中亚成矿域Erdenet斑岩型铜钼矿床和Oyu Tolgoi斑岩型铜金矿床对比

中亚成矿域位于北侧西伯利亚克拉通、南侧华北—塔里木克拉通及西侧东欧克拉通之间,与环太平洋成矿域和特提斯成矿域并称为全球三大成矿域,发育有一系列大型—超大型斑岩型铜金、斑岩型铜(金、钼)及斑岩型铜钼矿床。对比研究了中亚成矿域两个典型斑岩型矿床——Erdenet斑岩型铜钼矿床与Oyu Tolgoi斑岩型铜金矿床的矿床地质特征和与成矿相关的岩石地球化学特征异同。结果表明:Erdenet斑岩型铜钼矿床成矿斑岩岩性主要是花岗岩和花岗闪长岩,同时代发育的火山岩主要是安山岩、英安岩和流纹岩,属于钙碱性—高钾钙碱性系列; Oyu Tolgoi斑岩型铜金矿床成矿斑岩则主要是石英二长闪长岩,矿化后期的花岗闪长斑岩仅发育有弱矿化作用,同时代火山岩以英安质-玄武质岩石为主,主要属于高钾钙碱性系列。这两个矿床与成矿相关的岩石微量和稀土元素配分特征相似,均显示弧岩浆岩地球化学特征,但Erdenet斑岩型铜钼矿床显示出高Sr/Y和La/Yb值及低相容元素(Cr、Ni)含量,且与Oyu Tolgoi斑岩型铜金矿床相比,Erdenet斑岩型铜钼矿床具有相对富集的Sr-Nd-Hf同位素组成。结合区域地质背景资料认为:Erdenet斑岩型铜钼矿床成矿斑岩源于加厚新生下地壳物质的部分熔融作用,形成于蒙古—鄂霍茨克洋西段演化末期的陆缘弧环境; 而Oyu Tolgoi斑岩型铜金矿床成矿斑岩源于亏损地幔物质的分离结晶作用,形成于与古亚洲洋北向俯冲有关的大洋岛弧环境; 不同的构造背景形成了这两类具不同特征的斑岩型矿床。

Comparison Between Erdenet Porphyry Cu-Mo and Oyu Tolgoi Porphyry Cu-Au Deposits in the Central Asian Metallogenic Domain

The Central Asian metallogenic domain(CAMD)is located between the Siberian craton to the north, the North China-Tarim craton to the south, and the East Europe craton to the west. It's considered as one of the three major metallogenic domains in the world along with the Circum-Pacific and the Tethyan metallogenic domains. There exists a series of porphyry Cu-Au, Cu(Au, Mo)and Cu-Mo deposits, and the two representative deposits from them, namely Erdenet porphyry Cu-Mo and Oyu Tolgoi porphyry Cu-Au deposit, were chosen to make comprehensive comparisons in terms of geological characteristics and ore-related rocks geochemical features. Mineralizing porphyrys of Erdenet porphyry Cu-Mo deposit are mainly granites and granodiorites, and the volcanic rocks developing in the same period are primarily andesite, dacite and rhyolite, all of which show calc-alkaline to high-K calc-alkaline series rocks. Mineralizing porphyrys of Oyu Tolgoi porphyry Cu-Au deposit are mainly quartz monzodiorites, and the same period's volcanic rocks primarily consist of dacite-basaltic rocks, belonging to high K calc-alkaline series. The trace and rare earth elements of the ore-related rocks from the above two deposits show typical features of arc magmatic rocks. However, compared with Oyu Tolgoi porphyry Cu-Au deposit, Erdenet porphyry Cu-Mo deposit shows high Sr/Y and La/Yb ratios, low contents of compatible elements(Cr, Ni)and relatively enriched Sr-Nd-Hf isotopic compositions. Combined with the regional geological background of the study area, it is believed that the mineralizing porphyrys of Erdenet porphyry Cu-Mo deposit originate from the partial melting of the thickened young lower crustal material, and are formed in a continental arc tectonic setting during the end of the Mongol-Okhotsk ocean evolution, while Oyu Tolgoi porphyry Cu-Au deposit's mineralizing porphyrys generate from fractional crystallization of depleted mantle materials, and form in an island arc tectonic setting. Therefore, it can be concluded that Erdenet porphyry Cu-Mo and Oyu Tolgoi porphyry Cu-Au deposits develop different mineral resources, matching themselves' tectonic setting where they formed. The above conclusions may help us better understand the relationship between the metallogenic tectonic environment and the types of porphyry deposits in the CAMD, and then have significant influence for the exploration of porphyry mineral resources under different tectonic environments.