RESEARCH ON GROWTH RATES OF MANGANESE NODULES FROM NORTH PACIFIC

Abstract: Many research items on the manganese nodules from ocean bottom have been earned ouu but the growth rales of manganese nodules as well as their movements on the ocean bottom still puzzles the scientists. Various methods have bee created to answer these question. The trustworthy and acceptable methods are -²³⁰Th excess; -²³⁰Th / -²³²Th; -²³¹Pa; K / Ar and -¹⁰Be. Three manganese nodules have been analysed using -²³⁰Th excess and -²³⁰Th / -²³²Th methods in order to detect their growth rates. The procedures are as follows: Successive layers of specimens from top side and bottom side arc scraped; acid leaching; separation and purification of U and Th using Dowcsi-8 resin; TTA extraction and a counting. The growth rates of three nodules using two different methods a;e agreeable, ranging l-10mm / M.Yr. The last turnover of the noduics can be evaluated from the different activities of -²³⁰Th at the surface of top and bottom sides. The results range from 5 ×10⁴to 2.5 × 10⁵ycars, thereat -²¹⁰Pb profiles indicates that the turnover of the noduics didn ' t take place in the last 150 years.