53 10.24 10.15 36.45 28.73 1.25   1.84 191.01 141.65   0
CR-6 162.38 71.57 60.13 51.17 43.16 29.19 21.99 16.67 20.43 14.65 13.23 12.58 12.08 12.3 30.04 27.89 3.68   1.6 79.51 71.77   0
ES-2 300.96 152.78 119.1 97.32 75.15 45.86 30.83 22.23 28.99 17.6 15.07 14.22 12.94 12.95 69.9 74.25 12.97   6.3 471.51 496.36   0
ES-3 131.56 84.85 72.18 62.21 52.7 36.09 27.53 19.71 24.69 16.83 14.88 14 12.84 12.73 33.11 37.79 2.5   6.08 109.66 123.83   0
LS-3 226.37 122.64 98.81 84.65 67.81 42.81 30.07 20.5 27.01 16.05 13.61 12.75 11.37 11.41 49.72 49.35 3.14   4.81 325.55 353.2   0
LS-4 251.55 55.25 41.54 33.45 27.21 19.33 23.33 13.61 14.45 13.31 12.56 12.46 13.16 13.23 56.27 61.08 7.48   8.17 136.96 300.36   0
LV-1 278.09 145.05 104.38 95.9 75.17 46.39 30.93 22.63 29.58 17.91 15.28 14.39 12.83 12.8 63.14 69.62 3.62   4.63 322.22 363.31   0
SC-3 180.25 82.92 66.4 61.77 51.54 35.31 24.22 20.89 24.94 18.59 17.02 16.48 16.21 16.56 52.82 37.05 4.43   1.78 183.76 155.2   0
LS-6 140.12 75.83 66.7 58.86 50.45 35.28 27.01 20.34 24.75 17.76 15.83 14.99 13.88 13.77 23.99 46.77 3.26   3.64 137.14 254.24   0
LV-2 231.92 139.42 109.4 95.09 75.21 47.28 29.28 23.45 30.09 18.74 16.06 15.1 13.69 13.68 64.36 75.98 7.72   5.34 406.1 470.73   0
CR-5 152.72 83.15 58.38 41.64 28.85 15.82 8.26 7.96 9.94 6.32 5.72 5.5 5.96 6.26 32.51 139.88 2.01   5.24 333.95 441.83   0
33* 516.8 22.64 52.37 7.7 34.64 8.66 2.05 1.26 8.38 7.73 1.52 4.49 3.74 0.53 1.84 0.56 0.72   7.22 3.26 1.05    
1TIJBQ* 115.52 12.66 28.65 3.94 15.47 2.91 0.97 0.37 2.62 2.12 0.42 1.15 1.08 0.16 0.69 0.3 0.38   8.86 2.1 1.83    
529*   17.7 33.25 4.13 15.58 2.81 0.92 0.25 2.2 0.94 0.14 0.3 0.18 0.02 0.01 0.31 0.48   6.8 3.43 0.59    
538* 533.23 20.62 54.11 5.99 24.33 5.28 1.42 0.66 4.69 3.74 0.73 1.98 1.86 0.27 4.09 0.49 0.22   7.75 6.82 2.41    

Table 3 Sr, Nd and Pb isotopic values of selected samples from intrusive rocks associated with IOCG skarn mineralization in the Tatatila-Las Minas area. 

Muestra 87Sr/86Sr ɛSr 143Nd/144Nd ɛNd 206Pb/204Pb 207Pb/204Pb 208Pb/204Pb
SC-2 b1 0.7044 -1.4 0.5127 1.2 18.75 15.6012 38.4921
SC-2 b2 0.7045 0 0.5127 1.2 18.7 15.6004 38.449
SC-2 b3 0.7041 -5.7 0.5127 1.2 18.73 15.5966 38.4887
BQ-1 0.7059 19.9 0.5123 -6.6 18.68 15.6085 38.4041
RV-2 0.7059 19.9 0.5123 -6.6 18.65 15.6062 38.4562
RV-3 0.704 -7.1 0.5128 3.2 18.69 15.5993 38.4149
CR-5 0.7042 -4.3 0.5126 -0.7 18.75 15.5994 38.4601
LV-2 0.7039 -8.5 0.5128 3.2 18.74 15.5947 38.4433
Es-3 0.7042 -4.3 0.5127 1.2 18.72 15.5982 38.5354
LS-3 0.7037 -11.4 0.5128 3.2 18.67 15.58 38.3878
LS-6 0.704 -7.1 0.5128 3.2 18.68 15.5928 38.4449

The two dated samples from retrograde hydrothermal associations are chromian muscovite that corresponds to high-temperature phyllic assemblages from the Las Minas area, and zircon within pervasive potassic alteration assemblages from the Tatatila area, the 40Ar/39Ar analyses of samples from intrusive rocks were carried out at the Noble Gas Laboratory, Pacific Centre for Isotopic and Geochemical Research, University of British Columbia (Vancouver, British Columbia, Canada). The mineral separates were step-heated at incrementally higher powers in the defocused beam of a 10W CO2 laser (New Wave Research MIR 10) until fused. The gas evolved from each step was analyzed by a VG5400 mass spectrometer equipped with an ion-counting electron multiplier. All measurements were corrected for total system blank, mass spectrometer sensitivity, mass discrimination, radioactive decay during and subsequent to irradiation, as well as interfering Ar from atmospheric contamination and the irradiation interferences of Ca, Cl and K. The plateau and correlation ages were calculated using the Isoplot 3.09 software (Ludwig, 2003). Errors are quoted at the 2-sigma (95% confidence) level and are propagated from all sources except mass spectrometer sensitivity and age of the flux monitor. The full results and spectra are reported in Appendices 1 and 2 and summarized in Figure 4.

Figure 4 Outlines of 40Ar/39Ar age spectra (plateau ages) of intrusive host rocks to the IOCG skarn deposits in the Tatatila-Las Minas district, Veracruz. 

The 40Ar/39Ar analysis were performed at the Geochronology Laboratory of the Departmento de Geología, Centro de Investigación Científica y Educación Superior de Ensenada (CICESE, Mexico). The argon isotope experiments were conducted on a few flakes of fuchsite, hornblende, K-feldspar and biotite. The mineral grains were heated with a Coherent Ar-ion Innova 370 laser. The extraction system is on line with a VG5400 mass spectrometer. The sample and irradiation monitors, were irradiated in the Uenriched research reactor of University of McMaster in Hamilton, Canada, at position 5C. To block thermal neutrons, the capsule was covered with a cadmium liner during irradiation of chromian muscovite (“fuchsite”; Figure 5A and 5B) from the skarn gangue association in IOCG mantos, Santa Cruz mine (sample SC-1). The mineral grains were heated with a Coherent Ar ion Innova 370 laser. The extraction system is on line with a VG5400 mass spectrometer. The sample and irradiation monitors were irradiated in the U-enriched research reactor of University of McMaster in Hamilton, Canada, at position 5C. To block thermal neutrons, the capsule was covered with a cadmium liner during irradiation. To determine the neutron flux variations, aliquots of the irradiation monitor FCT-2 sanidine (28.201 ± 0.046 Ma; Kuiper et al., 2008) were irradiated alongside sample SC-1. Upon irradiation the monitors were fused in one step while the fuchsite sample was step-heated. The argon isotopes were corrected for blank, mass discrimination, radioactive decay of 37Ar and 39Ar, and atmospheric contamination. For the Ca neutron interference reactions, the factors given by Masliwec (1984) were used. The decay constants recommended by Steiger and Jäger (1977) were applied in the data processing. The equations reported by York et al. (2004) were used in all the straight line fitting routines of the argon data reduction. 40Ar/39Ar data are presented in Appendices 1 and 2, which includes the results of the individual steps, and the integrated, plateau and isochron ages, and their synthetic version in Figure 5. The analytical precision is reported as standard deviation (2σ). The error in the integrated, plateau and isochron ages includes the scatter in the irradiation monitors. With the exception of the first fraction, a well-defined straight line, with mean squared weighted deviations (MSWD) of 0.55 for n = 6, indicates an isochron age of 12.49 ± 0.09 Ma.

Figure 5 40Ar/39Ar age spectra (plateau and isochron ages) of a chromian muscovite (“fuchsite”) from the magmatic-hydrothermal retrograde assemblage of the IOCG skarn deposit in the Santa Cruz mine, Tatatila-Las Minas district, Veracruz. 

Zircon crystals were separated by means of panning from samples selected for U-Pb dating that are representative of various sets of rocks in the area: Au-Ag mineralized vein from Tatatila (sample TMG-5), and granodiorite to granite samples from the Santa Cruz (samples TMG-24 and SC-2), Carboneras (CR-5), Escalona (ES-3), Cinco Señores (5S-1), Boquillas (BQ-1), and Rancho Virgen (RV-2) areas. The sizes of the collected zircon crystals range between 20 and 90 μm in length. The U-Pb zircon analyses were performed with a quadrupole Thermo-X series ICP-MS with an Excimer (193 nm) laser ablation system by Resonetics, at the Isotopic Studies Laboratory (LEI), CGeo-UNAM, and following the procedure described by Solari et al. (2010). The data reduction was performed with the aid of the UPb.age in-house software (Solari and Tanner, 2011) and plotted with the Isoplot 3.0 software (Ludwig, 2003). See further technical aspects in González-León et al. (2017). U-Pb ages are displayed in Figures 6 and 7, Table 4 and Appendix 3.

Figure 6 Tera-Wasserburg U-Pb concordia diagrams and plots of weighted averages of individual 206Pb/238U ages of analyzed zircons, and pre-ablation SEM-CL images of zircons from a granodiorite intrusive from the Santa Cruz Mine (A), and from a potassic alteration assemblage that was pervasively developed on a granite-granodiorite intrusion in the village of Tatatila (B), from the Tatatila-Las Minas district, Veracruz. Solid-line ellipses, with blue square centers, are data used for age calculations; gray-line ellipses are data excluded from age calculations due to different degrees of Pb-loss and/or zircon inheritance. All U-Pb data are plotted with 2-sigma errors and all calculated weighted mean ages are also listed at the 2-sigma level. Original U(Th)-Pb data can be found for inspection in Table 5

Figure 7 Tera-Wasserburg U-Pb concordia diagrams for zircons from various intrusive bodies in the Tatatila-Las Minas area. (A) Post-mineralization dyke. (B to D) Syn-mineralization hypabyssal bodies whose age can be attributed to the prograde skarn associations. (E) Granitic intrusive that corresponds to the Permo-Triassic basement. Solid-line ellipses, with black square centers, are data used for age calculations; gray-line ellipses are data excluded from age calculations due to different degrees of Pb-loss and/or zircon inheritance. All U-Pb data are plotted with 2-sigma errors. Original U(Th)-Pb data can be found for inspection in Appendix 3

Table 4 U-Th-Pb analytical data for LA-ICPMS spot analyses on zircon grains for granitic units in Tatatila de Las Minas, Veracruz, Mexico. 

