The Ixtacamaxtitlán kaolinite deposit and sinter (Puebla State, Mexico): a magmatic‐hydrothermal system telescoped by a shallow paleoaquifer

Abstract

The Ixtacamaxtitlá n hydrothermal deposit is made up of a succession, from bottom to top, of: (1) a porphyritic subvolcanic body, crosscut by quartz veins, and a stockwork with subordinate sulfides (pyrite and chalcopyrite), showing propylitic alteration haloes overprinting a previous potassic alteration event (biotitization); (2) an overlying, kaolinized lithic-rich rhyolitic tuff; and (3) a layered opal deposit with preserved sedimentary structures. This vertical zonation, coupled with the distribution of the alteration assemblages, lead us to the interpretation of the whole as a porphyry-type deposit grading upwards to a barren, steam-heated, acid-leached, kaolinite blanket with a partially preserved silica sinter on top. Both the fluid inclusion study carried out on the veins and stockwork, and the stable isotopic analyses of the kaolinized bodies, suggest the presence of two major hydrothermal events. The older event is characterized by the occurrence of hot hypersaline fluids (up to 320°C and 36 wt% NaCl equivalents), likely of magmatic origin, closely associated with the emplacement of the underlying early Miocene porphyry-type deposit. The later event is characterized by the presence of cooler and dilute fluids (up to 140°C and 4 wt% NaCl equivalents) and by advanced argillic alteration close to the paleosurface. The calculated isotopic composition of water in equilibrium with the kaolinitic sequence plots close to and underneath the meteoric water line, partially overlapping the Los Humeros present-day geothermal fluids. This evidence coupled with the petrographic observations suggests that steam-heated phreatic waters altered the lithic-rich rhyolitic tuff. This would have occurred when acid vapors, exsolved from deeper hydrothermal fluids by boiling, reached the local paleowater table and condensed, after a sector collapse that changed the system from lithostatic to hydrostatic conditions.

Depósitos epitermales en México: actualización de su conocimiento y reclasificación empírica

“…Müller y Groves, 2000; Brathwaite et al, 2001;Müller et al, 2002;Strashimirov et al, 2002;Einaudi et al, 2003;Morales-Ramírez et al, 2003;Sillitoe y Hedenquist, 2003;Simpson et al, 2004;Tritlla et al, 2004). Lo que no ha sido tan evidente es la posible relación con otros tipos de depósitos.…”

“…Esta tendencia coincide con un cambio en la orientación del arco volcánico, siguiendo la apertura de la nueva trinchera al sur de México (Ferrari et al, 1999). Sin embargo, hay evidencias cuanto menos de una distribución "bipolar" de estos depósitos, teniendo en cuenta que la presencia de Pachuca-Real del Monte, Hidalgo, e Ixtacamaxtitlán, Puebla, constituyen evidencia de la presencia de depósitos del Mioceno al este de la Faja Volcánica Mexicana (Tritlla et al, 2004).…”

Características metalogenéticas de los depósitos de tipo pórfi do cuprífero en México y su situación en el contexto mundial

“…Recientemente se ha reportado además un nuevo depósito en el Estado de Puebla, cuyas características sugieren un ambiente de tipo pórfi do de cobre. Este depósito se denomina Ixtacamaxtilán (61), y consiste en un cuerpo subvolcánico coronado por un horizonte de caolinita, cortado por vetas de cuarzo y un stockwork con pirita y calcopirita, el cual está asociado a un plutón de granodiorita porfídica con una edad 40 Ar/ 39 Ar en biotitas de 17.83±0.06 Ma (Tritlla et al, 2004).…”