Resumen

DE PABLO, Liberto; DOVAL, Mercedes; LA IGLESIA, Angel  y  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, (Si_{30.600-30.150}Al_5760-5.220)(Ca_1890-1.800K_1080-0.810Mg_0.540-0450)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 (Si_0.890-0825Al_0.202-0.102)(K_0.072-020Ca_0.020-0.010Fe_0.050-0.010)O₂ in tuffaceous rocks northeast of Jalpa. KNa-heulandite, (Si_28.080Al_8.010)(K_4.680Na_2.250Ca_0.270Fe_0.180)O₇₂, KNa-chabazite, (Si_9.210-9.000Al_3.090-2.940)(K_0.750-1.180Na_0.360-1.260Ca_0.150-0.030Fe_0.210-0.090Mg_0.380-0.210) O₂₄, NaK-erionite, (Si_27.990Al_7.830)(K_2.000)(K_4.210Na_1.620Ca_0.090Fe_0.090Mg_0.180)O₇₂, and Na-phillipsite, (Si_12.080Al_3.920(Na_3.160K_0.240Ca_0.160Fe_0.040) 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 (Si_0.910-0.833Al_0.170-0.092) (K_0.101-0.050Na_{0-0.033-0.027})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.

Palabras llave : CaK-zeolites; KNa-zeolites; zeolites; Mexico.

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