摘要
Hangloa granitoids form part of the wide range calc-alkaline Pan-African granitic suites within the Adamawa Yade Domain(AYD)in Cameroon.There are several reports on metaluminous granitoids within this domain.The peraluminous suite has been locally reported and their petrogenesis is not fully understood.Petrography and whole-rock geochemistry were used to study the petrogenesis/formation of granitic rocks within this area.The results show that the granitoids are composed of quartzo-feldspathic,made up of granites,monzonites and quartz monzonites which were intruded in the Paleoproterozoic orthogneissic basement.The major and trace element compositions show that they are high-K calc-alkaline to shoshonites,with S-type affinity.The molar ratio A/CNK is>1.1,while the ratio of CaO+Na_(2)O/Al_(2)O_(3) is generally<1 making them strongly peraluminous.The REE shows enrichment in the LREE over the HREE,with(La/Yb)N varying from 11.9 to 53.32,(Dy/Yb)N from 0.77 to 2.13 and moderately negative Eu anomaly((Eu/Eu^(*))N range from 0.42 to 0.93).Most granite samples show depletion in P,with CaO/Na_(2)O<0.3 and Rb/Sr≤1 indicative of clay-poor metapelitic source,while the others show clay-rich metagreywackes sources.The strong peraluminosity,S-type affinity,high Ba/Sr,Ba/Rb and low Rb/Sr indicate they are crustal-derived.The compositional variation might be induced by the partial melting of different source materials followed by fractional crystallization of the granitic magma.The source nature requires fragments of Paleoproterozoic metasedimentary and metaigneous rocks derived from the collision between the north-central Cameroon block and the Congo Craton during the Pan-African.
基金
the financial and technical support received from the Geoscience Laboratories in Toulouse(LGT)France under L’Agence Universitaire de la Francophonie(AUF)project during the analysis of the samples and thin section preparation。
