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首页> 外文期刊>International Journal of Earth Sciences >Zircon U-Pb geochronology, and elemental and Sr-Nd-Hf-O isotopic geochemistry of post-collisional rhyolite in the Chiang Khong area, NW Thailand and implications for the melting of juvenile crust
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Zircon U-Pb geochronology, and elemental and Sr-Nd-Hf-O isotopic geochemistry of post-collisional rhyolite in the Chiang Khong area, NW Thailand and implications for the melting of juvenile crust

机译：泰国西北部清孔地区碰撞后流纹岩的锆石U-Pb地质年代学，元素和Sr-Nd-Hf-O同位素地球化学及其对幼年地壳融化的影响

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摘要

Volcanic rocks are widely exposed within the Chiang Khong-Lampang-Tak igneous zone in NW Thailand. A representative rhyolite sample from the Chiang Khong area yielded a zircon U-Pb age of 230.7 +/- 1.1 Ma (n = 20, MSWD = 0.98). The Chiang Khong rhyolites are characterized by low TiO2 (0.29-0.62 wt%) and MgO (0.04-0.82 wt%) with A/CNK values of 0.95-1.06 (one outlier at 1.47), and can be classified as highly fractionated I-type rhyolites. They are enriched in LILEs and LREEs, and depleted in HFSEs. Two representative samples have Sr-87/Sr-86 (i) ratios of 0.70497 and 0.70527, and the epsilon(Nd) (t) values fall at +1.1 and +1.3, respectively. epsilon(Hf) (t) and delta O-18 in zircon are between +4.7 to +12.0 and 5.3 to 5.9 aEuro degrees, respectively. Our geochemical data suggest that the Chiang Khong rhyolites formed by partial melting of juvenile mafic lower crust in a post-collisional setting. Deep crustal anatexis was probably induced by upwelling asthenospheric mantle, shortly after slab detachment subsequent to closure of the Paleo-Tethys.
机译：在泰国西北部的清孔-南邦-德发火地区内，火山岩被广泛暴露。来自清孔地区的代表性流纹岩样品的锆石U-Pb年龄为230.7 +/- 1.1 Ma（n = 20，MSWD = 0.98）。 Chiang Khong流纹岩的特点是TiO2低（0.29-0.62 wt％）和MgO（0.04-0.82 wt％），A / CNK值为0.95-1.06（一个离群值为1.47），可以归类为高度分馏的I-类型流纹岩。它们富含LILE和LREE，而HFSE却枯竭。两个代表性样品的Sr-87 / Sr-86（i）之比为0.70497和0.70527，ε（nd）（t）值分别降至+1.1和+1.3。锆石中的epsilon（Hf）（t）和δO-18分别在+4.7至+12.0和5.3至5.9 aEuro度之间。我们的地球化学数据表明，在碰撞后的环境中，由幼稚铁质下壳的部分融化形成的Chiang Khong流纹岩。在古特提斯封闭之后，板块脱离后不久，软流圈地幔上涌引起了深层地壳的缺乏。

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