Abstract
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 Al 2 SiO 5 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.
| Original language | English |
|---|---|
| Pages (from-to) | 60-78 |
| Number of pages | 19 |
| Journal | Journal of Mineralogical and Petrological Sciences |
| Volume | 114 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - Apr 1 2019 |
Fingerprint
All Science Journal Classification (ASJC) codes
- Geophysics
- Geology
Cite this
Felsite-nanogranite inclusions and three Al 2 SiO 5 polymorphs in the same garnet in ultrahigh-temperature granulites from Rundvågshetta, Lützow-Holm Complex, East Antarctica . / Hiroi, Yoshikuni; Hokada, Tomokazu; Kato, Mutsumi; Yanagi, Ayahiko; Adachi, Tatsuro; Osanai, Yasuhito; Motoyoshi, Yoichi; Shiraishi, Kazuyuki.
In: Journal of Mineralogical and Petrological Sciences, Vol. 114, No. 2, 01.04.2019, p. 60-78.Research output: Contribution to journal › Article
}
TY - JOUR
T1 - Felsite-nanogranite inclusions and three Al 2 SiO 5 polymorphs in the same garnet in ultrahigh-temperature granulites from Rundvågshetta, Lützow-Holm Complex, East Antarctica
AU - Hiroi, Yoshikuni
AU - Hokada, Tomokazu
AU - Kato, Mutsumi
AU - Yanagi, Ayahiko
AU - Adachi, Tatsuro
AU - Osanai, Yasuhito
AU - Motoyoshi, Yoichi
AU - Shiraishi, Kazuyuki
PY - 2019/4/1
Y1 - 2019/4/1
N2 - 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 Al 2 SiO 5 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.
AB - 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 Al 2 SiO 5 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.
UR - http://www.scopus.com/inward/record.url?scp=85065616996&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85065616996&partnerID=8YFLogxK
U2 - 10.2465/jmps.181118
DO - 10.2465/jmps.181118
M3 - Article
AN - SCOPUS:85065616996
VL - 114
SP - 60
EP - 78
JO - Journal of Mineralogical and Petrological Sciences
JF - Journal of Mineralogical and Petrological Sciences
SN - 1345-6296
IS - 2
ER -