甘肃北山大山头-黑山一带基性超基性岩成矿条件与找矿前景

甘肃北山大山头—黑山一带位于塔里木板块北缘北山裂谷带,区内与基性超基性岩有关的铜镍矿化较为普遍,含矿岩体多受庙庙井-西双鹰山及其次级断裂控制,成岩时代集中在358~397Ma,岩体的形成和演化与裂谷作用密切相关.区内与铜镍矿化有关的基性-超基性岩体规模较小,多期侵位且分异较好,具高Mg、低碱、低Ca和低Ti的特征,含矿岩相具有较高的Mg#,稀土元素配分形式较为平坦,LREE略富集,大离子亲石元素(Rb、Ba、Sr、U)相对富集,高场强元素(Nb、Zr、Hf)相对亏损.矿化岩体发育强度不高,但规模较大的Cu、Ni成矿元素异常,并有套合较好的磁、电异常.通过对区内已知及新发现的几处铜镍矿化基性-超基性岩体地质特征、岩石学特征及岩石地球化学特征等进行研究,结合近年来的地质找矿实践,认为该地区与铁质基性-超基性岩有关的铜镍成矿条件较好,具有进一步寻找岩浆型铜镍硫化物矿床的前景.

Metallogenic Conditions and Prospecting Potential of Mafic-ultramafic Rocks along Dashantou-Heishan Area in Beishan,Gansu Province

The Dahantou-Heishan area is located in northern margin of the Tarim plate, where mafic-ultramafic rocks related to mineralization are more widespread. The ore-bearing rock is more controlled by Miaomiaojing-Xishuangyingshan fracture and secondary faults, with the diagenetic age concentrated in the age of 358~397Ma. The formation and evolution of these rocks is closely related rifting. In this area, the copper-nickel mineralized mafic-ultramafic rock is small in scale, with multi-stage emplacement and good differentiation, as well as the features of high magnesium, low alkali, low calcium and low titanium. The ore-bearing facies have high Mg# values, and their REEs show relatively flat features in distribution patterns, with the slight enrichment of LREE, relative enrichment of LILE (Rb,Ba,Sr,U) and relative depletion of high field strength elements (Nb,Zr,Hf). The development degree of mineralized rock strength is not high, but large-scale copper and nickel mineralization anomalies are well developed, which can fit the magnetic and electrical abnormalities well. After carrying out the research on geological characteristics, petrological characteristics and rock geochemistry of several copper-nickel mineralized mafic-ultramafic rocks, and combining with the geological prospecting practices in recent years, it's considered that the ore-forming conditions for copper-nickel mineralization associated with ferruginous mafic-ultramafic rocks are very well, which has a potential to further search for copper-nickel magmatic deposits.