Stratigraphy, geochemistry and tectonic significance of the Tertiary Volcanic sequences of the Taxco-Quetzalapa region, Southern Mexico
Por:
Morán-Zenteno D.J., Alba-Aldave L.A., Martinez-Serrano R.G., Reyes-Salas M.A., Corona-Esquivel R., Ángeles-García S.
Publicada:
1 ene 1998
Resumen:
The volcanic rocks of the Taxco-Quetzalapa region, states of Gueirero and Morelos, are part of the Tertiary Volcanic Province of Southern Mexico (TVPSM) that extends from the State of Michoacán to the Isthmus of Tehuantepec region. This province is located between the Trans-Mexican Volcanic Belt (TMVB), of Miocene-Quaternary age, and the chain of Tertiary plutons that lies along the southwestern continental margin of Mexico. The volcanic sequences of the study region are distributed in three main areas: Taxco, Buenavista-Quetzalapa and Huautla. The Taxco volcanic sequence is constituted by three units of rhyolitic composition with a maximum total thickness of about 800 m. The lower unit (Acamixtla formation) consists of ignimbrites and welded breccias and includes vitrophyric layers. This unit is overlain by rhyolitic lava flows, moderately welded ign-imbrites, and vitrophyric layers (Tenería formation). The uppermost unit consists of moderately welded ignimbrites topped by a vitrophyre layer (Huizteco formation). K-Ar dates of the lower unit range from 35-38 Ma, whereas those of the upper units, from 31 to 32 Ma. The Ag, Zn and Pb Sulfide hydrothermal mineralization of the Taxco mining district is mainly hosted in the underlying sedimentary and metamorphic rocks. The Buenavista-Quetzalapa volcanic sequence is constituted by a series of dacitic lava flows and ignimbrites with a total thickness of about 900 m. The lower part of the sequence (Tilzapotla Formation) consists of a biotite-bearing ignimbrite of dacitic composition. The upper part of the sequence (Buenavista Formation) is constituted by dacitic lava flows interlayered with moderately to densely welded tuffs. These rocks are related to a caldera of about 20 km in diameter, which originated during the emission of the lower unit and underwent later resurgent activity. The volcanic sequence of the Huautla area is represented by biotite-bearing welded tuffs, dacitic to andesitic lava flows, as well as silicic ignimbrites and breccias. This sequence is intruded by quartz-trachyte bodies. The relationships between alkalis and SiO2, MgO and FeO* abundance in the studied samples indicate that the volcanic sequences belong to the calc-alkaline series, with the highest SiO2 abundance in the volcanic units of the Taxco area. REE patterns
Filiaciones:
Morán-Zenteno D.J.:
Instituto de Geología, Universidad National Autónoma de México, Delegación Coyoacán, 04510 D.F., Mexico
Alba-Aldave L.A.:
Instituto de Geología, Universidad National Autónoma de México, Delegación Coyoacán, 04510 D.F., Mexico
Martinez-Serrano R.G.:
Instituto de Geofísica, Universidad National Autónoma de México, Delegación Coyoacán, 04510 D.F., Mexico
Reyes-Salas M.A.:
Instituto de Geología, Universidad National Autónoma de México, Delegación Coyoacán, 04510 D.F., Mexico
Corona-Esquivel R.:
Instituto de Geología, Universidad National Autónoma de México, Delegación Coyoacán, 04510 D.F., Mexico
Ángeles-García S.:
Instituto de Geología, Universidad National Autónoma de México, Delegación Coyoacán, 04510 D.F., Mexico
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