中国西北地区中亚型造山—成矿作用的研究意义和进展

Progress in the Study of Central Asia-Type Orogenesis-Metallogenesis in Northwest China

地处欧亚大陆核心的中亚型造山带 ,由多条古生代缝合带与多个前寒武纪小陆块镶嵌 ,基此形成中新生代盆地—山脉耦合的构造格局 ,并具有独特的构造演化史和动力学机制。中亚型造山作用造就了丰富的矿产资源 ,矿床类型多样 ,超大型矿床汇聚 ,是解决我国 2 1世纪矿产资源问题的关键地带。但目前尚未查明其成矿规律、成矿机制和找矿方向 ,因而急需研究。

Located in the core of the Eurasian continent, the Central Asian orogens are characterized by the mosaic structures of several Late Paleozoic geosutures (e.g., the Kalamaili, the Erqs, the Dalabute, the Bayingou, and the Honliuhe ophiolite belts) and the multiple Precambrian blocks (e.g., Tarim, Ili, Junggar, and Hami blocks or terranes), the coupling of the Mesozoic - Cenozoic orogens (e.g., Tianshan, Jungguar and Altay) and the basins (e.g. Tulufan, Tarim and Junggar). It is different not only from the Alpine - Himalayan mountains, which are formed by collision of large continents, but also from the Andean mountains resulted from subduction of wide oceanic plate beneath giant continent plate. Therefore, the Central Asian orogens must represent a new type orogenesis featured by amalgamation of multiple blocks such as Ili, Junggar and Hami. The orogenic mechanism and distinctive tectonic evolution of the Central Asian orogens are very important in further study of the continental geodynamics. It has been well documented that there are many super large ore deposits of various types concentrated in the Central Asian orogenic area, and that the Hercynian orogenesis had resulted in large scale mineralization in Central Asian territories. This indicates that the southwest China will play a more important role in providing China with new mineral resources in the twenty first century. The porphyry copper deposits, epithermal gold deposits and massive sulfide polymetallic deposits, which were considered as the predominant mineralization type in the Circum-Pacific Rim, have also been found in large quantity in the Central Asian orogens, such as the Balqash porphyry copper belt in Kazakhstan, the Ashele-Keketale massive sulfide Cu-Pb-Zn belt in Altay within China, the Tianshan epithermal gold deposit belt in China (including Axi, Shiyingtan, Yuxi and Mazhuangshan gold deposis in China). The mesothermal gold deposits associated with regionally metamorphosed terranes of different ages are recently argued being formed during compressional to transpressional deformation processes at convergent plate margins in accretionary and collisional orogens and are consequently called as the orogenic type of gold deposits. This type of gold deposits are also frequently found in the Central Asian orogens, e.g., the Kanggu'er-Wangfeng gold deposit belt in Tianshan, the Qrqs gold deposit belt in Altay (including 5 large gold deposits), etc. The carbonaceous stratabound type gold deposits represented by the Muruntau deposits in western Tianshan and the Sowaya'erdun in southern Tianshan are the most important gold reserves in the Central Asian areas, which have only been found to be of great economic significance in the Central Asian orogens. However, the mineralization pattern and the metallogenic mechanism of this type of gold deposits, as well as the exploration direction are still unclear now. These problems are attracting more and more attentions of scientists both from China and abroad. The metallogenesis during Central Asian orogenesis is a key to the development of continental geodynamics and regional metallogeny.