Major ion geochemistry of the dissolved loads from the Changjiang River on eastern Qinghai-Xizang Plateau

The examination of major ion geochemistry is based on the field sampling of the dissolved loads from the Changjiang River on eastern Qinghai-Xizang Plateau in the years of 2000 and 2002. The analysis of the data has disclosed that the TZ⁺ values for the Changjiang River are higher than the mean values (1250 μ Eq)for all the rivers in the world, ranging mostly between 2000 and 3000 μ Eq and subordinately between 1000 and 2000 μ Eq. By and large, the abovementioned TZ⁺ values may be compared with those for other orogenic belts in the world. The river water is characterized by enriched HCO₃^-HCO₃^- > Si +Cl^-+SO₄^2-, Ca²⁺ > Mg²⁺ +Na⁺+ K⁺, implying that the river water is rich in Ca²⁺. The enrichment of HCO₃^- and Ca²⁺ in the river indicates that the carbonate rocks (especially limestone)should be interpreted as the weathered source rocks in the Changjiang drainage areas.