TITLE:
Petrography, Geochemistry and Relative Chronology of Quaternary Volcanic Formations in the Mermoz and Fann Sectors, West Senegal
AUTHORS:
Moussa Fall, Ibrahima Labou, Papa Moussa Ndiaye
KEYWORDS:
Quaternary Volcanism, Western Senegal, Emission Zone, Geochemistry, Con-tinental Intraplate
JOURNAL NAME:
International Journal of Geosciences,
Vol.14 No.8,
August
30,
2023
ABSTRACT: 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.