Amphibole zoning, a record of progressive oxidation during crystallization of mafic microgranular enclaves in the Kurobegawa Granitic Pluton

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Author(s)

    • WADA Hajime
    • Environmental System Science, Graduate School of Science and Technology, Shinshu University
    • OHTA Yasushi
    • Environmental System Science, Graduate School of Science and Technology, Shinshu University

Abstract

Sulfide, oxide, and amphibole in MME (mafic microgranular enclaves) in the young Kurobegawa Granitic Pluton (2 Ma) indicate that their textural and mineralogical features are characteristic of progressively oxidized magnetite-series granitoids. Hydrous mafic magma intruded into the chamber from the bottom and fragmented to form MME, subsequently vesiculated and floated through the chamber. The MME generally have sharp fine chilled margins and show no in situ mixing between the MME and the host granite. Amphibole, an early phase together with sulfides and plagioclase, began to crystallize just after the mafic magma intruded into the chamber bottom (10 km in depth) and then continued to crystallize as the MME floated. Amphibole shows strongly patchy zoning from brownish green pargasitic core to pale green magnesio-hornblende rim, with a systematic decreasing in Fe<SUP>2+</SUP>/(Fe<SUP>2+</SUP>+Mg) with Al<SUP>IV</SUP> decreasing toward the rim. Early sulfide precipitation followed by late -stage magnetite formation and the simultaneous decreasing in Fe<SUP>2+</SUP> during amphibole crystallization were resulted from progressive oxidation of iron in minerals. Transformation of sulfur species from SO<SUB>2</SUB> to H<SUB>2</SUB>S probably oxidized iron in the minerals in this hydrous magma on cooling, as suggested in previous models for large sulfur supplies and magma oxidation in subduction related volcanisms.

Journal

  • Journal of Mineralogical and Petrological Sciences

    Journal of Mineralogical and Petrological Sciences 98(4), 151-155, 2003-08-01

    Japan Association of Mineralogical Sciences

References:  23

Cited by:  1

Codes

  • NII Article ID (NAID)
    10011672289
  • NII NACSIS-CAT ID (NCID)
    AA11460926
  • Text Lang
    ENG
  • Article Type
    Journal Article
  • ISSN
    13456296
  • Data Source
    CJP  CJPref  J-STAGE 
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