CORRECTED ISOTOPIC RATIOS CORRECTED AGES (Ma)
Analisys/Zircon U# (ppm) Th# (ppm) Th/U 207Pb/206Pb† err %* 207Pb/235Pb† err %* 206Pb/238Pb† err %* 208Pb/232Pb† err %* Rho** % disc.*** 206Pb/238Pb† ±2σ * 207Pb/206Pb† ±2σ * Best Age (Ma) ±
Sample TMG-5 Granite-granodiorite (Tatatila de Las Minas, Veracruz) Mount ICGEO-100 (January 2017)
TMG-5-17 724 1273 1.76 0.04730 18.4 0.01170 20.5 0.00171 8.2 0.00057 14.4 0.399 7 11.0 0.9 11.8 2.4 690 330 11.0 ± 0.9
TMG-5-9 226 180 0.80 0.08800 21.6 0.02280 19.7 0.00178 6.2 0.00068 20.6 0.313 50 11.5 0.7 22.8 4.5 1620 410 11.5 ± 0.7
TMG-5-1 455 618 1.36 0.05180 18.0 0.01320 16.7 0.00179 5.4 0.00067 10.2 0.322 13 11.5 0.6 13.3 2.2 750 320 11.5 ± 0.6
TMG-5-13 343 437 1.27 0.07800 23.1 0.01870 24.6 0.00180 8.3 0.00067 13.2 0.339 38 11.6 1.0 18.8 4.6 1100 510 11.6 ± 1.0
TMG-5-23 345 367 1.06 0.07900 25.3 0.01860 23.7 0.00181 6.6 0.00065 14.7 0.280 37 11.7 0.8 18.6 4.4 1410 480 11.7 ± 0.8
TMG-5-6 204 141 0.69 0.06400 26.6 0.01660 24.7 0.00182 8.8 0.00068 19.1 0.356 30 11.7 1.0 16.6 4.1 1460 450 11.7 ± 1.0
TMG-5-14 232 155 0.67 0.07400 24.3 0.01990 22.1 0.00183 7.7 0.00072 15.3 0.346 41 11.8 0.9 19.9 4.4 1570 420 11.8 ± 0.9
TMG-5-8 212 189 0.89 0.08900 21.3 0.02210 20.4 0.00183 6.6 0.00053 22.6 0.322 47 11.8 0.8 22.1 4.5 1440 370 11.8 ± 0.8
TMG-5-4 268 240 0.89 0.07400 24.3 0.01720 22.1 0.00187 8.0 0.00060 20.0 0.363 31 12.0 1.0 17.3 3.8 1230 450 12.0 ± 1.0
TMG-5-20 255 221 0.87 0.07100 23.9 0.01770 23.7 0.00187 7.0 0.00069 17.4 0.293 32 12.0 0.8 17.7 4.2 1220 440 12.0 ± 0.8
TMG-5-28 167 157 0.94 0.08400 44.0 0.01880 38.8 0.00189 13.2 0.00068 22.1 0.341 35 12.2 1.6 18.8 7.2 1730 790 12.2 ± 1.6
TMG-5-24 156 126 0.81 0.07200 29.2 0.02030 27.6 0.00191 6.8 0.00076 21.1 0.247 39 12.3 0.9 20.2 5.6 1540 520 12.3 ± 0.9
TMG-5-22 313 324 1.04 0.05600 23.2 0.01560 23.1 0.00191 6.3 0.00063 17.5 0.272 22 12.3 0.8 15.7 3.6 840 470 12.3 ± 0.8
TMG-5-25 311 188 0.60 0.08300 16.9 0.02410 15.4 0.00192 6.3 0.00070 20.0 0.407 49 12.4 0.8 24.1 3.6 1530 340 12.4 ± 0.8
TMG-5-29 379 247 0.65 0.06500 16.9 0.01660 16.3 0.00192 5.7 0.00061 19.7 0.352 26 12.4 0.7 16.7 2.7 1090 330 12.4 ± 0.7
TMG-5-21 274 283 1.03 0.07400 21.6 0.01910 20.9 0.00195 7.2 0.00078 19.2 0.343 34 12.5 0.9 19.1 4.0 1440 420 12.5 ± 0.9
TMG-5-30 286 228 0.80 0.07100 22.5 0.01930 20.2 0.00195 5.1 0.00081 18.5 0.254 35 12.5 0.7 19.3 3.9 1590 410 12.5 ± 0.7
TMG-5-12 258 238 0.92 0.07900 24.1 0.02110 25.6 0.00195 9.7 0.00047 57.4 0.381 40 12.6 1.2 21.1 5.3 1170 450 12.6 ± 1.2
TMG-5-18 209 131 0.63 0.05200 30.8 0.01530 28.8 0.00196 6.6 0.00077 19.5 0.231 17 12.6 0.8 15.3 4.3 1130 520 12.6 ± 0.8
TMG-5-15 176 152 0.86 0.06300 23.8 0.01650 25.5 0.00197 7.6 0.00076 22.4 0.299 23 12.7 1.0 16.5 4.2 1030 450 12.7 ± 1.0
TMG-5-10 254 157 0.62 0.05800 27.6 0.01780 26.4 0.00197 6.1 0.00056 21.4 0.231 28 12.7 0.8 17.7 4.7 1310 480 12.7 ± 0.8
TMG-5-16 278 242 0.87 0.05100 25.5 0.01330 23.3 0.00197 7.1 0.00066 16.7 0.305 5 12.7 0.9 13.4 3.1 1080 420 12.7 ± 0.9
TMG-5-11 207 184 0.89 0.06300 23.8 0.01610 23.0 0.00198 7.6 0.00079 16.5 0.330 21 12.7 1.0 16.2 3.7 1280 460 12.7 ± 1.0
TMG-5-26 203 189 0.93 0.09700 25.8 0.02580 21.3 0.00198 7.6 0.00062 21.0 0.355 50 12.7 1.0 25.6 5.4 1790 480 12.7 ± 1.0
TMG-5-3 173 112 0.65 0.08100 23.5 0.02230 22.9 0.00202 8.9 0.00080 22.5 0.390 41 13.0 1.1 22.2 5.0 1620 460 13.0 ± 1.1
TMG-5-19 213 206 0.97 0.05700 36.8 0.01790 26.8 0.00204 7.4 0.00060 20.0 0.274 27 13.1 1.0 17.9 4.8 1420 500 13.1 ± 1.0
TMG-5-2 200 117 0.58 0.14100 23.4 0.03790 22.7 0.00210 9.0 0.00056 48.2 0.399 64 13.5 1.2 37.5 8.3 2350 410 13.5 ± 1.2
TMG-5-7 194 170 0.88 0.05200 32.7 0.01640 29.9 0.00219 7.3 0.00077 18.2 0.245 14 14.1 1.0 16.4 4.9 1180 520 14.1 ± 1.0
TMG-5-5 160 117 0.74 0.20500 17.6 0.06100 18.0 0.00226 7.5 0.00177 20.3 0.417 76 14.5 1.1 60.0 10.0 2950 410 14.5 ± 1.1
TMG-5-27 221 193 0.87 0.24200 19.8 0.08000 17.5 0.00259 10.0 0.00118 53.4 0.574 79 16.7 1.7 78.0 13.0 3110 320 16.7 ± 1.7
TMG-24-15 103 76 0.74 0.11900 31.9 0.02870 31.0 0.00203 10.8 0.00085 28.2 0.349 54.0 13.1 1.4 28.4 8.8 2270 620 13.1 ± 1.4
TMG-24-24 57 32 0.57 0.19000 63.2 0.05100 25.5 0.00204 14.7 0.00181 26.5 0.577 73.0 13.2 1.9 49.0 13.0 2940 2400 13.2 ± 1.9
TMG-24-20 63 34 0.54 0.14100 28.4 0.03800 28.9 0.00212 12.7 0.00091 50.5 0.440 63.0 13.7 1.7 37.0 11.0 2670 560 13.7 ± 1.7
TMG-24-10 175 70 0.40 0.07000 22.9 0.02160 22.7 0.00217 6.5 0.00095 24.2 0.284 35.0 14.0 0.9 21.5 4.9 1280 390 14.0 ± 0.9
TMG-24-8 110 93 0.85 0.14000 30.7 0.03430 27.4 0.00221 14.0 0.00083 28.9 0.512 58.0 14.2 2.0 33.9 9.2 2080 580 14.2 ± 2.0
TMG-24-18 64 44 0.68 0.12200 44.3 0.03700 43.2 0.00228 13.6 0.00137 35 0.314 59.0 14.7 2.0 36.0 15.0 2790 910 14.7 ± 2.0
TMG-24-4 574 534 0.93 0.05470 14.8 0.01630 14.1 0.00230 5.2 0.00077 10.5 0.370 10.0 14.8 0.8 16.4 2.3 700 280 14.8 ± 0.8
TMG-24-22 760 560 0.74 0.05240 15.3 0.01670 15.0 0.00233 4.3 0.00084 11.3 0.287 11.0 15.0 0.7 16.8 2.5 660 280 15.0 ± 0.7
TMG-24-21 2120 2370 1.12 0.04810 7.3 0.01540 7.8 0.00236 2.6 0.00074 6.6 0.338 2.0 15.2 0.4 15.5 1.2 333 140 15.2 ± 0.4
TMG-24-7 110 62 0.56 0.06000 46.7 0.01780 42.1 0.00238 8.4 0.00123 25.2 0.199 19.0 15.3 1.3 18.9 7.8 1800 710 15.3 ± 1.3
TMG-24-1 234 113 0.48 0.06900 30.4 0.02030 30.0 0.00238 6.7 0.00103 17.5 0.224 24.0 15.4 1.0 20.2 6.1 1150 550 15.4 ± 1.0
TMG-24-19 77 65 0.84 0.07200 41.7 0.02660 36.8 0.00243 9.1 0.00088 25 0.246 40.0 15.6 1.4 26.0 9.7 2050 740 15.6 ± 1.4
TMG-24-3 275 152 0.55 0.08300 16.9 0.02860 17.1 0.00243 7.0 0.00091 18.7 0.408 45.0 15.7 1.1 28.4 4.8 1580 350 15.7 ± 1.1
TMG-24-23 64 32 0.51 0.11900 34.5 0.03100 32.3 0.00244 11.1 0.00073 57.5 0.343 47.0 15.7 1.7 29.9 9.9 2170 680 15.7 ± 1.7
TMG-24-9 146 154 1.05 0.12800 16.4 0.04220 15.6 0.00246 6.9 0.00108 16.7 0.442 62.0 15.8 1.1 41.7 6.4 2160 320 15.8 ± 1.1
TMG-24-12 248 150 0.60 0.08900 24.7 0.02480 21.0 0.00246 6.5 0.00075 24 0.310 36.0 15.8 1.1 24.7 5.2 1630 380 15.8 ± 1.1
TMG-24-14 350 234 0.67 0.06800 17.6 0.02370 16.9 0.00246 5.7 0.00075 22.7 0.337 33.0 15.9 0.9 23.7 4.0 1280 370 15.9 ± 0.9
TMG-24-17 65 34 0.52 0.12600 33.3 0.03300 30.3 0.00250 13.2 0.00113 30.1 0.436 51.0 16.1 2.1 33.0 10.0 2640 710 16.1 ± 2.1
TMG-24-25 80 66 0.83 0.13800 51.4 0.04460 21.7 0.00251 10.8 0.00093 30.1 0.495 63.0 16.1 1.7 43.7 9.4 2300 2200 16.1 ± 1.7
TMG-24-5 115 48 0.41 0.08100 24.7 0.02860 23.4 0.00257 8.9 0.00098 33.7 0.382 42.0 16.5 1.5 28.3 6.7 1610 450 16.5 ± 1.5
TMG-24-16 65 31 0.47 0.19200 46.9 0.04400 29.5 0.00261 10.7 0.00123 43.9 0.363 60.0 16.8 1.8 42.0 13.0 2650 1000 16.8 ± 1.8
TMG-24-6 67 31 0.46 0.10500 43.8 0.03500 34.3 0.00263 12.2 0.00141 30.5 0.355 50.0 16.9 2.0 34.0 12.0 2010 720 16.9 ± 2.0
TMG-24-13 70 34 0.49 0.08100 54.3 0.01990 44.7 0.00262 14.1 0.00103 39.8 0.316 14.0 16.9 2.4 19.6 8.9 2430 880 16.9 ± 2.4
TMG-24-11 120 54 0.45 0.09900 34.3 0.02900 34.5 0.00264 10.6 0.00082 48.8 0.308 40.0 17.0 1.8 28.2 9.9 1970 700 17.0 ± 1.8
TMG-24-2 1550 930 0.60 0.05960 15.6 0.02240 14.7 0.00275 4.7 0.00065 44.6 0.321 21.0 17.7 0.9 22.5 3.3 640 310 17.7 ± 0.9

n = 30 Mean 206Pb/238U Age = 12.18 ± 0.21 (2 sigma, MSWD = 1.5; n = 26)

#U and Th concentrations (ppm) are calculated relative to analyses of trace-element glass standard NIST 610.

Isotopic ratios are corrected relative to 91500 standard zircon for mass bias and down-hole fractionation (91500 with an age ~1065 Ma; Wiedenbeck et al., 1995). Isotopic 207Pb/206Pb ratios, ages and errors are calculated following Paton et al. (2010).

*All errors in isotopic ratios are in percentage whereas ages are reported in absolute and given at the 2-sigma level. The weighted mean 206Pb/238U age is also reported in absolute values at the 2-sigma level. The uncertenties have been propagated following the methodology discussed by Paton et al. (2010).

**Rho is the error correlation value for the isotopic ratios 206Pb/238U and 207Pb/235U calculated by dividing these two percentage errors. The Rho value is required for plotting concordia diagrams.

***Percentage discordance values are obtained using the following equation (100*[(edad 207Pb/235U)-(edad 206Pb/238U)]/edad 207Pb/235U) proposed by Ludwig (2001). Positive and negative values indicate normal and inverse discordance, respectively.

Individual zircon ages in bold were used to calculate the weighted mean 206Pb/238U age and MSWD (Mean Square of Weigthed Deviates) using the computacional program Isoplot (Ludwig , 2003).

Table 5 Summary of geochronometric data obtained for host intrusive rocks and IOCG mineralization at the Tatatila-Las Minas area. 

Sample / location Association Method / mineral Age ± 2σ (Ma) Comments
Tatatila-Las Minas district
BQ-1a, BQ-1b / Boquillas Granite U-Pb / zircon 286 ± 2 Early Permian granitoids in the Permo-Triassic basement
CR-1 / Carboneras Granodiorite 40Ar/39Ar / biotite 24.60 ± 1.10 Pre-mineralization intrusive suite (late Oligocene to early Miocene)
CR-1 / Carboneras Granodiorite 40Ar/39Ar / HB 23.40 ± 2.50 Transition between the Sierra Madre Occidental and the Trans-Mexican Volcanic Belt?
CR-1 / Carboneras Granodiorite 40Ar/39Ar / HB 23.40 ± 2.50
BQ-1c / Boquillas Granite 40Ar/39Ar / KF 22.12 ± 0.74
RV-2 / Vaquería Granite 40Ar/39Ar / KF 20.67 ± 0.57
CR-1 / Carboneras Granodiorite 40Ar/39Ar / KF 19.04 ± 0.69
SC-2-b1 / Santa Cruz Granodiorite 40Ar/39Ar / biotite 16.34 ± 0.20 Syn-mineralization intrusive suite (middle to late Miocene)
SC-2a / Santa Cruz Granodiorite 40Ar/39Ar / biotite 15.43 ± 0.16
TMG-24 / Santa Cruz Qz-monzonite U-Pb / zircon 15.27 ± 0.36
5S-1 / Cinco Señores Granite U-Pb / zircon 15.09 ± 0.48
CR-5 / Carboneras Granodiorite U-Pb / zircon 15.05 ± 0.94 Matches with the middle to late Miocene age range of intrusive bodies of gabbroic to dioritic composition defined by Ferrari et al. (2005a) at the Palma Sola massif, east of the Tatatila-Las Minas area
BQ-1b / Boquillas Granite 40Ar/39Ar / biotite 14.60 ± 0.34
SC-2b / Santa Cruz Granodiorite 40Ar/39Ar / biotite 14.46 ± 0.15
SC-2b / Santa Cruz Granodiorite U-Pb / zircon 14.33 ± 0.38
BQ-1b / Boquillas Granite 40Ar/39Ar / biotite 13.92 ± 0.22
FSC-1 / Santa Cruz mineralization 40Ar/39Ar / CM 12.49 ± 0.09
TMG-5 / Tatatila mineralization U-Pb / zircon 12.18 ± 0.21
Es-3 / Escalona Granodiorite U-Pb / zircon 4.11 ± 0.11 Post-mineralization intrusives
Regional intrusive ages
Laguna Verde microdiorite 17 Cantagrel and Robin (1979), deemed as unreliable by Ferrari et al. (2005a)
Junique gabbro 40Ar/39Ar 15.62 ± 0.5 Ferrari et al. (2005a)
Plan de las Hayas hypabyssal rock 40Ar/39Ar 14.65 ± 0.32 Ferrari et al. (2005a)
Tenochtitlan to Junique granitic plutons 13.0 ± 1.0 López-Infanzón (1991)
9.0 ± 0.7
6.2 ± 0.6
Candelaria gabbro 12.3 and 12.9 Negendank et al. (1985)
El Limón hypabyssal rock 40Ar/39Ar / PL 10.9 ± 0.8 Ferrari et al. (2005a)
40Ar/39Ar 11.07 ± 0.2 Ferrari et al. (2005a)
Whole range of ages of magmatism in the Palma Sola massif 15.6 to 10.9 Ferrari et al. (2005a)
17 to 7.5 Camprubí (2009, 2013)

4. Results

The U-Pb ages of zircon crystals from granite, granodiorite, quartz-monzonite and monzodiorite are displayed in Figures 6 and 7, in Table 4, and Appendices 3 and 4. The sample from Carboneras (CR-5) yielded a U-Pb concordia lower intercept at 15.05 ± 0.94 Ma (MSWD = 2.5, n = 19; Figure 7C). Two samples from the Santa Cruz mine were dated; sample TMG-24 yielded a U-Pb concordant age at 15.27 ± 0.36 Ma (MSWD = 2 n = 14; Figure 6A), and sample SC-2b a weighted mean U-Pb age at 14.33 ± 0.38 Ma (MSWD = 2.6, n = 9; Figure 7B). The sample from Cinco Señores (5S-1) yielded a U-Pb weighted mean age at 15.09 ± 0.48 Ma (MSWD = 4.0, n = 8; Figure 7D). 40Ar/39Ar determinations in host intrusive samples as granodiorite, granite, monzodiorite and quartz-monzonite yielded two groups of ages: (A) late Oligocene to early Miocene, between 22.12 ± 0.74 and 19.04 ± 0.69 Ma for a pre-mineralization suite of intrusive bodies, and (B) middle to late Miocene, between 16.34 ± 0.20 and 13.92 ± 0.22 Ma for a syn-mineralization suite of intrusive bodies, all reported ages correspond to plateau ages.

