东昆仑夏日哈木镍成矿赋矿机理认识与找矿方向指示

Understanding of the Metallogenic Ore-Bearing Mechanism and Its Indication of Prospecting Direction in Xiarihamu Magmatic Ni Co Sulfide Deposit,East Kunlun Orogenic Belt,Northwestern China

东昆仑造山带夏日哈木超大型岩浆镍钴硫化物矿体全部赋存于Ⅰ号镁铁超镁铁质岩体内,118万t镍,23.8万t铜,4.3万t钴,是迄今为止全球造山带背景发现的规模最大的岩浆镍钴矿床。与传统的大火成岩省、大陆边缘裂谷等成矿构造背景认识明显不同,对其含矿性特点与成矿赋矿机理认识有助于揭示造山带背景岩浆镍钴硫化物矿床形成机制和成矿模式,指示进一步找矿方向和岩体含矿性评价,拓展东昆仑造山带镍钴硫化物矿床的找矿空间,实现找矿新突破。笔者通过对夏日哈木岩浆镍钴硫化物矿床的岩(矿)体地质特点、矿物学及地球化学的研究,并结合前人的区域构造背景研究成果及野外实际,发现地壳S的混染加入是导致夏日哈木镁铁超镁铁质岩浆硫化物熔离的关键因素,斜方辉石含量高的岩相更有利于赋存富矿体。提出夏日哈木超大型岩浆镍钴硫化物矿床是伴随古特提斯洋演化开始大陆裂解、镁铁超镁铁质岩浆多次脉冲叠加硫化物熔离成矿结果的认识,大断裂为地幔岩浆上侵提供了有利条件。东昆仑造山带沿昆北、昆中断裂带于夏日哈木镍钴硫化物矿床北西、南东方位发育的岩体、铁质系列的镁铁超镁铁质岩相是该区域进一步找矿的重要方向。

The Xiarihamu nickel-cobalt sulfide ore deposit in the East Kunlun orogenic belt is hosted in the No.1 mafic-ultramafic intrusion,with 1.18 million tons of Ni,238,000 tons of Cu,and 43,000 tons of Co,which is the largest magmatic nickel-cobalt deposit found in the orogenic belt to date.Its geological background is obviously different from the large igneous province and the continental marginal rifts.The profound analysis of Xiarihamu is helpful to reveal the formation mechanism and metallogeny of the magmatic nickel-cobalt sulfide deposits in the orogenic belt,to provide instructions for the prospecting direction,and to expand the prospecting space of nickel-cobalt sulfide deposits in the East Kunlun orogenic belt.Through the research work of geological characteristics,mineralogy,and geochemistry of the Xiarihamu magmatic nickel-cobalt sulfide deposit and in combination with previous research results and practice of regional tectonic background,we found that the crustal sulfur contamination is the key factor for the sulfide saturation.The lithofacies with a high content of orthopyroxene are very favorable for the occurrence of rich ore bodies.we proposed that the Xiarihamu giant magmatic nickel-cobalt sulfide deposit is the result of the continental break-up related to the Paleo-Tethys ocean evolution.The regional fault provided channels for the mantle-derived magma.The ferruginous mafic-ultramafic intrusions along the Northern Kunlun Fault and the Central Kunlun Fault to the northwest and southeast of the Xiarihamu nickel-cobalt sulfide deposit have the potential to be the magmatic Ni Co deposits.