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湘东北位于华南钦杭结合带的北西侧,是中国重要的金、铜、钴、铅和锌等多金属矿产地。该区燕山期岩浆活动异常强烈,其中所侵位的连云山二云母二长花岗岩位于区域性北东向长沙—平江断裂的南东侧,为强过铝质S型花岗岩。根据元素地球化学特征,可以将连云山二云母二长花岗岩分为两组,第一组具有较低的Eu-Sr-Ba和过渡金属元素Cr-Co含量,较高的CaO/Na_2O和FeO~T/(FeO~T+MgO)比值,指示了相对还原、干燥、贫泥质、富斜长石粗粒碎屑岩源区;相反,第二组则为相对氧化、富水和贫斜长石的富泥质源区。此外,二云母二长花岗岩大部分具有埃达克质岩地球化学特征。ε_(Nd)(t)=-13.36~-13.65、(~(87)Sr/~(86)Sr)_i=0.722 86~0.730 97,说明连云山二云母二长花岗岩为榴辉岩相的加厚下地壳部分熔融的产物。连云山二云母二长花岗岩还具有较高的Sm/Yb和Gd/Yb比值以及较低的锆石饱和温度,指示岩浆源区具有较高的压力和较低的温度。连云山二云母二长花岗岩的锆石LA-ICPMS U-Pb年龄为(145±1)Ma(MSWD=1.9)。结合华南地区晚中生代以来大地构造演化特征,湘东北连云山二云母二长花岗岩与古太平洋板块平俯冲至华南板块之下有关。约145 Ma,俯冲的古太平洋板块崩塌,下沉的俯冲板片和岩石圈地幔脱水,使得早已加厚的下地壳发生减压熔融,形成连云山二云母二长花岗岩。而当连云山二云母二长花岗岩的源区岩浆运移时,驱动了含金成矿流体的运移,其期后的岩浆热液形成了该区围绕连云山二云母二长花岗岩呈带状分布的多金属矿体。
Northeastern Hunan is located on the north west side of the Qinhang-Hangguang belt in southern China and is an important polymetallic mineral deposit of gold, copper, cobalt, lead and zinc in China. The Yanshanian magmatism was extremely anomalous in this area. The emplacement of the Lianyunshan two-mica monzogranite is located in the southeastern part of the NE-trending Changsha-Pingjiang fault and is strongly over-aluminous S-type granite. Based on the element geochemical characteristics, the Lianyunshan two-mica monzogranites can be divided into two groups. The first group has lower Eu-Sr-Ba and Cr-Co transition metal elements, higher CaO / Na2O and FeO ~ T / (FeO ~ T + MgO) ratio, indicating relatively reduced, dry, lean, plagioclase rich coarse-grained clastic source areas; on the contrary, the second group is relatively oxidized, Feldspar rich muddy source area. In addition, most of the mica monzogranite has the adakitic geochemical characteristics. (Nd) (t) = -13.36 ~ -13.65, (87) Sr / ~ (86) Sr) _i = 0.72286 ~ 0.73097, indicating that the Lianyunshan two mica monzogranite is eclogite facies Thickening of the lower crust partially melted product. The Lianyunshan mica monzogranite also has higher Sm / Yb and Gd / Yb ratios and lower zircon saturation temperature, indicating that the magmatic source region has higher pressure and lower temperature. The zircon LA-ICPMS U-Pb dating of the second mica-hosted granite in Lianyun Mountain was (145 ± 1) Ma (MSWD = 1.9). Combined with tectonic evolution of the tectonic evolution since the Late Mesozoic in southern China, the Lianyun-ductile magmatite and the Paleo-Pacific plate in the northeastern Hunan are subducted to subduction below the South China Plate. About 145 Ma, the collapse of the subducted Paleo-Pacific plate, the subducting subducting slab and the dewatering of the lithosphere mantle caused the already thickening lower crust to depressurize and fuse to form the Lianyunshan mica monzogranite. When the magmatic movement in the source area of Lianyun two-mica monzogranite drives the migration of the gold-bearing ore-forming fluids, the magmatic hydrothermal fluid formed in the area around the zone of the second mica-hosted granite in Lianyun Shan Shaped distribution of multi-metal ore body.