Massive Sulphide Deposits Related to the Volcano-Passive Continental Margin in the Altay Region

The Devonian volcano-passive continental margin in southern Altay is a significant volcanogenic massive sulphide metallogenic belt. Acidic volcanism has been dominant on the inner side of the volcano-passive continental margin, i.e., near the old land, resulting in a Pb-Zn metallogenic sub-belt, in which the ore deposits are hosted by sedimentary rocks in volcanic series, as represented by the large Koktal Pb-Zn deposits. In the central part of the margin far away from the old land, bimodal volcanic formations are well developed, forming volcanics-hosted Cu-Zn metallogenic sub-belts, e.g., the large-scale Ashele Cu-Zn deposit. The Qiaoxiahala sub-belt on the outer side of the margin near the ocean ridge is located at the spreading central trough, where ophiolite suites are developed. This type of deposits is rich in gold and copper, similar to the Cyprus-type Fe-Cu-Au metallogenic sub-belt in metallogenic environment (represented by the Qiaoxiahala medium-scale Fe-Cu-Au deposit). From the old land to th     

Geology, Genetic Types and Metallogeny of Gold Deposits in the Eastern Tianshan, Xinjiang

As a typical Palaeozoic island arc system, the eastern Tianshan area, Xinjiang, is different from eastern China but similar to the Meso-Cenozoic island arc metallogenic provinces along the coast of the Pacific Ocean in metallogenic environment, geology and geochemistry. Three types of gold deposits, ductile shear zone-hosted gold deposits (Kanggur ), magmatic hydrothermal gold deposits (Jinwozi) and volcanic- or subvolcanic-hosted gold deposits (Xitan and Mazhuangshan), have been identified in this area. Regionally, gold deposits are structurally controlled by the Kanggur Tag ductile shear zone, Shaquanzi fault, Hongliuhe fault and Yamansu fault. Generally, gold mineralization occurs in the transition zones from volcanic rocks to sedimentary rocks. The horizon bearing well-developed jasper is an important indicator for gold mineralization. Each of the three types of gold deposits has its distinctive metallogenic background and geological-geochemical characteristics.     

Tectono-Metallogenic System in the Altay Orogenic Belt, China

The Altay erogenic belt of China is an important metallogenic belt of base metals, rare metals and gold. The main orogenic-metallogenic epoch is the Hercynian (Late Palaeozoic). Hercynian orogeny underwent two tectonic stages: the early volcano-passive continental margin extension (D1-D2) and late subduction-collision (D3-P). There correspondingly developed two different metallogenic systems. One is the stratabound massive sulphide and iron metallogenic system related to volcano-passive continental margin, and the other is the epigenetic gold and granite-associated rare metals system formed by collision. Very few mineralizations were formed during the subduc-tion time.     

A Study of Occurrences of Ag in Pb-Zn-Cu Ore Deposits in China

A systematic study of occurrences of silver in 156 Pb-Zn-Cu ore deposits indicates that silver mainly occurs in nonferrous metal ore deposits in forms of association and paragenesis. It occurs mainly as independent minerals in nature and occasionally as ion adsorption, isomorphous or amorphous silver minerals. Nearly 190 silver minerals have been discovered in China. Their shapes, constituents, textures, grain sizes, embedded types, distribution patterns, mineral assemblages and metallogenic series suggest that these characteristics are closely related to geneses of deposits and dependent of ore-forming conditions. Pb, Zn and Cu sulphides are the main carrier minerals of silver. The partition of silver in ore is constrained by the mineralization intensity, grain size and embedded form of silver minerals and mineral assemblages.     

Qinling Orogenic Belt: Its Palaeozoic-Mesozoic Evolution and Metallogenesis

The formation, development and evolution of the Qinling erogenic belt can be divided into three stages: (1) formation and development of Precambrian basement in the Late Archaean-Palaeoproterozoic (3.0-1.6 Ga), (2) plate evolution (0.8-0.2 Ga), and (3) intracontinental orogeny and tectonic evolution in the Mesozoic.The Devonian (D) and Triassic (T) were the key transition period of the tectonic evolution of the Qinling orogenic belt. That is to say, in the Devonian, the Qinling micro-plate was separated from the northern margin of the Yangtze plate (passive continental margin). This period witnessed transition of the micro-plate from the compressional to ex-tensional state, and consequently three types of sedimentary basins were formed, namely, the rift hydrothermal basin in the micro-plate, restricted ocean basin in the south, and residual ocean basin resulting from collision on the northern margin. In the Triassic the Qinling area was turned into the intracontinental orogen.The Devonian and Triassic w