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Revista mexicana de ciencias geológicas

On-line version ISSN 2007-2902Print version ISSN 1026-8774

Abstract

DE PABLO, Liberto; DOVAL, Mercedes; LA IGLESIA, Angel  and  SORIANO, Jesús. CaK-clinoptilolite, KNa-chabazite, KNa-heulandite, KNa-erionite and Na-phillipsite from tuffaceous rocks, Province of the Mesa Central, Mexico. Rev. mex. cienc. geol [online]. 2014, vol.31, n.1, pp.116-126. ISSN 2007-2902.

This paper presents the occurrence, mineralogy and process of formation of CaK-clinoptilolite, KNa-chabazite, KNa-heulandite, KNa-erionite and Na-phillipsite in pyroclastic rocks from the Calvillo-Jalpa-Nochixtlán area in the Province of the Mesa Central, Mexico. CaK-clinoptilolite, (Si30.600-30.150Al5760-5.220)(Ca1890-1.800K1080-0.810Mg0.540-0450)O72, of 5.04-5.86 Si/Al, 0.83-0.86 Si/(Si+Al) and 0.26-0.31 (Na+K)/ (Na+K+Ca+Mg) ratios, free of Na, crystallized from siliceous alkaline pore fluids and glasses of composition (Si0.890-0825Al0.202-0.102)(K0.072-020Ca0.020-0.010Fe0.050-0.010)O2 in tuffaceous rocks northeast of Jalpa. KNa-heulandite, (Si28.080Al8.010)(K4.680Na2.250Ca0.270Fe0.180)O72, KNa-chabazite, (Si9.210-9.000Al3.090-2.940)(K0.750-1.180Na0.360-1.260Ca0.150-0.030Fe0.210-0.090Mg0.380-0.210) O24, NaK-erionite, (Si27.990Al7.830)(K2.000)(K4.210Na1.620Ca0.090Fe0.090Mg0.180)O72, and Na-phillipsite, (Si12.080Al3.920(Na3.160K0.240Ca0.160Fe0.040) O32, of 2.91-3.57 Si/Al, 0.74-0.78 Si/(Si+Al) and 0.72-0.97 (Na+K)/ (Na+K+Ca+Mg) ratios, dominant exchange cations K and Na, formed from siliceous alkaline high-pH fluids and glasses of composition (Si0.910-0.833Al0.170-0.092) (K0.101-0.050Na0-0.033-0.027)02 in tuffs northwest of Nochixtlán. The zeolites were formed in the Jalpa area by diagenetic alteration of the tuff; in the Nochixtlán area, enrichment of Na and formation of alkali-rich zeolites was attributed to alkaline saline brines in an open hydrologic system. They occur in Oligocene - early Miocene tuffaceous rocks associated to the volcanism of the Sierra Madre Occidental, exposed in the Calvillo-Jalpa-Nochixtlán area in the states of Aguascalientes and Zacatecas, in the Province of the Mesa Central, Mexico.

Keywords : CaK-zeolites; KNa-zeolites; zeolites; Mexico.

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