陈莉, 刘函, 贺娟. 滇西北休瓦促钨钼矿床两期岩浆作用的LA-ICP-MS锆石U-Pb年龄及矿床成因[J]. 地质通报, 2020, 39(6): 929-942.
    引用本文: 陈莉, 刘函, 贺娟. 滇西北休瓦促钨钼矿床两期岩浆作用的LA-ICP-MS锆石U-Pb年龄及矿床成因[J]. 地质通报, 2020, 39(6): 929-942.
    CHEN Li, LIU Han, HE Juan. LA-ICP-MS zircon U-Pb ages of the two phases of magmatism in the Xiuwacu W-Mo deposit, northwest Yunnan, and their implications for ore genesis[J]. Geological Bulletin of China, 2020, 39(6): 929-942.
    Citation: CHEN Li, LIU Han, HE Juan. LA-ICP-MS zircon U-Pb ages of the two phases of magmatism in the Xiuwacu W-Mo deposit, northwest Yunnan, and their implications for ore genesis[J]. Geological Bulletin of China, 2020, 39(6): 929-942.

    滇西北休瓦促钨钼矿床两期岩浆作用的LA-ICP-MS锆石U-Pb年龄及矿床成因

    LA-ICP-MS zircon U-Pb ages of the two phases of magmatism in the Xiuwacu W-Mo deposit, northwest Yunnan, and their implications for ore genesis

    • 摘要: 滇西北休瓦促矿区东、西部出露不同岩性的酸性侵入岩体,通过对2期岩浆作用成岩时代、地球化学特征的分析,结合前人研究成果探讨休瓦促矿床的成因。矿区东部黑云母花岗岩锆石U-Pb定年结果为214.9±1.3 Ma,西部花岗斑岩和二长花岗岩年龄分别为87.47±0.51 Ma和83.29±0.60 Ma;矿区获得的辉钼矿Re-Os年龄为82~86 Ma,与燕山晚期成岩年龄一致。地球化学特征分析显示,2期岩体表现出较一致的偏铝质-弱过铝质钾玄质系列特征,具有稀土元素右倾型配分模式,亏损高场强元素Nb、Sr、Zr、Hf,富集大离子亲石元素Rb、Th、U。Y-Nb和Yb-Ta图解表明,2期酸性侵入岩显示出了不同的构造背景,晚三叠世岩体落入同碰撞花岗岩范围,晚白垩世岩体落入板内花岗岩范围。结合矿区地质特征及前人流体包裹体,S、Pb、锆石Hf同位素研究结果,认为休瓦促钨钼矿床成矿物质主要来源于晚白垩世加厚下地壳的部分熔融,矿区断裂-裂隙系统为含矿岩浆-热液向上运移提供了通道,含矿热液温度的降低和大气降水的混合作用,使成矿物质在构造薄弱地带沉淀形成矿体。

       

      Abstract: Two phases of intrusive magmatism were developed in the Xiuwacu deposit, northwest Yunnan.This study focused on the geochronological and geochemical characteristics of these intrusive rocks so as to define the petrogenesis of the Xiuwacu deposit.The LA-ICP-MS zircon U-Pb dating results show that biotite granite from the east of Xiuwacu deposit was formed at 214.9±1.3 Ma, granite porphyry and monzogranite from the west of Xiuwacu deposit was formed at 87.47±0.51 Ma and 83.29±0.60 Ma.The results of the studies show that the molybdenite from the Xiuwacu deposit was formed at 82~86 Ma, corresponding to Late Yanshanian.The two phases of intrusions have similar geochemical characteristics, both belonging to the shoshonitic type and metaluminous to slight peraluminous series, with enrichment of LILE(Rb, Th, U)and depletion of HFSE(Nb, Sr, Zr, Hf).The Y-Nb and Yb-Ta discrimination diagrams indicate that the two phases of intrusions were formed in different tectonic environments.The Late Triassic intrusive rocks fall into the field of syn-collision granites while the Late Cretaceous intrusive rocks fall into the field of intra-plate granites.Based on comprehensive study with regional geology and acquired achievements in fluid inclusions, S and Pb isotopes as well as zircon Hf isotopes, the authors infer that the partial melting of thickened lower crust in the Late Cretaceous seems to have been the main metallogenic material source of the Xiuwacu deposit.The ore-bearing thermal fluid migrated along the fault-crack system in the Xiuwacu deposit, and then the W-Mo orebodies were formed at the favorable position along with the combined effect of both temperature decreasing and the mixing with meteoric water.

       

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