蒙古国南戈壁省曼莱-曼达赫铜金成矿带花岗闪长岩地球化学特征及地质意义

Geochemical Characteristics of Granodioritefrom Manley-Mandah Cu-Au Metallogenic Belt in South Gobi of Mongolia and Its Geological Significance

研究区位于蒙古国南戈壁省和东戈壁省北部地区,南蒙古成矿区曼莱-曼达赫铜金成矿带,出露华力西期花岗闪长岩、花岗岩及石炭纪—二叠纪火山岩,发育有石英脉型、斑岩型和构造蚀变岩型铜金矿化。近东西向区域构造控制了成岩成矿作用,花岗闪长岩株与区内铜金矿化具有成因上和时空上的密切关系。主矿体产于蚀变花岗闪长岩株中。地球化学研究表明:花岗闪长岩株具有高硅(SiO_2含量为61.3%～67.2%)、钙碱性(里特曼指数为2.07～2.34,AR-SiO_2图解中样品均落入钙碱性区)、高Sr(491×10^(-6)～631×10^(-6))、低Yb(0.8×10^(-6)～1.2×10^(-6))、低Y(7.8×10^(-6)～13×10^(-6))、高Sr/Y(42.7～80.9)、亏损重稀土以及无明显负Eu异常等岛弧背景下埃达克质岩石特征。基于区域成矿学研究,认为本区具有寻找大型斑岩型铜金矿的找矿前景。

The studying area is located in South Gobi and the northern part of East Gobi province of Mongolia, which belongs to Manley Mandah Cu Au metallogenic belt of southern Mongolia metallogenic area. The Hercynian granodiorite, granite and Carboni{erous Permian volcanic rocks were occurred in this area, with quartz vein type, porphyry type and alteration rock type copper gold mineralization. The nearly EW direction regional structures control the diagenesis and rain eralization, and the granodiorite intrusion is closely related to the origin and temperal spatial dis tribution of copper gold mineralization in this area. The main orebodies are occurred in altered granodiorite. The geochemical results show that these granodiorites have high SiO2 （61.3%- 67.2%）, calc alkaline （Rittman indexes range from 2.07 to 2.34, all samples fall into the calc al kaline areainAR SiO2 diagram）, Sr （491X10 6 631X10 6） and Sr/Y （42.7-80.9）, but they have low Yb （0.8×10 6 1.2×10 6） and Y （7.8×10 6 13×10 6）, with depleted HREE and no obvious negative Eu anomalies, showing the characteristics of adakitic rocks. Based on the regional metallogenetic study, it can be concluded that this area has the potential for prospecting large porphyry copper gold deposits.