Studies on Zircon - Host Rock/Sediment Association along Manimala River Meanders in Kerala

Comparative morphometric analysis of zircons from sediments and charnockite-quartzo-feldspathic gneiss-pegmatite rock units along the Manimala river valley in Kottayam and Alleppey districts of Kerala has brought to light a unimodal-bimodal size frequency distribution of zircons transported via a major meander near Komalam in Alleppey district. The slope variation in the up-mid (meander)-downstream zircons is 25°28' to 30°17'. The trapping of heavy minerals (0.002%-0.004%) by the meander has also affected the anticipated coastward enrichment of zircons. RMA plots for the rocks reveal the self-nucleated origin of zircons and the dispersion of trend lines suggests phases of zircon crystallization. Heavy minerals released from the rocks as revealed from zircon morphometry, are not carried through to the coast. Nevertheless, the coastward enrichment of Cu-Pb-Zn concentration indicates a steady flow right up to the coast of only the fine sediment fraction with these absorbed elements.