长江中下游铜陵地区宝山岩体地球化学研究  

Geochemistry of the Baoshan pluton in the Tongling region of the Lower Yangtze River Belt

作　　者：宁思远 汪方跃[1,2,3] 薛维栋 周涛发 NING Si-yuan;WANG Fang-yue;XUE Wei-dong;ZHOU Tao-fa(School of Resources and Environmental Engineering, Hefei University of Technology, Hefei 230009, China;Ore Deposit and Exploration Centre, Hefei University of Technology, Hefei 230009, China;University of Science and Technology of China, Hefei 230026, China;China University of Geosciences (Beijing), Beijing 100083, China)

机构地区：[1]合肥工业大学资源与环境工程学院,安徽合肥230009 [2]合肥工业大学矿床成因与勘查技术研究中心,安徽合肥230009 [3]中国科学技术大学,安徽合肥230026 [4]中国地质大学(北京),北京100083

出　　处：《地球化学》2017年第5期397-412,共16页Geochimica

基　　金：国家自然科学基金(41373035;41203028);合肥工业大学中央高校基本科研业务费专项资金(112-4115102017)

摘　　要：长江中下游地区与铜金矿床有关的埃达克岩成因仍然存在分歧。对铜陵宝山地区的侵入岩和其中的包体进行了系统的矿物学、岩石学和元素地球化学研究。结果表明:(1)宝山岩体岩性变化较大,从辉石闪长岩到花岗闪长岩均有;(2)暗色基性岩常常被淡色酸性的花岗闪长岩所包裹,部分界限呈过渡状态;(3)LA-ICPMS锆石U-Pb定年结果表明,宝山花岗闪长岩和其中的辉石闪长岩包体分别形成于(143.8±3.2)Ma(2σ,MSWD=2.3)和(142.9±2.9)Ma(2σ,MSWD=2.2),属于早白垩世;(4)宝山岩体地球化学特征表明其主体具有典型的埃达克岩特征,如较大SiO_2含量变化范围(52.88%~63.66%),高Al_2O_3含量(平均值为16.03%)、高Sr/Y(33.4~102,平均为72.9)和Sr/La比值,低Y和Yb含量、低(La/Yb)N(14.6~26.6,平均值为21.4)和K_2O/Na_2O(平均值为0.39)比值。(5)野外岩石接触关系和岩石地球化学特征表明,宝山埃达克质岩可能为岩浆混合成因,混合的两个端元分别为高硅和低硅端元。高硅端元为俯冲洋壳熔融形成的熔体并发生不同程度磁铁矿的结晶分异,而低硅端元为高Ni、Cr、V、Co的岩石圈地幔熔体。铜陵宝山岩体的地质与地球化学研究结果表明,铜陵地区中生代埃达克质岩和大规模铜金成矿作用可能形成于俯冲背景之下。The petrogenesis of adakitic intrusions in the Lower Yangtze River Belt has been hotly debated for thepast decade.The Baoshan pluton is located in the southwest of the Tongling district.Here we conducted asystematic mineralogical,petrological and geochemical study on the Baoshan rocks and mafic microgranularenclaves to understand their petrogenesis.The results indicate:(1)the Baoshan pluton is composed of severalkinds of magmatic rocks,e.g.,pyroxene diorite to granodiorite;(2)the mafic rocks are usually enrolled by felsicmagma,with or without distinctive boundaries;(3)U-Pb dating on zircons by LA-ICPMS suggests thatgranodiorite and pyroxene diorite enclaves were emplaced at(143.8±3.2)Ma(2σ,MSWD=2.3)and(142.9±2.9)Ma(2σ,MSWD=2.2),respectively;(4)the Baoshan pluton is similar to adakite in geochemical affinity,e.g.,awide-range of SiO2(SiO252.88%?63.66%),high Al2O3(averaging16.03%),high Sr/Y(33.4?102,average72.9)and Sr/La ratios,low Y and Yb,low(La/Yb)N(14.6?26.6,averaging21.4)and K2O/Na2O(averaging0.39)ratios;(5)the field contact relationship between mafic and felsic rocks and the geochemical characteristics of theBaoshan rocks indicate they were derived from magma mixing.The two end members of the Baoshan pluton arehigh-silica and low-silica end-members.High-silica end-member was formed by partial melting of subducted oceanic crust,followed by fractional crystallization of magnetite in varying degrees while upwelling.The other isthe lithospheric mantle,which has high Ni,Cr,V and Co contents.The Baoshan rocks may indicate that themagmatism and mineralization in Tongling,even the LYRB,were formed in a subduction system during theMesozoic time.

关 键 词：埃达克岩 岩浆混合 铜金矿床 俯冲 宝山岩体 铜陵地区 

分 类 号：P597[天文地球—地球化学]