柴达木西北缘古生代镁铁-超镁铁质岩体Cu-Ni成矿条件与找矿潜力分析  

Analysis on the Prospecting Potentiality and Cu-Ni Metallogenic Conditions of the Paleozoic Mafic-ultramafic in the Northwestern Margin of Qaidam Basin

作　　者：钱兵[1] 张照伟[1] 刘会文 邵继 王亚磊[1] 

机构地区：[1]国土资源部岩浆作用成矿与找矿重点实验室,陕西西安710054 [2]青海省核工业地质局,青海西宁810008

出　　处：《西北地质》2017年第1期35-49,共15页Northwestern Geology

基　　金：国土资源部公益性行业科研专项"拉陵灶火镍成矿赋矿机理及勘查技术研究示范"(201511020);国家自然科学基金青年基金"西昆仑赞坎条带状铁矿中高品位磁铁矿形成机制研究"(41603050)和"新疆东天山白鑫滩铜镍硫化物矿床岩石成因及成矿机制研究"(41602094);中国地质调查局"东昆仑铜镍多金属资源基地调查"二级项目(DD20160013)

摘　　要：柴达木盆地西北缘古生代镁铁-超镁铁质岩体侵位于古元古代金水口群变质岩系中,呈北东向带状分布,从西向东依次为牛鼻子梁、大通沟南山、青新界山西、柴达木大门口等。岩体多呈透镜状、脉状,岩石类型主要为橄榄辉石岩、二辉岩和辉长岩,岩体从核心到边缘依次出现橄榄岩→辉石岩→辉长岩的岩相分带特征。在岩体内已发现的镍铜矿化与橄榄岩和辉石岩关系密切。锆石U-Pb年代学及地质构造背景研究表明,大通沟南山岩体和柴达木大门口岩体形成于早古生代(458.3Ma、453Ma),可能为洋壳俯冲作用的产物。而牛鼻子梁岩体形成于晚古生代(402Ma),形成于区内构造演化过程中的碰撞造山晚期至造山后的张性环境。通过岩体野外特征、岩石学及地球化学综合研究,表明区内岩体在形成过程中发生了一定程度的结晶分异作用和地壳混染作用,显示出良好的镍铜矿形成条件。区内镁铁-超镁铁质岩石MgO含量为8.39%~31.15%,属含铜镍中等镁铁质岩石;m/f值介于2.0~4.6,平均值为3.8,属于铁质超基性岩类;Na_2O/K_2O平均值为2.4,这些含矿性指标均显示岩体具有良好的镍铜成矿条件。The Paleozoic mafic-ultramafic rocks, located in the northwestern margin of the Qaidam Basin, were emplaced in the Paleoproterozoic Jinshuikou Group , which spread in the north-east-ern direction with zonal distribution. From west to east, these rocks can be divided into Niubizil-iang intrusion, Datonggounanshan intrusion, Qingxinjieshan intrusion, and Qaidam Gate intru-sion. These mafic-ultramafic rock bodies are mainly occurred as vein and lenticular, with many rock types, such as , olivine pyroxenolite, websterite and gabbro. From the core to its edge , this complex is composed of peridotite, pyroxenite and gabbro. The mineralization of nickel and cop-per is closely related to peridotite and pyroxenite. Zircon U - Pb geochronology and geological background research show that Datonggounanshan intrusion and Qaidam Gate inrusionare proba-bly related to the subduction of oceanic crust in the Early Paleozoic （458. 3 Ma and 453 Ma ） , while the Niubiziliang intrusion was formed the Late Paleozoic period （402 Ma ） under the setting of from the late stage of the collisional orogenic to the post-orogenic extension. The comprehen -sive studies of the field observations, petrology and geochemistry show that the crystallization differentiation and crustal contamination were occurred in the magma chamber , implying that these intrusions have good potential of forming the copper and nickel ore. The MgO contents of the intrusions vary from 8. 39 % to 31. 15 % , their M/F ratios range from 2. 0 to 4. 6 , with an av-erage of 3.8, indicating that these intrusions belong to the ferruginous ultrabasic rocks. The av-erage value of K2O/ Na2O is 2. 4. The above data shows that the ultramafic rocks have good con-dition for the mineralization of nickel and copper.

关 键 词：找矿潜力 成矿条件 铜镍矿 古生代镁铁-超镁铁质岩体 柴达木盆地西北缘 

分 类 号：P618.41[天文地球—矿床学] P618.63[天文地球—地质学]