Neoproterozoic eclogites in the Paleoproterozoic Ubendian Belt of Tanzania: Evidence for a Pan-African suture between the Bangweulu Block and the Tanzania Craton

Boniface, Nelson and Schenk, Volker (2012) Neoproterozoic eclogites in the Paleoproterozoic Ubendian Belt of Tanzania: Evidence for a Pan-African suture between the Bangweulu Block and the Tanzania Craton Precambrian Research, 208 . pp. 72-89.

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Abstract

Geochronological, petrographic and geochemical data from eclogites of the Ufipa Terrane in the Ubendian Belt demonstrate that a Pan-African suture zone dated at 593 +/- 20, 548 +/- 39 and 524 +/- 12 Ma (zircon U-Pb SHRIMP) separates the Tanzania Craton from the Bangweulu Block along the Ubendian Belt. These new and surprising data indicate that during the amalgamation of the Gondwana Supercontinent there was a collision between the Archean Cratons of Tanzania and Bangweulu. A clockwise P-T path that climaxed at pressures of 15-20 kbar and temperatures of 610-790 degrees C were estimated for these eclogites. This indicates a relatively warm subduction with a geothermal gradient of about 10-11 degrees C/km. Magmatic precursor rocks of kyanite-free eclogites crystallized in the back-arc (group I eclogite) and island-arc (group II eclogite) tectonic settings. The light rare earth elements (LREEs) of group I eclogites range between 10 and 30 times chondritic values suggesting a depleted mantle source similar to that of mid oceanic ridge basalts (MORB). Group II eclogites display characteristic depletions of high-field-strength elements (Na, Ta, Zr and Hf) relative to LREEs that is typical for island-arc basalts. The U-Pb zircon ages at 593 +/- 20 and 524 +/- 12 Ma from the kyanite-free eclogites have a difference of about 70 Ma. The time interval of this much long is not likely to represent a single subduction event. Therefore, it is more likely that successive accretions of volcanic-arc rocks occurred at 593 +/- 20, 548 +/- 39 and 524 +/- 12 Ma. (C) 2012 Elsevier B.V. All rights reserved.

Document Type: Article
Research affiliation: Kiel University
OceanRep > The Future Ocean - Cluster of Excellence
ISSN: 0301-9268
Projects: Future Ocean
Date Deposited: 14 May 2014 10:20
Last Modified: 14 May 2014 10:20
URI: http://eprints.uni-kiel.de/id/eprint/23844

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