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

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.