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雅鲁藏布大峡谷地区主要有南迦巴瓦群 (Pt1 nj)、大拐弯群 (Mz)和冈底斯群 (Pt1 gd)三个岩石地层单元。其中大拐弯群主要分布在楔入体的东缘 ,主要由变玄武岩 /辉绿岩、辉石岩、镁质橄榄岩、石英岩和大理岩等组成 ,岩石类型和化学成分特征与蛇绿岩套类似。但其岩石化学性质与典型的大洋中脊蛇绿岩差别较大 ,形成环境为具有陆壳性质的中等—慢速扩张的小型洋盆 ,属陆间海 /弧后盆地。自 4 5Ma以来 ,该地区经历了强烈的褶皱、隆升和剥蚀作用 ,使下部地壳暴露地表并形成无与伦比的世界第一大峡谷。
The Brahmaputra Grand Canyon is dominated by three lithostratigraphic units, namely, the Namjag Bawa Group (Pt1 nj), Mz and Pt1 gd. Among them, the main bend group mainly distributes on the eastern edge of the wedge, and is mainly composed of altered basaltic rock, diabase rock, peridotite, magnesia peridotite, quartz rock and marble. The rock type and chemical composition are similar to ophiolite Similar sets. However, its petrochemical properties are quite different from that of the typical oceanic ridges and ophiolites, forming a medium-slow expanding small oceanic environment characterized by continental crust, which belongs to the continental sea / backarc basin. Since 45 Ma, the area underwent intense folds, uplift and denudation exposing the lower crust to the surface and forming the first Grand Canyon in the world.