The samples for 40Ar/39Ar different minerals such as biotite, hornblende, K-feldspar and fuchsite, were separated from each sample for analysis.

The 40Ar/39Ar determination in hydrothermal chromian muscovite (“fuchsite”) of the Santa Cruz mine yielded a plateau age of 12.49 ± 0.09 Ma (isochron age at 12.39 ± 0.1 Ma; Figure 5). The sample (TMG-5) from a potassic alteration assemblage that was pervasively developed on a granite-granodiorite intrusion in the village of Tatatila (thus corresponding to hydrothermal associations) yielded a U-Pb age of 12.18 ± 0.21 Ma, (2σ, MSWD = 1.5; n = 26; Figure 6B).

The sample ES-3 from Escalona corresponds to a dyke that crosscuts the IOCG mineralization and yielded a U-Pb weighted mean age at 4.11 ± 0.11 Ma (MSWD = 0.53, n = 8; Figure 7A). A sample from Boquillas (BQ-1a, BQ-1b) yielded a U-Pb weighted mean age at 286 ± 2 Ma (MSWD = 1.02, n = 6; Artinskian, early Permian; Figure 7E).

The intrusive rocks associated with the formation of IOCG deposits in the Tatatila-Las Minas area span compositions between those of sub-alkaline gabbros and granodiorites, and mostly concentrate in the granite, diorite and monzodiorite fields (Figure 8A). The geochemical affinity of the rocks is essentially metaluminous (Figure 8B), calc-alkaline (Figure 8C), and they plot within the fields of volcanic-arc granites (VAG) (Figure 9A) and I- and S-type granites (Figure 9B). Some samples have adakitic signatures (Figure 9D), mostly of the high-silica type (Figure 9E), thus indicating that their compositional variation is controlled mainly by partial melting (Figure 9C). Light rare-earth and large-ion lithophile elements (LREE and LILE) are slightly enriched in such rocks (Figure 10) with respect to heavy rare-earth and high field strength elements (HREE and HFSE), as is characteristic for rocks associated with subduction, and conform with the results obtained by Dorantes-Castro (2016). Radiogenic isotope data range as follows: 87Sr/86Sr between 0.7040 and 0.7059, ɛSr between -11.4 and 19.9, 143Nd/144Nd between 0.5123 and 0.5128, ɛNd between -6.6 and 3.2, and 206Pb/204Pb between 18.65 and 18.75 (Table 3; Figure 11). The distribution of such data is in accordance with that determined by Gómez-Tuena et al. (2003) for rocks from the Trans-Mexican Volcanic Belt.

Figure 8 Petrological discrimination diagrams from major elements in intrusions associated with IOCG skarn mineralization in the Tatatila-Las Minas district, Veracruz. (A) Silica vs. alkaline element bivariant diagram, adapted from Cox et al. (1979). (B) Alumina saturation diagram, adapted from Frost et al. (2001), with compositions of skarns from Meinert (1995). (C) AFM diagram, adapted from Irvine and Baragar (1971)

Figure 9 Petrological discrimination diagrams from trace elements in intrusive rocks associated with IOCG skarn mineralization in the Tatatila-Las Minas district, Veracruz. (A) Y+Nb vs. Rb, Y vs. Nb, Ta+Yb vs. Rb, and Yb vs. Ta diagrams for discriminating tectonic settings, adapted from Pearce et al. (1984). (B) Discrimination diagram for different granite sources, adapted from Whalen et al. (1987). (C) Discrimination diagram for the generation of magmas by fractional crystallization vs. variable degree of partial melting, adapted from Thirlwall et al. (1994). (D) Discrimination diagram for adakitic affinity, adapted from Martin (1986) with chondrite-normalized values Sun and McDonough (1989). (E) Discrimination diagrams for high-silica (HSA) and low-silica adakites (LSA), adapted from Martin and Moyen (2002, 2003) and Martin et al. (2005). Key: HSA = high-silica adakites (>60% SiO2), LSA = low-silica adakites (<60% SiO2), ORG = ocean ridge granites, VAG = volcanic arc granites, syn-COLG = syn-collision granites, WPG = within plate granites. 

Figure 10 Spider diagrams of REE (A) and trace element contents (B) normalized to chondrite (Sun and McDonough, 1989). 

5. Discussion

5.1. Age constraints

The ages (Figures 4 and 12; Table 5) of magmatic and hydrothermal episodes the Tatatila-Las Minas deposits range between 16.34 and 13.92 Ma for the associated intrusive bodies (all of them observed as direct contributors to prograde skarn formation), and between 12.49 and 12.18 Ma for hydrothermal minerals (retrograde skarn stages). It is important to emphasize that the analyzed rocks are not merely terms of an intrusive suite that included IOCG skarn generators, but IOCG skarn generators themselves, as the sampling strategy was directed to rocks spatially associated with such mineralization-whether prograde or retrograde. The discussion to follow relies on this fact. The maximum time gap between prograde and retrograde skarn associations thus determined spans ~1.5 My, which is similar to that defined for other skarn deposits (i.e., Camprubí et al., 2015). A late dyke that crosscuts the mineralization, in association with capping volcanic rocks of the Trans-Mexican Volcanic Belt, was dated at 4.11 Ma. The early Permian age obtained for intrusive rocks in the Las Minas area (286 ± 2 Ma) is likely to correspond to the Carboniferous-Permian arc (Ortega-Obregón et al., 2013; Kirsch et al., 2012), known as the Teziutlán massif, that constitutes the basement in the region and was dated at 269-252 Ma (K-Ar; López-Infanzón, 1991) and at 281-268 Ma (40Ar/39Ar; Iriondo et al., 2003).

Figure 11 Isotope variation diagrams for the Tatatila-Las Minas Miocene intrusive bodies associated with IOCG skarn mineralization. (A) Sr-Nd isotopes variation diagram. (B) Pb-Nd isotopes variation diagram. (C) Pb isotopes variation diagram. (D) ɛNd vs. ɛSr diagram that illustrates possible end-member sources for magmas, after DePaolo and Wasserburg (1979a, 1979b). Key = DMM = depleted MORB-mantle, EMI = enriched mantle I, EMII = enriched mantle II, HIMU = mantle component, MORB = 5°-15° NE Pacific Rise mid-ocean ridge basalts, NHRL = northern hemisphere reference line, TMVB = current volcanic front of the Trans-Mexican Volcanic Belt. See sources for all reference values in Gómez-Tuena et al. (2003), which is also the source of values represented as green dots in diagrams A to C that correspond to volcanic rocks from the Palma Sola area in the eastern TMVB. The magmatic fractionation and sediment recycling trends in the zoomed view of A are simplified after Hoffman and White (1982)

Figure 12 Summary of the U-Pb and 39Ar/40Ar ages obtained in this study for the intrusive rocks and IOCG skarn mineralization at the Tatatila-Las Minas area, Veracruz. 

A consistent range of ages between 24.60 and 19.04 Ma (late Oligocene to early Miocene; Figures 4 and 12; Table 5) has been additionally obtained, which corresponds to intrusive rocks that predate the syn-mineralization suite. Such ages also predate the earliest stage of magmatism that is associated with the Trans-Mexican Volcanic Belt (Gómez-Tuena et al., 2005, 2007) and are similar to those characteristic of the final stage of magmatic activity of the Sierra Madre Occidental (Ferrari et al., 2005b, 2007).

5.2. Petrologic affinity

The multielemental and isotopic geochemical determinations of IOCG skarn-related intrusive rocks at Tatatila-Las Minas are sound and congruent indicators of mostly intermediate to acid (Figure 8A), metaluminous (Figure 8B), and I- and S-type rocks (Figure 9B) that were emplaced in a subduction-related continental arc (Figure 9A), and high La/Yb ratios could also be obtained through high pressures in basaltic melt (Figure 9C; McPherson et al., 2006), since the late Oligoce to Miocene. In addition, these rocks are part of the medium- to high-potassium (not shown) calc-alkaline series, with adakitic signatures and a compelling isotopic affinity with the Trans-Mexican Volcanic Belt (TMVB). A sound adakitic affinity of most analyzed samples in the study area is determined by a general geochemical behavior (Tables 1 to 3; Figure 9D, E) that meets most of the characteristics of such petrological association (Table 6). If anything, Y and Yb contents appear to be significantly higher than in adakitic (Tables 3 and 6), a characteristic that will be addressed later on. Despite the possible occurrence of alkaline magmatism in the Palma Sola region in association with the Eastern Mexico Alkaline Province (EMAP; Demand and Robin, 1975; Negendank et al., 1985; Ferrari et al., 2005a), the formation of IOCG skarn deposits in the Tatatila-Las Minas district can be solely attributed to the TMVB, as no adakitic affinity has been consistently reported for the magmatism associated with the EMAP (see references in Camprubí, 2013). However, some ages of alkaline rocks in Palma Sola are much younger than syn-mineralization ages, with no associated mineralization. Then, the adakitic signatures found in the Palma Sola region are more likely to correspond to the volcanism of the TMVB rather than that of the EMAP. This is the first instance in which adakites are directly associated with the formation of any ore deposits in the TMVB-in this case, IOCG skarn deposits.

Table 6 Comparative table between the general geochemical composition of adakites (as of Mori et al., 2007; Richards and Kerrich, 2007) and of intrusive rocks at the Tatatila-Las Minas area. 

“Normal” adakites Tatatila-Las Minas
SiO2 (wt.%) ≥56 ~44 to 68
Al2O3 (wt.%) ≥15 ~14 to 21
MgO (wt.%) ~<3 <1 to ~11 Mostly <6.7 wt.%
Na2O (wt.%) 3.5 to 7.5 ~3 to 5
K2O/Na2O ~0.42 0.1 to 1.2 Mostly 0.4 to 0.6
HREE depleted depleted
Sr (ppm) ≥400 ~16 to 734
Y (ppm) ≤18 ~3 to 50 Mostly between 20 and 40 ppm
Yb (ppm) ≤1.9 ~0 to 16 Mostly <3 ppm
Cr (ppm) ≥30 ~2 to 439 9 out of 25 values are ≥30 ppm
Sr/Y ≥20 ~7 to 190
La/Yb ≥20 ~5 to 13
87Sr/86Sr ≤0.7045 0.7037 to 0.7059
ɛNd -0.1 to 1.7 -6.6 to 3.2
ɛSr -11.4 to 19.9

However, anomalously high Y and Yb contents (with respect to typical adakitic signatures) similar to those found in the Tatatila-Las Minas host rocks have been explained in adakites as to reflect some degree of interaction with alkaline or ultrapotassic rocks (Lu et al., 2013; Liu et al., 2017)-hence the high-potassium character of many of the studied rocks (?)-or due to crustal contamination (Zhang et al., 2017). Therefore, despite the likely dominant affinity of these rocks with the TMVB, some degree of interaction between their parental TMVB magmas and EMAP magmas cannot be ruled out at this stage of research. As a matter of fact, magmas with either affinity coexisted in the region, as evidenced by the formation of the Tatatila-Las Minas deposits (Negendank et al., 1985; Ferrari et al., 2005a; see also Figure 7 in Camprubí, 2009). Also, the occurrence of A-type granites (alkaline) is hinted at in some of the analyzed samples despite mostly belonging to I- and S-types (Figure 9B), but no affinity with within-plate granites was found (Figure 9A).

In addition, the data in this paper stand for the idea of a metallogeny of the TMVB in its own right, as established by Camprubí (2013). The ages of Miocene IOCG skarn-related magmatism in the Tatatila-Las Minas area (16.34 to 13.92 Ma) fit well within the ~19 to 10 Ma bracket defined by Gómez-Tuena et al. (2005, 2007) for the early stages of the TMVB, particularly in its eastern region, in which the adakitic signature of volcanism is conspicuous. Such continental magmatism display geochemical signatures that strongly evoke those of adakites, with the inherent likeliness that it may be associated with melting of the flattened subducted slab (Gómez-Tuena et al., 2005, 2007; Mori et al., 2007). Adakite is the common term that refers to magmas produced by melting of subducted oceanic crust under high pressures and in the presence of water (due to dehydration of the subducted slab). However, other processes for magma generation are possible in the generation of magmas with adakitic geochemical signatures (Defant et al., 2002; Richards and Kerrich, 2007; Rodríguez et al., 2007; Richards, 2011; Ma et al., 2015; Ribeiro et al., 2016; Deng et al., 2017; Keevil et al., 2019). The adakitic signatures at a regional scale in the TMVB are the very high Sr/Y ratios, depletion in Y and HREE, and Sr, Nd and Pb isotopic compositions that approximate to those of mid-ocean ridge basalts in the East Pacific Rise (Gómez-Tuena et al., 2005, 2007; Mori et al., 2007). Nonetheless, adakitic affinities do not necessarily imply that these magmas are derived from the melting of the subducted slab alone, and other geological mechanisms are also plausible for their inception or as relevant contributors to adakitic signatures, as discussed below.

