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首页> 外文期刊>Contributions to Mineralogy and Petrology >Primary fluids entrapped at blueschist to eclogite transition: evidence from the Tianshan meta-subduction complex in northwestern China
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Primary fluids entrapped at blueschist to eclogite transition: evidence from the Tianshan meta-subduction complex in northwestern China

机译：蓝胶岩向榴辉岩过渡的主要流体：来自中国西北天山俯冲俯冲复合体的证据

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摘要

The Tianshan is the first locality worldwide where primary fluids at blueschist to eclogite transition have been documented. Veins containing high-pressure minerals in massive host eclogites transitional to blueschists, or eclogite boudins surrounded by blueschists, indicate that a free fluid phase was present at the time of eclogitization. The high-pressure veins are predominantly composed of omphacite fibers with minor quartz or calcite. The transition from blueschist- to eclogite-facies parageneses occurs as "dehydration" halos around these veins. Clinozoisite, paragonite, glaucophane, and omphacite inclusions preserved in garnet porphyroblasts in wall eclogites document the transformation of blueschist to eclogite. C-axis-parallel, non-planar populations of fluid inclusions were trapped during the growth of omphacite in high-pressure veins and dehydrated wall rocks. Low salinity H2O + NaCl ± solid-bearing inclusions are preserved in omphacite fibers in veins and matrix omphacite of wall rocks. None of the isochores of these low salinity aqueous fluid inclusions intersect peak eclogite-facies metamorphic conditions, suggesting that, although the textural evidence constrains the entrapment of fluid inclusions to peak metamorphic conditions, their densities must have been modified during exhumation. The fluids are interpreted to have been derived from the host blueschist as a result of dehydration reactions such as 13 Gln+5 Czo=9 Prp+26 Jd+12 Di+19 Qtz+15 H2O and Gln+Pg=Prp+3 Jd+2 Otz+2 H2O. The similarity of vein and wall rock mineral compositions, fluid inclusion characteristics and O-isotope data also favor an internal source for the fluids. The major element composition of veins indicate that Si, Na, and Ca-rich aqueous fluids were released during dehydration at a depth of 50±10 km within a Paleozoic subduction zone.
机译：天山是世界上第一个记录了从蓝胶岩向榴辉岩过渡的主要流体的地区。过渡到blueschists的块状主榴辉岩中含有高压矿物的静脉，或blueschists包围的榴辉岩buudins，表明在磁化时存在自由流体相。高压脉主要由辉石岩纤维和少量石英或方解石组成。从蓝片岩相到榴辉岩相的共生转变是围绕这些静脉的“脱水”光晕发生的。保存在墙榴石中的石榴石成岩细胞中的斜长石，方解石，葡甲藻石和绿辉石夹杂物证明了blueschist向榴辉岩的转化。在高压脉和脱水的围岩中的绿辉石生长过程中，C轴平行的非平面流体包裹体被捕获。低盐度H2 O + NaCl±含固体的夹杂物保留在围岩的脉辉石纤维和基质辉石中。这些低盐度含水流体包裹体的等渗线都没有与峰榴辉岩相变质条件相交，这表明，尽管质地证据将流体包裹体的包裹性限制在峰值变质条件下，但在尸体化石过程中必须改变其密度。流体被认为是由于脱水反应（例如13 Gln + 5 Czo = 9 Prp + 26 Jd + 12 Di + 19 Qtz + 15 H2 和Gln + Pg = Prp + 3 Jd + 2 Otz + 2 H2 O。矿脉和围岩矿物成分的相似性，流体包裹体特征和O同位素数据也有利于流体的内部来源。脉的主要元素组成表明，富含磷，钠和钙的含水流体在脱水期间在古生代俯冲带内以50±10 km的深度释放。

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    《Contributions to Mineralogy and Petrology》 |2001年第1期|1-14|共14页
  • 作者

    Jun Gao; Reiner Klemd;

  • 作者单位

    Laboratory of Lithosphere Tectonic Evolution Institute of Geology and Geophysics Chinese Academy of Sciences P.O. 9825 Beijing 100029 China;

    Mineralogisches Institut Universität Würzburg Am Hubland 97074 Würzburg Germany;

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