Erosion and heavy mineral depletion of a placer mining beach along the south-west coast of India: Part II-Sedimentological and mineralogical changes

Mining of beach placers or heavy minerals (HM) has been going on along the Neendakara-Kayamkulam coastal sector of the SW India for the past several decades by two public sector undertakings. Rich concentrations of HM were reported consistently in the beach sediments of this coast in the past, but a systematic reduction in the concentration of the heavies has been reported during the past one and a half decades. This paper emanates from a programme of study launched to understand the mechanisms that manifest the reported changes in the morphology and mineralogy along this coast. A detailed study of the sedimentology and mineralogy of the beach and innershelf has been carried out based on surficial sediment sampling from the beach and innershelf and core sampling from the innershelf. The study confirmed the depletion in the HM concentration in the beaches of the Chavara coast after 2000. One of the factors that led to the depletion in HM concentration along this coast was the 2004 tsunami which brought down the concentration to as low as 2 % in the innershelf. In addition to the tsunami, the other factors responsible for the observed depletion of beach placers along the coast are excessive beach sand mining and construction of coastal structures.