粤北大宝山多金属矿床LA-ICP-MS锆石U-Pb和辉钼矿Re-Os定年及其地质意义  

Zircon LA-ICP-MS U-Pb and molybdenite Re-Os dating of the Dabaoshan polymetallic deposit in northern Guangdong Province and its geological implications

作　　者：王磊[1] 胡明安[2] 屈文俊[3] 陈开旭[1] 龙文国[1] 杨振[2] 

机构地区：[1]国土资源部武汉地质矿产研究所,湖北武汉430223 [2]中国地质大学资源学院,湖北武汉430074 [3]国家地质测试中心,北京100037

出　　处：《中国地质》2012年第1期29-42,共14页Geology in China

基　　金：国土资源部危机矿山接替资源找矿项目(220644088);钦杭成矿带(西段)基础地质调查综合研究项目(1212011085416)共同资助

摘　　要：对粤北大宝山多金属矿床次英安斑岩(样品ZK5803)中锆石LA-ICP-MS U-Pb定年结果为(174.6±1.5)Ma(MSWD=0.7),与矿区花岗闪长斑岩的形成年龄基本一致;3个斑岩型和矽卡岩型钼钨矿石辉钼矿Re-Os模式年龄为(163.2±2.3)Ma(样品CD-30)、(165.2±2.4)Ma(样品DB-18)和(163.4±2.4)Ma(样品CD-38),与层状铜铅锌矿中辉钼矿Re-Os模式年龄(164.7±3.0)Ma基本一致;上述4个样品给出的加权平均年龄为(164.0±2.5)Ma(MSWD=0.16);该成矿年龄与南岭地区其他钼多金属矿床形成时间一致,同属于华南地区中生代第二阶段成矿作用。矿床地质特征、流体包裹体氢氧同位素(δ18O=-3.75‰～7.0‰,δD=-50.7‰～-56.1‰)和矿石硫化物硫同位素(δ34S=-2.00‰～3.00‰)资料表明,该矿床为与矿区次英安斑岩和花岗闪长斑岩有成因联系的岩浆期后热液矿床。矿区各类矿床应为同一期成矿事件的产物,不同于前人认为的存在加里东期海底喷流沉积和燕山期叠加成矿,或燕山期两期成岩成矿的观点。结合岩石微量元素图解和前人研究结果,推测其成矿动力学背景为南岭地区后造山伸展环境。LA-ICP-MS U-Pb dating of zircons from subdacitic porphyry samples yielded a weighted mean 206Pb/238U age of 174.6±1.5 Ma（MSWD=0.7） in the Dabaoshan polymetallic deposit of northern Guangdong Province.Re-Os dating of three molybdenite samples from porphyry and skarn ores yielded consistent model ages from 163.2±2.3 Ma to 165.2±2.4 Ma.These ages are consistent with the molybdenite Re-Os model age（164.7±3.0 Ma） measured by Mao et al.for the stratiform Cu-Pb-Zn ore body,and they can yield a weighted mean of 164.0±2.5 Ma（MSWD=0.16）.These data imply that Mo-W and Cu-Pb-Zn mineralization in the ore district are products of the same mineralization event,which coincides closely with the event of Mo-polymetallic mineralization elsewhere in the Nanling region and corresponds to the second episode of Mesozoic metallogenesis in South China.Geological data,together with stable isotopic data of fluid inclusions（δ18O =-3.75‰～7.0‰,δD =-50.7‰～-56.1‰） and ore sulfides（δ34S =-2.00‰～3.00‰）,suggest that the Dabaoshan ore deposit is a magmtic hydrothermal ore deposit associated with the granodioritic porphyry and the subdacitic porphyry.This is different from previous studies which argue for the existence of superimposition of multiple mineralization events comprising Caledonian exhalative deposition and Yanshanian superimposed mineralization or two Yanshanian mineralization stages.Based on geochemical diagrams of Y＋Nb-Rb and Rb/30-Hf-Ta×3 in combination with previous studies,the authors suggest that the Dabaoshan polymetallic deposit is related to post-collisional lithosphere extension in the Nanling region of South China.

关 键 词：次英安斑岩 锆石 辉钼矿 LA-ICP-MSU-Pb定年 RE-OS定年 大宝山多金属矿床 

分 类 号：P597.3[天文地球—地球化学] P618.4[天文地球—地质学]