【作者】 肖润；

【导师】 莫宣学； 刘肇模；

【作者基本信息】 中国地质大学（北京） ， 矿物—岩石—矿床， 2003， 博士

【摘要】 西藏是我国重要的黄金产地之一，尤其班公错—怒江结合带，自古以来就是西藏的重要产金地，沿着班公错—怒江结合带一线，尚遗留有大量的古代采金遗迹。近10余年来，地质工作者在班公错—怒江结合带做了一些工作，证实该带是西藏最重要的黄金成矿带。随着找矿工作的开展，取得了一定的成果。但是随着西藏第一个大型金矿—崩纳藏布金矿探明并开采成功以来，受眼前利益的驱动，金矿工作处于遍地开花的局面，而理论研究工作却未受到应有的重视，以致岩金勘查工作未有明显的突破，影响了该区找矿工作布署和对该区找矿潜力的评价。西藏作为世界最大环球成矿带之一的阿尔卑斯—喜玛拉雅成矿带的重要组成部分，具有得天独厚的成矿条件，本应受到最大限度的重视，但因地处高原、气候恶劣、交通不便，长期以来一直是我国地质工作最落后的地区。随着西部大开发这个历史机遇的到来和科学技术水平的提高，利用新理论、新方法、新技术、新手段对该区进行以指导生产为主的科研工作，将是正确评价其找矿远景，指导找矿的行之有效的措施。 本论文以藏北改则地区为重点研究区，以区域成矿系统理论为指导，采用地质学、岩石学、矿床学、成因矿物学、同位素年代学以及物、化、遥相结合的方法，对改则地区的地质构造、岩浆活动、物化遥异常、各地质体的含金性及金的赋存状态、金与相关元素的组合特征、典型矿床特征、成矿时代、成矿过程及矿床形成后的破坏作用等进行了较详细的研究。 研究结果表明，区内金矿的形成不是孤立的，它与羌塘—三江板片和冈底斯—念青唐古拉板片的离散-俯冲-碰撞等一系列区域构造事件直接相关。在早-中侏罗世班公错—怒江边缘海扩张过程中，海底岩浆及其热液作用，为侏罗系木嘎岗日群和雁石坪群部分层位提供了大量的矿源，使其成为初始矿源层；早白垩世晚期，羌塘地块和冈底斯—念青唐古拉地块碰撞拼贴，造成了有利的构造条件、岩浆条件、成矿流体条件，形成矿床。 归纳起来，本文取得的新成果和新进展有以下几方面： 1．根据翟裕生院士的区域成矿学理论，对西藏改则地区区域构造背景、金矿床成矿控制因素及其产物、矿床形成后变化和保存的条件及机理、成矿系统的时空结构和物质结构等方面进行了较为系统的研究，并在此基础上尝试建立了区域成矿系统模型，为今后在该区部署金矿地质工作，提供了一定的理论依据。 2．对该区与成矿有密切关系的脉石英进行了成矿流体方面的研究。通过对石英矿物中的流体包裹体特征、成分、流体水的氢、氧同位素及其物理化学参数的分析与测定，论证了成矿流体的成分及物理化学条件。成矿流体的压力平均为687（10⁵Pa），主成矿期成矿温度平均为181℃，推算出成矿时的深度平均为2410 m。成矿过程是在两个体系混合作用下进行的，成矿流体属盐度较低的NaCl-H₂O体系和CO₂-NaCl-H₂O体系，早期和主成矿期成矿流体的盐度和密度没有明显的变化。 3．为了厘定改则地区金矿成矿热液活动的年代学，在改则地区的两个典型矿区，进行了K-Ar同位素年龄测定。结果表明，热液驱动成矿物质定位矿化开始阶段的年龄值93.86±2.11Ma，主要的金成矿作用发生在晚白垩世早期。 4．对本区含矿地层、岩浆岩及矿石矿物中微量元素、稀土元素及硫、铅、硅同位素和包裹体中水的氢、氧同位素进行了分析与较为系统的研究，证明本区岩金矿成矿物质主要来源：一是班公错—怒江边缘海扩张时期，海底喷流-炭质沉积及海底火山沉积作用，形成初始矿源层；二是冈底斯—念青唐古拉地块和羌塘地块碰撞拼贴时期，在岩浆演化过程中，岩浆热液系统中的成矿物质逐渐在晚期浓集，并在合适的构造部位形成矿床。更多还原

【Abstract】 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更多还原