Metamorphic P-T conditions and variation of REE between two garnet generations from granulites in the Sor-Rondane mountains, East Antarctica?
Metamorphic P-T conditions and variation of REE between two garnet generations from granulites in the Sor-Rondane mountains, East Antarctica?
复制标题
东南极洲 Sor-Rondane 山脉麻粒岩两代石榴石的变质 P-T 条件和稀土元素变化？
DOI：
10.1007/s00710-019-00680-0
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发表时间：
2019
影响因子：
1.8
通讯作者：
T
中科院分区：
文献类型：
--
作者：
Baba;S;Osanai;Y;Adachi;T;Nakano;N;Hokada;T;Toyoshima;T
本文描述了富铁麻粒岩的变质条件和稀土元素在峰值石榴石变斑晶和次生石榴石冠状岩之间的变化。富铁麻粒岩采自东南极南龙托根山脉，主要由堇青石、石榴石、尖晶石、条纹长石、钾长石、斜长石和斜方辉石或硅线石组成。根据条纹长石-中粗晶长石成分估计的温度、实验校准的地质温压计和P-T假剖面模型表明，岩石经历了900-950 °C和5.0 ± 0.5 kbar的超高温（UHT）变质条件。尖晶石中含有石英包裹体，也为超高温变质提供了证据。部分熔融的证据的特征在于存在无色带。第二代石榴石以尖晶石周围的冠状体的形式出现，是在超高温变质作用的峰值条件之后的等压冷却过程中形成的。石榴石冠状体和石榴石变斑晶具有明显的微量元素模式。结构证据和稀土元素地球化学表明，石榴石冠状体的发育受（1）反应物相和熔体的稀土元素组成和/或（2）富HREE副相（如，锆石和独居石）。
In this paper, we describe the metamorphic conditions of Fe-rich granulite and variations in rare earth elements (REE) between peak garnet porphyroblasts and secondary garnet coronae. The Fe-rich granulites were collected from Vesthaugen, Sør-Rondane Mountains, East Antarctica, and consist mainly of cordierite, garnet, spinel, perthite, K-feldspar, plagioclase, and orthopyroxene or sillimanite. Temperatures estimated from perthitc–mesoperthitic feldspar compositions, experimentally calibrated geothermobarometers and the modeling ofP-Tpseudosections suggest that the rocks experienced peak ultrahigh-temperature (UHT) metamorphic conditions of 900–950 °C and 5.0 ± 0.5 kbar. Spinel contains quartz inclusions that also provide evidence for UHT metamorphism. Evidence of partial melting is characterized by the presence of leucocratic bands. The second generation of garnet occurs as coronae around spinel, formed during isobaric cooling following the peak conditions of UHT metamorphism. Garnet coronae and garnet porphyroblasts have distinct trace element patterns. Textural evidence and REE geochemistry suggest that the development of garnet coronae was controlled by (1) the REE composition of reactant phases and melt and/or (2) the crystallization of HREE-rich accessory phases (e.g., zircon and monazite) during secondary garnet growth.