Abstract
Systematic exploration for beach placer minerals has been undertaken in the Chandipur area of the Balasore district on the NE Odisha coast of India. Beach and dune sands are ubiquitous along the 1–1.5 km-wide NNE-trending coast. Forty-three representative samples were collected from selected boreholes sampled by auger and dormer drilling at depths ranging from 6.0 m to 12.0 m. Detailed experimental studies show that the total heavy minerals (THM) grade of the study area varies from 0.4 to 11.2% with an average grade of 3.8% for the individual samples; the upper 5.50 m sand column with a grade of 5.2% is most significant. The heavy mineral assemblages, in decreasing volumetric percentages, are comprised of 55% ilmenite, 25% sillimanite, 11% pyriboles/others (pyroxene, amphibole, mica, coated grains etc.), 5.9% rutile, 1.5% leucoxene, 1.2% garnet, 0.5% zircon, and 0.4% magnetite. Texturally, elevated heavy mineral concentrations are drawn from +200 ASTM (+75 µm) and 120 ASTM (+125 µm) mesh size fraction; the 40 ASTM (425 µm) size fraction contains lowest THM. The overall concentration of heavy minerals shows variable distribution patterns from shore to littoral (inland), and the maximum concentration of THM is observed within the 1.5 m sandy surface horizon. The present study also addresses the down-core variation of heavy mineral assemblages and role of hydrodynamic conditions in the deposition of these wide-ranging placer minerals. The range of graphic mean sizes (Mz) varies from 2.19 to 2.60 (Φ), which corroborates the deposition of sediments in low energy condition in a fluctuating shoreline along the Chandipur coast. Linear discriminant function analysis is predominantly indicative of diversity in the depositional features under aeolian conditions in a shallow marine environment. CM and Tractive current plots indicate that the sediments are mainly formed by graded suspension and without any rolling conditions in the beach subenvironment in a tractive current field. Both the perennial (Panchpara River) and the ephemeral drainage systems (Dubdubi River) played a dominant role in transporting and supplying sediment flux consisting of radioactive mineral (monazite) assemblages in the study area. The present detailed exploration study reveals a new find of placer deposits with radioactive and non-radioactive mineral assemblages formed from diverse sources.
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