Journal of Petrology Advance Access originally published online on February 25, 2005
Journal of Petrology 2005 46(6):1243-1282; doi:10.1093/petrology/egi015
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Geochemical Evidence for Mantle Origin and Crustal Processes in Volcanic Rocks from Popocatépetl and Surrounding Monogenetic Volcanoes, Central Mexico
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
Elemental, isotopic, and mineral compositions as well as rock textures were examined in samples from Popocatépetl volcano and immediately surrounding monogenetic scoria cones of the Sierra Chichinautzin Volcanic Field, central Mexico. Magma generation is strongly linked to the active subduction regime to the south. Rocks range in composition from basalt to dacite, but Popocatépetl samples are generally more evolved and have mineral compositions and textures consistent with more complicated, multi-stage evolutionary processes. High-Mg calc-alkaline and more alkaline primitive magmas are present in the monogenetic cones. Systematic variations in major and trace element compositions within the monogenetic suite can mostly be explained by polybaric fractional crystallization processes in small and short-lived magmatic systems. In contrast, Popocatépetl stratovolcano has produced homogeneous magma compositions from a shallow, long-lived magma chamber that is periodically replenished by primitive basaltic magmas. The current eruption (1994present) has produced silicic dome lavas and pumice clasts that display mingling of an evolved dacitic component with an olivine-bearing mafic component. The longevity of the magma chamber hosted in Cretaceous limestones has fostered interaction with these rocks as evidenced by the chemical and isotopic compositions of the different eruptive products, contact-metamorphosed xenoliths, and fumarolic gases. Popocatépetl volcanic products display a considerable range of 87Sr/86Sr (0·703970·70463) and
Nd (+6·2 to +3·0) whereas Pb isotope ratios are relatively homogeneous (206Pb/204Pb 18·6118·70; 207Pb/204Pb 15·5615·60).
KEY WORDS: Popocatépetl; Sierra Chichinautzin Volcanic Field; arc petrogenesis; radiogenic isotopes
* Corresponding author: Telephone: +52 55 56224221. Fax: +52 55 55509395. E-mail: pschaaf{at}geofisica.unam.mx
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