Mid-crustal contact metamorphism around the Chimakurthy mafic-ultramafic complex, Eastern Ghats Belt, India
Mid-crustal contact metamorphism around the Chimakurthy mafic-ultramafic complex, Eastern Ghats Belt, India
复制标题
印度东高止山脉 Chimakurthy 镁铁质-超镁铁质杂岩周围的中地壳接触变质作用
DOI：
10.1007/s004100050331
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发表时间：
1997
影响因子：
3.5
通讯作者：
P. Sengupta
中科院分区：
文献类型：
--
作者：
S. Dasgupta;J. Ehl;M. Raith;P. Sengupta;P. Sengupta
摘要印度东高止山脉奇马库尔蒂基性-超基性火成杂岩接触带的泥质岩发生了热变质作用。岩石矿物学表现为黑云母-硅线石-石英-石榴石-钾长石的递进变化（组合I，距离侵入接触面150 m）为石榴石-尖晶石-堇青石-钾-尖晶石-硅线石（组合II，距离侵入接触面20 - 30 m）到堇青石-钾长石-（堇青石-斜方辉石-钾长石合晶岩后的）-尖晶石-FeTiAl氧化物（含/不含石榴石）（组合III和IV，距离侵入接触面5米），最后是尖晶石-斜方辉石-堇青石-钾长石（组合V，捕虏体）。组合III和IV中的氧化物矿物凝块类似于刚玉型岩石。最初的矿物反应涉及黑云母脱水熔融与部分偏析的熔体。低温矿物反应在很大程度上是扩散控制的，并且在微区中通常保存合晶和日冕结构。对KFMASH和FMAS系统的相关成岩格网中反应结构的解释以及结合地质温压法的解释表明，泥质岩在c. 6 kbar的压力沿加热-冷却轨迹在c. 750 ° C和C。1000 ° C。
Abstract Pelitic rocks were thermally metamorphosed at the contact of the Chimakurthy mafic-ultramafic igneous complex, Eastern Ghats Belt, India. The rocks show progressive change in mineralogy from biotite-sillimanite-quartz-garnet-K-feldspar (association I, 150 m from the intrusive contact) to garnet-spinel-cordierite-K-feldspar-sillimanite (association II, 20–30 m from the intrusive contact) to cordierite-K-feldspar-(cordierite-orthopyroxene-K-feldspar symplectite after osumilite)-spinel-FeTiAl oxides with/without garnet (associations III and IV, 5 m from the intrusive contact), and finally to spinel-orthopyroxene-cordierite-K-feldspar (association V, xenoliths). Oxide mineral clots in associations III and IV resemble emery-type rocks. Initial mineral reactions involved biotite-dehydration melting with partial segregation of the melt. Down-temperature mineral reactions were largely diffusion controlled and preservation of symplectitic and coronitic textures in microdomains is common. Interpretation of reaction textures in relevant petrogenetic grids for the sytems KFMASH and FMAS and combined with geothermobarometry suggest that the pelitic rocks were thermally metamorphosed at c. 6 kbar pressure along a heating-cooling trajectory within the temperature interval between c. 750 °C and c. 1000 °C.