Chemical analyses of Fe-Mn coatings separated from the margins of basaltic rocks from Transform Fault 'A' and from the the Rift Valley near 36°50'N in the Mid-Atlantic Ridge

In order to evaluate the possible influence of hydrothermal activity on Fe-Mn coatings found on the surfaces of basaltic rocks in the median part of Transform Fault "A", a few samples collected in different structural settings less than 2 km away from the hydrothermal fields. They were analysed along with samples further West in the Transform Valley (sample ARP 74-13-23) and from the top of the deepestescarpment of the inner West wall of the Rift Valley near 36'50'N (sample cyp 74-31-40). Chemical analyses were done by arc spectrometry using an ARL quantometer were made at the University of Strasbourg. This method consists of melting the sample in a mixture of lithium tetraborate and then introducing the melt into in a glycolated solvent prior analysis. Trace elements were determined using graphite discs . Na and K were determined by emission spectrometry (precision of +- 2.0%).