2.67 Ga high-Mg andesites from the Musoma-Mara greenstone belt, northern Tanzania

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dc.contributor.authorManya, Shukrani
dc.contributor.authorMaboko, Makenya A. H.
dc.date.accessioned2016-03-03T13:51:32Z
dc.date.available2016-03-03T13:51:32Z
dc.date.issued2008-07-01
dc.description.abstractNeoarchaean (2.67 Ga) High-Mg andesites occur in the Musoma-Mara greenstone belt, northern Tanzania. They are associated with dacites and Na-granitoids both of which are adakitic in composition. The high-Mg andesites are characterized by higher contents of MgO (2.42 – 9.47 wt %), Cr (41-797 ppm) and Ni (11-254 ppm) than those of normal island arc andesites. Their La/Yb ratios are 9.87 – 22.5 whereas their Sr/Y ratios are 20 – 131.These characteristics are similar to those shown by Cenozoic Setouchi High Magnesian Andesites (HMA). These rocks are characterized by 143Nd/144Nd ratios that range from 0.511062 ± 7 to 0.511308 ± 12 with corresponding εNd (t) of +0.44 and +1.81. The high contents of Mg, Cr and Ni argue in favour of equilibration of their parental magma with mantle peridotite whereas their relatively low La/Yb ratios argue against the involvement of garnet and amphibole as residual phases during partial melting. Thus, the high-Mg andesites are interpreted to have formed by partial melting of the mantle peridotite that has been fluxed by slab-derived fluids. Overall, the geochemical features of high-Mg andesites, their close association with adakitic rocks in the MMGB together with the short time interval taken for their emplacement are interpreted in terms of a ridge-subduction model. It is considered that such a model was important for generation of late Archaean continental crust.en_US
dc.identifier.citationManya, S. and MABOKO, M.A.H., 2008. 2.67 Ga high-Mg andesites from the Musoma-Mara greenstone belt, northern Tanzania. Geochimica et Cosmochimica Acta Supplement, 72, p.591.en_US
dc.identifier.urihttp://hdl.handle.net/123456789/579
dc.language.isoenen_US
dc.subjectGreenstone Belten_US
dc.title2.67 Ga high-Mg andesites from the Musoma-Mara greenstone belt, northern Tanzaniaen_US
dc.typeJournal Article, Peer Revieweden_US
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