5.3. Origin of adakitic compositions and linkage with ore deposits

The linkage between adakitic magmas and the variety of tectonomagmatic settings that the generation of such magmas entails is suggestive of a significant potential for the formation of associated ore deposits (González-Partida et al., 2003a, 2003b; Chiaradia et al., 2004; Sun et al., 2011; Deng et al., 2017; Keevil et al., 2019). Although the association between “adakites” and ore deposits normally refers to the classic definition of adakite magmas, the generation of such magma through melting of a subducted slab has been questioned (Richards and Kerrich, 2007; Richards, 2011). In the case of Tatatila-Las Minas, however, the intrusive rocks of adakitic-affinity associated with IOCG skarn mineralization have dominantly high-silica compositions (Figure 9E). This denotes that melting of basalt from the subducted slab would have effectively occurred, with subsequent reaction of the resulting melts with peridotites during their ascent through the mantle wedge (Defant and Drummond, 1990; Drummond and Defant, 1990; Martin et al., 2005). Also, the distribution of Nd and Sr isotopic compositions in the Tatatila-Las Minas intrusions point to magma fractionation as per their distribution (Figure 11A). ɛNd values in the analyzed rocks (between -6.6 and 3.2; Table 3) point to contributions of both relatively isotopically enriched and depleted magma sources for Nd, and represent mantle derived melts that were contaminated by continental crust lithologies, especially when correlated with ɛSr values (Figure 11D). As already highlighted by Gómez-Tuena et al. (2003), Pb isotopic compositions lie between those expected for subducted sediments and MORB (Figure 11B, 11C and Table 3), thus requiring an isotopically depleted source.

An association between adakites and the formation of IOCG skarn deposits was earlier established in Mexico for the late Cretaceous-early Paleocene Mezcala deposits in the Sierra Madre del Sur (Camprubí and González-Partida, 2017, and references therein). The formation of adakites in that locality has been linked to early stages of a subduction-related continental arc (González-Partida et al., 2003b), a feature that is explained by the switch from subduction-related oceanic arcs to continental arcs in southern Mexico during the Late Cretaceous (Camprubí, 2013, 2017). Besides the particular case of Mezcala, in these and the Tatatila-Las Minas deposits the formation of associated adakitic magmas can be explained by slab rollback or flattening subduction as younger portions of the subducted slab were being consumed (Morán-Zenteno et al., 1999; Ferrari and Rosas-Elguera, 1999; Gutscher et al., 2000; Gómez-Tuena et al. 2003; Keppie and Morán-Zenteno, 2005). Also, in both regions similar associations of different magmatic-hydrothermal types of deposits (i.e., IOCG, sulfide skarns, metalliferous porphyries, epithermal deposits; Camprubí, 2013, 2017) were produced. Such flattening of the subducted slab has been extensively documented along the entire Western Cordillera of North America and the Andes and explains the historical distribution of metallogenic provinces within them (Camprubí, 2017, and references within).

However, magmatic processes such as assimilation and fractional crystallization (AFC) or those occurring in melting-assimilation-storage-homogenization (MASH) zones in “normal” continental arc magmas may also account for adakitic compositions of intrusions in association with the subsequent formation of magmatic-hydrothermal ore deposits (Richards and Kerrich, 2007; Richards, 2011; Gatzoubaros et al., 2014; Lohmeier et al., 2019). fact, these processes can generate andesitic to dacitic differentiates with HREE-depleted normalized REE patterns, and high La/Yb and Sr/Y ratios (Feeley and Davison, 1994; Kay et al., 1999; Klepeis et al., 2003; Richards, 2011). However, AFC processes can be virtually ruled out as important contributors to the adakitic signal because Eu anomalies in this case are weak (Figure 10; see Chen et al., 2014). The absence of Eu anomalies would support the model by Richards (2011), as high water contents in typical adakitic rocks are characteristic of MASH zones. MASH interactions may involve partial melts of lower crustal rocks that may imprint high La/Yb and Sr/Y. Such signature is derived from high pressure fractionation in MASH zones with amphibole and garnet, which would produce high La/Yb ratios, and from the suppression of plagioclase fractionation due to high water content in the magmas, thus resulting in high Sr/Y ratios (see references in Richards, 2011). In low f S2 and high f O2 conditions underneath “normal” continental arcs, MASH processes may induce the formation of IOCG deposits in intra-arc settings (Richards and Mumin, 2013), thus producing an alternative scenario for the association between adakite-like and IOCG deposits. With regard to slab flattening underneath a continental arc due to steep subduction, Richards and Mumin (2013) argued about scarce to nil associated magmatic activity or the migration of magmatism toward back-arc settings. Interestingly, slab flattening would cause the dehydration of the slab and the subsequent hydration of the lithosphere, which would be too cold to melt. However, once the slab re-steepened, the temperature of the hydrated lithosphere would rise in contact with the asthenosphere, generating the partial melting of sub-continental mantle and subsequent vigorous volcanic flare-ups, thus reactivating the formation of magmatic-hydrothermal ore deposits-among them, IOCG deposits (see Figure 1 in Richards and Mumin, 2013). The formation of adakites in such specific settings and in association with magmatic-hydrothermal ore deposits has not been reported. However, the involvement of MASH-type processes in metallogeny has actually been invoked in the formation of continental-arc related magmatic-hydrothermal ore deposits nonetheless (Sun et al., 2011). The possibility of magma generation by MASH-type processes that followed re-steepening of the subducted slab with which the formation of IOCG deposits would be linked is particularly significant for the Tatatila-Las Minas case. Indeed, the formation of these deposits occurred during the late Miocene, once the subducted slab underneath the Trans-Mexican Volcanic Belt, in fact, re-steepened (see Figure 13 in Gómez-Tuena et al., 2003).

In summary, the most likely settings for the formation of parental adakitic magmas to the IOCG skarn deposits at Tatatila-Las Minas would be (1) a “normal adakitic” slab-melt setting with some crustal contamination, or (2) MASH-related adakitic compositions. However, these settings do not necessarily have to be considered as mutually exclusive in the generation of adakites with associated magmatic-hydrothermal ore deposits (Chen et al., 2014; Sun et al., 2018). To our reckoning, these settings cannot be effectively discriminated given the current wealth of data from the Tatatila-Las Minas district. In addition, it is possible that TMVB calc-alkaline and EMAP alkaline magmas underwent some kind of interaction that produced the intrusive bodies with which the studied IOCG skarn deposits are associated. Interestingly, despite the common tectonomagmatic affinity of all the Cenozoic magmatic rocks, the only samples that show high Y and Yb contents are those whose ages correspond entirely to the initial stages of the TMVB (not those older than 19 Ma). This, again, stands for different magmatic processes-albeit slightly-between TMVB and pre-TMVB rocks.

6. Conclusions

The iron oxide-Cu-Au deposits at the Tatatila-Las Minas district (central Veracruz) are skarn-related deposits that belong to the IOCG family, and associated Au-rich epithermal deposits also occur in the area. U-Pb and 40Ar/39Ar dating of these IOCG skarns yielded early to middle Miocene ages for prograde (16.34 to 13.92 Ma for the associated intrusive bodies) and retrograde (12.44 to 12.18 Ma for hydrothermal minerals) associations. Such ages and the geochemical affinity of host intrusive rocks (calc-alkaline to adakitic) that are directly involved in the formation of IOCG skarns match well with those previously established for the early stages of evolution of the Trans-Mexican Volcanic Belt (TMVB). A set of pre-TMVB Cenozoic rocks has been also dated between ~24.6 and 19 Ma.

The multi-elemental and isotopic geochemical study of IOCG skarn-related intrusive rocks determined that these are intermediate to acid, metaluminous, I- and S-type, medium- to high-potassium, typical calc-alkaline to adakitic rocks that are compatible with those expected for a continental volcanic arc such as the TMVB. Therefore, the studied deposits are likely to be ascribed to the metallogeny of the TMVB, which can be rightfully spoken of as an actual metallogenic province. Such a fact broadens the economic expectations of a province that has traditionally been overlooked by mineral exploration.

The prominent adakitic signal as found in the IOCG skarn-generating intrusive rocks has been regionally attributed to adakitic melts associated with flat subduction and the subsequent resteepening of the subducted slab-with independent evidence for crustal contamination. The results in this paper concur with such an interpretation. The general geochemical characteristics of these rocks, however, do not rule out the possibility that melting-assimilation-storage-homogenization (MASH) processes were involved in the generation of parental magmas. There are also hints that these magmas interacted with alkaline melts, which would likely be associated with the nearly contemporaneous EMAP. Only TMVB rocks display Y and Yb contents that would suggest such interaction-all other petrologic indicators suggest common characteristics for TMVB and pre-TMVB Cenozoic rocks. In both a adakitic and MASH scenarios, the most plausible stage at which the formation of IOCG skarn-associated magmas occurred would be once the flattened subducted slab re-steepened, thus allowing melting of either (or both) slab material or the hydrated lower lithosphere.

Acknowledgements

This paper constitutes a part of the dissertations of E.F.G. and G.H.A., who acknowledge the support of CONACyT through PhD and MSc grants, respectively. The Instituto de Geología UNAM is acknowledged for authorizing E.F.G. to carry on her PhD research along with her academic duties. Funding for this work was provided by CONACyT through the research grants 155662 to A.C. and “GEMex: Cooperación México-Europa para la investigación de sistemas geotérmicos mejorados y sistemas geotérmicos supercalientes” (within the 4.1 and 8.2 research sections: Determinación de propiedades petrológicas, de alteración hidrotermal, microtermométricas, geoquímicas, de isótopos estables y geocronológicos de afloramientos basamentales de áreas aledañas a Los Humeros y Acoculco, Pue.” to GEOMINCO S.A. de C.V. Additional funding was provided by the Instituto de Geología UNAM and the Centro de Geociencias UNAM through personal allocations. The radiogenic isotope determinations were carried out at the Centro de Geociencias UNAM with the assistance of Ofelia Pérez Arvizu and Carlos Ortega Obregón. The thin sections were elaborated by Juan Tomás Vázquez Ramírez of the Centro de Geociencias UNAM. FRX determinations were carried out at the Laboratorio Nacional de Geoquímica y Mineralogía-Instituto de Geología UNAM with the assistance of Rufino Lozano Santacruz. The separation of zircon crystals was carried out with the assistance of Teodoro Hernández Treviño of the Instituto de Geofísica UNAM. Assistance during field work was provided by Jesús Castro and Dunia Figueroa. Also, Figure 1 was drawn with the assistance of Rodrigo Delgado Sánchez. The authors are also grateful to Carl Nelson, Lisard Torró and Joaquín Proenza, the guest editors of the present special issue, and to three anonymous referees, whose comments helped to significantly improve this manuscript.

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Appendix

Appendix 1. Ar/Ar determinations dataset for intrusive rocks associated with the IOCG skarn deposits at the Tatatila-Las Minas district, Veracruz.

SC-2b biotite 

Laser Isotope Ratios
Power (%) 40Ar/39Ar 36Ar/39Ar 39Ar/40Ar 36Ar/40Ar Rho K/Ca %40Ar rad f 39 Ar 40Ar*/39ArK Age
2.30 80.48 5.38 0.25 0.03 0.01 0.001 0.00308 0.00030 0.041 0.82 8.07 0.07 6.502 44.84 ± 49.84
2.80 18.12 0.61 0.0603 0.0072 0.06 0.002 0.00331 0.00039 0.127 0.85 1.12 0.68 0.204 1.42 ± 14.86
3.20 6.76 0.29 0.0160 0.0013 0.15 0.006 0.00230 0.00021 0.392 0.61 31.25 1.92 2.115 14.71 ± 3.27
3.60 3.63 0.09 0.0059 0.0005 0.28 0.007 0.00156 0.00014 0.177 1.75 53.25 4.37 1.935 13.46 ± 1.13
4.00 2.59 0.12 0.0017 0.0003 0.39 0.019 0.00062 0.00010 0.266 11.07 81.43 8.20 2.108 14.66 ± 0.99
4.40 2.53 0.05 0.0018 0.0001 0.40 0.009 0.00064 0.00005 0.131 3.57 80.88 9.33 2.047 14.24 ± 0.45
4.90 2.22 0.03 0.00064 0.00011 0.45 0.007 0.00018 0.00005 0.002 2.26 94.31 17.55 2.095 14.57 ± 0.30
5.40 2.23 0.03 0.00061 0.00012 0.45 0.007 0.00020 0.00005 0.007 6.13 93.74 18.12 2.095 14.57 ± 0.33
6.00 2.16 0.03 0.00036 0.00011 0.46 0.007 0.00010 0.00005 0.006 11.46 96.74 17.02 2.093 14.55 ± 0.31
6.80 2.23 0.04 0.00076 0.00011 0.45 0.007 0.00027 0.00005 0.012 5.59 91.88 16.69 2.050 14.26 ± 0.33
7.80 2.31 0.03 0.00065 0.00048 0.43 0.006 0.00023 0.00021 0.002 11.76 93.05 4.86 2.154 14.98 ± 1.01
9.00 2.38 0.10 0.0039 0.0017 0.42 0.017 0.00160 0.00072 0.081 7.50 52.16 1.20 1.244 8.66 ± 3.59

J = 0.00381413 ± 0.00000572

Volume 39ArK = 1.073 x E-13 cm3 NPT

Integrated Date = 14.45 ± 0.15 Ma

Plateau age = 14.46 ± 0.15 Ma (2s, including J-error of .2%) MSWD = 1.3, probability=0.24 Includes 98.8% of the 39Ar steps 1 through 12

Inverse isochron (correlation age) results, plateau steps: Model 1 Solution (±95%-conf.) on 9 points

Age = 14.32 ± 0.17 Ma Initial 40Ar/36Ar =285 ± 20 MSWD = 0.89 Probability = 0.51

SC-2a biotite 

Laser Isotope Ratios
Power (%) 40Ar/39Ar 36Ar/39Ar 39Ar/40Ar 36Ar/40Ar Rho K/Ca %40Ar rad f 39 Ar 40Ar*/39ArK Age
2.30 69.56 2.97 0.23 0.02 0.01 0.001 0.00329 0.00028 0.034 16.20 1.67 0.07 1.164 8.15 ± 40.12
2.70 16.92 0.31 0.04089 0.00413 0.06 0.001 0.00240 0.00024 0.050 1.49 28.21 0.35 4.776 33.21 ± 8.48
3.10 9.92 0.15 0.02785 0.00281 0.10 0.002 0.00279 0.00028 0.016 2.09 16.75 1.02 1.662 11.63 ± 5.81
3.50 4.92 0.08 0.00914 0.00077 0.20 0.004 0.00183 0.00015 0.066 3.54 45.46 2.87 2.236 15.62 ± 1.62
3.90 3.05 0.07 0.00310 0.00017 0.33 0.008 0.00097 0.00006 0.282 23.59 70.78 8.02 2.158 15.08 ± 0.57
4.30 2.54 0.05 0.00126 0.00021 0.40 0.007 0.00045 0.00008 0.015 50.64 86.51 8.72 2.193 15.33 ± 0.52
4.70 2.41 0.05 0.00061 0.00010 0.42 0.008 0.00020 0.00004 0.037 36.10 93.89 10.16 2.263 15.81 ± 0.37
5.10 2.42 0.06 0.00082 0.00011 0.41 0.010 0.00028 0.00005 0.043 56.91 91.32 11.08 2.206 15.41 ± 0.44
5.50 2.34 0.06 0.00066 0.00011 0.43 0.010 0.00023 0.00005 0.076 34.03 93.04 15.34 2.174 15.20 ± 0.44
6.00 2.36 0.07 0.00090 0.00015 0.42 0.012 0.00032 0.00006 0.106 29.55 90.20 14.48 2.131 14.90 ± 0.54
7.00 2.43 0.04 0.00078 0.00012 0.41 0.007 0.00026 0.00005 0.002 21.57 91.95 19.82 2.230 15.59 ± 0.35
8.00 2.46 0.06 0.00087 0.00029 0.41 0.009 0.00029 0.00012 0.034 9.55 91.15 6.13 2.246 15.70 ± 0.71
9.00 2.49 0.08 0.00099 0.00034 0.40 0.012 0.00034 0.00014 0.056 7.68 89.80 1.93 2.234 15.61 ± 0.88

