大湄公河次地区构造单元划分

Division of the tectonic units in the Greater Mekong subregion

关键词:  大湄公河次地区  构造单元划分  陆块

Key words:  Greater Mekong region  division of tectonic units  continental block

摘要:

大湄公河次地区在地质构造上是西南三江构造带和华南加里东褶皱带的向南或南西的延伸。在理清了各构造单元的延伸趋势及其相互关系的基础上,对该区大地构造单元作了统一划分和对比。以印缅山脉结合带、澜沧江-文冬-劳勿结合带、金沙江-哀牢山-马江结合带作为主结合带,将该区划分为印澳板块、中缅马陆块、印支陆块和华南陆块4个一级单元。然后在亲冈瓦纳的中缅马陆块和亲华南型的印支陆块内再以次级结合带分别划分出4个二级构造单元:亲冈瓦纳型的西缅微陆块、腾冲-毛淡棉微陆块,保山-掸泰微陆块、临沧-景栋微陆块,亲华南型的景洪-帕府-东马来西亚微陆块、思茅-大叻微陆块、昆嵩微陆块和长山微陆块;华南陆块以越北斋江结合带为界分为扬子和华夏两微陆块。简要论述了各构造单元的基本地质特征,提出将可可西里-澜沧江-文冬-劳勿结合带作为南部冈瓦纳大陆和北部劳亚大陆的分界,指出昆嵩微陆块和长山微陆块是华夏微陆块的南西延伸,其西部的对应体可能是昌都微陆块。

Abstract:

Tectonically, the Greater Mekong subregion is the southward or southwestward extension of the Nujiang-Lancangjiang-Jinshajiang tectonic zone in southwestern China and the Caledonian fold zone in southern China. On the basis of the findings of the extension trends of individual tectonic units and their interrelations, the tectonic units in this region have recently been divided into four first-order tectonic units including the Indo-Australian plate, Sino-Burma-Malaysia block, Indo-China block and South China block, bounded by the Indo-Burma Ranges, Lancangjiang-Bentong-Raub and Jinshajiang-Ailaoshan-Song Ma suture zones. Moreover the Sino-Burma-Malaysia and Indo-China blocks may be separately subdivided into four second-order tectonic units, i.e. the Western Burma, Tengchong-Moulmein, Baoshan-Shan Thai and Lincang-Kengtung microblocks within the Sino-Burma-Malaysia block, and Jinghong-Phrae-Eastern Malaysia, Simao-Da Lat, Kon Tum and Truong Son microblocks within the Indo-China block, bounded by the secondary suture zones. The South China block is separated into the Yangtze and Cathaysia microblocks by the Chay River suture zone in northern Viet Nam. The Hoh Xil-Lancangjiang-Bentong-Raub suture zone is interpreted as the boundary between southern Gondwana Land and northern Laurasia Land. The Kon Tum and Truong Son microblocks are believed to be the southwestward extension of the Cathysia microblock, and the equivalent west of it may be the Qamdo microblock.