慢速扩张洋中脊热液成矿的典型实例——青藏高原北部德尔尼铜矿地质对比研究

A comparative study of the geology of Dur'ngoi copper massive sulfide deposit northern Qinghai-Tibet Plateau ——A typical example of hydrothermal metallogenesis in a slow spreading mid-ocean ridge

青海德尔尼铜矿是发育在青藏高原北部的块状硫化物矿床，其赋矿围岩为阿尼玛卿蛇绿岩套中的超基性岩，代表了古特提斯洋的残骸。通过对德尔尼铜矿的详细地质解剖，认为其保留了大量海底热液喷流的地质记录，包括：矿体上部普遍发育的薄层喷流岩；多孔状硫化物中保留下来的胶状结构、草莓结构和角砾结构；矿石的主要矿物组成；与黄铁矿碎屑同期形成的方解石、长英质胶结物；与大西洋Rainbow、TAG热液硫化物矿床相似的矿体分带性。根据洋脊玄武岩中TiO2全岩含量估算德尔尼蛇绿岩所代表的这一段古特提斯洋洋中脊为慢速一超慢速扩张洋中脊，半扩张速率为1．1～2．5cm／a。类比现今洋中脊热液硫化物成矿过程，认为德尔尼铜矿经历了海底喷流、冷却保存和俯冲侵位等3个阶段，其中海底喷流阶段可能与洋底核杂岩具有成因联系，俯冲侵位过程中的矿体和超基性岩、玄武岩受逆冲断层控制。与世界上其他陆地上保存的类似矿床相比，德尔尼铜矿时代年轻（石炭纪），矿床结构和构造及其围岩蚀变特征保存完整，是慢速一超慢速洋脊超基性围岩热液成矿作用的典型实例，可以称之为德尔尼型成矿作用，研究其成矿过程，对研究和理解现今洋中脊超基性岩系统热液成矿作用（尤其是深部成矿作用）具有重要的意义。

Qinghai Dur＇ngoi Cu Massive Sulfide Deposit is located in Northern Qinghai-Tibet Plateau. Its country rock is ultramafic rocks of A＇nyemaqen Ophiolite, which represent relicts of Paleo-Tethys Ocean. Dur＇ngoi Cu massive sulfide deposit is analyzed in detail, and considered it to preserve an abundance of geology record of subma- rine hydrothermal activities, which include： thin layers of exhalite on the top of the ore body; colloidal, framboi-dal, and brecciated textures preserved in porous sulfides; major minerals components; calcite or felsic minerals ce- menting pyrite breccia and similar zonation with the Atlantic hydrothermal complex rainbow and TAG. We esti- mated the spreading rate of the segment of Paleo-Tethys Ocean represented by Dur＇ngoi Ophiolite is through the bulk TiOz composition of basalts. Result turns out to be 1.1-2.5 cm/a. By analogy of the modern hydrothermal sulfide fields, it is put forward that Dur＇ngoi Cu massive sulfide deposit experience three major steps- submarine hydrothermal metallogenesis, submarine coiling, and subduction emplacement. The first step is supposed to be ge- netically related to oceanic core complex. In the third step, emplacement of ore body, ultramafic rocks, and basalts are controlled by thrust faults. Compared with similar deposits on land, Dur＇ngoi Cu massive sulfide deposit is younger （carboniferous） and much better preserved. It＇s a typical example of hydrothermal metallogenesis in slow spreading mid-ocean ridge, and can be called Dur＇ngoi type.