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首页> 外文期刊>Geology >Why is lawsonite eclogite so rare? Metamorphism and preservation of lawsonite eclogite, Sivrihisar, Turkey
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Why is lawsonite eclogite so rare? Metamorphism and preservation of lawsonite eclogite, Sivrihisar, Turkey

机译：钙钠榴石榴辉岩为何如此稀有？土耳其Sivrihisar的钙钠榴石榴辉岩的变质和保存

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摘要

A rare occurrence of lawsonite eclogite crops out in a belt of high-pressure rocks in the Sivrihisar Massif, Turkey. Although lawsonite eclogite is predicted to be common at depths of 45–300 km in subduction zones, lawsonite seldom survives exhumation. In the Sivrihisar Massif, lawsonite eclogite occurs as 5-cm-long to 3.5-m-long pods in lawsonite blueschist and blueschist facies quartzite and marble. We have identified >70 eclogite pods within an 14 km2 area; most of them are lawsonite bearing. Phase diagrams calculated for Sivrihisar eclogite bulk compositions indicate metamorphic conditions of 21– 24 kbar, 422–580 °C. High-pressure minerals (omphacite, lawsonite) are synkinematic with respect to the main fabric, and therefore preserve chemical and structural features of high-pressure subduction metamorphism. The presence of both pristine and retrogressed lawsonite eclogite within meters of each other suggests that lawsonite eclogite preservation is related to rapid exhumation and other factors. For example, the effects of exhumation-related deformation ± fluid infiltration may locally overprint some rocks, producing clinozoisite and/or epidote, whereas rocks that escape these effects retain primary lawsonite.
机译：在土耳其的西夫里希萨尔地块，高压岩带 中很少出现钙钠榴石榴辉岩。尽管预计 榴辉岩榴辉岩在俯冲带的45-300 km深度很普遍，但钠钙榴石很少能幸免于尸。 在西弗里希萨尔地块，钙钠榴石榴辉岩以5cm长的 到3.5m长的豆荚出现在堇青石的蓝晶岩和蓝晶岩相 石英岩和大理石中。我们在14 km 2 区域内确定了70多个榴辉岩豆荚。他们中的大多数是钙钠榴石。 Sivrihisar榴辉岩块状组成的 图 表示21–24 kbar，422–580 ℃的变质条件。高压矿物质（方英石，钙钠榴石）相对于主要织物具有运动学意义，因此保留了化学性质和高压俯冲变质作用的结构特征。 < / sup>原始的和渐进的钙钠榴石 彼此之间的距离都在数米之内，这表明钙钛矿榴辉石 的保存与快速发掘和其他因素有关。 例如，与发掘相关的变形± 流体渗透的影响可能会局部覆盖某些岩石，从而产生 斜长岩和/或附子，而逃逸这些岩石的岩石 效果保留主要的钙钠榴石。

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    《Geology》 |2006年第6期|473-476|共4页
  • 作者

    Donna L. Whitney; Peter B. Davis;

  • 作者单位

    Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA;

    Department of Geology and Geophysics, University of Minnesota, Minneapolis, Minnesota 55455, USA;

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