TTG magmatism in the Congo craton; a view from major and trace element geochemistry, Rb–Sr and Sm–Nd systematics: case of the Sangmelima region, Ntem complex, southern Cameroon

摘要: TTG rocks of the Sangmelima region (Ntem complex, Congo craton) in southern Cameroon range modal composition from charnockitic suite, tonalites to granodiorites. They display a wide spectrum SiO2 (54–76 wt%), including metaluminous intermediate (0.56 < A/CNK 1) and that are slightly peraluminous (1 1.08). Charnockites define trondhjemitic suite while granodiorites portray slight potassic calc-alkaline affinity. The primordial mantlenormalized spidergrams characterized by negative Nb–Ta anomalies, suggesting subduction related signature or melting crustal were formed along zones. More siliceous members rock suites enriched LILE. REE fractionation is shown 2 LaN/YbN 28 higher ratios 12 114 tonalitic 18 99 indicate source with garnet as restite phase. Samples overall lowest abundance show positive Eu anomaly represent small amounts magmas derived much feldspar contribution melt. Sr Nd systematics coupled Mg#–SiO2 compositions consistent derivation partial setting merely thickened Archaean crust eclogite facies basaltic proto-crust mantle material input. From Rb–Sr Sm–Nd whole-rock data, intrusion timing defined around 2900 Ma for suite. system biotite portrays post-emplacement reheating during Eburnean orogeny. intrusions major accretion event craton. � 2004 Elsevier Ltd. All rights reserved.