Occurrence and distribution of valuable heavy minerals in sand deposits of the Jamuna River, Bangladesh

Abstract

A mineralogical and chemical investigation of surface and subsurface samples from the upper, middle and lower parts of the Jamuna River was carried out with a view to assessing the distribution and recovery potential of the heavy minerals ilmenite and garnet. The HM component in the Jamuna sands is ~10% consisting predominantly of amphibole, epidote and garnet with significant amounts of opaque minerals (ilmenite, magnetite, titanomagnetite, etc). A greater abundance of garnet was present in the fine to medium sized fractions (125–250 µm) and lower garnet concentrations were observed in the very fine sized fraction (<63 µm). The fine size fractions also have increased amounts of clays and clay-like minerals. Potentially high value HMs such as zircon and rutile were also concentrated in the <63 µm size fractions.The ilmenite grains are characterised by TiO2 content between 34.2 and 52.8 wt-% with low levels of impurities. The garnet geochemistry is more variable but dominated overall by almandine-rich compositions. The characteristic heavy mineral suite of garnet, epidote, amphibole, kyanite, and staurolite, as well as the garnet and ilmenite chemistry reveals the sediments are derived from mixed source areas of varying metamorphic grade (low to high) facies and igneous rocks. Based on these results, the Jamuna River sands have good potential for recovery and exploitation of both garnet and ilmenite.