J = 0.00383360 ± 0.00000575

Volume 39ArK = 1.146 x E-13 cm3 NPT

Integrated Date = 15.44 ± 0.16 Ma

Plateau age = 15.43 ± 0.16 Ma (2s, including J-error of .2%) MSWD = 1.4, probability=0.16 Includes 99.58% of the 39Ar steps 3 through 13

Inverse isochron (correlation age) results, plateau steps: Model 1 Solution (±95%-conf.) on 11 points

Age = 15.30 ± 0.19 Ma Initial 40Ar/36Ar =287 ± 17 MSWD = 1.4 Probability = 0.19

SC-2-b1 biotite 

Laser Isotope Ratios
Power (%) 40Ar/39Ar 36Ar/39Ar 39Ar/40Ar 36Ar/40Ar Rho K/Ca %40Ar rad f 39 Ar 40Ar*/39ArK Age
2.30 84.01 12.49 0.25 0.05 0.01 0.002 0.0030 0.0003 0.017 1.16 9.49 0.03 7.973 55.48 ± 57.63
2.70 26.65 0.80 0.080 0.006 0.04 0.001 0.0030 0.0002 0.033 1.41 10.24 0.35 2.730 19.18 ± 12.66
3.10 8.91 0.15 0.0211 0.0012 0.11 0.002 0.0023 0.0001 0.058 1.71 30.11 1.16 2.684 18.86 ± 2.41
3.50 6.33 0.09 0.0134 0.0012 0.16 0.002 0.0021 0.0002 0.024 2.34 37.59 2.74 2.380 16.74 ± 2.42
3.90 3.56 0.07 0.0044 0.0003 0.28 0.005 0.0012 0.0001 0.080 12.29 64.39 7.24 2.291 16.11 ± 0.75
4.30 2.77 0.06 0.0016 0.0001 0.36 0.007 0.0005 0.0000 0.134 14.08 83.92 8.88 2.325 16.36 ± 0.43
4.70 2.72 0.05 0.0015 0.0003 0.37 0.007 0.0005 0.0001 0.043 14.88 84.62 11.60 2.305 16.21 ± 0.63
5.10 2.64 0.04 0.0012 0.0004 0.38 0.006 0.0004 0.0001 0.023 19.94 87.79 11.13 2.316 16.29 ± 0.81
5.70 2.66 0.06 0.0013 0.0003 0.38 0.009 0.0004 0.0001 0.042 12.00 86.87 15.75 2.313 16.27 ± 0.78
6.30 2.47 0.05 0.0007 0.0001 0.40 0.008 0.0002 0.0000 0.031 22.81 92.79 17.23 2.296 16.15 ± 0.41
7.00 2.62 0.05 0.0010 0.0002 0.38 0.008 0.0003 0.0001 0.028 19.58 89.91 15.08 2.357 16.57 ± 0.51
8.00 2.68 0.06 0.0012 0.0002 0.37 0.009 0.0004 0.0001 0.032 12.04 88.18 8.18 2.365 16.63 ± 0.61
9.00 5.26 0.32 0.0111 0.0013 0.19 0.012 0.0021 0.0003 0.440 2.75 37.91 0.63 1.993 14.02 ± 3.41

J = 0.00385940 ± 0.00000579

Volume 39ArK = 1.775 x E-13 cm3 NPT

Integrated Date = 16.34 ± 0.20 Ma

Plateau age = 16.34 ± 0.20 Ma (2s, including J-error of .2%) MSWD = 0.89, probability=0.55 Includes 99.97% of the 39Ar steps 2 through 13

Inverse isochron (correlation age) results, plateau steps: Model 1 Solution (±95%-conf.) on 13 points

Age = 16.01 ± 0.22 Ma Initial 40Ar/36Ar =308 ± 11 MSWD = 0.76 Probability = 0.68

RV-2 feldspar 

Laser Isotope Ratios
Power (%) 40Ar/39Ar 36Ar/39Ar 39Ar/40Ar 36Ar/40Ar Rho K/Ca %40Ar rad f 39 Ar 40Ar*/39ArK Age
2.70 138.70 2.29 0.48 0.02 0.01 0.000 0.0035 0.0002 0.062 0.61 -3.02 1.27 4.191 -30.25 ± 48.11
2.90 33.11 0.61 0.103 0.005 0.03 0.001 0.0031 0.0001 0.020 0.61 7.50 1.62 2.485 17.70 ± 10.08
3.20 18.27 0.41 0.054 0.003 0.05 0.001 0.0029 0.0001 0.022 0.63 12.94 5.42 2.367 16.87 ± 5.45
3.50 14.25 0.27 0.039 0.002 0.07 0.001 0.0027 0.0001 0.026 0.62 19.73 6.32 2.814 20.04 ± 3.74
3.80 8.72 0.19 0.020 0.001 0.11 0.002 0.0022 0.0001 0.011 0.60 32.84 9.32 2.866 20.40 ± 2.01
4.10 7.75 0.11 0.016 0.001 0.13 0.002 0.0021 0.0001 0.088 0.55 38.51 10.38 2.987 21.26 ± 1.63
4.40 7.45 0.10 0.016 0.001 0.13 0.002 0.0021 0.0001 0.055 0.55 38.68 8.01 2.886 20.54 ± 1.60
5.00 7.46 0.10 0.016 0.001 0.13 0.002 0.0020 0.0001 0.009 0.52 38.98 13.46 2.910 20.71 ± 1.56
5.40 7.32 0.10 0.015 0.001 0.14 0.002 0.0020 0.0001 0.018 0.62 39.52 10.73 2.893 20.60 ± 1.53
6.00 6.79 0.09 0.014 0.001 0.15 0.002 0.0019 0.0001 0.023 0.55 41.95 10.95 2.850 20.29 ± 1.33
7.00 6.98 0.09 0.014 0.001 0.14 0.002 0.0019 0.0001 0.032 0.48 42.79 10.43 2.988 21.27 ± 1.35
8.40 6.40 0.08 0.010 0.001 0.16 0.002 0.0016 0.0001 0.032 0.51 53.03 7.23 3.395 24.15 ± 1.09
10.00 5.87 0.08 0.009 0.000 0.17 0.002 0.0014 0.0001 0.054 0.51 58.66 4.87 3.447 24.51 ± 0.95

J = 0.00391100 ± 0.00000587

Volume 39ArK = 1.264 x E-13 cm3 NPT

Integrated Date = 22.10 ± 0.45 Ma

Plateau age = 20.67 ± 0.57 Ma (2s, including J-error of .2%) MSWD = 0.46, probability=0.90 Includes 86.6% of the 39Ar steps 2 through 11

Inverse isochron (correlation age) results: Model 1 Solution (±95%-conf.) on 11 points

Age = 21.5 ± 1.1 Ma Initial 40Ar/36Ar =288.5 ± 8.2 MSWD = 0.37 Probability = 0.95

CR-1 biotite 

Laser Isotope Ratios
Power (%) 40Ar/39Ar 36Ar/39Ar 39Ar/40Ar 36Ar/40Ar Rho K/Ca %40Ar rad f 39 Ar 40Ar*/39ArK Age
2.30 843.11 44.89 2.40 0.17 0.00 0.000 0.0028 0.0001 0.024 0.29 14.99 0.18 126.590 740.17 ± 164.17
2.70 62.40 1.87 0.18 0.01 0.02 0.000 0.0029 0.0001 0.142 0.41 13.41 3.99 8.376 59.39 ± 19.08
3.10 31.24 0.68 0.084 0.004 0.03 0.001 0.0027 0.0001 0.166 0.49 20.31 6.67 6.350 45.20 ± 8.51
3.60 18.97 0.37 0.050 0.003 0.05 0.001 0.0026 0.0001 0.136 0.67 21.03 15.14 3.992 28.55 ± 5.60
4.20 8.41 0.13 0.019 0.001 0.12 0.002 0.0020 0.0001 0.084 0.14 40.02 24.21 3.378 24.18 ± 2.09
5.00 6.36 0.10 0.012 0.001 0.16 0.002 0.0015 0.0001 0.053 0.11 54.96 29.43 3.511 25.13 ± 1.61
6.00 6.79 0.44 0.014 0.001 0.15 0.009 0.0017 0.0001 0.689 0.10 50.64 15.38 3.454 24.72 ± 3.37
7.00 5.37 0.30 0.010 0.001 0.19 0.010 0.0014 0.0002 0.400 0.11 59.22 5.01 3.193 22.86 ± 2.83

J = 0.00393680 ± 0.00000591

Volume 39ArK = 0.369 x E-13 cm3 NPT

Integrated Date = 25.10 ± 1.07 Ma

Plateau age = 24.6 ± 1.1 Ma (2s, including J-error of .2%) MSWD = 1.02, probability=0.39 Includes 89.2% of the 39Ar steps 4 through 8

Inverse isochron (correlation age) results: Model 1 Solution (±95%-conf.) on 8 points

Age = 21.0 ± 2.5 Ma Initial 40Ar/36Ar =335 ± 16 MSWD = 2.0 Probability = 0.06

CR-1 hornblende 

Laser Isotope Ratios
Power (%) 40Ar/39Ar 36Ar/39Ar 39Ar/40Ar 36Ar/40Ar Rho K/Ca %40Ar rad f 39 Ar 40Ar*/39ArK Age
2.30 357.33 104.57 1.17 0.38 0.00 0.001 0.0033 0.0004 0.005 0.16 2.29 0.11 8.217 58.28 ± 330.12
2.80 34.72 1.15 0.10 0.008 0.03 0.001 0.0027 0.0002 0.158 0.22 18.39 3.50 6.401 45.56 ± 17.77
3.20 17.36 1.66 0.040 0.007 0.06 0.006 0.0023 0.0004 0.318 0.52 31.13 9.87 5.411 38.58 ± 15.93
3.80 8.16 1.00 0.018 0.002 0.12 0.015 0.0017 0.0003 0.710 0.07 48.86 32.59 4.019 28.73 ± 7.73
4.30 5.91 0.75 0.012 0.002 0.17 0.022 0.0015 0.0004 0.519 0.07 55.41 23.80 3.296 23.60 ± 6.59
5.00 3.84 0.11 0.005 0.001 0.26 0.007 0.0007 0.0004 0.040 0.09 79.38 15.79 3.068 21.98 ± 3.07
6.00 5.87 0.40 0.009 0.003 0.17 0.012 0.0012 0.0006 0.142 0.10 63.35 8.51 3.737 26.73 ± 7.42
7.50 7.37 0.26 0.006 0.003 0.14 0.005 0.0006 0.0005 0.018 0.15 82.26 5.82 6.082 43.31 ± 7.32

J = 0.00393680 ± 0.00000591

Volume 39ArK = 0.079 x E-13 cm3 NPT

Integrated Date = 26.06 ± 2.30 Ma

Plateau age = 23.4 ± 2.5 Ma (2s, including J-error of .2%) MSWD = 1.19, probability=0.31 Includes 80.7% of the 39Ar steps 4 through 7

Inverse isochron (correlation age) results, plateau steps: Model 1 Solution (±95%-conf.) on 7 points

Age = 22.1 ± 2.8 Ma Initial 40Ar/36Ar =332 ± 23 MSWD = 0.76 Probability = 0.958

CR-1 feldspar 

Laser Isotope Ratios
Power (%) 40Ar/39Ar 36Ar/39Ar 39Ar/40Ar 36Ar/40Ar Rho K/Ca %40Ar rad f 39 Ar 40Ar*/39ArK Age
2.30 211.15 3.20 0.71 0.03 0.005 0.0001 0.0033 0.0002 0.015 0.78 0.17 1.73 0.355 2.55 ± 69.27
2.50 50.66 0.81 0.16 0.01 0.020 0.0003 0.0031 0.0001 0.098 0.58 6.78 2.61 3.436 24.60 ± 15.70
2.80 35.74 1.22 0.11 0.01 0.03 0.001 0.0031 0.0002 0.040 0.27 6.51 8.26 2.331 16.72 ± 11.56
3.10 14.13 0.44 0.039 0.002 0.07 0.002 0.0027 0.0002 0.037 0.29 18.52 16.26 2.622 18.80 ± 4.80
3.40 6.89 0.21 0.015 0.001 0.15 0.005 0.0021 0.0001 0.013 0.44 37.98 23.01 2.619 18.77 ± 1.95
3.80 7.05 0.14 0.016 0.001 0.14 0.003 0.0021 0.0001 0.053 0.30 36.76 17.69 2.596 18.62 ± 1.69
4.40 7.18 0.12 0.017 0.001 0.14 0.002 0.0022 0.0001 0.020 0.28 33.74 10.92 2.428 17.41 ± 1.71
5.20 7.04 0.11 0.015 0.001 0.14 0.002 0.0021 0.0001 0.006 0.22 38.20 7.66 2.695 19.32 ± 2.03
6.50 5.22 0.07 0.009 0.000 0.19 0.003 0.0016 0.0001 0.016 0.20 52.95 7.00 2.772 19.87 ± 1.08
8.50 5.99 0.08 0.010 0.001 0.17 0.002 0.0015 0.0001 0.017 0.20 54.58 4.86 3.277 23.47 ± 1.23

J = 0.00393680 ± 0.00000591 Volume 39ArK = 0.565 x E-13 cm3 NPT

Integrated Date = 20.10 ± 0.60 Ma

Plateau age = 19.04 ± 0.69 Ma (2s, including J-error of .2%) MSWD = 0.91, probability=0.50 Includes 95.1% of the 39Ar steps 1 through 9

