A Study on the Rate of Deep Sea Deposition in the Western North Pacific by Means of Ionium-Thorium Method

Abstract

1 to 2 grams of core-sampled deep-sea deposit is leached with a hot hydrochloric acid solution for one hour and thorium is separated by using exchange resin. A small amount of solution containing thorium is evaporated to dryness on a platinum disc with which a rays from ²³⁰Th and ²³²Th are measured with a ray spectrometer. From the ratio of a ray of ²³⁰Th (Io) and ²³²Th, the rate of deposition is estimated. For a sample collected at 34°25'N, 142°17'E from the depth of 7, 400 m, the rate of deposition of 6 mm/10³ y is obtained.