摘要
广丰铜山中酸性岩体侵位于华夏地块和扬子地块的结合部位——钦杭结合带东段。岩性为花岗闪长斑岩和石英闪长玢岩,与之伴生有中型矽卡岩型铜矿床。花岗闪长斑岩的锆石环带结构明显,Th/U值较大(0.40-1.07),为典型的岩浆锆石,LA-ICP-MS锆石U-Pb成岩年龄为171.0±1.6 Ma(n=15,MSWD=0.16)。主微量元素特征表明该套中酸性侵入岩属于高钾过铝—偏铝质I型花岗岩类,轻重稀土分异明显(LaN/YbN=10.53-38.37),无明显Eu异常(δEu平均值1.05),富集大离子亲石元素(Rb、Ba、Th、U、K),亏损Nb、Ta、Ti,低Y(〈10.4×10^-6)、Yb(〈0.93×10^-6),高Sr/Y比值(〉26),具有弧型岩石和埃达克质岩石的双重地球化学特征。综合研究表明,铜山矿区的中酸性岩石形成压力大于1.5GPa,熔体起源深度大于50km,源区为富含金红石的角闪榴辉岩,形成于古太平洋板块斜向俯冲的挤压后松弛阶段,由新元古代洋壳俯冲形成的增厚下地壳部分熔融形成。其埃达克质特性使其易于萃取、聚集铜金等成矿物质,因此具有扩大找矿的潜力。
The Tongshan intermediate-felsic rocks emplaced in conjunction area between Yangtze block and Cathaysian block,i.e.in the eastern part of the Qinhang conjunction areas.Tongshan intermediate-felsic rocks consist of granite diorite porphyry and quartz diorite porphyrite,accompanied with medium-sized skarn copper deposits.The zircons from granite diorite porphyry show distinct zonation structure with high Th/U ratios(0.40-1.07),suggesting that zircons are typical magmatic in origin.LA-ICP-MS zircon U-Pb dating yields an age of 171.0±1.6 Ma(n=15,MSWD=0.16).Major element and trace element characteristics indicate that the intermediate-acid intrusive rocks are high K peraluminous-aluminous I-type granitoid,with strong LREE/HREE fractionation(LaN/YbN=10.53-38.37)and no significant negative Eu anomalies(δEu average of 1.05).Enrichment of large ion lithophile elements(Rb,Ba,Th,U and K)and depletion of Nb,Ta and Ti,low contents of Y(〈10.4×10^-6)and Yb(〈0.93×10^-6),high Sr/Y ratio(26),suggest the rocks are of double geochemical characteristics of arc volcanic rock and adakite.Comprehensive study shows that the intermediate-felsic rocks formed at the pressure greater than 1.5GPa,magmatic source depth was more than 50 km,and the source region composition was rutile-rich amphibole eclogite facice rocks,which resulted from partial melting of thickening lower crust with relaxation environment after extension caused by the oblique subduction tectonic of the Paleo-Pacific Plate.The ore-forming materials were easily extracted and accumulated to form Cu-Au deposits from the magmatic melts with adakitic characteristics. Therefore,the Tongshan area has the potential of mineralization and is worth broadening exploration.
出处
《地质学报》
EI
CAS
CSCD
北大核心
2016年第6期1253-1267,共15页
Acta Geologica Sinica
基金
中国地质调查局地调项目"钦杭成矿带东段整装勘查区及重点勘查区勘查示范与综合研究(编号12120113065500)"资助成果
关键词
江西广丰
铜山中酸性侵入岩
埃达克质
锆石U-PB定年
地球化学
Guangfen County
Jiangxi Province
Tongshan intermediate-felsic intrusive rocks
adakite-like
zircon U-Pb dating
geochemistry