HEAVY MINERAL CONCENTRATION ON THE VISAKHAPATNAM-KONADA COAST AS EVIDENCED BY MAGNETIC-SUSCEPTIBILITY AND RADIOACTIVITY

Magnetic susceptibility, radioactivity, bulk density (rho) and texture of black sands from the Visakhapamam-Konada belt on the east coast of India were studied. The sands are fine-grained and well sorted with a nearly symmetrical distribution. Mass susceptibility (chi) and radioa ctivity (R.A.) are related to weight percentage of magnetic minerals a nd grain percentage of radioactive minerals respectively. The magnetic fraction is made up of magnetite and ilmenite. The radioactive minera ls present in the sands are monazite and rarely zircon. Susceptibility and R.A. of finer sieve fractions are high, reflecting higher proport ions of magnetic and radioactive minerals. Mass susceptibility, Radioa ctivity and bulk density of black sands are high south of outcropping rock formations across the coast, reflecting heavy mineral concentrati on. A structural aspect of the coast, namely the Eastern Chat formatio ns cutting across the coast, seems to be one of the controls on heavy mineral concentration.