Early Cambrian high pressure/low temperature metamorphism in the southeastern Tarim craton in response to circum-Gondwana cold subduction
Early Cambrian high pressure/low temperature metamorphism in the southeastern Tarim craton in response to circum-Gondwana cold subduction
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DOI：
10.1016/j.gsf.2023.101561
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发表时间：
2023-02
影响因子：
8.9
通讯作者：
Qian Liu;T. Tsunogae;Guochun Zhao;Sam Uthup;Kazuki Takahashi;Jinlong Yao;Yu Wu;Yigui Han
中科院分区：
文献类型：
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作者：
Qian Liu;T. Tsunogae;Guochun Zhao;Sam Uthup;Kazuki Takahashi;Jinlong Yao;Yu Wu;Yigui Han
早寒武世引发的环冈瓦纳俯冲被认为反映了现代板块构造的建立。目前构造体系中表明冷俯冲作用的低温压（T/P）比的变质岩尚未得到很好的研究。为了更好地了解环冈瓦纳俯冲作用并检验其与现代板块构造出现的可能联系，本研究重点关注塔里木克拉通东南部阿尔金塔格的蓝片岩相变质岩。矿物组合和化学、相平衡模型和石榴石中石英拉曼弹性地压测量表明，阿尔金北部的黝帘石蓝片岩和含蓝闪石 (Gln) 的石英片岩在 520–545 °C 和 16–19 kbar 下变质为硬钠石和绿帘石蓝片岩相。它反映了高压 (HP)/低温 (LT) 变质作用，低 T/Pratios <300 °C/GPa，热梯度 <10 °C/km。这些蓝片岩相变质岩在折返过程中在 <495 °C 和 <9.6 kbar 的 P-T 条件下经历了快速减压。 Ar-Ar 地质年代学记录了黝帘石蓝片岩样本的钠长岩 Ar-Ar 平台年龄为 520-506 Ma，而含 Gln 石英片岩样本的多硅白云母 Ar-Ar 平台年龄为 522-516 Ma，这表明 HP/LT 变质作用峰值发生在约 100 年前。第522章根据新的结果和来自主要冈瓦纳地块的现有数据，有人认为在冈瓦纳合并后的早寒武世，冷俯冲作用沿着环冈瓦纳深度运行。广泛的环冈瓦纳俯冲代表了地球历史上与现代板块构造的建立相关的最早的全球冷俯冲，正如所研究的早期寒武纪蓝片岩相变质岩所直接记录的那样，以及自早古生代以来平均T/Pof变质作用的急剧下降。
The circum-Gondwana subduction initiated by the early Cambrian has been suggested to reflect the establishment of the modern plate tectonics. The metamorphic rocks with low thermobaric (T/P) ratios indicative of cold subduction in the present tectonic regime have not been well investigated. To better understand the circum-Gondwana subduction and to test its possible link with the emergence of the modern plate tectonics, this study focused on blueschist-facies metamorphic rocks in the Altyn Tagh of the southeastern Tarim craton. Mineral assemblage and chemistry, phase equilibrium modelling, and quartz-in-garnet Raman elastic geobarometry reveal that the zoisite blueschist and glaucophane (Gln)-bearing quartz schist in northern Altyn Tagh were metamorphosed to lawsonite to epidote blueschist-facies at 520–545 °C and 16–19 kbar. It reflects high-pressure (HP)/low temperature (LT) metamorphism with lowT/Pratios of <300 °C/GPa and thermal gradients of <10 °C/km. These blueschist-facies metamorphic rocks underwent rapid decompression starting atP-Tconditions of <495 °C and <9.6 kbar during exhumation. Ar-Ar geochronology records paragonite Ar-Ar plateau ages of 520–506 Ma for the zoisite blueschist samples and phengite Ar-Ar plateau ages of 522–516 Ma for the Gln-bearing quartz schist samples, suggesting that the peak HP/LT metamorphism occurred prior to ca. 522 Ma. Based on new results and available data from the major Gondwana blocks, cold subduction was suggested to profoundly operate along circum-Gondwana in the early Cambrian after the amalgamation of Gondwana. The extensive circum-Gondwana subduction represents the earliest global cold subduction in Earth’s history associated with the establishment of the modern plate tectonics, as directly recorded by the studied early Cambrian blueschist-facies metamorphic rocks and a dramatic drop in the meanT/Pof metamorphism since the early Paleozoic.