Inverse isochron (correlation age) results: Model 1 Solution (±95%-conf.) on 9 points

Age = 19.01 ± 0.98 Ma Initial 40Ar/36Ar =296.0 ± 7.7 MSWD = 0.98 Probability = 0.44

BQ-1c feldspar 

Laser Isotope Ratios
Power (%) 40Ar/39Ar 36Ar/39Ar 39Ar/40Ar 36Ar/40Ar Rho K/Ca %40Ar rad f 39 Ar 40Ar*/39ArK Age
2.30 347.07 25.34 0.64 0.07 0.00 0.000 0.0018 0.0001 0.011 1.13 45.01 0.13 156.297 891.40 ± 86.60
2.70 164.62 4.48 0.39 0.02 0.01 0.000 0.0024 0.0001 0.004 0.54 29.20 1.06 48.110 323.22 ± 35.67
3.10 42.43 0.74 0.11 0.01 0.02 0.000 0.0026 0.0001 0.044 0.28 23.73 4.44 10.087 72.66 ± 11.14
3.50 18.10 0.28 0.042 0.002 0.06 0.001 0.0023 0.0001 0.075 0.29 32.17 6.71 5.833 42.37 ± 4.32
3.90 9.07 0.16 0.020 0.001 0.11 0.002 0.0022 0.0001 0.044 0.37 34.57 10.93 3.140 22.93 ± 2.72
4.30 6.80 0.12 0.014 0.001 0.15 0.003 0.0019 0.0001 0.030 0.40 41.86 12.11 2.850 20.82 ± 1.87
4.90 6.45 0.09 0.012 0.001 0.15 0.002 0.0017 0.0001 0.007 0.39 48.52 15.54 3.133 22.87 ± 1.62
5.60 6.04 0.09 0.011 0.001 0.17 0.003 0.0017 0.0001 0.018 0.38 50.36 14.55 3.046 22.25 ± 1.64
6.50 5.66 0.08 0.009 0.001 0.18 0.002 0.0016 0.0001 0.004 0.41 53.12 20.05 3.012 22.00 ± 1.23
7.50 6.21 0.09 0.007 0.001 0.16 0.002 0.0011 0.0001 0.016 0.32 67.83 14.50 4.218 30.74 ± 1.81

J = 0.00401420 ± 0.00000602

Volume 39ArK = 0.272 x E-13 cm3 NPT

Integrated Date = 24.15 ± 0.67 Ma

Plateau age = 22.12 ± 0.74 Ma (2s, including J-error of .2%) MSWD = 0.80, probability=0.52 Includes 73.2% of the 39Ar steps 5 through 9

Inverse isochron (correlation age) results, plateau steps: Model 1 Solution (±95%-conf.) on 5 points

Age = 21.4 ± 2.9 Ma Initial 40Ar/36Ar =304 ± 35 MSWD = 1.03 Probability = 0.36

BQ-1b biotite 

Laser Isotope Ratios
Power (%) 40Ar/39Ar 36Ar/39Ar 39Ar/40Ar 36Ar/40Ar Rho K/Ca %40Ar rad f 39 Ar 40Ar*/39ArK Age
2.30 409.99 15.09 1.42 0.086 0.00 0.000 0.0035 0.0002 0.006 0.94 -3.56 0.29 14.611 -110.64± 159.72
2.80 46.61 0.76 0.15 0.008 0.02 0.000 0.0033 0.0002 0.018 0.51 1.03 2.59 0.478 3.51 ± 16.43
3.10 23.90 0.44 0.08 0.004 0.04 0.001 0.0032 0.0002 0.132 0.65 5.39 8.90 1.289 9.45 ± 8.61
3.70 4.31 0.07 0.008 0.0004 0.23 0.004 0.0019 0.0001 0.115 1.68 44.20 8.94 1.904 13.94 ± 1.01
4.20 2.95 0.04 0.004 0.0002 0.34 0.005 0.0012 0.0001 0.030 2.02 64.12 18.93 1.893 13.86 ± 0.48
4.80 2.34 0.03 0.002 0.0001 0.43 0.006 0.0006 0.0001 0.011 1.65 81.49 26.94 1.907 13.96 ± 0.36
5.50 2.34 0.03 0.002 0.0002 0.43 0.005 0.0006 0.0001 0.011 1.34 80.42 15.97 1.882 13.78 ± 0.43
6.40 2.68 0.04 0.003 0.0003 0.37 0.005 0.0010 0.0001 0.035 0.77 70.14 9.51 1.882 13.78 ± 0.71
7.60 3.53 0.05 0.006 0.0004 0.28 0.004 0.0014 0.0001 0.057 0.49 57.57 5.60 2.033 14.87 ± 0.93
9.00 4.39 0.08 0.009 0.002 0.23 0.004 0.0020 0.0004 0.030 0.48 40.37 2.33 1.775 13.00 ± 4.07

J = 0.00401420 ± 0.00000602

Volume 39ArK = 0.483 x E-13 cm3 NPT

Integrated Date = 13.92 ± 0.22 Ma

Plateau age = 13.92 ± 0.22 Ma (2s, including J-error of .2%) MSWD = 1.14, probability=0.33 Includes 100% of the 39Ar steps 1 through 10

Inverse isochron (correlation age) results, plateau steps: Model 1 Solution (±95%-conf.) on 10 points

Age = 14.39 ± 0.26 Ma Initial 40Ar/36Ar =292.0 ± 7.5 MSWD = 0.96 Probability = 0.46

BQ-1b Biotite 

Laser Isotope Ratios
Power (%) 40Ar/39Ar 36Ar/39Ar 39Ar/40Ar 36Ar/40Ar Rho K/Ca %40Ar rad f 39 Ar 40Ar*/39ArK Age
3.40 5.62 0.56 0.0428 0.0034 0.18 0.02 0.00760 0.00093 0.753 2.90 -126.85 3.03 7.126 -53.12 ± 8.51
3.80 5.27 0.37 0.0256 0.0020 0.19 0.01 0.00485 0.00049 0.630 3.30 -44.84 8.95 2.362 -17.44 ± 4.97
4.30 2.11 0.15 0.0053 0.0010 0.47 0.03 0.00246 0.00048 0.334 8.64 26.36 15.06 0.557 4.09 ± 2.32
5.10 2.26 0.03 0.0010 0.0002 0.44 0.01 0.00038 0.00011 0.011 5.89 88.57 30.67 2.006 14.68 ± 0.58
5.90 2.18 0.03 0.0008 0.0002 0.46 0.01 0.00028 0.00009 0.005 6.01 91.34 25.88 1.989 14.56 ± 0.46
6.80 2.44 0.05 0.0018 0.0005 0.41 0.01 0.00063 0.00020 0.031 2.05 80.91 11.54 1.971 14.42 ± 1.10
8.00 2.67 0.05 0.0024 0.0009 0.38 0.01 0.00080 0.00033 0.012 2.12 76.10 4.86 2.032 14.87 ± 1.95

J = 0.00401420 ± 0.00000602

Volume 39ArK = 0.264 x E-13 cm3 NPT

Integrated Date = 14.13 ± 0.33 Ma

Plateau age = 14.60 ± 0.34 Ma (2s, including J-error of .2%) MSWD = 0.099, probability=0.96 Includes 73% of the 39Ar steps 4 through 7

Inverse isochron (correlation age) results, plateau steps: Model 1 Solution (±95%-conf.) on 4 points

Age = 14.33 ± 0.87 Ma Initial 40Ar/36Ar =307 ± 130 MSWD = 0.14 Probability = 0.87

FSC-1 Fuchsita 

Pwr 39Ar x 10-6 % 39Ar 40Ar/39ArK Age in Ma % 40Ar* 40Ar/36Ar 37ArCa/39ArK
0.6 0.668 0.08 33.6 12.03 140.99 48.56 a 23.27 385.11 0.003
1.5 4.769 0.57 2.57 2.18 11.18 9.47 b 7.65 319.96 1.58
2.2 14.443 1.74 0.39 0.76 1.71 3.3 c 1.68 300.54 0.044
2.7 38.246 4.61 2.5 0.39 10.88 1.67 d 25.18 394.94 0.008
3.4 43.922 5.3 3 0.18 13.04 0.77 e 55.38 662.25 0.003
4 145.819 17.59 2.87 0.06 12.47 0.26 f 72.32 1067.62 0.006
5 270.778 32.67 2.86 0.03 12.43 0.11 g 87.63 2388.74 0.004
6 140.591 16.96 2.87 0.03 12.46 0.12 h 95.72 6898.02 < 0.001
8 169.7 20.47 2.88 0.03 12.51 0.13 i 96.36 8120.85 < 0.001

Integrated results 

39Ar x 10-6 40Ar/39Ar K Age in Ma % 40Ar* 40Ar/36Ar 37ArCa/39ArK
828.9 2.84 0.04 12.33 0.16 65.29 851.36 0.013

J = 0.002419 ± 0.000010

Plateau age tp = 12.49 ± 0.09 Ma

Weighted mean of fractions e to i, representing 92.99% of 39Ar released in 5 consecutive fractions, MSWD = 0.18

Isochron age tc = 12.45 ± 0.11 Ma; (40Ar/36Ar)i = 300 ± 15, MSWD = 0.2 for n = 5 (e to i)

Appendix 2

Plateau age spectra and normal isochron diagrams in host intrusive bodies to the IOCG skam deposits at the Tatatila-Las Minas district, Veracruz.

Appendix 3

U-Pb isotope data from zircons in the intrusive rocks associated with IOCG skarns in the Tatatila-Las Minas area. 

