1 Identification and interpretation of ferruginous rock in tropical environment

In conclusion

Weathering of sulfidic mineralizations involves as for the other rocks, successive steps of primary then secondary minerals hydrolysis and mineral neogeneses. The term product, i. e. gossan, is a quas holoferruginous rock which may appear in fine as the only witness of a sulfidic mineralization.


Paleoweatherings of these sulfidic mineralizations consist of block cut out from their weathering profile, surely emptied from their substances due to present day but above all past huge climatic stresses. These are paleo-gossans whose roots have been inevitably hydrolyzed and probably effaced from landscape, without necessary connotation of transport.


Outcropping or sub-outcropping contemporaneous gossans should be structured in maintaining the typical zonations of supergene sulfidic weathering i. e. sulfo-phosphated, carbonated and other horizons, but nothing has been explored up to now in Burkina or in Togo for this purpose. Their presence proves that the neighbouring terranes as well as their ancient weatherings (domain of allitisation and monosiallitisation) or recent ones (domain of bisiallitisation) were maintained in situ. The occurrence of structured gossans, implying a morphology viewed as a whole or internal orientations of facies and structures, is hardly conceivable except if formed in situ.