西藏及西南三江深断裂构造格局新认识

西藏和西南三江地区是青藏地区断裂构造最为复杂区域,历经数十年研究,对该区断裂构造的认识仍存在分歧.笔者以最新实测航磁数据并结合重力资料为基础,从重、磁场特征与地质构造研究相结合角度出发,新编制了西藏及西南三江地区的断裂构造格架图.研究结果表明,在西南三江流域的金沙江深断裂、澜沧江深断裂和怒江深断裂自南向北西延伸,没有与西藏地区的近东西向断裂呈弧形连接,而是一组独立存在的北西向断裂,这是在特提斯断裂系统中新发现的一组北西向断裂,它与发育在西藏地区的近东西向断裂分属于不同的断裂系,与前人提出的金沙江缝合带、龙木错—澜沧江缝合带和班公湖—怒江缝合带的走向呈北西—近东西向弧形分布特征的看法存在差异.这组断裂的发现改变了对西藏—西南三江地区断裂构造格架的认识,这为今后大地构造研究提出新的启示.文章重点展现西南三江(金沙江、澜沧江、怒江)深断裂带在重、磁场上的西延状况,并探讨了西南三江深断裂与西藏地区近东西向深断裂呈相交关系特征,同时也表明重、磁资料用于断裂构造的研究具有重要意义.

A new understanding on the pattern of deep faults in Xizang and the southwestern Sanjiang area

Extremely complicated fault structures characterize Xizang and the Sanjiang (Jinsha River, Lanchang River, Nujiang River) region in southwest China. In spite of many years' study, different recognitions to this issue remain present. Based on new aeromagnetic data combining gravity data, beginning with combination of gravity and magnetic characteristics with geological structure, we compile a new map of fault structures in Xizang and the southwestern Sanjiang region. The results show that the deep faults along the Jinsha river, Lanchang river and Nujiang river are independent NW-striking faults which extend from the south to the north west, not connecting with the arc-like faults in Xizang which extend from the east to the west. These faults are newly discovered NW-striking faults in the Tethys fault system, which belong to a different fault system relative to EW-striking faults in Xizang. This opinion is different from the previous contend that the suture zones of Jinsha River, Lungmu Co-Lanchang river and Bangong Hu-Nujiang river extend towards NW-EW with arc distribution. This discovery of the faults has changed the recognition of fault structure framework of Xizang-Sanjiang areas, which lends light on the geotectonic research in the future. This paper also discusses the intersection relationship of faults between the Sanjiang area and Xizang and indicates that gravity and magnetic data are significant for the research on fault structure.