西藏多龙矿集区尕尔勤斑岩铜矿床年代学及地球化学——兼论硅帽的识别与可能的浅成低温热液矿床

发布时间：2018-04-29 15:53

本文选题：斑岩铜矿床 + 浅成低温热液矿床　；参考：《岩石学报》2017年02期

【摘要】：尕尔勤斑岩铜矿床是多龙超大型铜金矿集区内具有较大找矿潜力的矿床之一。本文以尕尔勤斑岩铜矿区内成矿花岗闪长斑岩及新发现的硅帽为研究对象,进行了矿床年代学、地球化学及找矿方向研究工作。尕尔勤矿床花岗闪长斑岩SiO_2含量在60.01%~62.81%之间,K_2O含量在1.86%~2.16%之间,Al_2O_3含量在15.12%~16.51%之间,属于钙碱性岩石系列。斑岩体锆石U-Pb年龄为124.4±0.4Ma(MSWD=0.42,n=25),属于早白垩世侵位;锆石εHf(t)值主要集中于1.15~9.71之间,tDMc模式年龄主要集中于559~1105Ma之间,表明岩浆岩区起源于具有幔源特征的深成熔体,而个别负εHf(t)值(-18.65,-19.75)的出现表明其受到了古老成熟地壳的轻微混染。斑岩体稀土元素显示为重稀土亏损的右倾分布型式,在原始地幔标准化图解中微量元素显示为Rb、Th、U、Sr等大离子亲石元素相对富集,而Nb、Ta、Ti、P、Zr等高场强元素相对亏损特征,体现出岛弧岩浆特有的地球化学特征,综合研究表明矿床形成与班公湖-怒江洋北向俯冲密切相关。硅帽中角砾状样品与层纹状(致密块状)样品地球化学特征具有明显区别,发育较少的层纹状硅帽样品可能为热水沉积与生物化学沉积共同作用形成的硅质岩,而大量存在的角砾状硅帽体现出明显热液充填交代成因特点,经地球化学剖面测量显示硅帽展布区域Cu、Au、Ag、Pb、Zn、As、Sb等成矿指示元素异常明显,结合高光谱矿物识别表明该区域存在浅成低温热液型矿床的巨大可能性,具有重要的勘查指示意义。
[Abstract]:Gaerqin porphyry copper deposit is one of the deposits with great prospecting potential. Based on granodiorite porphyry and newly discovered silicon cap in Galerqin porphyry copper deposit chronology geochemistry and prospecting direction are studied in this paper. The SiO_2 content of granodiorite porphyry in Gaerqin deposit is between 62.81% and 62.81%. The content of K _ 2O is between 1.86% and 2.16%. The content of Al2O3 is between 15.12% and 16.51%, which belongs to the calc-alkaline rock series. The U-Pb age of zircon in the porphyry is 124.4 卤0.4 Ma, which belongs to the early Cretaceous emplacement, and the zircon 蔚 HF t) is mainly concentrated in the range of 1.15 ~ 9.71, which indicates that the magmatic area originated from the deep melt with the characteristics of mantle source. However, the occurrence of some negative 蔚 HfT values (-18.65 ~ 19.75) indicates that they are slightly mixed by the ancient mature crust. The rare earth elements in the porphyry show a right-dip pattern of heavy REE depletion. In the primitive mantle standardization diagram, the trace elements show the relative enrichment of large ion lithophile elements, such as RbTH, UU, Sr, and so on, while the relative depletion characteristics of the high field strength elements, such as NbBU, Ta-TIAN, PI-Zr, and so on, show that the rare earth elements are relatively enriched. The geochemical characteristics of island arc magma are embodied. The comprehensive study shows that the formation of the deposit is closely related to the northward subduction of Bangong Lake-Nujiang River. The geochemical characteristics of breccia sample and laminar (dense block) sample are obviously different, and the less developed laminar siliceous cap sample may be siliceous rock formed by the interaction of hot water deposition and biochemistry deposition. However, a large number of brecciform silicon caps show obvious characteristics of hydrothermal filling metasomatism. Geochemical profile measurements show that the metallogenic indicator elements such as Cu-Au-Ag-PbPbPbPbPb-ZnAsAsSb, etc. in the distribution area of silicon cap are obviously abnormal. Combined with hyperspectral mineral identification, it is shown that there is a great possibility of epithermal hydrothermal deposits in this area, which is of great significance for exploration and indication.
【作者单位】：中国地质调查局成都地质调查中心;中国地质科学院矿产资源研究所国土资源部成矿作用与资源评价重点实验室;
【基金】：青藏专项优选项目(12120113037400) 中国地质调查局二级项目(DD20160015) 国家自然科学基金项目(41172077)联合资助
【分类号】：P618.41

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