Formation of the Late Permian Panzhihua plutonic-hypabyssal-volcanic igneous complex: Implications for the genesis of Fe-Ti oxide deposits and A-type granites of SW China

J. G. Shellnutt, B. M. Jahn

    Research output: Contribution to journalArticlepeer-review

    93 Citations (Scopus)

    Abstract

    The Late Permian (260 Ma) Emeishan large igneous province of SW China contains numerous magmatic Fe-Ti oxide deposits. The Fe-Ti oxide deposits occur in the lower parts of evolved layered gabbroic intrusions which are spatially and temporally associated with A-type granitic rocks. The 260 Ma Panzhihua layered gabbroic intrusion hosts one of the largest magmatic Fe-Ti oxide deposits in China and is coeval with a peralkaline A-type granitic pluton. The granite has intruded the overlying Emeishan flood basalts and fed at least one dyke which erupted onto the surface producing columnar jointed trachytes. The presence of syenodiorite between the layered gabbro and granite is evidence for compositional evolution from mafic to intermediate to felsic rocks. The syenodiorites have intermediate to felsic composition with SiO2 = 61 to 65 wt.%, MgO = 0.27 to 0.6 wt.% and CaO = 1.0 to 2.5 wt.% as compared to the granite SiO2 = 65 to 72 wt.%, MgO = 0.1 to 0.4 wt.%, CaO = < 1.0 wt.%. Primitive-mantle-normalized incompatible element plots show corresponding reciprocal patterns between the mafic and felsic rocks. The chondrite-normalized REE patterns show Eu anomalies changing from > 1(Eu/Eu* = 1.1 to 2.6) in the gabbroic intrusion, to < 1 in the syenodiorite (Eu/Eu* = 0.75 to 0.83), granites and trachytes (Eu/Eu* = 0.55-0.87). Previously published εNd(T) values from clinopyroxenes (εNd(T) = + 1.1 to + 3.2) of the gabbroic intrusion match the whole-rock values of the syenodiorite (εNd(T) = + 2.1 to + 2.5), granite and trachyte (εNd(T) = + 2.2 to + 2.9), suggesting that all rock types originated from the same mantle source. MELTS and trace element modeling confirm that all rock types can be generated by fractional crystallization of high-Ti Emeishan basalt. The jump in SiO2 from the gabbro to the syenodiorite is attributed to the en masse crystallization of the Fe-Ti oxides. The geological and geochemical data indicate that fractional crystallization of a common parental magma produced the layered gabbroic intrusion and Fe-Ti oxide deposit, the syenodiorite, granites and trachyte of the Panzhihua region, which thus form a genetically related plutonic-hypabyssal-volcanic complex. Other granite-gabbro complexes in the region likely formed in a similar manner.

    Original languageEnglish
    Pages (from-to)509-519
    Number of pages11
    JournalEarth and Planetary Science Letters
    Volume289
    Issue number3-4
    DOIs
    Publication statusPublished - 2010 Jan 31

    Keywords

    • A-type granite
    • Emeishan large igneous province
    • Fe-Ti oxide deposit
    • MELTS
    • Permian
    • layered gabbro
    • trachyte

    ASJC Scopus subject areas

    • Geophysics
    • Geochemistry and Petrology
    • Earth and Planetary Sciences (miscellaneous)
    • Space and Planetary Science

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