Research On Matellogenic Regularities And Prospecting Directions Of Gold Deposits At Gaize District, Tibet

Tibet is one of most significant gold-bearing areas in China Especially, Bangongcuo-Nujiang suture zone has long been an important gold-producing district since ancient time. There are still lots of gold mining remainders along Bangongcuo-Nujiang suture zone. Quite a lot geological survey and exploration in the suture zone have been done in last decade, proving that it is the most important gold metallogenic belt in Tibet. With the development in both theory and technology of mineral exploration, considerable progress has been made in mineral exploration in the belt. However, while gold mining bloomed all over Tibet, driven by momentary benefits, theoretical research has not been paid enough attention to since the first large gold deposit (Bongnazangbu) in Tibet was successfully prospected and mined. It gave negative effects on the assessment of potential of gold resources and exploration. As a result, no breakthrough in exploration of primary gold deposits has been made so far. Tibet as an integrate part of Alps-Himalayan metallogenic belt, one of giant word-class metallogenic belts, posses favorable conditions for the formation of gold deposits. Therefore, it should have been paid the most attention. Nevertheless, it remains the most underdeveloped region in geological survey and research in our country because of extremely high altitude and very bad traffic. Facing to a historical opportunity of large-scale exploitation of me West and advancement in science and technology, it is wise to conduct exploration-aiming research by using new theories, technology and methods so as to make correctly assessment of potential of gold resources and raise efficiency of gold exploration.Under the theory of regional metallogenic system, this paper, focusing on Gaize district in Tibet, conducted carefully research in geological structure, magma activity, geophysical anomaly, geochemical anomaly, gold-bearing geological bodies and gold occurrence state, association of gold with other related elements, characteristics of typical deposits, metallogenic age, metallogenic process, post-ore-forming destruction of deposits in Gaize district based on methods of geology, petrology, economic geology, genetic mineralogy, isotopic chronology, geophysical and geochemical prospecting, and remote sensing.The results suggest that the formation of gold deposits was related closely to a series of tectonic events during the period of dispersion-subduction-collision between Qiangtang-Sanjiang plate and Gangdise-Nianqingtanggula plate.It seems that submarine magmatism and hydrothermal activity provided abundant ore-forming material for partly strata of Mogaganri and Yanshiping formations during the extension of Bangongcuo-Nujian marginal sea in early-middle Jurassic. Therefore parts of Jurassic Mogaganri and Yanshiping formations became original source of ore-forming material. In later early Jurassic, the collision and collage between Qiangtang block and Nianqing-Tanggula block made favorable conditions in geological structure, magma and ore-forming fluids for the formation of gold deposits.New results and progress in this paper are summarized as follows:1. A model of regional metallogenic system in Gaize district has been established according to Zhai Yusheng's regional metallogenic theory on the basis of studies of tectonics settings, controlling factors and products of the formation of gold deposits, changes and preserving conditions of the deposits and their mechanism after the formation of the deposits, and the time-space structure and material structure of metallogenic system. This model will be helpful to deploying gold exploring in the region interested.2. Considerable progress has been made in the study of ore-forming fluids. The composition and physicochemical condition of ore-forming fluids were determined by the analysis of chemical composition, 6 D, 18O and physical chemistry parameters of fluid inclusions in quartz veins, which are closely related to gold mineralization in Gaize area. It was estimated the ore-f...