班公湖-怒江结合带西段多岛弧盆系时空结构初步分析

A preliminary study of the spatio-temporal framework of the archipelagic arc-basin systems in the western part of the Bangong-(Nujiang) suture zone, Xizang

关键词:  蛇绿混杂岩带  多岛弧盆系  特提斯洋  班公湖  西藏

Key words:  ophiolitic mélange zone  archipelagic (arc)-(basin) systems  Tethys Sea  Bangong Lake  Xizang

摘要:

笔者依据班公湖地区1:25万喀纳幅、日土县幅、羌多幅地质填图和专题研究工作取得的阶段性成果,将班公湖带的多岛弧盆系时空结构厘定为3条蛇绿混杂岩亚带。该3条亚带为盆地所隔,从北而南依次为班公湖带北亚带、班摩掌侏罗纪弧间盆地、班公湖带中亚带、日土-巴尔穷侏罗纪-早白垩世复合弧后盆地和班公湖带南亚带等。初步认为班公湖-怒江特提斯洋经历了晚三叠-早侏罗世往北俯冲、中晚侏罗世早期向北、往南双向俯冲、早白垩世往南俯冲等3次俯冲消亡阶段;同时,讨论了在班公湖带研究中存在的问题及其在反演班公湖-怒江结合带西段构造演化和在找矿方面的意义,以及进一步研究方向。

Abstract:

The archipelagic arc-basin systems in the western part of the Bangong-(Nujiang) suture zone may be discriminated into three ophiolitic mélange subzones that are separated by the local basins, including, from north to south, the northern Bangong subzone, Banmozhang Jurassic inter-arc bain, middle Bangong subzone, (Rutog)-(Barqiong) (Jurassic)-(Early) Cretaceous composite back-arc basin and southern Bangong subzone. The (Bangong)-(Nujiang) Tethys Sea once underwent three phases of subduction and consumption:northward subduction during the Late (Triassic) and (Early) Jurassic, northward and southward subduction during the early (Middle)-(Late) (Jurassic), and southward subduction during the Early Cretaceous. The collapse of the Yarlung Zangbo back-arc basin is interpreted to be synchronous with the (arc)-(continent) collision and collage in the Bangong Lake area, and thus the (Bangong)-(Nujiang) suture zone may be considered as the main suture zone after the subduction and (consumption) (of) (the) Tethys Sea.