摘要
西秦岭造山带广泛发育脉状金锑矿化,但其成矿时代和成矿物质来源仍存在争议,影响了对该区矿床成因的深入认识。甘南早子沟超大型金锑矿床位于西秦岭造山带,矿体赋存于三叠系古浪堤组板岩和中酸性侵入岩内,包括蚀变岩型矿化和脉状矿化两种样式,是研究脉状金锑矿化成矿年代学和成矿物质来源的理想选区。本研究选择早子沟金锑矿床脉状矿化中与辉锑矿、金密切共生的白云石为研究对象,系统分析了其Sm、Nd同位素组成。结果表明,早子沟金锑矿床脉状矿化白云石Sm含量为0. 3221×10^(-6)～4. 918×10^(-6),Nd含量为0. 5667×10^(-6)～22. 76×10^(-6)。147Sm/144Nd和143Nd/144Nd分别为0. 1306～0. 2891和0. 511847～0. 512141,Sm-Nd假等时线年龄为282. 5±5. 1Ma。白云石εNd(0)为-15. 42～-9. 70,εNd(t)为-13. 66～-12. 19,tDM2为2. 03～2. 10Ga,变化范围相对较窄,表明样品源区相同。εNd(t)值与秦岭及其周边地区对比显示,早子沟金锑矿床成矿流体与英安斑岩围岩具有相同的Nd源区,可能来源于扬子板块北缘或南秦岭的古元古代结晶基底。白云石Sm/Nd分馏很弱且成矿流体混染了古元古代结晶基底物质可能是Sm-Nd假等时线产生的原因。这表明白云石Sm-Nd同位素体系可能无法为西秦岭广泛发育的脉状(金)锑矿床提供正确年代学信息。
A lack of research on the geochronology and fluid sources of the Au-Sb lode vein style mineralization has hampered our understanding of the ore genesis in West Qinling.The giant Zaozigou Au-Sb deposit in the West Qinling is hosted in slate of the Triassic Gulangdi Formation and Early to Late Triassic intermediate to felsic sills and dikes.Mineralization is present as disseminated and stockwork veinlets in wallrock alteration zones of dikes and slates and/or stibnite-rich quartz ± dolomite veins,representing an ideal natural laboratory for investigation.The Sm-Nd isotopes of dolomites coexisting with stibnite and gold suggest that Sm and Nd concentrations range of 0.3221 × 10^-6~4.918 × 10^-6 and 0.5667 × 10^-6~22.76 × 10^-6,respectively.147 Sm/144 Nd and 143 Nd/144 Nd vary of 0.1306~0.2891 and 0.511847~0.512141,which has no geochronological implications for mineralization.The εNd(0),εNd(t),and tDM2 of dolomites vary of-15.42^-9.70,-13.66^-12.19,and 2.03~2.10 Ga,respectively.The relatively narrow εNd(t) compositions indicate a single source for the Nd.By comparing the εNd(t) values with those from the Qinling and its adjacent areas,we propose that the ore-forming fluid at Zaozigou is probably derived from the Paleoproterozoic basement of northern Yangtze block or the South Qinling mountain.The pseudo-isochrons may be caused by weak Sm-Nd isotope fractionations and oreforming fluid derived from the Paleoproterozoic basement.This understanding means the age of gold-stibnite-quartz-dolomite lode vein mineralization wide spread in the West Qinling can’t be determined by Sm-Nd isotope system of dolomite.
作者
于皓丞
李俊
邱昆峰
勾宗洋
耿建珍
刘文刚
庞瑶
王博雄
YU HaoCheng;LI Jun;QIU KunFeng;GOU ZongYang;GENG JianZhen;UU WenGang;PANG Yao;WANG BoXiong(State Key Laboratory of Geological Processes and Mineral Resources,and School of Earth Science and Resources,China University of Geosciences,Beijing 100083,China;Tianjin Center,China Geological Survey,Tianjin 300170,China;Sichuan Earthquake Administration,Chengdu 610041,China;Zaozigou Gold Mine,Hezuo 747000,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第5期1519-1531,共13页
Acta Petrologica Sinica
基金
国家重点基础研究发展计划(2015CB452605)
国家自然科学基金项目(41702069
41403045)
中国地质大学(北京)基本科研业务费(2652018125
2652018141)
博士后国际交流计划派出项目(20170108)
高等学校学科创新引智计划(B07011)
矿床地球化学国家重点实验室开放基金(201704)联合资助
