Petrography, Geochemistry and Relative Chronology of Quaternary Volcanic Formations in the Mermoz and Fann Sectors, West Senegal

Detailed work on Quaternary volcanism has been carried out in the Mermoz and Fann sectors of western Senegal. In sector, main emission zone is a collapsed crater located at intersection three major fractures: NE-SW, NW-SE N-S. The lithological succession this sector comprises, from bottom to top: 1) substratum with its base Eocene limestones which lie sands surmounted by stratified tuffs; 2) vesicular ball dolerite deforms 3) dark early breccia; 4) two generations basanites: first vesicular, second non-vesicular; 5) clear intermediate breccia finally 6) late breccia. contains several zones, most are currently ocean. lavas may have reached coast through E-W NE-SW faults. includes scoria-rich volcanic breccias; generation non-vesicular mesocrate (D1); melanocrate (D2); basanites geochemical characteristics studied compatible very enriched deep magmatic source garnet lherzolite type lower mantle. magma would risen form mantle plumes faults continental intraplate context.