Felsite–nanogranite inclusions and three Al<sub>2</sub>SiO<sub>5</sub> polymorphs in the same garnet in ultrahigh–temperature granulites from Rundvågshetta, Lützow–Holm Complex, East Antarctica

DOI Web Site 11 Citations 63 References
  • HIROI Yoshikuni
    Department of Earth Sciences, Chiba University National Institute of Polar Research
  • HOKADA Tomokazu
    National Institute of Polar Research Department of Polar Science, SOKENDAI
  • KATO Mutsumi
    Department of Earth Sciences, Chiba University Present address: Nittetsu Mining Consultants Co., Ltd.
  • YANAGI Ayahiko
    Department of Earth Sciences, Chiba University Present address: Graduate School of Life and Environmental Sciences, University of Tsukuba
  • ADACHI Tatsuro
    Department of Environmental Changes, Faculty of Social and Cultural Studies, Kyushu University
  • OSANAI Yasuhito
    Department of Environmental Changes, Faculty of Social and Cultural Studies, Kyushu University
  • MOTOYOSHI Yoichi
    National Institute of Polar Research Department of Polar Science, SOKENDAI
  • SHIRAISHI Kazuyuki
    National Institute of Polar Research

Bibliographic Information

Other Title
  • Felsite–nanogranite inclusions and three Al2SiO5 polymorphs in the same garnet in ultrahigh–temperature granulites from Rundvågshetta, Lützow-Holm Complex, East Antarctica

Abstract

<p>Ultrahigh–temperature (UHT) granulites characterized by the parageneses of sapphirine + quartz and orthopyroxene + sillimanite + garnet + quartz are found in Rundvågshetta, Lützow–Holm Complex (LHC), East Antarctica. In this study, we report previously undocumented features of the UHT pelitic granulites, including the presence of felsite–nanogranite inclusions (FNIs), which are interpreted to have formed by the supercooling of melt inclusions in garnet, and the presence of three Al2SiO5 polymorphs within the same garnet porphyroblast. Whereas sillimanite is present as inclusions in garnet and in the matrix, kyanite occurs as inclusions in garnet and andalusite appears in FNIs. Porphyroblastic garnet is compositionally zoned with Mg–rich cores surrounded by Fe– and Mn–rich rims, indicating homogenization and later modification of Fe, Mg, and Mn. Ca contents oscillate from core to rim, which may be a remnant of growth zoning and suggests compression before high–temperature decompression. Integration of these new data with those previously documented leads to the inference of a rapid change in pressure–temperature conditions during regional UHT metamorphism in the late Neoproterozoic to early Paleozoic Gondwana–forming collisional orogen. Locally occurring intimate intergrowths of kyanite/sillimanite + sapphirine + garnet ± quartz in garnet may be a breakdown product of Mg–rich staurolite and thus may be a link between high–pressure and UHT metamorphism.</p>

Journal

Citations (11)*help

See more

References(63)*help

See more

Related Projects

See more

Keywords

Details 詳細情報について

Report a problem

Back to top