青藏高原东部长江流域盆地陆地化学风化研究

Subaerial chemical weathering in the Changjiang drainage systems on eastern Qinghai-Xizang Plateau

关键词:  青藏高原东部  长江  流域盆地  陆地化学风化

Key words:  eastern Qinghai-Xizang Plateau  Changjiang River  drainage basin  subaerial chemical weathering

摘要:

长江河水主要离子由流域盆地碳酸盐岩的风化所控制,沱沱河和楚玛尔河受蒸发盐岩影响较为明显;河水溶质载荷Si,Si/TZ^+*,Si/(Na^*+K)等指标表明,长江流域盆地地表硅酸盐岩风化还是浅表层次的;金沙江地表化学剥蚀速率为1.74×10³mol/yr·km²,雅砻江为1.69×10³mol/yr·km²,大渡河为1.57×10³mol/yr·km²,岷江为1.88×10³mol/yr·km²,长江河源区楚玛尔河为2.32×10³mol/yr·km²,沱沱河为1.37×10³mol/yr·km²,流域地表化学剥蚀速率可与世界上其它造山带的河流进行对比。

Abstract:

The major ions from the Changjiang River tend to be dominantly controlled by the weathering of the carbonate rocks in the Changjiang drainage systems on eastern Qinghai-Xizang Plateau.For instance, the major ions from the Tuotuo and Qumar Rivers in Qinghai are mostly originated from the weathering of evaporites. The indexes of Si, Si/TZ^+* and Si/(Na^*+K) for the dissolved loads in the river water indicate the superficial weathering of the silicate rocks in the Changjiang drainage systems. The subaerial chemical denudation rates are 1.74×10³ mol/km² per year for the Jinsha River, 1.69×10³ mol/km² per year for the Yalong River, 1.57×10³ mol/km² per year for the Dadu River, 1.88×10³ mol/km² per year for the Minjiang River, 2.32×10³ mol/km² per year for the Qumar River, and 1.37×10³ mol/km² per year for the Tuotuo River. The preceding values for the chemical denudation rates in the study area may be compared with those for the rivers in other orogenic belts in the world.