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Progress in the Study of Central Asia-Type Orogenesis - Metallogenesis in Northwest China
- CHEN Yan-jing
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2000, 6(1):
17-22.
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Located in the core of the Eurasian continent, the Central A sian oro gens are characterized by the mosaic structures of several Late Paleozoic geosut ures (e.g., the Kalamaili, the Erqs, the Dalabute, the Bayingou, and the Honliuh e ophiolite belts) and the multiple Precambrian blocks (e.g., Tarim, Ili, Jungga r, 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 Ju nggar). It is different not only from the Alpine - Himalayan mountains, which ar e formed by collision of large continents, but also from the Andean mountains re sulted from subduction of wide oceanic plate beneath giant continent plate. Ther efore, the Central Asian orogens must represent a new type orogenesis featured b y amalgamation of multiple blocks such as Ili, Junggar and Hami. The orogenic me chanism 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 var i ous types concentrated in the Central Asian orogenic area, and that the Hercynia n orogenesis had resulted in large scale mineralization in Central Asian territo ries. 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 po r phyry copper deposits, epithermal gold deposits and massive sulfide polymetallic deposits, which were considered as the predominant mineralization type in the C ircum-Pacific Rim, have also been found in large quantity in the Central Asia n orogens, such as the Balqash porphyry copper belt in Kazakhstan, the Ashele-K eketale massive sulfide Cu-Pb-Zn belt in Altay within China, the Tianshan epit he rmal gold deposit belt in China (including Axi, Shiyingtan, Yuxi and Mazhuangsha n gold deposis in China). The mesothermal gold deposits associated with regional ly metamorphosed terranes of different ages are recently argued being formed dur ing compressional to transpressional deformation processes at convergent plate m argins in accretionary and collisional orogens and are consequently called as th e 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 deposi t belt in Tianshan, the Qrqs gold deposit belt in Altay (including 5 large gold d eposits), etc. The carbonaceous stratabound type gold deposits represented by th e Muruntau deposits in western Tianshan and the Sowaya'erdun in southern Tiansha n are the most important gold reserves in the Central Asian areas, which have on ly 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. T hese problems are attracting more and more attentions of scientists both from Ch ina and abroad. The metallogenesis during Central Asian orogenesis is a key to t he development of continental geodynamics and regional metallogeny.
