ESTIMATION OF CHEMICAL WEATHERING OF SOURCE ROCKS IN ALAKNANDA RIVER BASIN A DISSERTATION Submitted in partial fulfillment of the requirements for the award of the degree of MASTER OF SCIENCE in APPLIED GEOLOGY By PRATAP TAPAN SAHOO to \ OV TIRCIV DEPARTMENT OF EARTH SCIENCES INDIAN INSTITUTE OF TECHNOLOGY ROORKEE ROORKEE-247 667 (INDIA) JUNE, 2013 I - n_

Abstract

Rock—water interaction leading to chemical weathering of minerals and rocks, has a siniiicant role in moulding the Earth's surface. Rock weathering is a key process in the evolution of Earth surface and knowledge about such processes and the different controlling factors helps to understand the past and also to predict changes in the future Earth surface processes. Understanding river water chemistry is essential to have an idea of chemical weathering of provenance rocks and also to know the relationship between dissolved load characteristics of a river. In the present study, multiannual data have been obtained from different published literatures to understand and establish a relationship of the bed rocks of Alaknanda River on the river water composition. This has been carried out by analyzing the major ion chemistry by various geochemical plots such as, triangular plots and from calculations of apportionment of various sources with the help of a forward model after Zhu et al.. 2013. The result of this study sho\s that the dominant cations are Ca2 and Mg2 where as the dominant anion is ilCO3 in the river water. The estimation shows that maximum contribution of major components are derived from the dissolution ofevaporites followed by weathering of silicates and carbonates.