新疆哈密地区新月地金矿地质、地球化学特征及构造背景

Geological and Geochemical Characteristics and Tectonic Setting of the Xinyuedi Gold Deposit,Hami,Xinjiang

新月地金矿位于康古尔断裂南侧韧性剪切带中,矿体赋存于下石炭统干墩组碎屑岩中。岩浆岩以闪长玢岩、花岗斑岩为主,与成矿关系密切。矿区内共发现6条矿化蚀变带,5条金矿体,矿体长40~100 m,厚0.95~1.3 m,金品位1.08×10^-6~2.15×10^-6。伴生铅锌银矿,铅锌品位分别为Pb:0.55%、Zn:0.51%,Ag:13.8×10^-6。构造环境判别图解表明,区内花岗岩为造山类花岗岩,经后造山作用改造,具与俯冲带有关的岛弧构造环境特征。闪长岩具岛孤和活动大陆边缘弧岩浆岩特征,沉积碎屑岩具大陆岛弧构造环境特征。结合区域地质演化特征,认为北天山洋壳向塔里木大陆板块俯冲,形成含矿物质来源,后造山运动作用的塔里木板块与准噶尔板块碰撞,形成韧性剪切带,该过程伴有中浅成和浅成侵入岩体形成,与浅成侵入体相伴的热液及矿质沿剪切带上升,当与大气降水混合时,发生了矿质沉淀和蚀变作用,形成韧性剪切带蚀变岩型金矿体。

Xinyuedi gold deposit is located about 80 km south of Hami city,and the ductile shear zone to the south of Kanggur fault.Ore bodies occur in clastic rocks of Gandun Formation of Lower Carboniferous.Magmatic rocks are mainly dioritic porphyry and granite porphyry,which are closely related to mineralization.Six mineralization alteration zones and five gold orebodies were found in the mining area.The orebody is 40~100m long and 0.95~1.3 m wide.The gold grade is(1.08~2.15)×10^-6.The grade of lead and zinc is 0.55% and 0.51%respectively,and that of Ag is 13.8×10^-6.The discriminant diagram of tectonic environment shows that the granite in this area is orogenic granite,and after post-orogenesis,it has the characteristics of island arc tectonic environment related to subduction zone.Diorite is characterized by island-isolated and active continental margin arc magmatic rocks;sedimentary clastic rocks are characterized by continental island-isolated tectonic environments.Combined with regional geological evolution,it is considered that the northern Tianshan oceanic crust subducted toward the Tarim continental plate,forming mineral-bearing sources,post-orogeny,forming ductile shear zones,and passing through Tarim.The collision between the plate and the Junggar plate is accompanied by the formation of intermediate-shallow and hypabyssal intrusive rocks.The hydrothermal and mineral materials associated with the hypabyssal Intrusive Rocks rise along the shear zone.When mixed with the atmospheric precipitation,the mineral precipitation and alteration occur and the altered rock-type gold deposits in the shear zone are formed.