赣南西华山钨矿床成矿金属来源的铅同位素示踪

Lead Isotopes for Tracing Metallogenic Metal Sources of the Xihuashan Tungsten Deposit in the Southern Jiangxi, China

西华山钨矿床位于南岭构造岩浆带的东段北侧、赣南北东向池江大断裂南向弧形弯转部位,是一个百年大型石英脉型钨矿床。为探讨其成矿金属来源,对该矿床矿石硫化物进行了铅同位素分析,并结合已有氢-氧、硫同位素、稀土元素及流体包裹体的研究成果讨论了其成因。结果显示,24个不同中段矿石硫化物样品的206Pb/204Pb值为18.681~18.815,207Pb/204Pb值为15.714~15.789,208Pb/204Pb值为38.961~39.187,铅同位素组成分布集中,与西华山花岗岩长石铅同位素组成基本一致,表明二者具有密切成因联系。铅构造模式及Δγ-Δβ成因分类图解分析表明,矿床成矿物质应来自壳幔混合成因的西华山花岗岩。

The Xihuashan tungsten deposit is located in the NE-to SW-trending turning part of the Chijiang deep fracture in northern part of the eastern Nanling tectonomagmatic belt. It is a giant quartz vein type tungsten deposit which has been mined over a century. In this paper, in order to discuss the source of its ore-forming materials, we have analyzed lead isotopes of sulfides in its ores and discussed its metallogenesis based on the combined data of previous studies including H-O-S isotopes, REE geochemistry, and fluid inclusions of the deposit. The results show that lead isotopic compositions of sulfides from ores of different levels are generally concentrated with 206Pb/204Pb values of 18.681-18.815, 207Pb/204Pb values of 15.714-15.789, and 208Pb/204Pb values of 38.961-39.187, respectively. They are basically consistent with those of feldspars in the Xihuashan granite, indicating a close genetic relationship. The plumbotectonics model and Δγ-Δβ diagram of genetic classification of lead isotopes of sulfides in ores show that the ore-forming materials were mainly originated from the Xihuashan granite which was formed by the mixed crust-and mantle-derived magmas.