Estimation of Material Loss due to Chemical Weathering of Some Rocks in Sri Lanka

Abstract

The processes of weathering reduce the materials from the parent rocks. The material loss due to weathering can be estimated by a fundamental method because the remaining residual materials have strong relationship with their parent rock. The objective of this basic research is to find out the weight loss with the increase of chemical weathering in Sri lankan rocks. This may be an important data to calculate sedimentation rates in the reservoirs. Irregular samples from fresh rocks and differently weathered grades of each rock were collected from different localities without disturbing the structures. Bulk density and the porosity of each sample were measured. The total number of samples was about 300 from 73 locations. The results show the decrease of bulk density and the increase of porosity and weathering. It indicates that some materials moving away and separate from the original place create voids within the same volume during the processes of chemical weathering. The total loss of material is about 18 - 29 % by weight from the fresh rock stage to highly weathered stage. Increase of porosity goes up to 38 % in highly weathered rocks.