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Geochemical Evidence for Mantle Origin and Crustal Processes in Volcanic Rocks from Popocatepetl and Surrounding Monogenetic Volcanoes, Central Mexico |
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| Authors: | SCHAAF PETER; STIMAC JIM; SIEBE CLAUS; MACIAS JOSE LUIS |
| Institution: | 1 LABORATORIO UNIVERSITARIO DE GEOQUÍMICA ISOTÓPICA (LUGIS), INSTITUTO DE GEOFÍSICA AND INSTITUTO DE GEOLOGÍA, UNIVERSIDAD NACIONAL AUTÓNOMA DE MÉXICO (UNAM), 04510 MÉXICO, D.F., MEXICO 2 PHILIPPINE GEOTHERMAL INC., 12TH FLOOR, CITIBANK TOWER, 8741 PASEO DE ROXAS BLVD., MAKATI CITY, PHILIPPINES 3 DEPARTAMENTO DE VULCANOLOGÍA, INSTITUTO DE GEOFÍSICA, UNAM, 04510 MÉXICO, D.F., MEXICO |
| Abstract: | Elemental, isotopic, and mineral compositions as well as rocktextures were examined in samples from Popocatépetl volcanoand immediately surrounding monogenetic scoria cones of theSierra Chichinautzin Volcanic Field, central Mexico. Magma generationis strongly linked to the active subduction regime to the south.Rocks range in composition from basalt to dacite, but Popocatépetlsamples are generally more evolved and have mineral compositionsand textures consistent with more complicated, multi-stage evolutionaryprocesses. High-Mg calc-alkaline and more alkaline primitivemagmas are present in the monogenetic cones. Systematic variationsin major and trace element compositions within the monogeneticsuite can mostly be explained by polybaric fractional crystallizationprocesses in small and short-lived magmatic systems. In contrast,Popocatépetl stratovolcano has produced homogeneous magmacompositions from a shallow, long-lived magma chamber that isperiodically replenished by primitive basaltic magmas. The currenteruption (1994–present) has produced silicic dome lavasand pumice clasts that display mingling of an evolved daciticcomponent with an olivine-bearing mafic component. The longevityof the magma chamber hosted in Cretaceous limestones has fosteredinteraction with these rocks as evidenced by the chemical andisotopic compositions of the different eruptive products, contact-metamorphosedxenoliths, and fumarolic gases. Popocatépetl volcanicproducts display a considerable range of 87Sr/86Sr (0·70397–0·70463)and  Nd (+6·2 to +3·0) whereas Pb isotope ratiosare relatively homogeneous (206Pb/204Pb 18·61–18·70;207Pb/204Pb 15·56–15·60). KEY WORDS: Popocatépetl; Sierra Chichinautzin Volcanic Field; arc petrogenesis; radiogenic isotopes |
| Keywords: | : Popocaté petl Sierra Chichinautzin Volcanic Field arc petrogenesis radiogenic isotopes |
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