湘东北连云山二云母二长花岗岩的年代学和地球化学特征:对岩浆成因和成矿地球动力学背景的启示

发布时间：2018-03-27 19:55

本文选题：连云山二云母二长花岗岩　切入点：湘东北地区　出处：《地学前缘》2017年02期

【摘要】：湘东北位于华南钦杭结合带的北西侧,是中国重要的金、铜、钴、铅和锌等多金属矿产地。该区燕山期岩浆活动异常强烈,其中所侵位的连云山二云母二长花岗岩位于区域性北东向长沙—平江断裂的南东侧,为强过铝质S型花岗岩。根据元素地球化学特征,可以将连云山二云母二长花岗岩分为两组,第一组具有较低的Eu-Sr-Ba和过渡金属元素Cr-Co含量,较高的CaO/Na_2O和FeO~T/(FeO~T+MgO)比值,指示了相对还原、干燥、贫泥质、富斜长石粗粒碎屑岩源区;相反,第二组则为相对氧化、富水和贫斜长石的富泥质源区。此外,二云母二长花岗岩大部分具有埃达克质岩地球化学特征。ε_(Nd)(t)=-13.36~-13.65、(~(87)Sr/~(86)Sr)_i=0.722 86~0.730 97,说明连云山二云母二长花岗岩为榴辉岩相的加厚下地壳部分熔融的产物。连云山二云母二长花岗岩还具有较高的Sm/Yb和Gd/Yb比值以及较低的锆石饱和温度,指示岩浆源区具有较高的压力和较低的温度。连云山二云母二长花岗岩的锆石LA-ICPMS U-Pb年龄为(145±1)Ma(MSWD=1.9)。结合华南地区晚中生代以来大地构造演化特征,湘东北连云山二云母二长花岗岩与古太平洋板块平俯冲至华南板块之下有关。约145 Ma,俯冲的古太平洋板块崩塌,下沉的俯冲板片和岩石圈地幔脱水,使得早已加厚的下地壳发生减压熔融,形成连云山二云母二长花岗岩。而当连云山二云母二长花岗岩的源区岩浆运移时,驱动了含金成矿流体的运移,其期后的岩浆热液形成了该区围绕连云山二云母二长花岗岩呈带状分布的多金属矿体。
[Abstract]:Northeast Hunan is located in the north and west of Qinghang binding belt in South China. It is an important gold, copper, cobalt, lead, zinc and other polymetallic mineral areas in China. The Yanshanian magmatic activity in this area is extremely strong. The emplacement of Lianyunshan Ermica monzogranite is located on the south east side of the Changsha-Pingjiang fault, which is strong peraluminous S type granite, according to the geochemical characteristics of elements, the granite is located on the south side of the Changsha-Pingjiang fault in the north and east direction of the region. Lianyunshan Ermica monzogranite can be divided into two groups. The first group has lower Eu-Sr-Ba and transition metal element Cr-Co content and higher CaO/Na_2O / FeO~T/(FeO~T ratios, indicating relative reduction, dryness, poor muddy and plagioclastic coarse clastic source area. The second group, on the other hand, is a source of relatively oxidized, water-rich and poor plagioclase. Most of the dichakite granites have the geochemical characteristics of adakite. 蔚 Shijiao Ndlangtou -13.36 ~ 13.65% ~ (87) S / P ~ (86) ~ (86) S\ + + ~ (86) S\ + + ~ (86) S\ + + ~ (86) S\ + +\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%\%? It also has higher Sm/Yb / Gd/Yb ratios and lower zircon saturation temperature. The zircon LA-ICPMS U-Pb age of the Lianyunshan monomorphite is 145 卤1 卤1 MaMS-WDX 1.9, which is combined with the tectonic evolution characteristics of late Mesozoic in southern China, indicating that the magmatic source region has higher pressure and lower temperature, and that the zircon LA-ICPMS U-Pb age of Lianyunshan monomorphite is 145 卤1. Lianyunshan monomorphite monzogranite in northeastern Hunan is related to the flat subduction of the paleo-Pacific plate below the South China plate. About 145 Ma. the subducted paleo-Pacific plate collapses and the sinking subduction plate and lithospheric mantle are dehydrated. The already thickened lower crust was reduced and melted to form the Lianyunshan Ermite monzomorphic granite. When the source magma of the Lianyunshan Ermica monzomorphic granite migrated, the migration of gold-bearing ore-forming fluids was driven. The magmatic hydrothermal fluid formed a polymetallic ore body in this area around Lianyunshan Ermica monzogranite.
【作者单位】：中国科学院广州地球化学研究所矿物学与矿床学重点实验室;加拿大里贾纳大学地质系;中国科学院大学;湖南省地质矿产勘查开发局402地质队;中南大学地球科学与信息物理学院;
【基金】：科技部国家重点研发计划项目(2016YFC0600401) 中国地调局项目“湖南省金井-九岭地区矿产远景调查”(资[2014]01-019-026)
【分类号】：P618.2

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