CORRECTED ISOTOPIC RATIOS CORRECTED AGE (Ma)
Analisys/Zircon U# (ppm) Th# (ppm) Th/U 207Pb/206Pb† err %* 207Pb/235U† err %* 208Pb/232Th† err %* Rho** % disc.*** 206Pb/238U ± 2s* 207Pb/235U ± 2s* 207Pb/206Pb ± 2s* Best Age (Ma) ± 2s
Sample ES-3 Escalona dyke (Tatatila de Las Minas, Veracruz)
ES-3-3 772 282 0.37 0.169 16 0.0137 16.1 0.00058 6.4 0.00076 12.2 0.4 73 3.7 0.2 13.8 2.2 2520 190 3.7 ± 0.2
ES-3-11 1045 1075 1.03 0.097 18.6 0.0083 16.9 0.00061 6.9 0.00024 10 0.411 53 3.9 0.3 8.4 1.4 1710 230 3.9 ± 0.3
ES-3-4 472 374 0.79 0.14 24.3 0.0116 23.3 0.00062 8.9 0.00036 20.5 0.382 66 4 0.4 11.7 2.7 2400 180 4.0 ± 0.4
ES-3-13 1031 1276 1.24 0.149 14.1 0.0122 10.7 0.00064 8.3 0.0003 10.2 0.781 67 4.1 0.3 12.3 1.3 2340 130 4.1 ± 0.3
ES-3-5 730 893 1.22 0.089 24.7 0.0079 21.5 0.00064 7 0.00029 10.3 0.327 48 4.1 0.3 7.9 1.7 1270 310 4.1 ± 0.3
ES-3-14 761 827 1.09 0.102 15.7 0.009 15.6 0.00065 6.6 0.00026 12 0.427 54 4.2 0.3 9.1 1.4 1740 130 4.2 ± 0.3
ES3-18 830 762 0.92 0.21 13.8 0.019 11.6 0.00065 7 0.0004 7.8 0.601 78 4.2 0.3 19.1 2.2 2870 120 4.2 ± 0.3
ES-3-12 250 255 1.02 0.198 22.2 0.0178 20.2 0.00065 8.3 0.00035 22.6 0.41 77 4.2 0.4 17.9 3.6 2930 160 4.2 ± 0.4
ES3-21 818 946 1.16 0.122 18.9 0.0106 17 0.00065 6.6 0.00026 10.5 0.39 61 4.2 0.3 10.7 1.8 1930 220 4.2 ± 0.3
ES-3-23 839 1113 1.33 0.086 22.1 0.0076 19.7 0.00065 8.3 0.00025 13.8 0.42 46 4.2 0.4 7.7 1.6 1320 290 4.2 ± 0.4
ES-3-20 602 343 0.57 0.105 23.8 0.0099 21.2 0.00065 8.3 0.00032 20.5 0.39 58 4.2 0.4 10 2.1 1750 260 4.2 ± 0.4
ES-3-15 717 798 1.11 0.206 11.2 0.0192 9.9 0.00069 7.6 0.00045 9.3 0.767 77 4.4 0.3 19.3 1.9 2882 91 4.2 ± 0.3
ES-3-19 300 276 0.92 0.256 19.1 0.0226 19.5 0.00069 9.2 0.00042 16.4 0.472 80 4.4 0.4 22.6 4.3 3230 210 4.4 ± 0.4
ES3-1 384 497 1.29 0.251 17.9 0.0253 13.4 0.00069 9.6 0.00045 12.5 0.714 83 4.4 0.4 25.4 3.4 3210 220 4.4 ± 0.4
ES-3-22 575 573 1 0.41 29.3 0.037 27 0.00071 9.6 0.00068 14.5 0.353 88 4.6 0.4 37 10 3920 280 4.6 ± 0.4
ES-3-2 425 357 0.84 0.19 20.5 0.0182 19.8 0.00074 7.6 0.00049 15.7 0.385 74 4.7 0.4 18.2 3.6 2770 190 4.7 ± 0.4
ES-3-10 502 616 1.23 0.22 15.9 0.0241 15.4 0.00079 6.5 0.00043 14 0.423 79 5.1 0.3 24.1 3.6 3050 130 5.1 ± 0.3
ES-3-16 583 839 1.44 0.217 19.4 0.0248 21.8 0.00079 9.6 0.00055 18.1 0.44 80 5.1 0.5 26 5.6 3070 220 5.1 ± 0.5
ES-3-9 272 135 0.5 0.32 12.8 0.0367 11.7 0.00086 7.4 0.0015 12.7 0.635 85 5.5 0.4 36.5 4.2 3570 140 5.5 ± 0.4
ES-3-8 342 140 0.41 0.35 14 0.0425 11.5 0.00094 7.5 0.00184 14.1 0.649 86 6 0.5 42.2 4.8 3742 98 6.0 ± 0.5
ES-3-17 454 512 1.13 0.354 13 0.0464 10.1 0.00095 7.1 0.00086 10.2 0.698 87 6.1 0.4 46 4.6 3730 130 6.1 ± 0.4
ES-3-7 468 622 1.33 0.522 8.8 0.104 10.6 0.00145 8.3 0.00157 7.6 0.782 91 9.3 0.8 100.2 9.9 4347 78 9.3 ± 0.8
ES-3-6 204 204 1 0.569 15.3 0.174 13.2 0.00221 8.6 0.00363 12.7 0.65 91 14.2 1.2 162 20 4390 160 14.2 ± 1.2
n = 23 Mean 206Pb/238U Age = 4,11 ± 0,11
(2 sigma, MSWD = 0.53; n = 8)
Sample CR-5 Carbonera intrusive (Tatatila de Las Minas, Veracruz)
CR-5-4 264 341 1.29 0.16500 19.4 0.05290 16.1 0.00245 9.4 0.00128 10.2 0.584 70 15.7 1.5 52.2 8.1 2600 210 15,7 ± 1,5
CR-5-3 178 242 1.36 0.07600 34.2 0.02080 36.1 0.00249 7.2 0.00088 14.8 0.200 23 16.0 1.1 20.7 7.6 1490 180 16,0 ± 1,1
CR-5-15 188 321 1.71 0.10300 15.5 0.03350 12.8 0.00250 6.8 0.00092 7.4 0.530 52 16.1 1.1 33.4 4.3 1740 180 16,1 ± 1,1
CR-5-10 368 524 1.42 0.13500 14.8 0.04430 12.6 0.00251 4.8 0.00106 6.0 0.378 64 16.2 0.8 44.9 5.7 2110 140 16,2 ± 0,8
CR-5-7 503 889 1.77 0.10500 11.4 0.03850 11.9 0.00255 7.5 0.00104 7.5 0.624 57 16.4 1.2 38.3 4.5 1820 140 16,4 ± 1,2
CR-5-8 535 1006 1.88 0.17200 12.2 0.05990 11.7 0.00261 4.6 0.00115 6.1 0.393 71 16.8 0.7 58.9 6.7 2540 150 16,8 ± 0,7
CR-5-1 114 162 1.42 0.20400 21.1 0.07100 16.9 0.00269 8.2 0.00126 11.1 0.484 75 17.3 1.4 70.0 12.0 2800 180 17,3 ± 1,4
CR-5-2 179 238 1.33 0.10900 24.8 0.04140 21.3 0.00272 7.7 0.00119 11.8 0.363 57 17.5 1.4 41.0 8.5 1910 260 17,5 ± 1,4
CR-5-13 158 235 1.49 0.18800 13.8 0.07060 11.9 0.00271 6.3 0.00127 7.9 0.527 75 17.5 1.1 69.0 7.9 2800 170 17,5 ± 1,1
CR-5-12 283 438 1.55 0.16600 14.5 0.06130 12.7 0.00273 5.5 0.00135 9.6 0.432 71 17.6 1.0 60.2 7.5 2520 180 17,6 ± 1,0
CR-5-18 270 407 1.51 0.19200 11.5 0.06960 12.1 0.00273 8.1 0.00140 10.7 0.668 75 17.6 1.4 70.4 8.8 2750 120 17,6 ± 1,4
CR-5-5 173 237 1.37 0.13300 13.5 0.05040 12.1 0.00277 6.1 0.00110 10.0 0.507 64 17.8 1.1 49.8 5.9 2180 160 17,8 ± 1,1
CR-5-16 227 344 1.52 0.14000 17.1 0.05220 14.6 0.00279 6.1 0.00127 5.7 0.419 65 17.9 1.1 51.5 7.4 2130 200 17,9 ± 1,1
CR-5-14 205 347 1.69 0.12600 16.7 0.04740 14.6 0.00284 6.0 0.00111 8.5 0.411 61 18.3 1.1 46.9 6.6 2170 240 18,3 ± 1,1
CR-5-17 273 384 1.41 0.14000 20.0 0.05060 17.2 0.00284 6.3 0.00123 8.9 0.369 63 18.3 1.1 50.0 8.4 2210 210 18,3 ± 1,1
CR-5-6 226 347 1.54 0.21400 16.8 0.08300 16.9 0.00288 9.7 0.00155 6.5 0.576 77 18.6 1.8 81.0 13.0 2960 120 18,6 ± 1,8
CR-5-9 100 114 1.14 0.27000 14.1 0.10800 13.0 0.00299 8.4 0.00225 13.3 0.645 81 19.2 1.6 103.0 12.0 3240 150 19,2 ± 1,6
CR-5-11 118 147 1.25 0.21800 13.3 0.08900 12.4 0.00301 7.0 0.00173 9.2 0.564 77 19.4 1.3 85.8 9.9 3100 100 19,4 ± 1,3
CR-5-19 129 155 1.20 0.28800 12.2 0.13100 13.0 0.00346 5.5 0.00234 10.3 0.423 82 22.3 1.2 124.0 15.0 3420 150 22,3 ± 1,2
n = 19 Concordia lower intercept Age = 15.05 ± 094
(2 sigma, MSWD = 2.5; all data)
Sample 5S-1 Cinco Señores intrusive (Tatatila de Las Minas, Veracruz)
5S-1-13 883 1600 1.81 0.08500 11.8 0.02500 9.6 0.00221 3.7 0.00075 4.1 0.381 43 14.2 0.5 25.1 2.3 1280 190 14,2 ± 0,5
5S-1-6 730 680 0.93 0.07900 16.5 0.02230 16.6 0.00223 5.8 0.00077 11.8 0.351 36 14.3 0.8 22.4 3.6 870 300 14,3 ± 0,8
5S-1-16 424 68 0.16 0.15400 16.9 0.05390 18.0 0.00229 6.6 0.00468 16.9 0.364 72 14.8 1.0 53.1 9.2 2500 210 14,8 ± 1,0
5S-1-11 424 402 1.45 0.08300 19.3 0.02660 19.2 0.00231 5.2 0.00102 7.0 0.271 44 14.9 0.8 26.6 5.0 1210 300 14,9 ± 0,8
5S-1-3 424 3630 2.84 0.08480 9.2 0.02690 7.8 0.00233 2.8 0.00074 3.5 0.358 45 15.0 0.4 27.0 2.1 1320 160 15,0 ± 0,4
5S-1-12 424 1200 1.96 0.08540 10.4 0.02780 10.4 0.00237 3.1 0.00082 4.0 0.295 45 15.3 0.5 27.8 2.8 1270 180 15,3 ± 0,5
5S-1-8 424 180 1.13 0.08900 19.1 0.03030 17.2 0.00238 5.5 0.00093 9.3 0.318 49 15.3 0.9 30.2 5.1 1330 310 15,3 ± 0,9
5S-1-19 424 671 1.86 0.08100 16.0 0.02750 17.1 0.00241 3.7 0.00079 6.4 0.216 44 15.5 0.6 27.5 4.8 1180 240 15,5 ± 0,6
5S-1-7 424 302 1.30 0.08750 9.1 0.02930 9.2 0.00249 3.7 0.00081 6.6 0.401 45 16.0 0.6 29.3 2.7 1410 180 16,0 ± 0,6
5S-1-5 424 634 1.55 0.17200 17.4 0.05980 14.7 0.00257 8.2 0.00109 13.8 0.555 72 16.5 1.3 58.8 8.4 2530 270 16,5 ± 1,3
5S-1-17 424 284 1.37 0.14700 10.9 0.05320 10.2 0.00260 4.2 0.00119 6.1 0.417 68 16.7 0.7 52.5 5.2 2240 170 16,7± 0,7
5S-1-15 424 149 0.86 0.16000 23.8 0.05800 32.8 0.00264 7.6 0.00173 30.6 0.231 70 17.0 1.3 57.0 17.0 2410 310 17,0 ± 1,3
5S-1-4 424 213 1.12 0.15000 10.7 0.05510 9.3 0.00265 4.2 0.00131 9.2 0.448 69 17.0 0.7 54.4 4.9 2330 160 17,0 ± 0,7
5S-1-10 424 53 0.76 0.17900 21.8 0.07000 18.6 0.00272 8.8 0.00247 14.2 0.475 75 17.5 1.5 69.0 13.0 2480 450 17,5 ± 1,5
5S-1-14 424 45 0.83 0.18300 27.3 0.06900 23.2 0.00277 9.4 0.00179 15.1 0.405 73 17.9 1.7 66.0 15.0 2010 570 17,9 ± 1,7
5S-1-20 424 75 0.58 0.38200 12.6 0.13500 18.5 0.00278 8.6 0.00464 10.6 0.466 86 17.9 1.5 127.0 21.0 3730 180 17,9 ± 1,5
5S-1-18 424 137 0.93 0.15600 17.3 0.06160 15.4 0.00281 6.4 0.00175 10.3 0.415 70 18.1 1.1 60.4 9.0 2410 240 18,1 ± 1,1
5S-1-1 424 273 1.23 0.20700 20.8 0.08100 23.5 0.00282 6.4 0.00167 12.0 0.272 77 18.2 1.1 78.0 17.0 2670 340 18,2 ± 1,1
5S-1-2 424 212 1.12 0.13200 23.5 0.05500 25.5 0.00287 7.3 0.00137 17.5 0.287 66 18.4 1.3 54.0 13.0 2070 350 18,4 ± 1,3
5S-1-9 424 345 1.31 0.23700 15.2 0.09340 9.9 0.00302 6.6 0.00187 11.8 0.672 79 19.4 1.9 90.3 8.4 3030 250 19,4 ± 1,9
n = 20 Mean 206Pb/238U Age = 15,09 ± 0,48
(2 sigma, MSWD = 4.0; n = 8)
SC-2b-6 318 178 0.56 0.27600 8.3 0.06680 7.0 0.00189 5.8 0.00195 7.7 0.827 81 12.1 0.7 65.6 4.4 3300 140 12,1 ± 0,7
SC-2b-20 583 305 0.52 0.08300 13.3 0.02360 13.1 0.00199 3.6 0.00089 8.5 0.276 46 12.8 0.5 23.6 3.0 1260 210 12,8 ± 0,5
SC-2b-7 365 405 1.11 0.06030 14.8 0.01670 16.2 0.00210 4.5 0.00067 11.8 0.279 19 13.5 0.6 16.8 2.7 230 260 13,5 ± 0,6
SC-2b-5 275 194 0.71 0.07100 15.5 0.02060 13.1 0.00213 4.5 0.00079 7.9 0.340 34 13.7 0.6 20.7 2.7 840 270 13,7 ± 0,6
SC-2b-8 259 208 0.80 0.08900 13.5 0.02570 11.7 0.00216 5.1 0.00098 9.2 0.436 46 13.9 0.7 25.7 3.0 1280 280 13,9 ± 0,7
SC-2b-25 263 243 0.92 0.07000 15.7 0.02010 14.4 0.00217 4.6 0.00080 8.6 0.319 31 14.0 0.7 20.1 2.9 830 250 14,0 ± 0,7
SC-2b-23 231 159 0.69 0.07100 21.1 0.02030 22.7 0.00223 4.4 0.00102 10.8 0.196 30 14.4 0.6 20.4 4.5 590 410 14,4 ± 0,6
SC-2b-21 260 201 0.77 0.06200 16.1 0.01780 18.0 0.00225 5.3 0.00080 8.5 0.297 23 14.5 0.8 18.8 3.1 480 280 14,5 ± 0,8
SC-2b-4 251 169 0.67 0.06800 17.6 0.02050 17.6 0.00225 3.5 0.00086 11.6 0.202 29 14.5 0.5 20.5 3.6 660 340 14,5 ± 0,5
SC-2b-22 376 352 0.94 0.10800 11.1 0.03260 9.5 0.00226 3.9 0.00095 7.9 0.409 55 14.6 0.6 32.5 3.0 1740 190 14,6 ± 0,6
SC-2b-10 227 151 0.67 0.06300 17.5 0.01900 16.8 0.00226 5.3 0.00084 13.1 0.315 24 14.6 0.8 19.1 3.2 560 350 14,6 ± 0,8
SC-2b-18 350 266 0.76 0.13400 12.7 0.04150 12.3 0.00227 4.4 0.00131 9.2 0.358 64 14.6 0.7 41.1 4.9 2090 210 14,6 ± 0,7
SC-2b-14 298 230 0.77 0.10400 12.5 0.03230 11.8 0.00228 5.3 0.00118 11.0 0.447 54 14.7 0.8 32.2 3.7 1640 210 14,7 ± 0,8
SC-2b-9 266 181 0.68 0.07600 17.1 0.02480 13.7 0.00229 4.4 0.00098 8.9 0.319 41 14.7 0.7 24.8 3.4 870 290 14,7 ± 0,7
SC-2b-2 266 174 0.65 0.05780 13.0 0.01820 12.6 0.00230 3.4 0.00087 9.6 0.268 19 14.8 0.5 18.3 2.3 410 260 14,8 ± 0,5
SC-2b-3 366 311 0.85 0.11400 11.4 0.03500 11.7 0.00232 4.3 0.00108 7.9 0.368 57 14.9 0.7 34.8 4.0 1820 200 14,9 ± 0,7
SC-2b-24 265 184 0.69 0.08700 13.8 0.02860 13.6 0.00233 4.7 0.00106 9.4 0.346 47 15.0 0.7 28.6 3.8 1220 270 15,0 ± 0,7
SC-2b-15 219 150 0.68 0.06700 16.4 0.02050 18.5 0.00234 5.1 0.00085 10.4 0.277 29 15.1 0.8 21.2 3.8 740 320 15,1 ± 0,8
SC-2b-13 219 170 0.78 0.12400 19.4 0.03900 30.8 0.00237 7.2 0.00108 39.8 0.233 60 15.2 1.1 38.0 11.0 1790 280 15,2 ± 1,1
SC-2b-12 190 108 0.57 0.14300 12.6 0.04930 13.2 0.00241 4.1 0.00151 11.3 0.315 68 15.5 0.7 48.6 6.3 2220 250 15,5 ± 0,7
SC-2b-19 278 191 0.69 0.10800 13.9 0.03480 14.4 0.00244 5.3 0.00103 12.6 0.371 55 15.7 0.8 34.6 4.8 1720 220 15,7 ± 0,8
SC-2b-16 579 587 1.01 0.07530 10.5 0.02490 9.2 0.00245 4.5 0.00084 4.9 0.486 37 15.8 0.7 25.0 2.3 950 250 15,8 ± 0,7
SC-2b-1 399 176 0.44 0.18800 7.4 0.06480 10.0 0.00248 4.0 0.00249 9.6 0.402 75 16.0 0.7 63.6 6.1 2740 130 16,0 ± 0,7
SC-2b-11 176 105 0.59 0.06420 15.3 0.02580 19.8 0.00301 8.3 0.00110 12.7 0.420 25 19.4 1.6 25.7 5.0 540 300 19,4 ± 1,6
SC-2b-17 280 207 0.74 0.24000 8.8 0.09510 6.9 0.00304 4.3 0.00272 4.8 0.616 79 19.6 0.9 92.1 6.0 3080 130 19,6 ± 0,9
n = 23 Mean 206Pb/238U Age = 14,33 ± 0,38
(2 sigma, MSWD = 2.6; n = 9)
Sample BQ-1a Boquillas intrusive (Tatatila de Las Minas, Veracruz)
BQ-1a-11 986 1860 1.89 0.05520 2.7 0.20090 3.4 0.02631 1.5 0.00803 2.1 0.443 10 167.4 2.5 185.8 5.9 431 58 167,4 ± 2,5
BQ-1a-18 716 651 0.91 0.05740 3.1 0.23740 3.0 0.03048 2.5 0.00823 3.4 0.811 10 193.6 4.7 216.2 6.0 496 64 193,6 ± 4,7
BQ-1a-20 900 820 0.91 0.05510 2.7 0.24630 3.9 0.03260 2.9 0.01198 3.3 0.748 8 206.8 5.9 223.6 7.9 414 61 206,8 ± 5,9
BQ-1a-9 302 133 0.44 0.05380 3.3 0.25160 3.6 0.03335 1.7 0.01286 3.5 0.473 7 211.5 3.5 227.5 7.4 400 75 211,5 ± 3,5
BQ-1a-8 504 131 0.26 0.05480 4.4 0.26100 4.2 0.03484 1.9 0.01255 4.0 0.443 6 220.8 4.0 235.4 9.0 391 95 220,8 ± 4,0
BQ-1a-14 541 196 0.36 0.05820 4.1 0.28000 4.3 0.03496 1.8 0.01299 3.6 0.420 12 221.5 3.9 250.7 9.2 513 89 221,5 ± 3,9
BQ-1a-17 532 240 0.45 0.05270 3.0 0.26300 3.3 0.03667 1.4 0.01336 2.5 0.424 2 232.1 3.2 236.9 7.1 299 68 232,1 ± 3,2
BQ-1a-12 306 81 0.26 0.05390 3.3 0.27300 3.7 0.03730 1.8 0.01297 4.1 0.483 4 236.0 4.1 244.7 8.3 369 75 236,0 ± 4,1
BQ-1a-23 248 15 0.06 0.05040 4.8 0.26200 5.0 0.03750 1.8 0.01704 5.7 0.365 1 237.3 4.2 240.0 10.0 190 100 237,3 ± 4,2
BQ-1a-10 382 166 0.43 0.05560 3.1 0.28200 3.9 0.03753 2.2 0.01296 3.9 0.553 6 237.5 5.0 252.1 9.0 414 74 237,5 ± 5,0
BQ-1a-4 372 177 0.48 0.05330 4.7 0.27500 5.1 0.03759 2.5 0.01358 4.8 0.486 4 237.9 5.8 247 12.0 320 110 237.9 ± 5.8
BQ-1a-6 368 144 0.39 0.05350 3.9 0.28200 4.3 0.03861 1.9 0.01399 3.4 0.438 3 244.2 4.5 251.6 9.2 325 89 244.2 ± 4.5
BQ-1a-24 277 35 0.13 0.05230 4.4 0.27800 5 0.03875 2.1 0.01460 6.8 0.415 1 245.1 5.0 248 11 276 91 245.1 ± 5.0
BQ-1a-2 338 125 0.37 0.05380 3.5 0.28500 4.6 0.03933 2.2 0.01371 2.7 0.485 2 248.6 5.4 253 11 358 80 248.6 ± 5.4
BQ-1a-7 261 31 0.12 0.05670 3.9 0.30900 4.5 0.03994 1.9 0.01593 5.2 0.426 8 252.4 4.8 273 11 472 80 252.4 ± 4.8
BQ-1a-25 418 198 0.47 0.06810 7.5 0.38200 5.5 0.04060 3.4 0.01481 5.7 0.627 22 256.8 9.0 328 15 870 120 256.8 ± 9.0
BQ-1a-19 471 95 0.2 0.05230 2.9 0.29320 3.3 0.04118 1.5 0.01327 4.1 0.458 1 260.1 3.9 262.1 7.7 298 65 260.1 ± 3.9
BQ-1a-13 391 298 0.76 0.05250 4.4 0.32400 4.3 0.04479 1.9 0.01447 2.5 0.429 1 282.5 5.1 285 10.0 294 92 282.5 ± 5.1
BQ-1a-15 318 312 0.98 0.05260 3.4 0.32400 3.7 0.04492 1.8 0.01437 2.4 0.475 1 283.2 4.8 284.8 8.9 292 78 283.2 ± 4.8
BQ-1a-3 405 387 0.96 0.05190 3.5 0.33000 4.2 0.04582 2.1 0.01378 4.1 0.484 0 288.8 5.8 289 11.0 266 73 288.8 ± 5.8
BQ-1a-5 764 64 0.08 0.05950 2.9 0.38500 8.3 0.04690 7.9 0.01183 5.2 0.949 11 295.0 23.0 331 26.0 588 67 295.0 ± 23.0
BQ-1a-16 104 55 0.53 0.05450 4.8 0.37500 5.1 0.05100 1.8 0.01807 4.3 0.348 2 320.6 5.5 328 14.0 391 97 320.6 ± 5.5
BQ-1a-1 765 55 0.07 0.06470 1.7 0.46800 4.5 0.05210 3.5 0.01440 9.7 0.770 16 327.0 11.0 389 14.0 759 35 327.0 ± 11.0
BQ-1a-26 664 209 0.31 0.06600 2.4 0.49700 3 0.05424 1.8 0.01046 4.2 0.599 17 340.5 6.0 410 10.0 805 55 340.5 ± 6.0
BQ-1a-21 1069 120 0.11 0.07010 2.9 0.55900 7 0.05790 4.3 0.01490 24.8 0.619 20 363.0 15.0 451 23.0 928 52 363.0 ± 15.0
BQ-1a-22 703 246 0.35 0.09140 1.9 1.86600 4.9 0.14920 3.9 0.06560 6.7 0.797 16 896.0 33.0 1069 35.0 1454 38 1454.0 ± 38.0
n = 23
Sample BQ-1b Boquillas intrusive (Tatatila de Las Minas, Veracruz)
BQ-1b-4 322 97 0.3 0.08020 7.9 0.33700 5.9 0.03160 5.1 0.02010 9 0.853 33 201.0 12.0 299 18.0 1210 160 201.0 ±
BQ-1b-1 642 453 0.71 0.05120 3.9 0.26010 3.5 0.03683 1.9 0.01248 2.8 0.537 1 233.2 4.4 234.6 7.4 240 73 233.2 ± 4.4
BQ-1b-16 684 544 0.8 0.06170 4.1 0.31400 4.8 0.03699 1.8 0.01275 4.2 0.379 15 234.1 4.2 277 11.0 672 82 234.1 ± 4.2
BQ-1b-11 507 176 0.35 0.05630 2.8 0.28920 3.1 0.03715 1.5 0.01102 4.2 0.462 9 235.1 3.3 257.7 7.2 450 61 235.1 ± 3.3
BQ-1b-3 295 24 0.08 0.06660 3.8 0.35400 4.2 0.03849 1.7 0.03100 8.7 0.411 21 243.4 4.2 307 11.0 824 76 243.4 ± 4.2
BQ-1b-14 142 11 0.08 0.06070 4.8 0.33800 5.3 0.04043 1.9 0.01930 10.4 0.362 13 255.5 4.8 294 13.0 580 110 255.5 ± 4.8
BQ-1b-10 567 346 0.61 0.05570 2.9 0.34800 3.2 0.04471 1.8 0.01464 3 0.566 7 282.0 4.9 303.1 8.2 426 63 282.0 ± 4.9
BQ-1b-6 474 286 0.6 0.05360 3 0.33400 3.6 0.04500 2.2 0.01414 3.7 0.619 3 283.7 6.2 292.8 8.9 341 63 283.7 ± 6.2
BQ-1b-15 284 127 0.45 0.05910 3 0.36900 3.5 0.04521 1.5 0.01505 3.5 0.427 11 285.0 4.2 318.6 9.3 557 67 285.0 ± 4.2
BQ-1b-13 331 155 0.47 0.05390 3.5 0.34200 4.1 0.04553 1.5 0.01488 3.2 0.370 4 287.0 4.2 298 10.0 343 77 287.0 ± 4.2
BQ-1b-5 923 1400 1.52 0.05310 2.1 0.33080 2.4 0.04556 1.4 0.01457 1.7 0.599 1 287.2 4.1 290 6.1 342 45 287.2 ± 4.1
BQ-1b-12 301 151 0.5 0.06200 3.1 0.41500 3.4 0.04849 1.4 0.01651 2.7 0.422 13 305.2 4.2 352 10.0 662 63 305.2 ± 4.2
BQ-1b-7 263 199 0.76 0.05510 6.5 0.36800 6 0.04852 2 0.01566 4.5 0.334 4 305.4 6.0 317 17.0 390 150 305.4 ± 6.0
BQ-1b-18 185 138 0.75 0.05660 4.6 0.37200 4.8 0.04887 1.7 0.01557 3.4 0.351 4 307.6 5.1 321 13.0 444 99 307.6 ± 5.1
BQ-1b-17 151 74 0.49 0.07000 3.9 0.48400 3.9 0.04952 2 0.02109 3.1 0.499 23 311.5 6.0 402 13.0 920 80 311.5 ± 6.0
BQ-1b-8 395 80 0.2 0.05570 3.1 0.40300 4 0.05254 1.8 0.01546 4.6 0.465 4 330.1 6.0 343 11.0 412 59 330.1 ± 6.0
BQ-1b-2 1780 146 0.08 0.07330 1.9 0.84000 6.9 0.08380 5.4 0.02510 6.8 0.778 16 519.0 26.0 619 28.0 1018 37 5190 ±
BQ-1b-9 637 312 0.49 0.08090 1.4 2.22700 2 0.20010 1.2 0.0596 1.7 0.632 1 1176 13.0 1191 14.0 1216 27 1216.0 ± 27
n = 18

