摘要
仙人岩岩体位于湖南水口山矿田的南部。岩体内外接触带上均见有不同程度的金、铜、钼、锌等矿化,反映出岩体与成矿存在着内在联系。二长岩中锆石的LA-MC-ICP-MS年代学研究表明,其U-Pb加权平均年龄值为(156.09±0.46)Ma(MSWD=1.4),显示为燕山早期侵位。锆石Lu-Hf同位素原位分析结果表明,176 Hf/177 Hf值为0.282 243～0.282 904,εHf(t)值为-15.55～7.87,峰值在-10左右,Hf同位素二阶段模式年龄(TDM2)为703～2 188Ma,峰值在1 800Ma左右,指示岩浆为壳幔混合来源。结合岩体的地球化学特征,认为仙人岩岩体主要来源于中元古代基底的重熔,是在中晚侏罗世地壳拉张减薄构造背景下形成的。另外,对比分析了仙人岩岩体与水口山岩体的的岩石地球化学特征,前者分异演化程度相对较弱,这可能是其不利于形成同类矿床的原因。
The Xianrenyan pluton is located in the south of Shuikoushan ore field,Hunan Province.There develops Au,Cu,Mo and Zn mineralization in inner and outer contact zones of the pluton,which shows the colse relationship between the pluton and the metallic mineralization.Zircon LA-MC-ICP-MS U-Pb age of the monzonite suggests a weighted mean age of（156.09±0.46） Ma（MSWD=1.4） which implies that the pluton was emplaced in Early Yanshanian period.The in-situ Hf isotopic analysis reveals 176Hf/177Hf ratios in the zircon range from 0.282 243 to 0.282 904,and εHf（t） from-15.55 to 7.87（with peak value around-10）,and the two stage Hf model ages（TDM2） from 703 Ma to 2 188 Ma（with peak value around 1 800 Ma）,which indicates that parental magma of the pluton was derived from the mixed sources of the lower crust and mantle.Based on the geochemistry of the rocks,it can be concluded that the monzonite was mainly resulted from remelting of the Mesoproterozoic basement rocks and formed in Middle and Late Jurassic when the crust was in an extension-thinning geodynamic setting.In addition,the authors compare and analyze the lithogeochemical characteristics of the Xianrenyan pluton and the Shuikoushan stock.The fact that the Xianrenyan pluton has a weaker differentiation than the Shuikoushan pluton gives the reason for its unfavorable gold mineralization.
出处
《吉林大学学报（地球科学版）》
EI
CAS
CSCD
北大核心
2012年第6期1740-1756,共17页
Journal of Jilin University：Earth Science Edition
基金
全国危机矿山找矿专项(20089927)
中央高校基本科研业务费专项资金项目(2011PY0164)
关键词
仙人岩
二长岩
锆石U-PB定年
HF同位素
地质意义
金矿床
Xianrenyan
monzonite
zircon U-Pb geochronology
Hf isotope
geological significance
gold deposits
