Chemical composition of ferromanganese crusts recovered in the South China Sea during the SO49 Cruise of R/V Sonne

Five ferromanganese crusts and 6 ferromanganese nodules samples collected by the Joint Chinese-West Germany Geophysical Investigation Team in May—June, 1987 during the SO49 cruise of the R/V Sonne. They 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 1. 625 g/kg and 2. 167 g/kg respectively. This concentration is 1—2 times higher than that in Pacific ferromanganese nodules, 5—6 times higher than that found in North Pacific sediments, and 10—20 times higher than that found 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.