Heavy Mineral Analysis of Jamuna River Sediments, Bangladesh

The Jamuna is one of the world’s most heavily sediment-laden braided river. Despite a major host for heavy mineral resources, the sediments of the Jamuna river are sparsely studied. A mineralogical and SEM-EDS investigation has been carried out in the middle part (along Sirajganj and Jamalpur district of Bangladesh) of the Jamuna river to appraise the grain size parameter, texture, depositional environment, heavy mineral distribution, and elemental composition of the heavy minerals. The results show that sediment samples are very fine to fine sand, moderate to well sorted, near symmetrical to strongly fine skewed, and mesokurtic to very leptokurtic. Uniform to graded suspension mechanisms are the processes for sediment deposition. Heavy minerals accumulation ranges from 0.5% to 9.33%, and the assemblages are predominantly marked by epidote, amphibole, followed by opaque (magnetite and ilmenite), garnet, zircon, sillimanite, apatite, tourmaline, rutile, kyanite, staurolite, monazite, chlorite, and titanite. The percentage of amphibole, garnet, and zircon decreases downstream and epidote increases in the same direction. The calculated zircon-tourmaline-rutile index (ZTR) varied between 3 to 13%, average apatite-tourmaline index (ATi), garnet-zircon index (GZi), rutile-zircon index (RuZi) and staurolite-zircon index (SZi) values are 54.55%, 75%, 38.68%, and 30% respectively. The Brahmaputra-Jamuna river sediments are derived from mixed-source regions (e.g., Shillong Plateau, Indo-Burman Ranges, and the Himalayas). The abundance of sub-angular to angular, high relief heavy mineral grains with sharp edges on the surface, conchoidal fractures, deep troughs, and breakage blocks infer that the provenance is close to the depositional area. The presence of rounded to sub-rounded, smoother surface with adhering particles, arcuate steps, and low to medium relief indicate the long-distance transportation of heavy mineral grains through fluvial environment.