西藏唐格矽卡岩型铜多金属矿床A型花岗岩的识别及其对成岩成矿的指示
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P597;P618.41;P588.12

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中国地质调查局项目(121201004000160901-47,WKZB1911BJM300369-001)和西藏自治区专项基金项目(201904,ZXZJ2020005,54000021210200001048)联合资助。


Recongnition of A-type granite and its implication for magmatism and mineralization in Tangge skarn-type Cu-polymetallic deposit, Tibet
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    摘要:

    研究目的】唐格矽卡岩型铜多金属矿区位于南冈底斯陆缘火山-岩浆弧西段,矿区内铜多金属成矿与石英斑岩体成岩作用关系密切,但对矿区内发育的石英斑岩体研究较少,对于进一步理解矿床成因与指导找矿勘查有一定制约。【研究方法】本文首次报道了矿区内石英斑岩岩石地球化学、锆石U-Pb年龄及Hf同位素结果。【研究结果】石英斑岩表现出富硅(SiO2=73.97%~76.85%)、富铝(Al2O3=13.03%~14.06%)、高钾(K2O=2.2%~4.68%),高FeOT(0.97%~1.80%)、FeOT/MgO(3.57~8.22)、A/CNK(1.14~4.24)特征;稀土元素总量高(∑ REE=478.59×10-6~532.71×10-6)、稀土配分曲线呈明显的右倾型或“海鸥型” ;富集Rb、Th、U、K、Pb大离子亲石元素(LILE),亏损高场强元素(HFSE) Nb、Ta、Ti、P及大离子亲石元素Ba、Sr等元素; Rb含量低(69.64×10-6~249×10-6,小于270×10-6),10000Ga/Al=2.54~2.71,显示出后碰撞铝质A型花岗岩的地球化学特征。LA-ICP-MS锆石U-Pb年龄为(78.0±0.9) Ma,表明其形成时代为晚白垩世。石英斑岩中锆石的εHft)均为正值(1.5~5.3,均值3.6),显示了较均一的Hf同位素组成; Hf同位素二阶段模式年龄T2DM=1052~806 Ma,均值912 Ma (<1.0 Ga),指示岩浆主要来源于新生长英质下地壳的部分熔融。【结论】结合区域地质资料,认为唐格铝质A型花岗岩是形成于印度大陆向北俯冲于欧亚大陆引起的碰撞后伸展构造环境。唐格石英斑岩中Cu、Pb、Zn、Au背景含量较高,说明铝质A型花岗岩为唐格矽卡岩型铜多金属矿提供了一定的成矿物质。冈底斯带自东向西在69~89 Ma至少存在一次与晚白垩世岩浆作用有关的铜多金属成矿作用,其唐格矽卡岩型铜多金属矿是冈底斯带中段南部在燕山晚期造山后岩浆活动的成矿响应。

    Abstract:

    This paper is the result of mineral exploration engineering.
    [Objective] The mineralization of Tangge skarn-type Cu-polymetallic ore district, located in the western part of the Gangdese volcano-magmatic arc, is closely related to the diagenesis of quartz porphyry in the mining area. There is little research on the quartz porphyry developed in the mining area, which restricts the further understanding of the genesis of the deposit and the guidance of prospecting and exploration.[Methods] We firstly reports zircon U-Pb age and Hf isotope, and petrogeochemistry of quartz porphyry in the Tangge ore district.[Results] The quartz porphyry is characterized by high silicon (SiO2=73.97%-76.85%), aluminum (Al2O3=13.03%-14.06%), potassium (K2O=2.2%-4.68%), FeOT(0.97%-1.80%) contents, and high FeOT/MgO ratios (3.57-8.22) and A/CNK=values(1.14-4.24). The quartz porphyry have high REE (∑REE=478.59×10-6-532.71×10-6) and its chondrite-normalized REE distribution patterns diagram show obvious right-leaning or"gull"type. They are enriched in Rb, Th, U, K and Pb, depleted in Nb, Ta, Ti, P, Ba and Sr. The low contents of Rb (69.64×10-6-249.00×10-6, less than 270×10-6) and high 10000×Ga/Al ratios (2.54-2.71), indicate that the quartz poyphyry are post-collisional and aluminous A-type granite. LA-ICPMS zircon dating for quartz porphyry yields a weighted mean age of (78.0 ±0.9) Ma, suggesting that they formed in the Late Cretaceous. Their zircons have positive εHf(t) values (+1.5-+5.3, averages of +3.6), showing a relatively homogeneous Hf isotopic composition. Two-stage Hf model ages (T2DM=1052-806 Ma, averages of 912 Ma, less than 1.0 Ga), indicate that they were mainly generated by partial melting of the juvenile felsic lower crust.[Conclusions] Combined with previous research, we proposed that the Tangge quartz porphyry were formed in the post-collisional extensional tectonic environment, which was resulted from the northward subduction of the Indian contient to the Eurasian continent. Tangge quartz porphyry has relatively high background content of Cu, Pb, Zn and Au, which suggest that genetical relationship between the aluminous A-type granitic magmatism and Tangge skarn-type Cu mineralization. It is inferred that Gangdese Belt at least develops a period of Cu polymetallic mineralization related to Late Cretaceous magmatism during 69-89 Ma, however, Tangge skarn-type Cu polymetallic deposits response to magmatism in the middle segment of the Southern Gangdese Belt during late Yanshanian.

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赵亚云,刘晓峰,杨春四,张小强,刘远超,郑常云,龚福志,华康. 西藏唐格矽卡岩型铜多金属矿床A型花岗岩的识别及其对成岩成矿的指示[J]. 中国地质, 2022, 49(2): 496-517.
ZHAO Yayun, LIU Xiaofeng, YANG Chunsi, ZHANG Xiaoqiang, LIU Yuanchao, ZHENG Changyun, GONG Fuzhi, HUA Kang. Recongnition of A-type granite and its implication for magmatism and mineralization in Tangge skarn-type Cu-polymetallic deposit, Tibet[J]. Geology in China, 2022, 49(2): 496-517(in Chinese with English abstract).

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  • 收稿日期:2019-11-20
  • 最后修改日期:2022-03-08
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  • 在线发布日期: 2022-05-12
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