Occurrence and depositional character of monazite deposit in the offshore and coastal zone around South-West region in Sri Lanka

Abstract

Onshore or offshore, ocean offers us a larger number of industrial minerals. Monazite is one of these minerals found on beach placers in north eastern and south western coastal region of Sri Lanka. Our study area, both onshore and offshore from south western region, encompasses Induruwa and Polkotuwa. This research is focused on analyzing the depositional character of monazite and to evaluate the suitability as an ore deposit. Our methodology comprised of in-situ sampling periodically in predetermined locations and laboratory testing for monazite concentration by grain size analysis and observation though microscope. Results show significant correlation between the monazite concentration in the coastal zone and monsoonal changes. Further, accumulation of this Monazite is significantly controlled by coastal morphology. However, the absence of monazite in the offshore region contradicts with United Nations Revolving Fund for Natural Resources Exploration results. In this study, we have identified three coastal areas; Maha Induruwa, Kalutara and Polkotuwa for exploiting Monazite as an ore deposit. In these hotspots, Monazite concentration ranges from 2.2 % to 9.1%, especially during south western monsoon. Therefore we propose to mine them only during south western monsoon, digging lm surface layer and extracting monazite by collecting only <256fim fraction.