Resumo

PUY-ALQUIZA, María Jesús et al. The mine tailings as construction material in the viceregal period: case study in Guanajuato City, Mexico. Bol. Soc. Geol. Mex [online]. 2019, vol.71, n.2, pp.543-564.  Epub 30-Out-2019. ISSN 1405-3322.  https://doi.org/10.18268/bsgm2019v71n2a18.

The colonization of Guanajuato and its environs began in the decade of 1540-1550, when some Spaniards entered the territory of Guanajuato for the purpose of the distribution of ranches, in search of valuable minerals, and to evangelize. In the following years, the silver-gold deposits were discovered. From the earliest records, it can be deduced that the mineral deposits were discovered in about 1552, and more intensely in the year 1557. Mining production generated large amounts of mine tailings. The first mining haciendas were established along the Guanajuato River, promoting the human settlements and development of the city of Guanajuato. The haciendas in Guanajuato were a very well-developed economic system. As they grew up, they became federal states, which were self-sufficient with their main objective to benefit from the ore obtained from the mines. The design and architectural style of these haciendas were determined by their activity, so, the material they used for their construction was adobes composed of mud and mine tailings, taken from the surroundings of the Guanajuato River. In this work, we study the physical, mechanical and chemical properties of six samples of adobe bricks, collected from several buildings of the seventeenth and eighteenth centuries in Guanajuato city (Mining Hacienda San Juan Nepomuceno, Mining Hacienda San Jeronimo, Mining Hacienda Duran, Mining Hacienda San Clemente, Mining Hacienda Purisima and Mining Hacienda Rayas) in Mexico. The adobe specimens were investigated by the techniques of Inductively Coupled Plasma Mass Spectrometry, X-Ray Diffraction and Scanning Electron Microscopy, in order to know their chemical and mineralogical composition; likewise, some analyzes were performed to determine their mechanical properties (simple compressive strength), physical properties (granulometry, real density, total porosity and moisture content), and biological properties (organic material content). These studies aim to establish a basis of knowledge, essential for the safety assessment of adobe constructions, and to contribute to the conservation of the adobe architecture. The analytical results support that the six adobe samples exhibited different behavior, depending on the property tested. Adobe samples have a higher percentage of fines (70%). According to the Unified Soil Classification System, the adobes studied correspond to silt of low compressibility. Inductively Coupled Plasma Mass Spectrometry analysis showed that adobe bricks share the same chemical composition, varying the concentration of heavy metals (Cu, Be, Zn, Sn, Pb, Ni, Co, V, Sb, Hg and Cr). The Cu, Zn, Pb and Sn presented in the adobes indicate that they were the product of a metallurgical process. The presence of Hg indicates that the method of benefit was by amalgamation used in the sixteenth, seventeenth and eighteenth centuries in the New Spain to obtain silver. With respect to the results obtained in X-Ray Diffraction, we confirmed the presence of 17 major minerals: Quartz, Orthoclase, Calcite, Faujasite Na and K, Erionite-K, Gismondine, Illite, Schuetteite, Sphalerite, Zinkenite, Sanidine, Sidorenkite, Zircon, Sepiolite, Brushite, Fizelyte and Gypsum; most of them are the product of the process of benefit of the mineral by the method of amalgamation.

Palavras-chave : mine tailings; mining hacienda; viceregal period; Guanajuato city; Inductively Coupled Plasma Mass Spectrometry; X-Ray Diffraction.

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