摘要
北祁连走廊南山加里东火山岛弧带前缘为弧前俯冲杂岩增生地体。它由多重的增生火山岛弧、复理石增生楔、高压变质滑脱带及蛇绿岩残片组成,为早古生代古祁连洋壳自SW在NE俯冲于阿拉善地块之下的结果。俯冲过程的高压变质阶段经历了中温高压的初期、降温增压的主期而进入降压增温的驰后期。提出了450—500Ma期间,中祁连地块向北俯冲、阿拉善地块向南增生的海沟后退的俯冲动力学模式。
The Caledonian orogenic belt of the Northern Qilian Mountains may be divided into the following eight tectonic units: (1) Tulaishan ophiolite zone, (2) Zhou-langnanshan subduction complex accretionary terrane, (3) Zhoulangnanshan volcanic island arc zone, (4) Zhoulangnanshan north slope back-arc basin, (5) Silurian remnant sea basin, (6) Devonian molasse basins, (7) Post-Devonian superimposed basin, and (8) Jintieshan nappe.The Zhoulangnanshan Caledonian subductive complex accretionary terrane with the characteristics of plate convergence and complicated constitutions is a high-strain zone composed of poly-volcanic island arcs, fore-arc flysch accretionary wedges, glau-cophane schists and ophiolitic melange zone. Its deformation mechanism is predominantly 'simple shear' and the sense of shear is from NE to SW. The metamorphism related to subduction is as follows: the first phase (M1): low T/low P greenschist-facies metamorphism; the second phase (M2): low T/high P blueschist-facies metamorphism and the third phase (M3): retrogressive low T/low P greenschist-facies metamorphism. The high-pressure metamorphism (M2), which occurred during subduction, underwent medium T/high P metamorphism of the initial stage, cooling/progressive compression of the main stage and heating/decompression of the lag stage. Finally, a 'retrotrench' subduction dynamic model characterized by the northward subduction of the central Qilian plate and the southward accretion of the Alxa plate during 450Ma-500Ma is presented in this paper.
出处
《地质学报》
EI
CAS
CSCD
北大核心
1994年第1期1-15,共15页
Acta Geologica Sinica
基金
国家自然科学基金(批准号:4870127)
关键词
杂岩
增生地体
动力学
俯冲过程
subduction complex accretionary terrane, poly-texture, subduction dynamics of retrotrench
