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| Titel |
Melting and remobilization of felsic protoliths through mafic recharge: evidence from basalt-trachyte mingling in Mumbai, Deccan Traps |
| VerfasserIn |
Georg Zellmer, Hetu Sheth, Yoshiyuki Iizuka, Yi-Jen Lai |
| Konferenz |
EGU General Assembly 2010
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 12 (2010) |
| Datensatznummer |
250032807
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| Zusammenfassung |
| Contrasting, mingled magmas are widespread, and often erupt at volcanoes, or form intrusive
bodies. Field evidence, petrography, mineral chemistry, and whole-rock major, trace and Pb
isotope chemistry of trachytes and their mafic enclaves from the Manori-Gorai area of
Mumbai, in the Deccan Traps flood basalt province, are used here to assess the petrogenetic
processes that operated to produce these rocks. Local hybridization has occurred and has
produced hybrid trachytes and intermediate rocks such as a quartz monzonite. Feldspar
crystals have complex textures and an unusually wide range in chemical composition.
Crystals from the trachytes cover the alkali feldspar compositional range and include
plagioclase crystals with Ca contents up to An47. Crystals from the mafic enclaves are
dominated by plagioclase An72-90, but include orthoclase microphenocrysts and other
feldspars covering the entire compositional range sampled in the trachytes. And
feldspars from the hybridized quartz monzonite yield mineral chemical clusters of
An80-86, An47-54, Ab94-99, Or45-60 and Or96-98, all sampled within individual
phenocrysts.
We show that these feldspar crystals provide a record of remobilization of felsic
protoliths by influx of mafic magmas, followed by magma mixing and hybridization
processes that result in bulk rock major and trace element variations which can be
modeled by essentially simple bulk mixing. However, heterogeneities in Pb isotopic
compositions of trachytes and their microscopic to meter-sized enclaves are observed on
the scale of individual outcrops, likely reflecting initial variations in the isotopic
compositions of the involved magmas and protoliths, and provide evidence for
one or more shallow trachyte magma chambers disturbed by multiple injections of
trachytic, porphyritic alkali basaltic, and variably hybridized magmas from depth. |
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