胶东中生代构造体制转折过程中流体演化和金的大规模成矿

Fan HR,Hu FF,Yang JH,Shen K and Zhai MG.2005.Fluid evolution and large-scale gold metallogeny during Mesozoic tectonic transition in the eastern Shandong province.

胶东是我国最大的金矿产出集中区,依据矿床和矿点的密集程度,可分为招远-莱州-平度、蓬莱-栖霞、牟平-乳山三个成矿带,区域内金矿类型可主要分为石英脉型和蚀变岩型。高精度的单矿物 Ar-Ar、Rb-Sr 同位素及热液锆石离子探针测年研究业已证买,金成矿的时代为120±10Ma,金矿床载金矿物-黄铁矿、矿石-黄铁矿石英脉、控矿围岩-花岗岩和变质岩等及伴生脉岩的 Sr-Nd 放射性同位素研究也证明,金成矿物质具有多源性,既来自于控矿围岩-花岗岩和变质岩,又来自于幔源的岩浆岩,流体包裹体研究表明,各类金矿具有一致的成矿流体介质条件,为低盐度 H_2O-CO_2-NaCl±CH_4流体,金成矿温度、压力条件近似,主成矿温度为170～335℃,成矿压力为70～250MPa。氢氧等稳定同位素结果表明,成矿流体可能来源于与金矿床伴生的基性幔源岩浆脱水形成的岩浆水,但在地壳浅部遭受到大气降水的混合。因此,胶东各类型金矿是在同一成矿背景下形成的矿床,与区域内中生代构造体制转折作用有关,也是中生代构造体制转折的表现形式之一。

The Jiaodong Peninsula or eastern Shandong gold province, the most important gold producer in China, is located in the southeastern margin of the North China craton. The gold deposits in the Jiaodong are divided into three gold belts, respectively Zhaoyuan-Laizhou-Pingdu, Penglai-Qixia and Muping-Rushan from west to east. They occur as gold-bearing quartz veins and disseminated- and stockwork-style ores adjacent to fault zones. Most of the gold deposits comprise a quartz-K-feldspar, quartz-pyrite, quartz-base metal sulfide, and quartz-carbonate paragenetic sequence. Obtained Ar-Ar,Rb-Sr isochron ages and hydrothermal zircon SHRIMP U-Pb age dating give gold mineralization time at 120±10Ma. The Sr, Nd isotopic compositions of pyrites and the associated rocks suggest that the ore-forming materials were probably derived from a mixed source. Fluid inclusion studies show that ore-forming fluids of gold deposits are consistent in the whole Jiaodong Peninsula with similar mineralizing temperature and pressure conditions. The fluids are characterized by H2O-CO2-NaCl±CH4. The best mineralizing temperature and pressure are 170～335℃ and 70～250 MPa, Oxygen and hydrogen isotope data show that metamorphic fluid contribution is minimal and that ore fluids are of magmatic origin. Gold deposits in the Jiaodong Peninsula are formed in the same mineralizing-geodynamic circumstance, and related with Mesozoic tectonic transition in the eastern China. Gold metallogeny is one of expression form of Mesozoic tectonic transition.