巴基斯坦达什特卡恩斑岩型铜矿地质特征及找矿潜力

Geological Features and Prospecting Potential of the Dashet-e-Kain Porphyry Copper Deposit in Pakistan

达什特卡恩斑岩型铜矿位于巴基斯坦查盖斑岩型铜矿带北端的阿富汗-巴基斯坦边境上,迄今为止,矿区内已发现有两个规模很大的铜矿化体。笔者在以往勘查资料和野外地质找矿工作的基础上,对成矿地质背景、矿床地质特征、矿床地球化学和地球物理特征及找矿潜力进行了初步分析。矿区出露东西两个矿化体,主要与两个英云闪长斑岩岩株以及一个侵入角砾岩管有关;斑岩体中蚀变以钾化和绢英岩化为主,泥化较弱,青磐岩化分布在蚀变带最外围。氧化矿石矿物以孔雀石和硅孔雀石为主,次生矿石矿物以辉铜矿和铜蓝为主,原生矿石矿物以黄铜矿和斑铜矿为主。1∶1万土壤地球化学测量显示西部矿化体铜元素异常面积约0.45 km2,平均值482.97×10-6,东部角砾岩矿化体异常面积约0.32 km2,平均值2238×10-6,矿区钼含量平均值为21×10-6,经调查铜异常为矿致异常。激发极化法测量显示西部异常范围小,电阻率很低,在45~90 m范围内可能是含硫化物所致,而东部异常范围大,电阻率低,经查证与热液侵入角砾岩管有关。在西部矿化体施工了3个钻孔进行异常查证,结果显示铜平均含量0.079%~0.28%。经分析研究认为,在达什特卡恩深部具有良好的找矿前景。

The Dashet-e-Kain porphyry copper deposit is located in the famous Pakistan Chagai porphyry copper belt in the northern border between Pakistan and Afghanistan. So far,two large copper orebodies have been founded in this place. Based on the collection of previous exploration data and field geological prospecting results,we have made a preliminary analysis about metallogenic geological background,geological,geochemical and geophysical characteristics and prospecting potential of this deposit. The results show that there are two orebodies exposed in the west and east of the district,which are mainly related with two tonalitic porphyry stocks as well as an intrusive breccia pipe. Potassic and phyllic alteration spreads in the porphyry. The argillic alteration zone poorly developed and porpylitic alteration is distributed in the outermost of the alteration zone. Oxidation ore minerals are primarily malachite and chrysocolla,secondary sulfide ore minerals are chalcocite and covellite. Primary sulfide ore minerals are chalcopyrite and bornite. The 1∶ 10000 soil geochemical survey reveals that the copper anomaly area of the western orebody is about 0. 45 km2 with average value of 482. 97 × 10-6,and the anomaly area of the eastern breccia orebody is about 0. 32 km2 with average value of 2238 × 10-6. Molybdenum content is very low with an average value of 21 ×10-6. Induced polarization shows that the western anomaly area is small with very low resistivity in the range of 45 ~ 90 m,which may be caused by containing sulfide. While the eastern anomaly area is large with low resistivity. After verification,it is related with hydrothermal intrusive breccia. In the western orebody,3 drill holes have been completed,which show that copper average grade is 0. 079% ~ 0. 28%. It is concluded that there is a good prospecting potential in the subsurface of this area.