班怒成矿带中段雄梅地区碰撞后含铜岩浆岩类型、时代及成因  

Chronology, types and genesis of post-collisional copper bearing magmatic rocks in the Xiongmei area, the middle part of the Bangong Co-Nujiang metallogenic belt

作　　者：黎心远 曲晓明[1] 马旭东[1] 陈伟[1] 孙渺 LI Xinyuan;QU Xiaoming;MA Xudong;CHEN Wei;SUN Miao(Institute of Wiineral Resources,Chinese Academy of Geological Sciences,Beijing,100037;School of Geosciences and Resources,China University of Geosciences,Beijing,100083)

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《地质学报》2020年第4期1264-1281,共18页Acta Geologica Sinica

基　　金：西藏申扎县雄梅1∶5万矿产地质调查项目(N1604)资助的成果.

摘　　要：雄梅地区位于西藏班公湖-怒江成矿带中段申扎县,区内分布有舍索矽卡岩型铜多金属矿,雄梅斑岩型铜钼矿,以及桑日、苦嘎矽卡岩铜矿点,相应地发育多套含铜岩浆岩。本文通过系统的锆石U-Pb年龄、全岩Pb同位素及岩石地球化学分析,厘定了这些含铜岩浆岩的时代和成因类型。初步查明它们先后形成于约110Ma(舍索,雄梅,苦嘎)和80Ma(桑日)两个岩浆活动阶段。雄梅地区岩浆活动的时代及源区具有明显的后碰撞阶段特征,其中雄梅矿区的含矿花岗闪长斑岩具高铝、钙碱性特征,为由泥砂质沉积岩生成的S型花岗岩。舍索、桑日、苦嘎矿区的含矿岩体均为I型,显示原岩为火成岩。岩石地球化学表明这些含矿岩体富集大离子亲石元素(Rb、Sr、Th、Pb),亏损高场强元素(Nb、Ta、Ti),显示出俯冲沉积物组分对岩浆形成产生过重要影响。在早白垩世时期,俯冲板片断离,大量的软流圈物质上涌并参与岩浆活动,促使上地壳组分熔融,携带大量成矿元素形成含矿岩浆岩,在近地表形成雄梅、舍索及桑日矿床;晚白垩世时期,加厚的岩石圈在重力作用下拆沉,减薄的岩石圈在上涌地幔的底侵作用下发生熔融,形成桑日矿床。The Xiongmei area is located in the Shenzha County in the middle part of the Bangong Co-Nujiang metallogenic belt in Tibet comprising many different types of copper-bearing magmatic rocks. These include Shesuo skarn copper polymetallic deposits, Xiongmei porphyry copper-molybdenum deposits, Sangri karn copper deposits and Kuga skarn copper deposits. In this paper, the chronology and genetic types of these copper-bearing magmatic rocks have been determined by systematic zircon U-Pb age determinations, whole-rock Pb isotope, and petrogeochemical analysis. Preliminary data indicates that they were formed in successive magmatic stages dated to ~110 Ma(Shesuo, Xiongmei, Kuga) and 80 Ma(Sangri). The ore-bearing granodiorite porphyry in the Xiongmei mining area is an S-type granite formed from argillaceous sedimentary rocks with high aluminium and calc-alkaline characteristics. The ore-bearing rocks in the Shesuo, Sangri and Kuga mining areas are I-type, indicating that the original rocks were igneous. Geochemical analyses shows that these ore-bearing rocks are rich in large ion lithophile elements(Rb, Sr, Th, Pb) and depleted in high field strength elements(Nb, Ta, Ti), indicating that the subducted sediment components have had an important influence on magma formation. During the early Cretaceous, the subducted plate fragments broke off, a large number of asthenospheric material upwelled and participated in magmatic activities. This triggered the melting of upper crustal components and formed ore-bearing magmatic rocks with a large number of ore-forming elements, forming Xiongmei, Shesuo and Sangri deposits near the surface. During the late Cretaceous, the thickened lithosphere was dismantled and subsided under the action of gravity. The thin lithosphere melted under the underthrust of the upwelling mantle, forming the Sangri deposits.

关 键 词：雄梅地区含铜岩浆岩 锆石U-PB定年 岩石地球化学 PB同位素 碰撞后阶段 

分 类 号：P588.11[天文地球—岩石学] P612[天文地球—地质学]