新疆西天山北达巴特斑岩型铜钼矿床铅同位素组成及成矿物质来源示踪

Lead isotopic composition and metallogenic material source tracing of Beidabate porphyry copper molybdenum deposit in western Tianshan, Xinjiang

北达巴特斑岩型铜钼矿床位于西天山造山带北部。矿区钼矿化分布于流纹斑岩体内部,铜矿化受断裂构造控制,分布于流纹斑岩与地层的接触带附近。据矿物组合特征与交代关系,将成矿过程划分为3个阶段:早期石英—辉钼矿阶段,中期黄铁矿—黄铜矿—石英阶段,晚期萤石—黄铜矿阶段。对早阶段辉钼矿与晚阶段黄铜矿分别进行了Pb同位素分析。辉钼矿的^(208)Pb/^(204)Pb值为38.125~38.179,^(207)Pb/^(204)Pb值为15.570~15.575,^(206)Pb/^(204)Pb值为18.293~18.311,Pb同位素构造判别投点落在地壳和地幔范围内,有向造山带线靠近的趋势,指示成矿物质主要来源于地幔,流纹斑岩提供了主要的钼来源。黄铜矿^(208)Pb/^(204)Pb值为38.202~38.257,^(207)Pb/^(204)Pb值为15.581~15.621,^(206)Pb/^(204)Pb值为18.239~18.246,Pb同位素判别投点落在造山带演化线附近,表明成矿物质为地幔与地壳混合来源,流纹斑岩与上泥盆统托斯库尔他乌组凝灰岩可能为成矿提供了主要的铜来源。

Beidabate porphyry copper molybdenum deposit is located in the north of the western Tianshan orogenic belt.Molybdenum mineralization in the mining area is mainly distributed in the rhyolitic porphyry,and copper mineralization is mainly distributed in the contact zone between rhyolitic porphyry and stratum and its developed fault structure.According to the characteristics of mineral assemblage and metasomatic relationship,the metallogenic process is divided into three stages:early quartz molybdenite stage,middle pyrite chalcopyrite quartz stage and late fluorite brass stage.Based on Pb isotope analysis of Molybdenite in the early metallogenic stage and chalcopyrite in the main late stage.The ^(208)Pb/^(204)Pb value of molybdenite is 38.125~38.179,^(207)Pb/^(204)Pb value is 15.570~15.575,^(206)Pb/^(204)Pb Pb value is 18.293~18.311.The ^(208)Pb/^(204)Pb value of chalcopyrite is 38.202~38.257,^(207)Pb/^(204)Pb value is 15.581~15.621,^(206)Pb/^(204)Pb value is 18.239~18.246.Through the analysis of the projection points in the Pb isotopic structural model map of the sample,the Pb projection points of the molybdenite sample fall within the crust and mantle,and tend to approach the orogenic belt line,indicating that the ore-forming material may come from the mantle.The Pb projection point of chalcopyrite sample is near the evolution line of orogenic belt,indicating that the ore-forming material may come from surrounding rock and mantle.