Accumulations métallifères dans les sédiments récents de la région du Vema Channel (Atlantique sud)

Abstract

Observations and chemical analyses carried out on samples of cores drilled in the Vema Channel show that decarbonitized levels near the hydrographic lysocline are markedly rich in metalliferous elements and overlain by small polymetallic nodules as also in the nearest zone of the deep-water—sediment interface. Study of the samples from those two types of sedimentation zones defines the chemical correlations characterising these sediments which have apparently deposited at different rates. It emphasizes the influence of diagenesis on metalliferous grade of the nodules and shows that, however complex, metallisation is not haphazard: it follows a cycle which seems to be particularly connected with both the oxydo-reductive evolution of the environment and current velocity.