摘要
长江中下游贵池矿集区是我国铜金成矿带的重要组成部分,成矿与岩浆作用关系密切。铜铃坡地区位于扬子板块东南缘,该区含矿石英闪长玢岩锆石原位LA-ICP-MS U-Pb定年结果为148.4±1.0Ma。元素地球化学分析显示铜铃坡石英闪长玢岩SiO 2含量为58.5%~62.8%,具有高Al2O3(>15.8%)、相对高MgO含量(2.66%)、高Ba(>1000×10^-6)和Sr含量(>500×10^-6)、高Sr/Y(>42)和(La/Yb)N(>8.8)比值、低Yb和Y含量、低K2O/Na2O(0.55~0.82)比值,显示埃达克岩石地球化学特征。富集轻稀土和大离子亲石元素,亏损Nb、Ta等高场强元素。锆石的εHf(t)值变化于-18.5~12.4,两阶段模式年龄t DM2=1.0~2.6Ga。少量的正εHf(t)值,指示源区可能有亏损地幔物质的贡献。部分较老的继承锆石(2095Ma)指示了古元古代基底物质的存在。铜铃坡含矿石英闪长玢岩的地球化学特征与长江中下游中生代埃达克质岩相似,来源于有限俯冲沉积物贡献的俯冲洋壳部分熔融,在上升过程中不仅与富集地幔发生相互作用,同时混染了古老地壳物质。锆石氧逸度的研究表明,铜铃坡岩浆岩具有很高的氧逸度。石英闪长玢岩中磷灰石结晶时流体中HF、HCl的活度分别为0.00049mol/L和0.018mol/L,表明岩浆结晶早期分异的初始岩浆流体中HF和HCl的含量特征,暗示铜铃坡花岗质岩浆分异的初始岩浆流体富含挥发性组分Cl,能与成矿元素Cu形成稳定络合物,从而有利于Cu成矿。
The Guichi region is one of the most important non-ferrous metal ore districts in the Lower Yangtze River Metallogenic Belt,where the formation of Cu-Au deposits has close genetic relations with adakitic intrusions.Tonglingpo copper deposit in Guichi is located near the southeastern boundary of Yangtze plate.LA-ICP-MS zircon U-Pb dating of the Tonglingpo ore-bearing quartz diorite porphyrite suggests that the emplacement age is 148.4±1.0Ma.The ore-bearing quartz diorite porphyrite has high SiO2 contents(58.5%~62.8%),Al 2 O 3(>15.8%)and MgO concentrations(av.2.66%),high Ba(>1000×10^-6)and Sr(>500×10^-6)contents,high Sr/Y(>42)and(La/Yb)N(>8.8)ratios,and low Y and Yb contents,low K2O/Na 2 O(0.55~0.82),showing geochemical characteristics of adakitic rocks.They are enriched in light rare earth elements and large ion lithophile elements,but are depleted in high field strength elements such as Nb and Ta.Tonglingpo ore-bearing quartz diorite porphyrite hasεHf(t)values of-18.5~12.4 and second model ages of 1.0~2.6Ga.Some positiveεHf(t)values suggests the contribution of depleted mantle materials in its magma sources.The inherited zircons in the samples from Tonglingpo suggest that Palaeoproterozoic basement(2095Ma)was involved with the generation of Tonglingpo magma.The geochemistry of Tonglingpo is similar to the Mesozoic adakitic rocks in the Lower Yangtze River Metallogenic Belt,derived from partial melting of subducted paleo-Pacific Plate,assimilated with Yangtze lower crust and remelting of Meso-Neoproterozoic crust/sediments.Zircon geochemistry characteristics show that the Tonglingpo intrusion has high oxygen fugacity.Assuming ideal site mixing of F^-,Cl^- and OH^- in apatite,concentrations of HF and HCl in the hydrothermal fluid during the crystal of quartz diorite porphyries in Tonglingpo are calculated to be 0.00049 and 0.018 mol/L,indicating that the hydrothermal fluids derived from magma included amount of Cl- that may form stable complexes with Cu.Furthermore,it is evident that this magma has potential to form Cu deposit.
作者
古黄玲
杨晓勇
邓江洪
段留安
陈林杰
GU HuangLing;YANG XiaoYong;DENG JiangHong;DUAN LiuAn;CHEN LinJie(School of City and Environment,Hunan University of Technology,Zhuzhou 412007,China;Key Laboratory of Crust-Mantle Materials and Environments,School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,China;Yantai Geological Survey Center of Coastal Zone,China Geological Survey,Yantai 264004,China;No.321 Geological Team,Anhui Bureau of Geology and Mineral Resources,Tongling 244033,China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2020年第1期205-224,共20页
Acta Petrologica Sinica
基金
国家重点研发计划(2016YFC0600404)
国家自然科学基金项目(41673040)
安徽国土资源科技项目(2015-K-1)联合资助
关键词
埃达克质岩
锆石U-Pb定年
HF同位素
板块俯冲
氧逸度
铜铃坡地区
长江中下游
Adakitic rocks
Zircon U-Pb dating
Hf isotope
Pacific plate subduction
Oxygen fugacity
Tonglingpo area
Lower Yangtze River Metallogenic Belt
