Separate episodes of eclogite and blueschist facies metamorphism in the Aegean metamorphic core complex of Ios, Cyclades, Greece
Separate episodes of eclogite and blueschist facies metamorphism in the Aegean metamorphic core complex of Ios, Cyclades, Greece
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希腊基克拉泽斯岛爱琴海变质核杂岩中榴辉岩和蓝片岩相变质作用的单独事件
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发表时间：
1999
期刊：
影响因子：
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通讯作者：
Gordon Lister
中科院分区：
文献类型：
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作者：
M. Forster;Gordon Lister
希腊爱琴海基克拉迪群岛蓝片岩和榴辉岩同时出露。它们的共存已被解释为不同岩性之间的成分变化和过渡榴辉岩蓝片岩相条件下的单一变质幕已被提出。然而，在一个保存异常完好的榴辉岩石香肠的织物和显微结构的详细研究揭示了几个不同的矿物生长事件的不同序列，所有的高压变质作用的条件下。最早的变质矿物共生确认是蓝片岩相，蓝闪石轴承组合。随后发生了榴辉岩相变质作用，在此认为这种变质作用遍及整个岩体。这一时期的变质矿物生长被广泛的蓝片岩相退积所覆盖，早期形成（榴辉岩相）组合的水化±交代作用。这些水化反应导致了蓝片岩相（公元前）中一段时期的变斑矿物生长。40 Ma），使早期形成的榴辉岩相组合基本消失。绿辉石+石榴子石组合残留的榴辉岩相事件只保留在核心的基性岩香肠，因为流体是无法穿透它们。早期蓝片岩组合的证据现在仅作为包体保存在石香肠核心的榴辉岩石榴石中。这种变质矿物生长模式可能具有重要的构造意义，因为它与爱琴海地区高压变质带的变质演化模式一致。
Abstract Blueschists and eclogites outcrop together throughout the Cyclades, Aegean Sea, Greece. Their coexistence has been explained by compositional variation between different lithologies and a single metamorphic episode under transitional eclogite—blueschist facies conditions has been proposed. However, a detailed study of the fabrics and microstructures in an exceptionally well-preserved eclogite boudin reveals a distinct sequence of several different mineral growth events, all under conditions of high-pressure metamorphism. The earliest metamorphic mineral paragenesis recognized is a blueschist facies, glaucophane-bearing assemblage. Eclogite facies metamorphism followed, which is suggested here as being pervasive throughout the rock mass. This period of metamorphic mineral growth was overprinted by widespread blueschist facies retrogression, with hydration ± metasomatism of earlier formed (eclogite facies) assemblages. These hydration reactions were responsible for a period of porphyroblastic mineral growth in the blueschist facies (prior to c. 40 Ma) which largely obliterated the earlier formed eclogite facies assemblages. Omphacite + garnet assemblages relict from the eclogite facies event are preserved only within the cores of the mafic boudins because fluid was not able to penetrate them. Evidence for the early blueschist assemblage is now preserved only as inclusions within the eclogitic garnets in the core of the boudin. This pattern of metamorphic mineral growth may have significant tectonic implications, as it is consistent with the pattern of metamorphic evolution across the high-pressure metamorphic belt of the Aegean region.