北秦岭南台钼多金属矿床成岩成矿年龄及锆石Hf同位素组成  

Rock-forming and ore-forming ages of the Nantai Mo polymetallic deposit in North Qinling Mountains and its zircon Hf isotope composition

作　　者：柯昌辉[1] 王晓霞[1] 杨阳[2] 齐秋菊 樊忠平 高非 王修缘[6] 

机构地区：[1]中国地质科学院矿产资源研究所,国土资源部成矿作用与资源评价重点实验室,北京100037 [2]中国地质大学,北京100083 [3]有色金属华东地质勘查局资源调查与评价研究院,南京210007 [4]西北有色地质勘查局713总队,河南商洛726000 [5]陕西有色金属控股集团有限公司,陕西西安710075 [6]金堆城钼业集团有限公司,陕西渭南714000

出　　处：《中国地质》2012年第6期1562-1576,共15页Geology in China

基　　金：地质调查项目(1212010012012、1212010811033);公益性行业专项课题(200911007-09)联合资助成果

摘　　要：南台钼多金属矿床是北秦岭典型的斑岩-矽卡岩型矿床,矿区内出露的岩浆岩主要有花岗斑岩、石英斑岩脉和爆破角砾岩,花岗斑岩内及接触带发育斑岩型和矽卡岩型钼多金属矿化。锆石LA-ICPMS定年测得花岗斑岩的U-Pb年龄为(151±1)Ma(N=12,MSWD=0.32),矿区内6件辉钼矿的Re-Os同位素模式年龄介于(146±2)～(151±2)Ma,其加权平均年龄为(148.8±1.7)Ma(N=6,MSWD=0.84)。成岩年龄与成矿年龄在误差范围内基本一致,表明南台钼多金属矿床形成于晚侏罗世,与其以北的华北克拉通南缘的主要斑岩型钼矿床大规模成矿时间一致。该花岗斑岩的锆石Hf同位素组成显示:176Hf/177Hf初始比值介于0.281 864～0.282 454,εHf(t)=-28.8～-7.9,两阶段模式年龄TDM2为2 654～1 506 Ma,均变化于一个较宽的范围,表明花岗斑岩的源区物质具有多源的特征,其中以壳源组分为主,可能有少量幔源组分的混入,暗示了成矿物质也可能主要来源于地壳,但地幔组分对成矿也有贡献。The Nantai Mo polymetallic deposit is a typical porphyry-skarn deposit in North Qinling Mountains,the magmatic rocks in this deposit include granite-porphyry,quartz porphyry veins and explosion breccia,and there occur porphyry-type and skarn-type Mo polymetallic mineralizations within and around the granite-porphyry body.The granite-porphyry from the Nantai Mo polymetallic deposit is dated at（151±1）Ma（N=12,NSWD=0.32）by using zircon U-Pb LA-ICPMS.Six molybdenites samples from the deposit yield Re-Os isotope model ages ranging from（146±2）Ma to（151±2）Ma,with an weighted average of（148.8±1.7）Ma（N=12,NSWD=0.84）.The granite age and the metallogenic age are consistent with each other within the error limits,suggesting that the Nantai Mo polymetallic deposit was formed in the late Jurassic period,consistent with the formation epoch of the main porphyry-skarn type molybdenum deposits on the southern margin of North China Block.The zircon Hf isotope composition of the granite-porphyry has a large variation,with initial ratios of 176Hf/177Hf ranging from 0.281 864 to 0.282 454,εHf（t） from-28.8 to-7.9,and two-stage model ages from 2654Ma to 1506Ma.These data suggest that granite-porphyry was probably derived form several sources dominated by curstal materials with the addition of small amouts of mantle materials,and the old crust was dominated by the contribution of juvenile components.Therefore,the source of the metallogenic material for the Nantai Mo polymetallic deposit was probably the same as that of the granite.

关 键 词：北秦岭 南台钼多金属矿 锆石U-Pb年龄 RE-OS年龄 HF同位素 

分 类 号：P618.65[天文地球—矿床学] P597[天文地球—地质学]