A common high-pressure metamorphic evolution of interlayered eclogites and metasediments from the 'ultrahigh-pressure unit' of the Tianshan metamorphic belt in China
A common high-pressure metamorphic evolution of interlayered eclogites and metasediments from the 'ultrahigh-pressure unit' of the Tianshan metamorphic belt in China
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DOI：
10.1016/j.lithos.2014.12.006
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发表时间：
2015-06
期刊：
影响因子：
3.5
通讯作者：
Ji‐Lei Li;R. Klemd;Jun Gao;Tuo Jiang;Yun-Hui Song
中科院分区：
文献类型：
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作者：
Ji‐Lei Li;R. Klemd;Jun Gao;Tuo Jiang;Yun-Hui Song
利用钻取的榴辉岩、大理岩和石英云母片岩的岩石学和矿物学资料，研究了天山（超）高压/低温变质带变质火山岩和变质沉积岩的变质演化。榴辉岩主要由不同量的石榴子石、绿辉石、石英和绿柱石组成，大理石中方解石含量大于95 vol. %石英和云母片岩，含少量方解石、方解石、钠长石和石榴石。利用石榴石等温热压法，伪截面计算榴辉岩和石英云母片岩揭示了一个共同的变质演化下HP条件下的两种岩石类型，也是一致的温度估计的大理石使用传统的测温。层间榴辉岩和石英云母片岩的统一P-T路径，以及兼容的温度数据的大理石，文件，整个岩石套件构成一个连贯的高压单元在高峰变质条件和折返。因此，榴辉岩的原岩和伴生的沉积物被认为经历了相同的变质演化。此外，对采自中国天山（U）高压/低温带北方的高压岩石的研究结果不支持最近提出的由北方“相干超高压单元”和南方“相干高压单元”组成的构造模式。
Petrological and mineralogical data of interlayered eclogite, marble and quartz–mica schist from a drill core are used to constrain the metamorphic evolution of metavolcanics and intercalated metasediments in the Tianshan (ultra-)high-pressure/low-temperature [(U)HP/LT] metamorphic belt, NW China. The eclogite mainly consists of varying amounts of garnet, omphacite, quartz and zoisite, the marble of calcite (> 95 vol.%) with minor zoisite and phengite, and the schist of quartz and mica with minor calcite, chlorite, albite and garnet. Using garnet isopleth thermobarometry, pseudosection calculations for the eclogite and quartz–mica schist reveal a common metamorphic evolution under HP condition of both rock types that is also consistent with the temperature estimates for the marble using conventional thermometry. The uniform P–T paths of the interlayered eclogite and quartz–mica schist, as well as compatible temperature data of the marble, document that the whole rock suite constitutes a coherent HP unit during peak metamorphic conditions and exhumation. Thus protoliths of eclogite and associated sediments are believed to have undergone the same metamorphic evolution. In addition, the data gained by the present study of the HP rocks, which were collected in the northern part of the Chinese Tianshan (U)HP/LT belt, do not support the recently proposed tectonic scheme that this metamorphic terrane consists of a northern “coherent UHP unit” and a southern “coherent HP unit”.