Heavy Minerals from Gopalpur Coast, Odisha with Special Reference to Ilmenite: Implication to Provenance

Abstract

The intertidal zone as well as sand dunes of Gopalpur coast, Odisha contains heavy minerals of varying proportions ranging from 6.51 to 8.45 wt% out of > 63 µm fractions. The heavy mineral assemblages are ilmenite, magnetite, garnet, sillimanite, zircon, rutile and hornblende of which ilmenite is dominant. Electron probe micro analysis of ilmenite grain indicates that it contains TiO₂ in the range of 50.72% to 58.96% and FeO 37.4% to 57.15% in addition to Cr₂O₃ (0 to 0.12%), NiO (0 to 0.27%), MnO (0.06% to 2.04%) and MgO (0.17% to 2.16%). Mn/Mg ratios show lower values (0.13 to 2.76) for most of the samples, indicating basic rock source such as pyroxene granulites. Few ilmenite grains are having higher Mn/Mg values varying between 4.55 and 6.58, might have been derived from charnockite and khondalites in the hinterland. Scanning electron microscope photographs of ilmenites show sub-rounded to rounded grains with few grains having angular to sub-angular feature. Their micro morphological features indicate effect of mechanical and chemical weathering. Flattened striated surface with grooves feature may be due to mechanical weathering. Etch marks and pits may be due to differential chemical action in low energy sub-aqueous environment of deposition.