北祁连干沙鄂博稀土元素矿床地质和矿床地球化学特征  

Geological and geochemical characteristics of Ganshaebo REE deposit in North Qilian Orogen, Gansu Province

作　　者：黄增保[1] 李葆华[2] 董晓燕[2] 傅太宇 许龙[2] 高昆丽 陈晨 郑慧 朱永新[1] HUANG ZengBao;LI BaoHua;DONG XiaoYan;FU TaiYu;XU Long;GAO KunLi;CHEN Chen;ZHENG Hui;ZHU YongXin(Geological Survey of Gansu Province, Lanzhou 735000, Gansu, China;College of Earth Science, Chengdu Universityof Technology, Chengdu 610059, Sichuan, China)

机构地区：[1]甘肃省地质调查院,甘肃兰州7310010 [2]成都理工大学地球科学学院,四川成都610059

出　　处：《矿床地质》2019年第1期129-143,共15页Mineral Deposits

基　　金：国家自然科学基金项目(编号:41372094);中国地质调查局地质调查项目"中国矿产地质与成矿规律综合集成和服务(矿产地质志)(编号:DD20160346)"的资助

摘　　要：干沙鄂博稀土元素矿床位于北祁连造山带中段,是该地区唯一大型稀土元素矿床。矿体产于早泥盆世碱性岩体及其接触带中,围岩蚀变表现为霓长岩化、碳酸岩化和萤石化,矿石类型主要为霓辉正长岩型和霓辉正长斑岩型,矿物组合为氟碳钙铈矿+黄铜矿+霓辉石+钠长石+钠闪石+萤石+方解石。通过详细的岩相学和矿相学观察,划分出4个成矿期,包括岩浆成矿期(Ⅰ)、早期热液成矿期(Ⅱ)、晚期热液成矿期(Ⅲ)和表生成矿期(Ⅳ)。其中,早期热液成矿期为主成矿期,包括3个成矿阶段:霓石-钠长石-氟碳钙铈矿阶段(Ⅱ_1)、钠闪石-氟碳钙铈矿阶段(Ⅱ_2)、霓石-方解石-氟碳钙铈矿阶段(Ⅱ_3)。脉石矿物石英的δ^(18)O值为7.3‰～11.3‰,δD值为-89.4‰～-68.8‰,δ^(13)C_(V-PDB)值为-10.5‰～-7.9‰,表明成矿流体以岩浆热液为主,有大气降水的参与。矿石中硫化物δ^(34)S_(V-CDT)值介于-7.1‰～-1.3‰之间,平均-4.4‰,总硫同位素δ^(34)S_(ΣS)为-3.9‰;矿石硫化物铅同位素组成基本一致,^(206)Pb/^(204)Pb、^(207)Pb/^(204)Pb和^(208)Pb/^(204)Pb比值分别为18.417～18.524、15.637～15.769和38.425～38.863,与矿区早泥盆世含矿碱性岩体岩石铅同位素组成十分相似,推测成矿物质主要来源于该碱性岩体。The Ganshaebo REE deposit is located in the middle section of the North Qilian Mountain, and is the only REE deposit in North Qilian Orogen. The orebodie are mainly hosted in the Early Devonian alkaline complexes and the contact zone between the alkaline complexes and country rocks. The alteration of the ore deposit is characterized by fenitization, carbonatization and fluoritization. Ore types are dominated by aegirine syenite ore and aegirine syenite porphyry ore, which are mainly composed of the mineral assemblage of parasite+copper+aegirine+albite+riebec kite+fluorite+calcite. Four metallogenic periods and six mineralization stages are confirmed according to vein crosscutting relationships, mineral assemblage and mineralography as follows: magmatic period (Ⅰ), early hydrothermal period (Ⅱ), late hydrothermal period (Ⅲ), and epigenetic oxidation period (Ⅳ). Among them, early hydrothermal period is the main metallogenic period, which is composed of three mineralization stages: aegirne-albite-parisite stage (Ⅱ1), riebeckite-parisite stage (Ⅱ2), and aegirne-calcite-parisite stage (Ⅱ3). Hydrogen, oxygen and carbon isotope analyses indicate that δ18O of quartz from ores range from 7.3‰ to 11.3‰,δD of quartz ranges from -68.8‰ to -89.4‰, and δ13CV-PDB of quartz ranges from -7.9‰ to -10.5‰, suggesting that the ore-forming fluid of the Ganshaebo deposit is mainly a mixed fluid of magma and meteoric water. The δ34SV-CDT values of sulfide minerals range from -1.3‰^-7.1‰(averagely -4.4‰), and lead isotopic compositions of ores are basically stable, with 206Pb/204Pb, 207Pb/204Pb and 208Pb/204Pb ratios of galenite being 18.417~18.524, 15.637~15.769 and 38.425~38.863, respectively, similar to features of the ore-bearing alkaline complexes in Ganshaebo REE deposit. It is suggested that the lead and sulfur in ores from the Ganshaebo deposit might have mainly come from magma, and thus the ore-forming materials were most likely derived from the alkaline complexes in Ganshaebo REE deposit.

关 键 词：地球化学 稀土元素矿床 氢、氧、碳、硫和铅同位素 干沙鄂博矿床 北祁连造山带 

分 类 号：P618.44[天文地球—矿床学]