引用本文：陈柏林.2019.东昆仑五龙沟金矿田地质特征与成矿地质体厘定[J].地质学报,93(1):179-196. CHEN Bailin.2019.Geological characteristics of the Wulonggou gold ore field and determination of metallogenic geological bodies in East Kunlun Mountains[J].Acta Geologica Sinica,93(1):179-196.
Geological characteristics of the Wulonggou gold ore field and determination of metallogenic geological bodies in East Kunlun Mountains
Institute of Geomechanics, Chinese Academy of Geological Sciences, Beijing, 100081
Abstract:The Wulonggou gold ore field is located in the middle part of East Kunlun orogenic belt, which hosts several gold deposits occurring mainly along three NWW- trending fault fracture zones, i.e. Yanjingou, Yinshigou- Hongqigou and Sandaoliang- Kushuiquan zones. Comprehensive analysis of the geological characteristics indicates that gold deposits are low- middle temperature hydrothermal in genesis and mineralization type is altered rocks in structural fracture zones. Gold mineralization occurred at about 195~319℃ of temperature, mineralization material derived mainly from the crust with part from the mantle, and ore- forming fluid was mixing of magmatic water and meteoric water. The mineral assemblage is characterized by fine- grained pyrite, fine needle arsenopyrite and invisible grains of gold. Comparison study was conducted in aspects such as spatial distribution of geological bodies and deposits, correlation of geological bodies and ore- forming materials, as well as the diagenetic epoch and metallogenetic epoch between geological bodies and deposits. The results show that the Hongqigounao gneissic granodiorite belongs to metallogenic geological bodies of the Wulonggou gold deposits and provides most of ore- forming elements. A large amount of elongated diorite are entrapped within the geological bodies and minerals underwent distinct ductile deformation, suggesting characteristics of syntexis with dominant crust material and minor mantle material, and emplacement of syn- tectonic intrusive rock under the condition of NE- trending stress in Early Indo- Chinese epoch about 239～244 Ma. During the process of syntexis, the addition of mantle material brought more metallic elements, and syn- tectonic emplacement facilitated gold element easily to activate and migrate into mineralization process under the influence of directional stress. Based on Rb- Sr isochron age of quartz fluid inclusion, the gold deposits formed at about 237 Ma, indicating that mineralization occurs in Early Indo- Chinese epoch, followed the replacement of the disseminated pyrite- rich granitic complex at 210 Ma. The gold deposits are controlled by ore- bearing geological bodies (Hongqigounao granodiorite) and NWW- trending structural belts, with gold mineralization occurring in the NWW- trending structural belts about 1～3.0 km far away from ore- bearing geological bodies. If no NWW- trending structural zone with effect range of the metallogenic geological bodies, there are no space for Au- bearing bodies. Even the places in which there are NWW- trending structural zones far from effect range of ore- forming geological bodies, gold mineralization weakens quickly. The direction of further prospecting for gold deposits should concentrate on the places with well- developed NWW- trending structural belts, on which the Hongqigounao gneiss granodiorite still
impose its influence, or the places close to hidden geological bodies.