西藏甲玛铜多金属矿床矽卡岩中辉钼矿铼-锇同位素定年及其成矿意义
Re-Os Isotopic Dating of Molybdenite in Skarn from the Jiama Copper-Polymetallic Deposit of Tibet and Its Metallogenic Significance
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摘要: 西藏甲玛铜多金属矿床中辉钼矿是主要的矿石矿物，普遍发育，产出于不同的矿石类型（角岩型、矽卡岩型、斑岩型）矿石中。辉钼矿大多分布于裂隙、节理面上和石英脉或不同岩性岩石中。矽卡岩型矿石中辉钼矿呈微细粒浸染状、团斑状、脉状等，直接分布于矽卡岩中或矽卡岩中后期的石英脉中。采集西藏甲玛铜多金属矿床矽卡岩型矿石中不同产状的辉钼矿，进行铼-锇同位素测年，得到等时线年龄为（15.34±0.10） Ma，模式年龄变化于（15.21±0.22） Ma～（15.50±0.22）Ma，说明甲玛的辉钼矿成矿年龄集中在15 Ma左右。结合前人的年代学研究成果，认为甲玛铜多金属矿成矿时代与冈底斯斑岩铜矿带斑岩铜矿的成矿年龄相近，可以否定甲玛铜多金属矿海底喷流沉积成矿成因的观点，为甲玛铜多金属矿的成矿成因和斑岩-矽卡岩型矿体的深部找矿提供了理论依据。Abstract: Different molybdenites were collected from the Jiama copper polymetallic deposit for Re-Os isotopic dating. The isochron age of (15.34±0.10) Ma, and model age of (15.21±0.22) Ma～(15.50±0.22) Ma were obtained. This results are similar to the data from the previous Re-Os dating results, which indicates that the mineralization age of molybdenites in Jiama is around 15 Ma. According to Re-Os dating results of other molybdenite from porphyry copper deposits in Gangdese belt, which is considered to have the similar mineralization age with that of the Jiama copper polymetallic deposit, it provides a reference for further study on geological genesis of the Jiama copper polymetallic deposit and a theoretical basis for deep earth prospecting of porphyry-skarn ore bodies.
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Key words:
- the /
- Jiama /
- copper /
- polymetallic
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