藏南扎西康矿集区深部结构与成矿:来自地球物理的证据

扎西康矿集区是近年藏南发现的最具找矿潜力的多金属矿富集区.但是由于工作条件所限,矿集区开展的地球物理工作程度不高,深部结构和地质信息不明,严重制约了矿集区成矿作用与成矿潜力等重要地质问题研究.为了查明西藏扎西康矿集区深部地质结构,探讨成矿作用的深部机制,在扎西康地区开展了重力、磁法和大地电磁等测量,利用二维小波分解重磁异常和反演的密度、电性结构模型,结合岩石物理性质和地质资料综合分析,认为错那洞片麻岩穹窿在地球物理场上具有3层结构,且下部单元(核部)以淡色花岗岩为主,向北侧延伸到扎西康矿区深部,和矿集区近南北向断裂带、其他次级断裂共同组成了扎西康叠加改造锑铅锌银多金属矿床的控岩、控矿、赋矿系统.处在高低电性块体分区的错那洞变质穹窿形成机制可能与藏南拆离系有关,而错那洞岩体深部延伸、岩浆侵位、就位过程驱动了流体循环,在其他因素参与影响下,共同作用了扎西康矿床的形成.

Deep Structure and Mineralization of Zhaxikang Ore-Concentration Area,South Tibet: Evidence from Geophysics

The Zhaxikang ore-concentration area (ZOCA) is the most abundant polymetallic ore enrichment area discovered recently in the South Tibet. However, the geophysical work carried out in the ore -concentrated areas is not sufficient due to the limited working conditions, and the deep structure and geological information are not clear, which seriously restricts the understanding of its mineralization and potential of the ore-concentrated areas and other important geological problems. In order to find out the deep geological structure and to discuss the deep mechanism of mineralization, measurements of gravity, magnetic and magnetotelluric were carried out in Zhaxikang area. By using gravity and magnetic anomalies due to two-dimensional wavelet decomposition, density and electrical structure model, and analyses of petrophysical and geological properties, it is indicated that there were 3-layers in geophysics of the Cuonadong gneiss dome. In addition, lower unit (core) mainly consisted of leucogranite, which extends north into the deep of the Zhaxikang Pb-Zn polymetallic deposit. The leucogranite combined with N-S normal faultsystem and other secondary faults made up the ore -forming system of the Zhaxikang overprinting and remobilization ore deposit. The Cuonadong gneiss dome was located in high and low zones of electrical blocks, with formation mechanism likely related with the South Tibet Detachment System (STDS). On the other hand, deep extension of Cuonadong rock and emplacement of leucogranite drove fluid circulation, and the Zhaxikang deposit was formed in combination with influence of other factors.