湖南宝山铜-钼多金属矿床成岩成矿的U-Pb和Re-Os同位素定年研究  

U-Pb and Re-Os isotope geochronology of Baoshan Cu-Mo polymetallic ore deposit in Hunan province.

作　　者：路远发[1] 马丽艳[2] 屈文俊[3] 梅玉萍[4] 陈希清[4] 

机构地区：[1]长江大学地球化学系 [2]宜昌地质矿产研究所,宜昌443003 [3]国家地质实验测试中心,北京100037 [4]宜昌地质矿产研究所.宜昌,443003

出　　处：《岩石学报》2006年第10期2483-2492,共10页Acta Petrologica Sinica

基　　金：中国地质调查局地质调查项目(1212010560901);同家重点基础发展规划项目(G1999043201);长江大学科研发展基金项目部分成果

摘　　要：湖南宝山是一个 Cu-Mo-Pb-Zn-Ag 多金属矿床,成因上与花岗斑岩、花岗闪长斑岩关系密切,矿床以宝岭倒转背斜(宝山中区)为中心,空间上具有明显的蚀变与矿化分带,其中心部位(宝山中区)的矿体产在花岗闪长斑岩(花岗斑岩)的内外接触带,围岩蚀变主要为矽卡岩化,成矿元素组合以 Cu-Mo 为主,而宝山东区、宝山西区及北部的财神庙矿区则主要为产于石炭系碳酸盐岩中的铅锌艰矿化。通过对与成矿作用关系密切的花岗闪长斑岩中锆石 SHRIMP U-Pb 同位素测年,获得了高精度的花岗闪长斑岩的成岩年龄为158±2Ma (MSWD=0.26,Probability=0.61,n=12),与前人(伍光英等,2005)的 SHRIMP 数据合并计算则可得到一个161±1Ma(MswD=0.66,Probability=0.42,n=23)的高精度 U-Pb 和谐年龄。该年龄可以代表宝山矿区中酸性小岩体的成岩年龄。通过对含矿矽卡岩中辉钼矿 Re-Os 同位素测年,获得辉钼矿的成矿年龄为160±2Ma。因此,本文认为宝山矿床成岩与成矿具有同时性,花岗闪长斑岩与宝山矿床的形成有成因联系。通过对区域上已获得的成岩-成矿年龄资料的综合对比分析,表明湘南乃至整个南岭中段地区中生代大规模岩浆作用与成矿第一高峰期为155～165Ma,宝山多金属矿床正是华南这一高峰期的产物。这为进一步研究区域成矿规律提供了重要同位素年代学依据。Baoshan Cu-Mo-Pb-Zn-Ag polymetallic ore deposit is located at the west of Guiyang county, Hunan Province. This deposit is genetically related to the granodioritic porphyry and granitic porphyry. The mineralization at Baoshan shows an apparent spatial zonation, which centered within the Baoling reverse anticline. The orebodies at the center zone are located in the inside and outside contact zones of granodioritic （granitic） porphyry, which are dominantly skarn-type Cu-Mo mineralization. The orebodies at the periphery, such as the eastern Baoshan, the western Baoshan and the Caishenmiao deposit, were mainly Pb-Zn-Ag mineralization occurring in the Carboniferous carbonate rocks. Based on the precise SHRIMP U-Pb dating of zircons, we obtained an age of 158 ± 2Ma （MSWD = 0. 26, Probability = 0. 61, n = 12） for the granodioritic porphyry related to the mineralization. Combining our data with those previous published SHRIMP data （ Wu et al. , 2005 ） , we got a precise U-Pb concordant age of 161 ± 1Ma （ MSWD = 0.66, Probability = 0. 42, n = 23）, which can represent the intrusive age in the Baoshan ore-field. Based on the precise Re-Os dating of the molybdenite from skarn-type ore, the mineralization age is 160 ± 2Ma. In this paper, we suggest that both granitic rocks and ore deposits at Baoshan have the same formational ages, which indicate that the granodioritic porphyry is genetically related to the Baoshan deposit. Compiling all available ages for granitiods and mineralization in the region, we suggest that 155 - 165Ma was the first peak stage for Mesozoic large-scale magmatism and mineralization in Hunan and in the middle segment of the Nanling Ranges. During this period, the Baoshan polymetalic deposits were formed. Our new data provide important isotope chronology evidence for further study of the regional mineralization rules.

关 键 词：铜钼多金属矿床 花岗闪长斑岩 锆石SHRIMP U—Pb定年 辉钼矿RE-OS定年 宝山 湖南 

分 类 号：P597.3[天文地球—地球化学] P588.13[天文地球—地质学]