摘要
班公湖-怒江洋的形成演化是认识班公湖-怒江成矿带成矿地质背景的关键,近几年中国地质调查局在青藏高原部署了大量1∶50000区域地质调查工作,取得了很多重要发现。对班公湖-怒江结合带两侧关键性海陆沉积地层对比研究,认为南羌塘地块与拉萨地块晚古生代-晚三叠世地层沉积特征及岩石组合基本一致,二者在班公湖-怒江中生代洋盆形成以前是一个整体,为冈瓦纳大陆北缘被动陆缘环境。班公湖-怒江洋在早中侏罗世裂解形成,至中侏罗世趋于稳定且范围最大;向北俯冲消减作用始于中晚侏罗世,晚侏罗世-早白垩世演化为残留海,早白垩世中晚期出现短暂的裂解,致使海水重新灌入;晚白垩世班公湖-怒江洋盆进入闭合后的隆升造山阶段,发生了残留盆地迁移,形成了磨拉石建造。班公湖-怒江洋类似古加勒比海(现今墨西哥湾地区)的形成机制,并与大西洋、太平洋的形成过程关系密切。对于班公湖-怒江洋的闭合和冈底斯弧的形成,本文提出了另一种可能解释,即,新特提斯洋向北俯冲下,岩浆弧逐步南迁,在弧后形成了一系列伸展性质的弧后盆地,两者组成微陆块由北向南逐渐增生形成了现今的拉萨地体,持续向北俯冲也导致了班公湖-怒江洋最终闭合。
The formation and evolution of the Bangong-Nujiang Ocean is the key to understanding the geological background of the metallogenic belt. In recent years, the China Geological Survey has deployed many 1:50000 regional geological surveys in the central part of the Tibetan Plateau, and has many new discoveries. Based on the latest regional geological mapping, we compared the stratigraphy of the north and south sides of the Bangong-Nujiang suture zone, and reconstructed the Paleogeography. The Late Paleozoic to Late Triassic sedimentary characteristics and rock associations of the Qiangtang terrane are basically consistent with the Lhasa terrane, suggesting that these two terranes were connected before the opening of the Bangong-Nujiang Ocean occurring in the passive margin of northern Gondwana. According to the structure and distribution of the oceanic basin, the Bangong-Nujiang Ocean is probably initiated by the sinistral strike-slip after the collision of the ancient Tethys in the early Middle Jurassic. The ocean was stable and the most broadly distributed during the Middle Jurassic, and has been residual sea by Late Jurassic-Early Cretaceous because of Bangong-Nujiang Tethys oceanic crust north-ward subduction since Middle-Late Jurassic. The residual sea had a transient extension in the Early Cretaceous, and closed in the Late Cretaceous ending with orogenic uplifting, which led to the migration of residual basins and the molasse formation in a foreland basin. The modern analogy of the Bangong-Nujiang Ocean is Caribbean Sea which has similar inception mechanisms. During collision of the India and Eurasia plates in Jurassic-Cretaceous, the deformation of the ancient Tethys margin was superimposed, such as the residual basin and the accretionary complex of the ancient Tethys domain. In this paper, with the example of Bangong-Nujiang metallogenic belt, we emphasized the importance of the limestone, flysch and volcanic rocks, which are the keys to understand the temporal and spatial evolution of the paleo-ocean. The
作者
宋扬
曾庆高
刘海永
刘治博
李海峰
德西央宗
SONG Yang;ZENG QingGao;LIU HaiYong;LIU ZhiBo;LI HaiFeng;DEXI YangZong(MNR Key laboratory of Metallogeny and Mineral Assessment, Institute of Mineral Resources. Chinese Academy of Geological Sciences, Beijing 100037 ,China;Tibet Bureau of Geology and Mineral Exploration and Development, Lhasa 850000, China;Tibet Institute of Geological Survey, Lhasa 850000, China)
出处
《岩石学报》
SCIE
EI
CAS
CSCD
北大核心
2019年第3期625-641,共17页
Acta Petrologica Sinica
基金
中国地质调查局项目(DD20160026
DD20190167)
自然资源部杰出青年人才培养计划联合资助
