Metabasite intercalations in Precambrian metasedimentary sequences from Namibe Province, southwestern Angola, show strong geochemical affinity with komatiites and komatiitic basalts. Rb-Sr systematics, probably "perturbed" by polymetamorphic processes, as well as by crustal contamination and alteration, seem to indicate two main thermal events, at 2.0 Ga (initial 87Sr/86Sr = 0.70194) and 0.9 Ga (initial 87Sr/86Sr = 0.70614), respectively, roughly corresponding to the Early Proterozoic (Eburnean) cratonization, and to the beginning of the Pan-African event. However, Sm-Nd isotopic data display an errorchron of 3.1±0.1 Ga (initial 143Nd/144Nd = 0.50868) consistent with the values inferred by both DM (depleted mantle: 3.4±0.3 Ga) and CHUR (chondritic mantle: 3.2±0.4 Ga) model ages, suggesting an of Early middle Archean magmatism in SW-Angola.
Metabasites from Namibe Province, SW-Angola: An Archean komatiitic magmatism? / A., Alberti; Castorina, Francesca; P., Comin Chiaramonti. - In: ANAIS DA ACADEMIA BRASILEIRA DE CIÊNCIAS. - ISSN 0001-3765. - STAMPA. - 71:4(1999), pp. 894-909.
Metabasites from Namibe Province, SW-Angola: An Archean komatiitic magmatism?
CASTORINA, Francesca;
1999
Abstract
Metabasite intercalations in Precambrian metasedimentary sequences from Namibe Province, southwestern Angola, show strong geochemical affinity with komatiites and komatiitic basalts. Rb-Sr systematics, probably "perturbed" by polymetamorphic processes, as well as by crustal contamination and alteration, seem to indicate two main thermal events, at 2.0 Ga (initial 87Sr/86Sr = 0.70194) and 0.9 Ga (initial 87Sr/86Sr = 0.70614), respectively, roughly corresponding to the Early Proterozoic (Eburnean) cratonization, and to the beginning of the Pan-African event. However, Sm-Nd isotopic data display an errorchron of 3.1±0.1 Ga (initial 143Nd/144Nd = 0.50868) consistent with the values inferred by both DM (depleted mantle: 3.4±0.3 Ga) and CHUR (chondritic mantle: 3.2±0.4 Ga) model ages, suggesting an of Early middle Archean magmatism in SW-Angola.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.