Multiphase solid inclusions in zoisite-bearing eclogite: evidence for partial melting of ultrahigh-pressure metamorphic rocks during continental collision
Multiphase solid inclusions in zoisite-bearing eclogite: evidence for partial melting of ultrahigh-pressure metamorphic rocks during continental collision
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含黝帘石榴辉岩中的多相固体包裹体：大陆碰撞期间超高压变质岩部分熔融的证据
DOI：
10.1016/j.lithos.2014.04.004
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发表时间：
2014-07-01
期刊：
影响因子：
3.5
通讯作者：
Hu, Zhaochu
中科院分区：
文献类型：
--
作者：
Chen, Yi-Xiang;Zheng, Yong-Fei;Hu, Zhaochu
研究了苏鲁造山带超高压变质带榴辉岩中石榴石和绿辉石中的多相固体包裹体。研究结果为深俯冲陆壳折返过程中的局部深熔作用提供了岩石学证据。MS包裹体有三种类型：（1）斜长石+石英，（2）斜长石+石英+钾长石，（3）重晶石+斜长石+钾长石+/-绿帘石/绿帘石。寄主矿物在MS包裹体周围多呈放射状裂隙。第一和第二类型的MS夹杂物进行了分析，其本体组成，产生高SiO2和Na 2 O，但非常低的FeO + MgO + TiO 2与可变K2 O的第二类型。典型MS包裹体的微量元素分析结果除Sr、Ba和Rb等大离子亲石元素外，一般都很低。这些特征表明不同的起源为三种类型的MS夹杂物。第一类MS包裹体主要来源于钠云母的脱水熔融，而第二类MS包裹体主要来源于钠云母和多硅白云母的脱水熔融。第三类MS包裹体可能是变质流体与寄主矿物相互作用的产物，因为重晶石充填在寄主矿物的裂隙中。与石英共存的高尖形也表明了蛇绿岩的破裂，为剥露过程中石榴石的生长提供了成分。因此，多硅白云母和钠云母等含水矿物的分解是超高压榴辉岩深熔作用的主要驱动力。蛇绿岩中MS包裹体的主量和微量元素组成主要取决于俯冲通道脱水熔融矿物学反应中所涉及的含水矿物种类。(C)2014爱思唯尔有限公司版权所有。
Multiphase solid (MS) inclusions in both garnet and omphacite were investigated for zoisite-bearing eclogite from the ultrahigh-pressure (UHP) metamorphic zone in the Sulu orogen. The results provide petrological evidence for local anatexis during exhumation of deeply subducted continental crust. There are three types of MS inclusions: (1) plagioclase + quartz, (2) plagioclase + quartz + K-feldspar, and (3) barite + plagioclase + K-feldspar +/- zoisite/epidote. The host minerals mostly exhibit radial fractures surrounding the MS inclusions. The first and second types of MS inclusions were analyzed for their bulk compositions, yielding high SiO2 and Na2O but very low FeO + MgO + TiO2 with variable K2O for the second type. Trace element analyses of representative MS inclusions yield generally very low concentrations except such large ion lithophile elements as Sr, Ba and Rb. These features suggest different origins for the three types of MS inclusions. The first type of MS inclusions would be primarily derived from dehydration melting of paragonite, whereas the second type of MS inclusions would be derived from dehydration melting of both paragonite and phengite. The third type of MS inclusion may result from the interaction between metamorphic fluid and host mineral in view of the occurrence of barite as a filling phase in the fractures of host minerals. Zoisite breakdown is also indicated by its highly cuspate shape in coexistence with quartz, providing components for growth of garnet during the exhumation. Therefore the anatexis of zoisite-bearing UHP eclogite is primarily driven by the breakdown of hydrous minerals such as phengite and paragonite. The major and trace element compositions of MS inclusions in the edogites mainly depend on the species of hydrous minerals involved in the mineralogical reactions of dehydration melting in subduction channel. (C) 2014 Elsevier B.V. All rights reserved.