%0 Journal Article
%T Petrology of the Late Cretaceous peralkaline rhyolites (pantellerite and comendite) from Lake Chad, Central Africa
%A Mbowou G I B
%A Lagmet C
%A Nomade S
%A Ngounouno I
%J Journal of Geosciences
%D 2012
%I 
%R 10.3190/jgeosci.118
%X Late Cretaceous peralkaline rhyolites (69.4 ¡À 0.4 Ma (2¦Ò analytical, 1.9 Ma full external uncertainty, 40Ar/39Ar sanidine single crystal laser dating) from Lake Chad are the oldest lavas of the ¡°Cameroon Hot Line¡±. These lavas (pantellerite and comendite), consisting of quartz ¡À alkali feldspar ¡À fluoro-arfvedsonite ¡À augite-hedenbergite ¡À aegirine ¡À fayalite (Fa97-99) and ilmenite, are characterized by a progressive increase in the total REE contents and the magnitude of the negative Eu anomaly owing to the alkali feldspar-dominated fractionation. Two groups of peralkaline rhyolites have been distinguished according to mineralogical and geochemical data. Both, group-1 (LaN/YbN: 8.4-9.0; Zr/Nb:   8) and group-2 (LaN/YbN: 10.7-12.6; Zr/Nb:   6) are genetically related. The peralkaline rhyolites from Lake Chad could not be solely the product of fractional crystallization from a basaltic parental magma. The influx of F-rich fluids could have greatly modified the composition of rhyolitic magmas as attested by the presence of fluoro-arfvedsonite.
%K petrology
%K geochemistry
%K Cretaceous
%K peralkaline rhyolites
%K Lake Chad
%K Cameroon Line
%U http://www.jgeosci.org/content/jgeosci.118_mbowou.pdf