印度洋大地构造背景及其构造演化——印度洋底大地构造图研究进展

印度洋底大地构造图(1∶1 500万)基于最新地球物理数据,结合中国大洋调查航次积累的地貌、地质、地球物理和矿产资源资料编制,综合反映印度洋底及周缘地质、地貌、地球物理和资源分布等特征,将为理解和推进印度洋盆构造演化和资源分布研究提供理论支撑。本文介绍了该图编制的思路和方法、数据来源、图面内容和大地构造单元划分,认为印度洋盆具有多微陆块、多期扩张、多洋底高原、无震海岭和"入"字形洋中脊等特征。在前人研究基础上,将印度洋盆地构造演化归纳为3个阶段:(1)冈瓦纳大陆裂解与洋盆初始张开(侏罗纪-白垩纪中期);(2)洋盆持续张开与扩张中心跃迁(白垩纪中期-古近纪初期);(3)印度板块与欧亚板块俯冲碰撞及非洲板块裂解(新生代)。在扩张中心跃迁式的发育形式下,现今印度洋盆多微陆块、多期扩张中心和"入"字形的洋中脊基本构造格局在古近纪早期便已形成。

The tectonic setting and evolution of Indian Ocean——Research progress of tectonic map of Indian Ocean

The Tectonic Map of Indian Ocean(1:15 000 000) is compiled to reflect the integrated geology,geomorphology,geophysics,and resource character of Indian Ocean. It is based on newly updated geophysical data,and combines materials obtained through COMRA cruises. The map aims to provide theory support for promoting the research of Indian Ocean tectonic evolution and resource distribution. The compiling methods,data,map content,and tectonic division is introduced in this paper. This paper further analyzed the tectonic pattern of Indian Ocean,which is recognized as various micro-continents,multiple spreading episodes,enriched oceanic plateaus and aseismic ridges,and λ-pattern mid-ocean ridges. Based on previous studies,three stages of tectonic evolution of Indian Ocean is revealed: (1)Breakup of Gondwana Continent and initial seafloor spreading (Jurassic-Mid Cretaceous),(2) seafloor spreading accompanied with spreading center jump (Mid Cretaceous-early Paleogene),and (3) closing of Neo-Tethys Ocean and rifting of East African Rift (Cenozoic). The modern pattern of various micro-continents,multiple spreading episodes,and λ-pattern mid-ocean ridges took shape in early Paleogene.