南海铁锰结核(壳)的稀土元素地球化学

GEOCHEMISTRY OF RARE EARTH ELEMENTS IN FERROMANGANESE NODULES (CRUSTS) OF THE SOUTH CHINA SEA

于1987年5—6月间,中、西德在南海进行地球科学调查,获得5个铁锰结壳、6个铁锰结核样品。本文在利用X荧光法测定15个稀土元素的基础上,对南海铁锰结核(壳)的稀土丰度、配分模式与伴生元素的关系以及稀土的来源作了较为详细的探讨。研究表明,南海铁锰结核(壳)的平均丰度为1625×10^(-6),铁锰结核为2167×10^(-6),分别要比太平洋结核高1—2倍,比太平洋北部沉积物高3—4倍,比南海沉积物高10—20倍;结核和结壳的稀土经球粒陨石标准化后的配分模式基本相同,Ce正异常,Eu亏损不明显;与伴生元素、沉积物及岩石稀土对比研究表明,结核(壳)中稀土主要来自南海中酸性岩类风化、淋漓后缓慢沉积。

Five ferromanganese crusts-and 6 ferromanganese nodules samples collected by the Joint Chinese-West Germany Geophysical Investigation Team in May-June, 1987 were analyzed for their rare earth element contents by means of X-Ray fluorescent spectrometry. On the basis of study of 15 rare earth elements detected, the relationship among rare earth element concentration, source, as well as distribution pattern and associated elements was discussed in detail. Results show that 1) The average concentration of rare earth elements in South China Sea ferromanganese crusts and nodules was 1625×10-6 and 2167×10-6 respectively. This concentration is 1-2 times higher than that in Pacific ferromanganese nodules, 5-6 times higher than that in North Pacific sediments, and 10-20 times higher than that in South China Sea sediments. 2) Distribution pattern of rare earth elements in ferromanganese nodules and crusts are basically the same. Ce is positively abnormal and Eu deficit is not obvious. Results of comparative study of associated elements, sediments, and rare earth elements of rocks show that rare earth elements in ferromanganese nodules and crusts were deposited mainly in South China Sea medium-acidic rocks after they had undergone weathering and wetting.