Zircon U-Pb geochronology, geochemical and Sr-Nd-Hf isotopic compositions of the Triassic granite and diorite dikes from the Wulonggou mining area in the Eastern Kunlun Orogen, NW China: Petrogenesis and tectonic implications
Zircon U-Pb geochronology, geochemical and Sr-Nd-Hf isotopic compositions of the Triassic granite and diorite dikes from the Wulonggou mining area in the Eastern Kunlun Orogen, NW China: Petrogenesis and tectonic implications
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DOI：
10.1016/j.lithos.2014.07.015
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发表时间：
2014-09
期刊：
影响因子：
3.5
通讯作者：
Q. Ding;Shaoyong Jiang;F. Sun
中科院分区：
文献类型：
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作者：
Q. Ding;Shaoyong Jiang;F. Sun
五龙沟矿区位于中国西北部的东昆仑造山带，以广泛的花岗岩岩浆作用、韧性断层、矽卡岩型铜铅锌矿化和造山金矿化为特征。八路沟花岗岩脉位于五龙沟东北部，发育矽卡岩型铜铅锌矿化；黄龙沟闪长岩脉位于该区中部，为黄龙沟金矿脉切割而成。这项研究调查了这些岩石的主量元素和微量元素成分、锆石 U-Pb 年代和 Sr-Nd-Hf 同位素成分。三个巴鲁沟花岗岩岩脉样本得出的平均锆石 U-Pb 年龄约为 244 Ma（安尼阶），两个黄龙沟闪长岩岩脉样本得出的平均锆石 U-Pb 年龄约为 215 Ma（诺里阶）。因此，五龙沟地区的矽卡岩型矿化形成于安尼世早期（~244 Ma），造山金矿化形成于215 Ma之后。安尼西亚巴鲁沟花岗岩岩脉为准铝质至微过铝质，碱含量高，为 7.19-9.57 wt.%，Zr + Nb + Ce + Y 含量高，Fe2O3T/MgO 比值高，Rb/Nb 和 Y/Nb 比值高，表明亲和力为 A 型。诺里安黄龙沟闪长岩岩脉为准铝质岩脉，Al2O3 含量较高（15.61–16.40 wt.%），Mg# 值较高（0.49–0.54），Sr 含量相对较高（370–507 ppm），Sr/Y 比值较高，(La/Yb)N 比值较高，HREE 和 Y 含量较低，表明其为类埃达克岩。 高镁闪长岩。安尼西亚花岗岩脉的初始 87Sr/86Sr (ISr) 比率为 0.707289 至 0.708981，εNd(t) 值为 - 3.6 至 - 3.1，锆石 εHf(t) 值为 - 3.9 至 + 1.3。诺里安闪长岩岩脉的初始 87Sr/86Sr (ISr) 比率为 0.709166 至 0.709529，εNd(t) 值为 - 5.7 至 - 5.1，锆石 εHf(t) 值为 - 4.9 至 - 1.0。 Sr-Nd-Hf同位素数据表明，安尼西亚花岗岩脉很可能源自中元古代镁铁质下地壳的部分熔融，而诺里亚闪长岩脉很可能源自地幔橄榄岩的部分熔融，而地幔橄榄岩是通过添加中元古代俯冲沉积物衍生的熔体而交代的。我们认为，阿尼西斯花岗岩岩脉是在原特提斯洋板块闭合后的碰撞后环境中就位的，俯冲环境与古特提斯洋板块向北俯冲有关，而诺里安闪长岩岩脉是在古特提斯洋板块俯冲期间就位的。
The Wulonggou mining area in the Eastern Kunlun Orogen of NW China is characterized by extensive granitoid magmatism, ductile faulting, and skarn-type Cu–Pb–Zn and orogenic gold mineralizations. The Balugou granite dike, which hosts skarn-type Cu–Pb–Zn mineralizations, is located in northeast Wulonggou, whereas the Huanglonggou diorite dike, which is cut by the Huanglonggou gold veins, is located in the central part of the area. This study investigated the major and trace-element compositions, zircon U–Pb dates, and Sr–Nd–Hf isotopic compositions of these rocks. Three Balugou granite dike samples yielded an average zircon U–Pb age of ~ 244 Ma (Anisian), and two Huanglonggou diorite dike samples yielded an average zircon U–Pb age of ~ 215 Ma (Norian). Therefore, the skarn-type mineralizations in the Wulonggou area formed during the early Anisian (~ 244 Ma), and the orogenic gold mineralizations formed after 215 Ma. The Anisian Balugou granite dike is metaluminous to slightly peraluminous and has high alkali contents of 7.19–9.57 wt.%, high Zr + Nb + Ce + Y contents, high Fe2O3T/MgO ratios, and high Rb/Nb and Y/Nb ratios, which suggest an A-type affinity. The Norian Huanglonggou diorite dike is metaluminous and has high Al2O3contents (15.61–16.40 wt.%), high Mg# values (0.49–0.54), relatively high Sr contents (370–507 ppm), high Sr/Y ratios, high (La/Yb)Nratios, and low HREE and Y contents, which suggest an adakite-like high-Mg diorite. The Anisian granite dike has initial87Sr/86Sr (ISr) ratios of 0.707289 to 0.708981, εNd(t) values of − 3.6 to − 3.1, and zircon εHf(t) values of − 3.9 to + 1.3. The Norian diorite dike has initial87Sr/86Sr (ISr) ratios of 0.709166 to 0.709529, εNd(t) values of − 5.7 to − 5.1, and zircon εHf(t) values of − 4.9 to − 1.0. The Sr–Nd–Hf isotopic data suggest that the Anisian granite dike was likely derived from partial melting of dominantly Mesoproterozoic mafic lower crust, whereas the Norian diorite dike was likely derived from partial melting of mantle peridotite that was metasomatized by the addition of Mesoproterozoic subducted sediment-derived melts. We propose that the Anisian granite dike was emplaced in a post-collision environment after the closure of the Proto-Tethys in a subduction setting associated with the northward subduction of the Paleo-Tethys oceanic plate, whereas the Norian diorite dike was emplaced during the subduction of the Paleo-Tethys oceanic plate.