Abstract
Granulite-facies orthogneisses of andesitic to dacitic composition in the Usambara Mountains of north eastern Tanzania yield a Sm-Nd whole rock isochron age of 815 ± 58 Ma and an initial ε(Nd) value of 4.1. This age is interpreted as dating Sm-Nd fractionation during extraction from the mantle and immediate subsequent crystallisation of the granulite protolith during an event of regional calc-alkaline magmatism in the area. Isotopic and geochemical characteristics of the rocks are consistent with a convergent margin setting for the magmatism with minimal contamination by older continental crust. The isotopic data from the Usambara Mountains demonstrate that Neoproterozoic crust formation in the Arabian-Nubian Shield and parts of the Mozambique Belt was broadly contemporaneous.
Original language | English |
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Pages (from-to) | 227-242 |
Number of pages | 16 |
Journal | Precambrian Research |
Volume | 113 |
Issue number | 3-4 |
DOIs | |
Publication status | Published - Jan 31 2002 |
Keywords
- Crust formation
- Granulites
- Mozambique Belt
- Sm-Nd geochronology
- Tanzania
ASJC Scopus subject areas
- Geology
- Geochemistry and Petrology