| dc.creator |
Manya, Shukrani |
|
| dc.creator |
Maboko, Makenya A. H. |
|
| dc.date |
2016-03-03T13:51:32Z |
|
| dc.date |
2016-03-03T13:51:32Z |
|
| dc.date |
2008-07-01 |
|
| dc.date.accessioned |
2018-03-27T08:56:46Z |
|
| dc.date.available |
2018-03-27T08:56:46Z |
|
| dc.identifier |
Manya, 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. |
|
| dc.identifier |
http://hdl.handle.net/123456789/579 |
|
| dc.identifier.uri |
http://hdl.handle.net/123456789/3975 |
|
| dc.description |
Neoarchaean (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. |
|
| dc.language |
en |
|
| dc.subject |
Greenstone Belt |
|
| dc.title |
2.67 Ga high-Mg andesites from the Musoma-Mara greenstone belt, northern Tanzania |
|
| dc.type |
Journal Article, Peer Reviewed |
|