武家沟铜(金)矿成矿预测及远景分析

Metallogenetic targets and prospect analyses of the Wujiagou copper-gold deposit,Shanxi province

武家沟一带成矿地质条件优越,附近已探明不少铜金矿床,但矿床系列中尚缺少受剪切构造带控制的层状矽卡岩型铜(金)矿床类型。使用地球化学、地球物理方法,预测和勘查半隐伏—隐伏铜(金)矿床,是今后地质找矿的必由之路。武家沟矿区出露地层为太古界涑水群和元古界中条群,主要由一套片麻岩、花岗岩和大理岩组成;由3条近EW向韧性剪切带和一组近SN向压(扭)向断裂组成的扭动剪切构造体系,控制了区内岩浆岩的就位和热液矿产的分布;武家沟闪长(斑)岩体呈长条状,NE向展布,倾向SE。铜金矿化体赋存于余元下组不纯大理岩中,属Ⅲ号剪切带控制,呈NE向展布,与多金属矿化矽卡岩带展布方向基本一致。铜(金)矿化体呈浸染状、细脉状、细脉-浸染状等分布于矽卡岩中或其内侧。激电异常规模大,强度高,梯度清晰,中心明显,覆盖了整个金属矿化矽卡岩带,激电测深证明激发极化体总体向西南侧伏,与地质测量结果相一致。地球化学异常亦是东北段出现强大Cu异常,而西南段仅出现矿上元素异常,与地质物探成果完全吻合。可以有根据的预测,武家沟是一个具有相当规模的隐伏铜(金)矿床。

Certain known Cu-Au deposits around Wujiagou show an advantageous geological setting for metallogenesis in this area. Yet the ore fields lack the layered skarn type of Cu-Au deposits controlled by the shearing-zones. It is thus significant to target this type of mineral deposits that are not exposed or at depth through geochemical and geophysical methodologies. The exposed strata in the Wujiagou ore filed belong to the Sushui Group of Archaean age and the Zhongtiao Group of Proterozoic age, consisting mainly of gneisses, granitoids and marbles. The occurrence of granitoids and mineral deposits is primarily controlled by three EW-orientated ductile-shearing zones and one NS-striking compressing-shearing fault belt. The Wujiagou diorite porphyries, shaped as a strip, extend in NE and dip toward SE. The NE-striking Cu-Au metallogenetic belt is hosted by the impure marbles of the Yuyuanxia Formation and controlled by shearing zone III, according with the occurrence of the poly-metallic mineralization skarn zone. Cu-Au mineralization disseminated or as veinlets is distributed in skarns. Polarization anomalies of the mineralized skarn are in large scale and manifest high intensity and the apparent gradient and center, suggesting that the polarized bodies generally plunge toward SW. This corresponds to the fact that intense Cu anomalies mark the NE part of the geochemical anomalies, whereas the SW part is only identified by related halo elements. Consequently, there is a large scale of Cu-Au deposit at depth in Wujiagou.