云南德钦鲁春铜铅锌矿床硫铅氢氧同位素特征及地质意义

S,Pb,H,O isotopic characteristics of the Luchun Cu-Pb-Zn deposit,Deqin County,Yunnan and geological implications

鲁春铜铅锌矿床位于中咱-中甸板块和昌都-思茅板块之间的金沙江构造带中部,矿体长约3 km,厚度在1.06～16.35 m之间。其赋矿围岩为火山沉积岩系,容矿构造为印支期逆断层。鲁春铜铅锌矿床矿石中硫化物的δ34S值变化于3.5‰～6.8‰之间,硫化物的206Pb/204Pb比值为18.554～18.656,207Pb/204Pb比值为15.662～15.752,208Pb/204Pb比值为38.801～39.009。石英流体包裹体的HO182δO值变化范围为2.74‰～1.25‰,δDV-SMOW变化范围为107‰～123‰。鲁春铜铅锌矿床的硫铅氢氧同位素分析结果表明,该矿床成矿物质来源于地幔,部分来源于岩浆,在成矿流体上升过程中,有壳源物质的加入。早二叠世晚期金沙江洋盆向西俯冲形成了一系列逆断层,同时导致下地壳部分熔融,引发大规模的火山岩浆作用。在晚三叠世早期,构造背景由挤压环境到伸展环境的转折期,这些逆断层具有张性的特点,为后期的成矿热液提供了有利的容矿构造。上升的岩浆为地幔楔内的成矿流体提供了通道。岩浆内的部分成矿流体进入白茫雪山花岗闪长岩体附近的逆断层富集成矿。

The Luchun Cu-Pb-Zn deposit is situated in the middle section of Jinshajiang tectonic belt between Zhongza-Zhongdian plate and Changdu-Simao plate. Ore bodies are 1.06-16.35 m wide and extend discontinuously over 3 km. It is hosted by volcanic sedimentary rocks. The ores were deposited in pre-existing thrust faults in Indosinian. The δ34S values of sulfides from copper ores change from 3.5‰-6.8‰. The 208Pb/204Pb, 207Pb/204Pb and 206Pb/204Pb of sulfide ores range between 38.801-39.009, 15.662-15.752 and 18.554-18.656, respectively. The values of the fluid in quartz inclusion change from -2.74‰ - -1.25‰. The δDV-SMOW values of the fluid in quartz inclusion were -107‰ - -123‰. These sulfur, lead, hydrogen and oxygen compositions indicate that the ore-forming materials originated from mantle, with contributions from the magma, with addition of crust materials during ore-forming fluids ascending. The research shows that the Jinshajiang Oceanic plate subducted to west, in the late Early Permian, resulting in the formation of a series of thrust faults, and lower crust partial melting, which triggered extensive volcanic-magmatic processes. In the early Late Triassic, which was a time of transition from collision-related compression to extension in the Jinshajiang tectonic belt, the thrust faults were tensional, which is favorable for ore-forming fluids. The ascending magma provided a channel for the ore-forming fluid from the mantle wedge. Ore-forming fluid in the magma entered the gently dipping thrust faults near the Yangla granodiorite, resulting in mineralization.