金沙江造山带碰撞后地壳伸展背景——火山成因块状硫化物矿床的重要成矿环境

The Post-collisional Crustal Extension Setting: an Important Mineralizing Environment of Volcanic Massive Sulfide Deposits in Jinsha Orogenic Belt

近年来对金沙江造山带区域地质、矿床地质和岩石地球化学新资料的研究和典型火山成因块状硫化物(VHMS)矿床的解剖,金沙江造山带的VHMS成矿作用主要发生于早二叠世晚期—晚二叠世海相弧火山岩和晚三叠世裂谷盆地海相火山岩中,构成西南三江地区一条重要的多金属块状硫化物成矿带。成矿带内晚三叠世碰撞后地壳伸展背景下形成的上叠裂谷盆地是其VHMS成矿作用的主体,盆地中火山活动从早期的双峰式火山岩演变为晚期的中酸性火山岩,岩石地球化学特征与孤火山岩有明显的区别,反映其形成于伸展背景。伸展盆地的早期阶段,在双峰火山岩组合的高钾流纹质火山岩系中产出鲁春式VHMS矿床,具有Zn-Cu-Pb-Ag金属组合特征,形成于深水环境;伸展盆地的晚期阶段,在中酸性火山岩系与上覆碳酸盐岩接触带中产出赵卡隆式VHMS矿床,具有Ag-Fe-Pb-Zn金属组合特征,形成于浅水环境;盆地的末期阶段,在滨浅海相磨拉石碎屑岩中产出里仁卡式石膏矿床。金沙江造山带碰撞后地壳伸展背景下VHMS成矿作用的研究,对于造山带中的找矿工作具有重要的指导意义。

In recent years, on the basis of research on new materials of regional geology, geology of ore deposits, lithogeochemistry and anatomy of typical volcanic massive sulfide (VHMS) deposits in the Jinsha orogenic belt, the important mineralization of VHMS deposits occurred mainly in the marine arc-volcanic rocks during the late Early Permian-Late Permian and the marine volcanic rocks of rifting basin in the Late Triassic. The VHMS deposits along the Jinsha orogenic belt constitute an important mineralizing zone of polymetallic massive sulfide de-posits of the Sanjiang area (means three rivers area, i. e. , Jinsha River, Nujiang River and Lancang River) , in southwestern China. The superimposed rifting basins formed in the post-collisional crustal extension setting in the Late Triassic were the important pilling area of VHMS mineralization. The volcanism in the rifting basins e-volved from the early-stage bimodal-volcanic rocks to the late-stage intermediate-acidic volcanic rocks and was distinctive from the arc-volcanic rocks in lithogeochemical features, indicating the tectonic extension setting. In the early stage of the extension basin, the 'Luchun type' VHMS deposits showing the association feature of el-ements (Zn-Cu-Pb-Ag) formed in the high-K rhyolite of the bimodal rocks and developed in the deep-water fa-cies. In the late stage of the extension basin, the 'Zhaokalong-type' VHMS deposits showing the association feature of elements (Ag-Fe-Pb-Zn) formed in the contract strip between the intermediate-acidic volcanic rocks and the overlying carbonate rocks and developed in the shallow-water facies. In the terminal stage of the exten-sion basin, the 'Lirenka-type' gypsum deposits were formed in the mollasse clastic rocks of the littoral-shallow facies. The research on the mineralization of the volcanic massive sulfide (VHMS) deposits in the post-collision-al crustal extension setting has an important guiding meaning for the ore prospecting work in the orogenic belt.