胶北地体金矿富集的构造环境

TECTONIC SETTING AND GOLD MINERALIZATION OF THE JIAOBEI TERRANE

金矿密集的胶北隆起区是一个独立的地体,具有典型的早前寒武克拉通的一系列特征.目前没有资料表明胶东群和花岗岩能为胶北大型或中型的金矿床提供足够的成矿物质.而从胶北地体构造环境的研究表明,从克拉通周边高级和高压变质带以及下行的板块和板片大量转移出来的成矿物质到克拉通内部,形成了许多重要的金矿床和成矿带.

The Jiaobei uplifted block clustered with numerous gold deposits is an independent terrane, which is separated from the Luxi terrane by the Danlu fault to the west, from the Liannan terrane by the Pingdu-Laixi fault to the south, from the Jiaodongnan-Sudongbei-Huanghai terrane by the Rongcheng-Haizhou eclogite belt to the east. The Jiaobei terrane is a typical Precambrian craton, which exhibits a series of characteristics. Similarities to the southern Africa and the Zimbabwe cratons are obvious, particularly in the development of a circum-cratonic high-grade metamorphic mobile belt along the boundary faults. The main differences of this terrane from the southern Africa craton are recognized in its intense Mesozoic tectonism and magmatism. The Jiaobei terrane underwent cyclic intense tectonism and magmatism, particularly during the Mesozoic time. The Jiaobei terrane is situated on the active continental margin of the Eurasia plate. The Archean Jiaodong Group (3000-2550 Ma) and the Early proterozoic Qishan Group2550-2300 Ma), which contain greenstones of the first and the second stages respectively, constitute the metamorphic core, which is surrounded by the Middle and Upper part of the Early proterozoic Jianshan-Fenzishan Group (2300-1885 Ma), giving the precambrian Jiaobei terrane an 'onion structure' similar to that in the Canadian shield. The EW, NE and NNE trending major fault systems controlled the formation and distribution of the granitoids and related gold deposit and mineralization zones; The first one comprises a set of boundary and basement faults; the latter two are considered to be genetically related to the subduction of the Mesozoic pacific plate.No evidence suggests the Jiaodong Group and the granites being the gold source of so many deposits of large and intermediate sizes within the Jiaobei terrane. In the light of the tectonic setting of the Jiaobei terrane, it is possible that a large quantity of ore-forming materials extracted from the circum-cratonic high-grade and high pressure metamorphic belts and from the down-going plates and slabs were transferred to the craton interior, resulting in the formation of many important gold deposits and EW, NE and NNE trending gold belts.