青海省巴硬格莉沟地区花岗岩的地质特征及其成矿意义

青海省中部巴硬格莉沟地区的成矿作用受北西向的哇洪山—温泉构造岩浆岩带控制。区内广泛出露的印支燕山期花岗岩以及在断裂带附近矿化异常的地质特征表明 :印支—燕山期构造岩浆活动是巴硬格莉沟地区Cu、Pb、Zn、Ag等多金属矿成矿的主导因素 ,在哇洪山—温泉构造岩浆岩带 ,NS向、EW向的复合构造控制了本区内矿体和矿脉的展布。对区内花岗岩的地球化学特征研究表明 ,巴硬格莉沟地区中酸性岩类属于改造型的花岗岩类 ,花岗岩的K -Ar同位素年龄为印支期 ,且与矿石的Pb同位素年龄相近 ,说明巴硬格莉沟成矿时期与成岩年龄接近 ;并且推测成矿元素与花岗岩应来自同一源区。局部破碎变质带内花岗岩类中Cu、Pb、Zn成矿元素含量的相关性说明多金属成矿元素来自同一围岩 ,总体显示成矿不但严格受构造控制 ,而且成矿后期改造对它的叠加作用也十分显著。巴硬格莉沟地区加里东期以后的构造岩浆活动主要聚集了以碱质中酸性岩为主的花岗岩类 ,致使Cu、Pb、Zn、Ag为主的成矿元素分异并且重新富集。在北西向碱质酸性岩石系列附近遗留了规模大且同方向展布的断裂系列 ,在不同的构造部位多处出现成矿异常分别显示该区可能存在隐伏矿体。

THE GEOLOGICAL FEATURE AND METALLOGENIC SIGNIFICANCE OF GRANITE IN THE BAYINGGELIGOU AREA, QINGHAI PROVINCE

The Bayinggeligou area is located in the central Qinghai Province.Its mineralization is controlled by the Wahongshan-Wenquan NW structural magmatic belt.The extensive outcrops of Indosinian and Yanshanian granites and the mineralization anomalies near the fault belt indicate that the Indosinian structural magmatic movement is a dominant factor which affects the mineralizations of Cu, Pb, Zn and Ag in the Ba-yinggeligou area. The NS, EW complex structures controlled by the Wahongshan structural magmatic belt control the occurrences of ore bodies and lodes. The paper explains mineralizations of granites in the Ba-yinggeligou area by researching the geochemical feature. In the Bayinggeligou area, the geochemical feature indicates the neutral-acidic rocks belong to reformation type of granites. K-Ar isotopic age of the granite is of Indo-Chinese epoch that closes to Pb isotopic age of the ores. This indicates that mineralization epoch in the Bayinggeligou area is close to the diagenetic epoch. Pb isotope compositions of the ores are nearly the same as that of the granites, so it can be inferred that ore-forming elements and granite may come from the same source. The relevance among Cu, Pb and Zn in the granites in local fractured metamorphic belts shows that polymetallic ore-forming elements come from the same wall rock. Mineralization is not only severely controlled by structures but also obviously affected by later superimposition and reformation. To sum up, tectono-magmatic movement of Post-Caledonian age in the Bayinggeligou area accumulated alkaline acidic granitics, which caused Cu,Pb,Zn and Ag differentiation and reenrichment. Gigantic faults that extend in the same direction in the vicinity of NW alkaline acidite series and mineralization anomaly in different tectonic places reveal that there may be concealed ore bodies in this region.