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

作　　者：Moussa Fall Ibrahima Labou Papa Moussa Ndiaye Moussa Fall;Ibrahima Labou;Papa Moussa Ndiaye(Department of Geology, Faculty of Science and Technology, Cheikh Anta Diop University, Dakar, Senegal;National Superior School of Mines and Geology, Cheikh Anta Diop University, Dakar, Senegal)

机构地区：[1]Department of Geology, Faculty of Science and Technology, Cheikh Anta Diop University, Dakar, Senegal [2]National Superior School of Mines and Geology, Cheikh Anta Diop University, Dakar, Senegal

出　　处：《International Journal of Geosciences》2023年第8期733-766,共34页地球科学国际期刊（英文）

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

关 键 词：Quaternary Volcanism Western Senegal Emission Zone GEOCHEMISTRY Con-tinental Intraplate 

分 类 号：P58[天文地球—岩石学]