In:
Bulletin de la Société Géologique de France, EDP Sciences, Vol. 178, No. 5 ( 2007-09-01), p. 331-342
Abstract:
Magmatic charnockitic rocks and TTG (tonalite-trondhjemite-granodiorite) plutons intruded successively the Archaean greenstone belts of the Ntem Complex, at the northwestern margin of the Congo Craton. Geochemical data, zircon Pb-Pb ages, and Sr-Nd isotope studies, constrain the magmatic features, the genetical timing, and the geodynamic settings of these different suites. Charnockites and TTGs are characterized by high Al2O3 contents, high Na/K ratio, low Th content, LREE enrichment, HREE depletion, negative anomalies in Nb, Ta, and Ti, and positive anomalies in Sr. The Pb-Pb zircon ages indicate that charnockites were emplaced at ca. 2900 Ma and TTGs, which cross-cut the charnockites, at ca. 2830 Ma. TDM Nd mean crustal residence ages of both suites range between 3.10 and 2.93 Ga. The charnockites show slightly positive initial εNd2.9Ga (+0.3 to +1.3), whereas the TTGs have slightly negative values (+0.1 to −1.5). The charnockitic and TTG magmas may have resulted from different partial melting processes of the primitive Archaean basaltic crust and contaminated mantle, possibly in a hot slab subduction convergent regime. They contribute to a two-stage crustal growth of the Archaean craton.
Type of Medium:
Online Resource
ISSN:
1777-5817
,
0037-9409
DOI:
10.2113/gssgfbull.178.5.331
Language:
English
Publisher:
EDP Sciences
Publication Date:
2007
detail.hit.zdb_id:
2747870-1
detail.hit.zdb_id:
2175250-3
SSG:
13
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