广东永宁那程金矿区花岗岩:地球化学特征、成因与构造环境  

Geochemistry,Petrogenesis and Tectonic Setting of the Peraluminous Granites in the Nacheng Gold Deposit,Yongning,Guangdong

作　　者：吴继承[1] 李己华 李太兵[1] 李永光[1] 

机构地区：[1]中国人民武装警察部队黄金技术学校,湖北襄樊441002

出　　处：《矿物岩石地球化学通报》2010年第4期364-372,共9页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：黄金指挥部金矿勘察资助项目(HJXX09-02)

摘　　要：本文对出露于那程金矿区花岗岩体进行了详细的岩石学、地球化学及年代学研究,重点讨论了岩体的成因。那程金矿区花岗岩体主要由石英（30%～35%）、钾长石（30%～35%）和斜长石（25%～28%）组成,副矿物有锆石和磷灰石等。地球化学分析显示,岩石总体具高硅、富碱、高钾、高铝和低镁、低钙的特征,K2O/Na2O1,里特曼指数σ为1～2.43,属高钾钙碱性系列。岩石铝饱和指数（A/CNK）大于1.1,具强过铝质＂S＂型花岗岩的特征。稀土配分模式为右倾＂V＂字形态,轻重稀土分馏明显,（La/Yb）N=1.51～9.66,具较强的负铕异常（δEu=0.31～0.74）;地球化学特征反映其岩浆有源于泥质岩的＂低温＂和源于砂岩的＂高温＂两种类型,至少有两种岩浆来源,形成于同碰撞构造环境。The Nacheng granite locates in the Yong ning area,Guangdong Province.This paper studied petrographical and chronological characteristics of this granite as well as its petrogenesis and geological significance.The Nacheng granite mainly consists of quartz（40%～50%）,orthoclase（25%～30%）,palgioxlase（15%～20%） with minor accessory minerals of quartz apatite and magnetite.Geochemical analyses show that the manziying granite has high content of SiO2（75.56%）,K2O（4.72%）,Al2O3（13.34%） and total alkali（Na2O＋K2O=7.49%）,but relatively low MgO（0.04%～1.29%） and CaO（0.39%～2.21%）.The ratios of K2O/Na2O are generally higher than 1.The Rittmann indexes are between 1～2.43,belonging to the high-K calc-alkaline series.The values of A/CNK vary from 1.12 to1.32 with an average of 1.10,showing the characteristics of peraluminous S type granites.Trace element analyses show that the Nacheng granite has relatively high REE content of 82.6×10^-6～225.68×10^-6,and displays right-inclined V-shape REE patterns with relatively high fractionations of LREE and HREE[（La/Yb）N=1.51～9.66]and pronounced negative Eu anomalies（δEu=0.31～0.74） in the chondrite-normalized REE diagrams,suggesting a typical crust-derived grandite.The magmas may be divided into two types： ＂low-temperature＂ type from mudstones and ＂high-temperature＂ type from sandstones.The Nacheng granites were formed from the post-orogenic tectonic setting.

关 键 词：S型花岗岩 同碰撞 强过铝 地球化学特征 广东 

分 类 号：P588.121[天文地球—岩石学]