TITLE:
Comparative Geochemical Study of the Tertiary and Quaternary Lavas of Western Senegal and the Cape Verde Islands: Geodynamic Implications
AUTHORS:
Diomaye Yatte, Dinna Pathé Diallo, Ibrahima Sagna
KEYWORDS:
Western Senegal, Basalts, Tertiary, Quaternary, Cape Verde
JOURNAL NAME:
International Journal of Geosciences,
Vol.6 No.11,
November
18,
2015
ABSTRACT: The western area of
Senegal was the site of a basic volcanism in the Tertiary and Quaternary. That
volcanism had caused the formation of alkaline olivine basalts, basanites and
nephelinites from microlitic and porphyritic texture to dolerite texture. The
geochemistry of major elements shows that the Quaternary basalts are more
aluminous and more siliceous, but they contain less magnesium, less iron and
less calcium than the Tertiary basalts. Two types of basalt occur here, based
on the characteristics of the major elements in the Tertiary lavas: the highly
undersaturated basalts of the Cape Verde Peninsula and the slightly
undersaturated basalts of the Thiès Plateau. The characteristics of the trace
elements reveal shallow interactions due to the contamination and/or
assimilation, and to the fractional crystallization, but not due to the
heterogeneity of the source. The strong enrichment in light rare earth elements
(LREE) and the slight enrichment in heavy rare earth elements (HREE), the
anomalies which are negative in K and Pb and positive in Nb, Ta and Eu of the
Tertiary and Quaternary basalts of Western Senegal and similar anomalies of the
same elements (Pb not analyzed) described in the Cape Verde islands, allow us
to establish links between the petrogenetic mechanisms that had caused the
formation of the basalts of this Islands and Western Senegal. Moreover, the
volcanic activity in Western Senegal (of continental lntraplate type) and that
of the Cape Verde Islands (oceanic intraplate type) are probably related to the
hot spot located on the vertical of the Cape Verde.