阿尔泰铜矿带南缘希勒克特哈腊苏斑岩铜矿的发现及其意义

Discovery of the Xileketehalsu porphyry copper deposit on the southern margin of the Altay copper metallogenic belt

希勒克特哈腊苏铜矿位于阿尔泰铜矿带南缘,即原卡拉先格尔斑岩铜矿带内。初步的研究和钻孔资料表明,铜矿体完全受斑岩体(石英闪长斑岩和花岗闪长斑岩)控制,矿石具细脉浸染状构造,金属矿物主要为黄铜矿和黄铁矿以及少量的磁铁矿、斑铜矿和镜铁矿。其中磁铁矿形成早于黄铜矿,指示了岩浆具有较高的氧化状态。矿化蚀变分带与斑岩铜矿基本相似,岩体内见钾长石化、黑云母化、硅化和黄铁矿化,接触带见石英绢云母化,围岩见青磐岩化。含矿斑岩的地球化学特征表明其属于埃达克岩(adakite):高SiO2(63%～66%)、高Al2O3(15%～17%)、富集Sr(378×10-6～447×10-6)、无负Eu异常、亏损Y(10×10-6～14×10-6)和Yb(1.3×10-6～1.5×10-6)以及低的Sr同位素初始值(0.70439)、高的(εNd)t(+6.9～+8.2)和低的δ18OV-SMOW(<10‰)。其Rb-Sr等时线年龄为(332.8±8.5)Ma,为早石炭世侵位的产物,其形成与蒙古洋板块向南俯冲造成的洋壳部分熔融有关,因此其成矿地质背景与世界巨型斑岩铜矿十分相似。另外,在希勒克特哈腊苏铜矿外围还有数个与其十分相似的铜矿点,因此该地区展示了良好的找矿前景,同时也是中国又一个潜在的斑岩铜矿带。

The Xileketehalasu copper deposit is situated on the southern margin of the Altay copper metallogenic belt, i.e., inside the original Kalaxiangeer porphyry copper belt. The preliminary study and drilling have revealed that copper orebodies are completely controlled by quartz diorite porphyry and granodiorite porphyry. The ores have veinlet and veinlet-disseminated structures. Chalcopyrite and pyrite are dominant metallic minerals with minor magnetite, bornite and specularite. Magnetite formed earlier than chalcopyrite, suggesting relatively highly oxidized magma. Its mineralization and alteration zoning essentially resemble those of typical porphyry copper deposits. K-feldspar, biotite, silicate, and pyrite alteration zones occur within the porphyry, and the quartz-sericite alteration zone is distributed in the contact between the porphyry and its wall rocks, whereas the propylitic zone occurs in the country rocks. The geochemistry of the mineralized porphyry characterizes adakite: high SiO2 (63%-66%) and Al2O3 (15%-17%), enrichment in Sr (378×10-6-447×10-6), no negative Eu anomalies, depletion in Y(10×10-6-14×10-6)and Yb (1.3×10-6-1.5×10-6, and low initial Sr isotopic value (0.70439), high (εNd)t values (+6.9-+8.2) and low δ18OV-SMOW (<10‰). The Rb-Sr isochron age for the porphyry is 332.8±8.5 Ma, belonging to Early Carboniferous. Its petrogenesis is related to partial melting of oceanic crust due to southward subduction of the Mongolian ocean plate. Therefore, its metallogenic geological setting is very similar to the famous supergiant porphyry copper deposits in the world. In addition, there are some copper occurrences with similar features in the surrounding areas of the deposit. Therefore the area has good ore prospects and is another potential porphyry copper belt in China.