한국대지 자생광물의 특성

Abstract

The survey areas A and B are located in the south Korea Plateau, north of Ulleung Basin. Southeastern slope of A is very steep (slope angle, 5-15°) withthe water depth of 850 m to 2,200 m. Several kinds of rock samples were obtained; granite, tuff breccia, basalt, phosphorite, ferromanganese oxideswith various size (5 to 30 cm in long axis). Some of three former are partiallyor entirely coated with ferromanganese oxide or phosphorite. Ferromanganesecrust (AD-05-A) contains Mn (39.9%), Ba (1.1%), Co (567.0 ppm), Ga (298.2 ppm) and Mo (210.2 ppm), respectively. Phosphorite boulder (BD-05-06) is enriched in P (14.6%) and U (251.3 ppm). Iron oxide-coatings (BD-07-08) are characterized by high content of Fe (2.2-41.7%) and V (208-382 ppm).Phosphorite boulders and phosphorite-coated rock samples are generallydistributed in the upper slope area at the water depth of 1,000 to 1,2,00 m,probably just below the Oxygen Minimum Zone(OMZ). Phosphorus content(14.6% on the average) is higher than that (13.8%) of other oceanic phosphorites.Ferro-manganese nodules/crusts were collected at the deeper water depth than phosphorite. Although sediments are deposited at relatively a rapid rate (0.09-0.13 cm/yr), the precipitation of P, Mn, and Fe seems tohave continued on the nuclei such as rock boulders which are exposed to,perhaps, relatively strong currents.Further studies about the formation mechanisms of these authigenic minerals in the Korea Plateau, East Sea with aspects of paleoceanography,biogeochemistry, and sedimentology.