东昆仑拉陵高里河沟脑地区晚三叠世花岗闪长斑岩年代学、岩石地球化学及Hf同位素特征
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本文为第二次青藏高原综合科学考察研究(STEP)项目(编号:2019QZKK0702)、青海省系列地质图件数据处理与洋板块地质研究(编号:DD20- 029)和青海省地质矿产勘查开发局项目(编号:青地矿科\[2021\]61号)的成果


U- Pb age, geochemical and Hf isotopic characteristics of Late Triassic granodiorite porphyry in Gounao area of Lalinggaoli River, Eastern Kunlun Mountains
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    摘要:

    本文对东昆仑拉陵高里河沟脑花岗闪长斑岩开展详细的全岩地球化学、LA- ICP- MS锆石U- Pb年代学、锆石Hf同位素研究,确定其形成时代,并探讨其岩石成因及成岩构造背景。结果显示,花岗闪长斑岩LA- ICP- MS锆石U- Pb年龄为231. 1±1. 2 Ma,指示其侵位于晚三叠世早期。全岩K2O/Na2O值为0. 69~0. 71,Mg#值为40. 5~41. 6,里特曼指数σ为1. 90~2. 09,A/CNK=1. 01~1. 03,属弱过铝质中—高钾钙碱性岩石系列。岩石的轻重稀土元素分异明显,(La/Yb)N值为19. 54~25. 52,具弱负Eu异常(δEu为0. 96~0. 97),富集大离子亲石元素K、Rb、Ba、Th,亏损高场强元素Nb、Ta、Ti等,具有高的Sr含量(606. 0×10-6~647. 9×10-6)和Sr/Y值(60. 38~62. 99),较低的Y(9. 62×10-6~10. 66×10-6)和Yb(0. 86-6~0. 92×10-6)含量,显示Adakite(高锶低钇中酸性岩)的地球化学特征。锆石Hf同位素εHf(t)值介于-6. 93~-2. 94,地壳模式年龄(TDM2)范围为1. 45~1. 70 Ga。综合分析表明,拉陵高里河沟脑花岗闪长斑岩形成于东昆仑洋壳俯冲末期至局部碰撞的转换阶段,岩浆源于高压条件下的加厚下地壳部分熔融。

    Abstract:

    Through the study of granodiorite porphyry in Lalinggaoli River, East Kunlun, it provides an important basis for the subduction collision orogenic process of the Paleotethys Ocean, and also provides further basic data support for the next prospecting work in this area.Methods:Detailed petrogeochemistry, LA- ICP- MS zircon U- Pb geochronology and zircon Hf isotope studies of granodiorite porphyry in Gounao area of Lalinggaoli River,are carried out to determine its formation age, and discuss the petrogenesis and diagenetic tectonic setting. Results:The zircon U- Pb age of granodiorite porphyry is (231.1±1.2) Ma, which indicated that the emplacement occurred in the early Late Triassic. The K2O/Na2O values of the whole- rock were 0.69~0.71, Mg# values were 45.3~46.02, σ values were 1.90~2.09, and A/CNK 1.01~1.03, which belong to weak peraluminous medium—high potassium calc- alkaline rock series. The samples have obvious differentiation of light and heavy REE elements (La/Yb)N values of 19.54~25.52, slight negative Eu anomaly (δEu 0.96~0.97), enriched in large ion lithophile elements K, Rb, Ba, Th, and depleted high field strength elements Nb, Ta, Ti. The samples have high Sr content (606.0×10-6~647.9×10-6) and Sr/Y value (60.38~62.99), low Y (9.62×10-6~10.66×10-6) and Yb (0.8610-6~0.92×10-6), showing an adakitic geochemical characteristics. Zircon Hf isotope εHf(t) values ranged from -6.93 to -2.94, corresponding to the distribution range of crustal model age (TDM2) from 1.45 to 1.70 Ga .Conclusions:Comprehensive analyses show that granodiorite porphyry was formed in the transition setting from the subduction of Eastern Kunlun oceanic crust to local collision, and was sourced in the partial melting of thickened lower crust under high pressure.

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刘建栋,张焜,王秉璋,王春涛,李五福,张新远,曹锦山,袁锦鹏,李青,陈丽娟.2023.东昆仑拉陵高里河沟脑地区晚三叠世花岗闪长斑岩年代学、岩石地球化学及Hf同位素特征[J].地质论评,69(1):2023010019,[DOI].
LIU Jiandong, ZHANG Kun, WANG Bingzhang, WANG Chuntao, LI Wufu, ZHANG Xinyuan, CAO Jinshan, YUAN Jinpeng, LI Qing, CHEN Lijuan.2023. U- Pb age, geochemical and Hf isotopic characteristics of Late Triassic granodiorite porphyry in Gounao area of Lalinggaoli River, Eastern Kunlun Mountains[J]. Geological Review,69(1):2023010019.

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  • 收稿日期:2022-09-30
  • 最后修改日期:2023-02-03
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  • 在线发布日期: 2023-02-19
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