西藏雄梅铜矿区含矿斑岩与非含矿斑岩成因对比研究  

Comparative study of genesis of ore_bearing porphyry and barren porphyry in Xiongmei copper deposit,Tibet

作　　者：王佳奇[1] 曲晓明[2] 马旭东[2] 范淑芳[2] 宋扬[2] 

机构地区：[1]中国地质大学地球科学与资源学院,北京100083 [2]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,北京100037

出　　处：《矿床地质》2016年第3期437-455,共19页Mineral Deposits

基　　金：国家科技支撑计划项目(编号:2011CB403203);中国地质调查局青藏专项(编号:12120113037300)联合资助的成果

摘　　要：西藏雄梅铜矿床是近年来在班公湖_怒江成矿带中段新发现的一处斑岩铜矿床,该矿床的发现使得班公湖_怒江成矿带真正具备了"带"的概念,大大地拓宽了找矿远景。文章通过对雄梅铜矿区斑岩体的LA_ICP_MS锆石U_Pb定年,发现矿区存在2套斑岩:一套是前人测定的年龄为106.7 Ma的含矿斑岩;另一套是本文测定的非含矿斑岩,3个年龄分别是(121.8±2.3)Ma(MSWD=0.32)、(122.8±2.1)Ma(MSWD=1.16)、(121.5±2.5)Ma(MSWD=0.54)。两套斑岩的岩性虽然都是花岗闪长斑岩,但非含矿斑岩比含矿斑岩含有更多的钾长石,矿化强度大大减弱。岩石地球化学分析结果表明,两套斑岩虽然都富集大离子亲石元素(LILE)Rb、Ba、Th、U、K、Pb,亏损高场强元素(HFSE)Nb、Ta、Ti,具有碰撞后岩浆作用的共同特征,但在岩浆源区和成因上显示出明显的差异。含矿斑岩和非含矿斑岩均属于强过铝质S型花岗岩,然而前者源区组成为杂砂岩,后者源区则以泥质岩为主。岩浆分异过程中,含矿斑岩受斜长石和钾长石的分离结晶控制,非含矿斑岩则受钾长石和黑云母的分离结晶控制。The Xiongmei copper deposit is a newly-discovered porphyry copper deposit which belongs to the middle segment of the Bangong Co-Nujiang metallogenic belt. The meaning of this deposit lies in that it breaks the limi- tation of prospecting, makes this metallogenic belt own the real meaning of ore belt, and vastly broadens the promising prospecting areas. The authors found two groups of porphyries by using LA-ICP-MS zircon U-Pb dating of porphyry body in the Xiongmei copper deposit. One group of porphyry is ore-bearing porphyry and its age is （106.7 ± 0.48） Ma（MSWD = 0.92; the other group of porphyry is barren porphyry with its three age parts being （ 121.8 ± 2.3） Ma （MSWD = 0.32 ）, （ 122.8 ± 2.1 ） Ma （MSWD = 1.16）, and （ 121.5 ± 2.5 ） Ma （MSWD= 0.54）. Although the two groups of porphyries are all granodiorite-porphyry, the barren porphyries have more potassium feldspar and less intensity of mineralization than the ore-bearing porphyries. The petrogeo- chemical analysis indicates that the two groups of porphyries are enriched in large ion lithophile elements （LILE） of Rb, Ba, Th, U, K, Pb and depleted in high field strength elements （HFSE） of Nb, Ta, Ti, and show es- sential characteristics of post-collisional magmatic rocks, but there are some obvious differences in magma sources and petrogenesis. Ore-bearing porphyry and barren porphyry all belong to strongly peraluminous S-type grani- toids, but the sources of the ore-bearing porphyry are composed of greywacke and the sources of barren porphyry are based on argillaceous rock. In the magmatic differentiation process, ore-bearing porphyries are controlled by the fractional crystallization of plagioclase and potash feldspar, whereas the barren porphyries are controlled by the fractional crystallization of potash feldspar and biotite.

关 键 词：地球化学 含矿斑岩 非含矿斑岩 岩石成因 锆石U_Pb年龄 雄梅铜矿 

分 类 号：P618.41[天文地球—矿床学]