%0 Journal Article
%T Petrology of very high temperature crustal xenoliths in the Puente Negro intrusion: a sapphire-spinel-bearing Oligocene andesite, Mixteco terrane, southern Mexico
%A Ortega-Guti¨¦rrez
%A Fernando
%A Martiny
%A Barbara M.
%A Mor¨¢n-Zenteno
%A Dante J.
%A Reyes-Salas
%A A. Margarita
%A Sol¨¦-Vi£¿as
%A Jes¨²s
%J Revista mexicana de ciencias geol¨®gicas
%D 2011
%I Universidad Nacional Aut¨®noma de M¨¦xico
%X this study presents petrologic, chemical, geochronological and isotopic data, as well as petrogenetic interpretations about a unique subvolcanic locality in southern mexico that contains deep-seated xenoliths and xenocrysts (igneous and metamorphic), albeit affected by extreme pyrometamorphism during rapid ascent in a composite andesitic dike. the intrusion has a k-ar age of 29.2 ¡À 0.3 ma on volcanic matrix and 30.5 ¡À 0.6ma on hornblende xenocrysts,and it ispart of an arc-related regional magmatic event in southern mexico. this magma at puente negro intruded quartzo-feldspathic gneisses and micaceous schists of the paleozoic acatl¨¢n complex. xenoliths consist of high-grade garnet-bearing gneisses, aluminous metapelites, impure quartzites, and abundant hornblende-rich gabbroic rocks. garnet, corundum (including purple-blue sapphire), spinel, and aluminous orthopyroxene constitute the main types of deep-seated xenocrysts derived from disaggregation of metamorphic rocks in the andesite. low pressure assemblages with tridymite, spinel, al-silicates (mullite and sillimanite), two pyroxenes, fe-ti oxides, and high-silica anatectic glasses indicate peak temperatures of pyrometamorphism above 1100 c. decompression coronas of spinel-plagioclase-orthopyroxene ¡À corundum ¡À glass aboutpolyphase garnetporphyroblasts inplagioclase-orthopyroxene-spinel restitic gneisses, al-rich orthopyroxene coring al-poor orthopyroxene xenocrysts, spinel-plagioclase-corundum xenocrystic pseudomorphs probably after garnet, and local preservation of orthopyroxene-sillimanite and garnet-hypersthene-spinel-quartz assemblages strongly support interaction of original basaltic magmas with the lower crust. aluminum in orthopyroxene (up to 11.6 al2o3 wt. %) coexisting with spinel, ilmenite-magnetite pairs, and fe/mg partitioning between orthopyroxene and spinel in garnet coronas yield decompression metamorphic temperatures around 990 ¡ãc, whereas coexisting hornblende-plagioclase and two pyroxenes in gabb
%K crustal xenoliths
%K pyrometamorphism
%K sapphire xenocrysts
%K arc basalt
%K mixteco terrane
%K southern mexico.
%U http://www.scielo.org.mx/scielo.php?script=sci_abstract&pid=S1026-87742011000300019&lng=en&nrm=iso&tlng=en