Study On The Characteristics Of Wall Rock Alteration And Metallogenic Model Of Rongruri Gold Mine In Tibetan Maizhokunggar County

Wall rock alternation grows from the surroundings of gold ore body, which is the significant and direct symbol for exploring the gold ore body and concealed ore body. We can not only improve the ability to predict the gold mineralization, and also deepen our knowledge on genesis of ore deposits and mineralization by analyzing the types and characteristics of wall rock alternation.Nongruri gold mine of Tibetan Maizhokunggar County locates the position of earth structure in the eastern section of southern Gangdise compound tectonomagmatic zone of Gangdise - Himalayan tectonic zone in Qinghai-Tibet Plateau. The open ground layer of the targeted area, with a Linbuzong formation of the upper middle layer of Jura and Lower Cretaceous Series, which is constituted by Epimetamorphic rocks mainly of metasandstone, slate and phyllite; strong Phase of Yanshan - Himalaya magrnatism mainly presents as acid magmatic intrusion. In this area, the geologic structure is complicated. Rupture, cleavage and diaclases develop greatly, and rupture of late stage parallel distribute along with nearly SN direction generally and superposition on the east-west direction structure of early period, which forms the basic tectonic framework of this area. Studies have shown that rupture in nearly SN direction is the important guiding mine and host structure of the deposits, which has a close relationship of formation of gold mine deposits.The development of wall rock alternation in the mining area is obviously controlled by rupture, distributing generally in the surroundings and both sides of the rupturing place. The main types of alternation includes pyritization, sericitization, siliconization, albitization, realgarization, cinnabarization, clayzation and carbonatization, among which, sericitization, siliconization, pyritization, cinnabarization and realgarization develop inside the mineralized bodies, have the closest relations with gold mineralization, and is a significant symbol for exploring mines. The form of alteration zone is relevant to the structure. Since the tectonic hydrothermal is acting for many times, they alternation types and strength are increasing, with frequent superposition of types of alternations, which make the zoning of wall rock alternation not obvious.Gold mineralization in controlled by the rupture zone distributed in nearly SN direction and Granodiorite porphyry. By analyzing the characteristics of gold mineralization and wall rock alternation, it is found that the hydrothermal alternation closely related to the gold mineralization can be divided into four stages, early sericite - quartz - pyrite period, medium-term gold-bearing - quartz (sericite) - pyrite period, gold-bearing - quartz - stibnite - realgar (orpiment) period, and later period quartz - carbonate period, among which the gold-bearing - quartz - stibnite - realgar (orpiment) period is the main mineralization period.By means of analogy of surrounding deposits and domestic similar deposits, combining with the characteristics of gold mineralization and wall rock alternation and the alternated mineral assemblage, it is found that the ore-forming fluid of Nongruri gold mine originates from paleostructure-endomagmatic hydrothermal, as well as atmospheric precipitation possibly; in the mineralization the characteristics of low hydrothermal temperature and low mineralization depth shows that it belongs to typical hypergene epithermal hydrothermal gold deposit. The formation has a close relationship with magmation of Himalaya period. The magmatic hydrothermal is the main source of the mineralization materials of gold deposit, and also provides part of the thermodynamic conditions for the formation of gold deposit. For the following NS tectogenesis, on the one hand, it forms the rising passage of hydrothermal, on the other hand, the structure, hydrothermal fluid, formed in the tectogenesis, driving by the thermal force and structural dynamics, is uprising continuously along the favorable rupture, and extracting activated mineralization materials by means of diffusion, penetration and altera-tion. Along with the change of the temperature, pressure and some other elements, the property of ore-bearing solution has changed, which finally precipitates, concentrates and mineralizes under the appropriate physical and chemical environment.