云南省德钦县红坡牛场铜金矿区果腊复式岩体年龄、地球化学特征及其构造与找矿意义

Geochronology and geochemical characteristics of the Guola complex intrusion in the Hongponiuchang Cu-Au mining area of Deqin area,Yunnan Province,and its tectonic and prospecting significance

位于江达-维西火山弧铁-铜-铅-锌多金属成矿带的德钦县红坡牛场铜金矿床,是与果腊复式侵入体有关的矽卡岩型-热液型多金属矿床。LA-ICP-MS锆石U-Pb数据表明,复式岩体核部(石英二长岩)侵位年龄为226.4±2.0Ma,边部(石英闪长玢岩)为36.59±0.22 Ma,显示为印支期和喜马拉雅期2期岩浆活动的产物。核部石英二长岩具高SiO 2(65.8%~68.5%)和低MgO(1.40%~2.17%)含量,属高钾钙碱性系列;高Sr,低Yb与Y含量证实其埃达克岩属性。地球化学特征及对比表明其很可能起源于加厚的陆壳底部,源区物质相当于榴辉岩的组成,而非俯冲洋壳熔融的产物。边部石英闪长玢岩具低SiO2(55.8%~56.6%),高MgO(6.45%~7.50%;Mg#=52.4~62)、Cr(228×10^-6~353×10^-6)和Ni(72.3×10^-6~90.0×10^-6),为典型的高镁闪长岩。地球化学特征显示其为下地壳物质在地幔深部发生熔融的产物。研究成果为金沙江古特提斯洋演化提供了新的年代学约束,在江达-维西火山弧带发现喜马拉雅期岩浆活动,对于重新认识该矿床成因及后续江达-维西带成矿规律总结和找矿方向具有重要的指导意义。

The Hongponiuchang copper-gold deposit,located in the middle part of the Jiangda-Weixi volcanic arc Fe-Cu-Pb-Zn polymetallic metallogenic belt,is a skarn-hydrothermal polymetallic deposit related to the Guola complex intrusion.Zircon LA-ICP-MS U-Pb geochronology shows that the emplacement ages of the complex are 226.4±2.0 Ma and 36.59±0.22 Ma for the center(quartz monzonite)and the rim(quartz diorite porphyrite),respectively,suggesting that the complex represents the magmatic product of both Indosinian and Himalaya periods.The quartz monzonite as the center of complex has high SiO 2(65.8%~68.5%)and low MgO(1.40%~2.17%)content and represents high-K calc-alkali series;High Sr and low Yb and Y content indicates its adakitic characteristics.The geochemical characteristics and comparisons indicate that it was probably derived directly from the bottom of the thickened crust,with source material similar to the composition of the eclogite instead of the melting product of subduction oceanic crust.The quartz diorite porphyrite in the rims has low SiO 2(55.8%~56.6%)and high MgO(6.45%~7.50%),Cr(228×10^-6~353×10^-6),and Ni(72.3×10^-6~90.0×10^-6)values,indicating a typical high-magnesium diorite.Geochemical characteristics show that it is the product of melting of the lower crust at the depth of the mantle.This study has provided new geochronologic constraint for the evolution of the Jinshajiang Paleo-Tethys Ocean,and discovered the Himalayan magmatic activity in the Jiangda-Weixi arc belt,thus being of great significance to the genesis for the Hongponiuchang copper-gold deposit and the summary of the metallogenic regularity as well as the study of prospecting direction.