Nanogranitoid inclusions with grandidierite in mafic granulite from Austhovde, Lützow-Holm Complex, East Antarctica
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- HIROI Yoshikuni
- Department of Earth Sciences, Chiba University National Institute of Polar Research
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- HOKADA Tomokazu
- National Institute of Polar Research Department of Polar Science, SOKENDAI
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- ADACHI Tatsuro
- Department of Environmental Changes, Faculty of Social and Cultural Studies, Kyushu University
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- SHIRAISHI Kazuyuki
- National Institute of Polar Research
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- MOTOYOSHI Yoichi
- National Institute of Polar Research
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- GREW Edward S.
- School of Earth and Climate Sciences, University of Maine
説明
<p>Grandidierite, (Mg,Fe)Al3O2(BO3)SiO4, was found in a garnet-clinopyroxene-ilmenite-rich mafic granulite from Austhovde in the Late Neoproterozoic to Early Cambrian Lützow-Holm Complex (LHC), East Antarctica, the first reported occurrence of this borosilicate in a mafic granulite. It occurs in one of the many nanogranitoid inclusions (NIs) in garnet. Quartz, sodic plagioclase, myrmekite, K-feldspar, epidote and biotite are also found only as inclusions in garnet. Garnet porphyroblasts show marked compositional zoning: Ca increases and Mg decreases from the core to rim with little change in Fe and Mn contents except for the outermost rim. Anorthite content of inclusion plagioclase increases from core to rim of host garnet in parallel with increase in garnet Ca towards the rim. This together with the distinctly different mineral assemblages within and exterior to garnet porphyroblasts suggests that partial melting took place and produced melts were extracted leaving a mafic and calcic restite. Partial melting also occurred locally in garnet porphyroblasts consuming different hydrous mineral inclusions to produce various NIs ranging from K-feldspar-rich to K-feldspar-free. Subsequent decompression at high temperatures resulted in breakdown of garnet to orthopyroxene + calcic plagioclase with further consumption of quartz, such that none remained in the matrix of the granulite. Grandidierite may have formed by a reaction between a trapped boron-bearing aluminous granitic melt and host garnet upon cooling.</p>
収録刊行物
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- Journal of Mineralogical and Petrological Sciences
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Journal of Mineralogical and Petrological Sciences 118 (ANTARCTICA), n/a-, 2023
一般社団法人 日本鉱物科学会
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詳細情報 詳細情報について
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- CRID
- 1390296066522958592
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- ISSN
- 13493825
- 13456296
- http://id.crossref.org/issn/13456296
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- 本文言語コード
- en
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- データソース種別
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- JaLC
- Crossref
- KAKEN
- OpenAIRE
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- 抄録ライセンスフラグ
- 使用不可