#U and Th concentrations (ppm) are calculated relative to analyses of trace-element glass standard NIST 610.

Isotopic ratios are corrected relative to 91500 standard zircon for mass bias and down-hole fractionation (91500 with an age ~1065 Ma; Wiedenbeck et al, 1995). Isotopic 207Pb/206Pb ratios, ages and errors are calculated following Paton et al. (2010).

*All errors in isotopic ratios are in percentage whereas ages are reported in absolute and given at the 2-sigma level. The weighted mean 206Pb/238U age is also reported in absolute values at the 2-sigma level. The uncertenties have been propagated following the methodology discussed by Paton et al. (2010).

**Rho is the error correlation value for the isotopic ratios 206Pb/238U and 207Pb/235U calculated by dividing these two percentage errors. The Rho value is required for plotting concordia diagrams.

Appendix 4

Age and trace element data for LA-ICPMS spot analyses on zircon grains for intrusive units in Tatatila de Las Minas, Veracruz, Mexico. 

Age (Ma) ± 2s P Ti Y Nb La Ce Pr Nd Sm Eu Gd Tb Dy Ho Er Yb Lu Hf Pb Th U
Sample ES-3 Escalona dyke
ES5-1 4,4 ± 0,4 530 11,3 2380 3,06 0,113 25,0 0,511 9,10 15,60 1,66 74,1 21,20 217 78,6 319 547 103 8880 0,45 497 384
ES5-2 4,7 ± 0,4 200 26,3 2290 2,08 0,057 12,7 0,456 5,99 11,71 1,67 60,5 18,40 204 74,2 316 549 108 7910 0,43 357 425
ES5-3 3,7 ± 0,2 -380 8,9 1162 1,77 0,038 16,6 0,080 2,14 4,65 0,82 25,0 7,70 93 36,6 166 331 69 9650 0,55 282 772
ES5-4 4,0 ± 0,4 -270 8,9 1240 2,91 0,000 20,5 0,087 1,51 2,40 0,54 20,2 6,91 87 38,1 188 409 88 9580 0,36 374 472
ES5-5 4,1 ± 0,3 580 10,4 2810 3,16 0,058 27,4 0,525 10,28 19,30 2,35 89,9 26,20 274 94,5 385 650 123 7750 0,49 893 730
ES5-6 14,2 ± 1,2 840 22,0 1170 1,42 0,102 16,6 0,127 3,20 5,10 0,92 30,9 10,50 100 36,8 160 290 60 9800 0,75 204 204
ES5-7 9,3 ± 0,8 350 20,0 3230 3,43 0,120 30,1 0,910 14,40 25,20 3,09 103,9 31,10 320 108,9 443 696 134 8620 1,09 622 468
ES5-8 6,0 ± 0,5 370 6,5 747 1,42 0,032 12,0 0,125 1,54 3,00 0,35 16,5 5,10 62 23,9 110 223 46 10810 0,37 140 342
ES5-9 5,5 ± 0,4 10 6,8 792 1,45 0,000 12,3 0,081 2,10 3,30 0,39 17,5 5,68 66 25,3 114 220 46 9990 0,36 135 272
ES5-10 5,1 ± 0,3 200 11,3 1880 2,44 0,026 20,7 0,316 7,29 14,55 1,80 59,9 18,20 183 62,3 256 420 82 9260 0,41 616 502
ES5-11 3,9 ± 0,3 370 10,1 2270 3,02 0,075 40,5 0,410 7,40 12,60 1,07 59,7 19,30 206 74,8 319 537 106 9770 0,75 1075 1045
ES5-12 4,2 ± 0,4 40 21,9 1561 1,43 0,031 10,3 0,378 5,70 10,60 1,32 44,6 13,90 145 50,8 218 381 77 7770 0,19 255 250
ES5-13 4,1 ± 0,3 730 6,5 3380 3,65 0,095 37,6 0,748 12,99 23,10 2,36 102,6 30,90 325 113,3 462 750 141 8350 0,71 1276 1031
ES5-14 4,2 ± 0,3 80 13,5 3070 2,78 0,076 27,1 0,690 10,48 20,50 2,26 93,7 28,40 289 102,7 421 721 139 7530 0,56 827 761
ES5-15 4,4 ± 0,3 50 13,4 2424 2,33 0,046 24,5 0,507 8,55 16,20 1,85 71,4 22,17 229 80,9 337 563 110 8950 0,47 798 717
ES5-16 5,1 ± 0,5 150