Metallogenic type,tectonic setting,and resource potential of Ertix gold ore belt in northern Xinjiang
YAN ShengHao~1, WANG YiTian~1, ZHANG ZhaoChong~2, CHEN BaiLin~3 and CHEN Wen~4 (1 Institute of Mineral Resources, CAGS, Beijing 100037, China; 2 Institute of Geology, CAGS, Beijing 100037, China; 3 Institute of Geomechanics, CAGS, Beijing 100081, China; 4 Laboratory of Isotope Geochronology, Institute of Geology, CAGS, Beijing 100037, China)
Primary gold deposits have become the main source of gold production in the Altay region since the 1980s, although this region teemed with placer gold in history. Nevertheless, no large-size primary gold deposits have been found in the past 20 years. Based on extensive field geological survey and isotopic chronological study, combined with data available, the authors intend to discuss the metallogenic types and tectonic setting of gold deposits in the Altay region in the light of the evolution of the orogenic belt and, what is more, attempt to answer the questions of the gold potential and ore-search prospects in the terrane at the province scale by a comparative study with some typical orogenic gold provinces of Paleozoic orogenic belts in the world. A comprehensive review of the principal characteristics of gold deposits in the Altay region has led the authors to reach some new conclusions: the major primary gold deposits are confined in the highly-stressed and epimetamorphic structural belt; the mineralization style, mineral assemblage, and ore-forming fluid are similar to those of epizonal orogenic gold deposits defined by Groves et al. (1998); isotopic ages of gold deposits are clustered in the range of 310～270 Ma, corresponding to Late Carboniferous to Early Permian; gold mineralization is associated with the post-collisional structural-magmatic activities at the late stage of the Hercynian orogeny; the tectonic setting of the gold metallogeny seems to be the diapiric upwelling of asthenosphere mantle due to the delamination of the lithosphere mantle during the post-orogeny stage, which resulted in the prominent temporal-spatial coupling relationship of the gold deposits to the mantle-derived mafic-ultramafic intrusive bodies and alkali-rich granitoids; the associated gold deposits can be classified into three subtypes, namely, gold in VMS and SEDEX Fe-Cu-PbZn deposits , gold in porphyry-skarn Cu-Mo deposits , and gold in magmatic Cu-Ni sulfide deposits. A comparative study shows that there actually exist the necessary tectonic setting, geological conditions and regional metamorphic fluid system in the Altay region. The discovered medium-small size gold deposits and numerous ore spots may merely represent the upper part of the regional mineralization system, whereas the main part has not yet been denuded and uplifted because of the crustal thrusting-napping since Mesozoic. Due to the Caledonian and Hercynian orogenic events, the formerly-formed orogenic gold deposits in the central part of the Altay region (Kalong-Keketuohai-Qinghe) had almost been denuded and changed into the widely distributed placer gold deposits. On the contrary, the southern Altay region (probably including the Nuoerte region), which possesses abundant Devonian to Carboniferous volcanic rocks, and, especially, the known Fe-Cu-Pb-Zn mineralization belt, are most favorable targets in search for orogenic and associated gold deposits.
【Fund】： 国家重点基础研究发展规划项目(2001CB409807);; 国家科技攻关项目(2001BA609A-07-02)的部分成果
【CateGory Index】： P618.51
【CateGory Index】： P618.51