藏北商旭金矿床的构造控矿机制研究

Orogenic gold deposits have a unique temporal and spatial association with orogens, including accretionary and collisional orogens. However, the mechanism of structural control of the gold deposits in collisional orogens is unclear. For this purpose, we choose Shangxu orogenic gold deposit which located in the Bangong-Nujiang suture zone in northern Tibet. Firstly, combining DEM data, geological structural interpretation on the basis of ETM+ and ASTER image will be used to establish a stereo image of regional structure farmwork. Then, based on the large scale geological structure mapping of mining area, X-ray fabric analysis, magnetic fabric analysis and EBSD analysis will be combined to study on faults, rocks and folds. Finally, through a comprehensive analysis and study, we will find out the characteristics of ore controlling structures, recover the evolution of tectonic stress field, and answer the scientific question of the mechanism of structural control of the gold deposits in collisional orogens. The research has extremely important scientific and practical significance to enrich the understanding of coupling relationship between structure and mineralization, and discuss the metallogenic potential of orogenic gold deposits in the Bangong-Nujiang suture zone in northern Tibet.

造山型金矿既可以发育于增生型造山环境，也可以发育于陆-陆碰撞造山环境，但陆-陆碰撞造山背景下金矿的构造控矿机制尚未明确。针对这一科学问题，本项目拟通过ETM/ASTER数据构造解译与构造解析等方法开展研究。选取青藏高原班公湖-怒江缝合带中的商旭金矿床为研究对象，基于区域尺度的ETM/ASTER数据构造解译，结合DEM数据建立区域构造格架的立体影像图；通过矿区尺度的大比例尺地质构造填图，采用岩石X光组构分析、岩石磁组构分析和EBSD分析等关键技术，进行断层构造分析、岩石变形组构分析和褶皱变形分析；综合分析遥感解译和构造解析的结果，查明控矿构造特征，恢复构造应力场的演化过程，最终回答陆-陆碰撞造山背景下金矿床构造控矿机制这一科学问题。研究结果对于丰富对构造-成矿耦合关系的认识以及探讨青藏高原班公湖-怒江缝合带内造山型金矿的成矿潜力，都具有极为重要的科学意义和现实意义。

造山型金矿既可以发育于增生型造山环境，也可以发育于陆-陆碰撞造山环境，但陆-陆碰撞造山背景下金矿的构造控矿机制尚未明确。针对这一科学问题，本项目选取青藏高原班公湖-怒江缝合带中的商旭金矿床为研究对象：（1）基于区域尺度的ETM数据构造解译，建立区域构造格架，得知区域主要展布一组近东西向断裂；（2）通过矿区尺度的大比例尺地质构造填图，进行断层构造分析和褶皱变形分析，查明NWW向断裂是商旭矿区内主要的控矿构造和容矿构造；（3）基于ETM/ASTER数据的提取矿区铁染/黄铁矿化遥感蚀变信息，并与控矿构造、矿体叠加分析：黄铁矿化在商旭矿区分布相对集中，尤其是中段和西段；黄铁矿化一级、黄铁矿化二级蚀变相对集中的部位与矿区已知控矿断裂、已知矿体等吻合较好；（4）通过碎屑锆石U-Pb数据奇异性分析、Hf同位素分析，综合构造、成矿等特征，对陆-陆碰撞造山背景下金矿床的构造-成矿耦合关系取得阶段性认识：商旭金矿形成于早白垩世班公湖-怒江缝合带中段拉萨-羌塘地块的碰撞时期，木嘎岗日群受到不同地块之间的挤压应力发生构造变形，在挤压变形晚期构造环境发生转换的过程中，围岩中应力释放促使区域发育金矿化。