地质通报2017，Vol.36Issue(5)：857-866,10.
湘东北七宝山铜多金属矿床成矿时代及成矿物质来源——石英脉Rb-Sr定年和S-Pb同位素组成
Age and sources of the ore-forming material for the Qibaoshan Cu-polymetallic deposit in Hu'nan Province:Evidence from quartz vein Rb-Sr isotopic dating and S-Pb iso?topes
摘要
Abstract
The Qibaoshan Cu-polymetallic deposit, located in the west section of the Qinzhou-Hangzhou metallogenic belt ,is the largest Cu-polymetallic deposit in northeastern Hu'nan Province. However, the data of the deposit age are very insufficient. Based on quartz minerals Rb-Sr isotopic dating of the Qibaoshan deposit, the authors tried to obtain the age. The results show that the Rb-Sr isochron age is 153.4±2.0Ma(MSWD=1.8), initial 87Sr/86Sr=0.71849±0.00026, nearly identical with the quartz porphyry (153Ma to 155Ma) in the ore district in age, which suggests that the genesis of the Qibaoshan deposit was closely related to the quartz porphy?ry. The diagenesis and mineralization were both in the Yanshan period. The authors analyzed S, Pb isotope data of the pyrite to iden?tify the mineral sources of the Qibaoshan Cu-polymetallic deposit and obtained the following data: δ34S=3.24‰~ 4.84‰ for the ore, with an average of 4.198‰;δ34S=2.22‰~3.86‰for the rock, with an average of 2.805‰. Theδ34S values change overall in a small range, and theδ34S values of the rock change even in a smaller range, more close to the value of 0, which suggests that the sul?fur in the rock was most possibly derived from the mantle;and the sulfur in the ore came from the main mantle mixed with a small amount of crustal sulfur. The changes of lead isotopes are also in small ranges: 206Pb/204Pb change in the range of 18.315~18.396 for the ore, with an average of 18.359; 207Pb/204Pb change in the range of 15.629~15.737, with an average of 15.675; 208Pb/204Pb change in the range of 38.376~38.856, with an average of 38.609. The values for the rock change in a similar range. These data show that lead isotope composition of the Qibaoshan Cu-polymetallic deposit has a lower crust (thorium-rich and uranium-depleted) characteris?tics. A comprehensive analysis of the Sr-S-Pb isotopic system of the Qibaoshan deposit indicates that the ore-forming material was derived from the ore gas-liquid fluid, resulting from the deep magma evolution and differentiation in the same evolution process as the quartz porphyry. At the same time, the host rock might have extracted a small amount of minerals from the wall rock to take part in the mineralization process through the circulating convection effect of heating groundwater, resulting in quartz porphyry intrusion and crystallization.关键词
湖南七宝山/Rb-Sr法测年/S-Pb同位素组成/成矿年龄/成矿物质来源Key words
Rb-Sr dating/S-Pb isotopic compositions/age of mineralization/sources of the ore-forming material/Qibaoshan Cu-polymetallic deposit/Hu'nan Province分类
天文与地球科学引用本文复制引用
胡俊良,陈娇霞,徐德明,吴昌雄,张鲲,刘劲松,刘阿睢,刘重芃..湘东北七宝山铜多金属矿床成矿时代及成矿物质来源——石英脉Rb-Sr定年和S-Pb同位素组成[J].地质通报,2017,36(5):857-866,10.基金项目
中国地质调查局项目《钦杭成矿带(西段)重要金属矿床成矿规律及找矿方向研究》(编号:1212011085405)、《钦杭成矿带西段资源远景调查评价》(编号:12120113067200)、《湖北木子店—安徽吴家店地区矿产地质调查》(编号:12120113068000) （西段）
