Evidence for a Neoproterozoic ocean in south-central Africa from mid-oceanic-ridge-type geochemical signatures and pressure-temperature estimates of Zambian eclogites

John, T., Schenk, V., Haase, K., Scherer, E. and Tembo, F. (2003) Evidence for a Neoproterozoic ocean in south-central Africa from mid-oceanic-ridge-type geochemical signatures and pressure-temperature estimates of Zambian eclogites Geology, 31 (3). pp. 243-246. DOI 10.1130/0091-7613(2003)031<0243:efanoi>2.0.co;2.

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Abstract

Precambrian eclogites, metagabbros, and gabbros occur in an similar to200-km-long by 40-km-wide zone in central Zambia. Pressure-temperature (P-T) estimates of kyanite-bearing eclogites (kyanite eclogites) throughout the zone give temperatures of 590-750 degreesC at minimum pressures of 20 kbar. Phengite-bearing eclogites equilibrated at 720-755 degreesC and 26-28 kbar and show evidence for a clockwise P-T path. These P-T conditions imply a low geothermal gradient of similar to8 degreesC/km and a subduction depth of similar to90 km. The eclogites, metagabbros, and gabbros show incompatible element patterns similar to those of recent mid-oceanic-ridge basalts, and thus are interpreted to represent former oceanic crust. The low geothermal gradient indicates a cold subducted oceanic lithosphere, implying long-lived, fast convergence and a relatively large (>1000 km) associated ocean basin. A Sm-Nd isochron defines an age of 595 +/- 10 Ma for the eclogite facies metamorphism. These results imply that a Neoproterozoic suture zone exists between the Congo and Kalahari cratons. Suturing occurred during the same orogenic cycle that formed the Zambezi belt and is related to the assembly of Gondwana.

Document Type: Article
Keywords: eclogites Gondwana assembly Neoproterozoic Rodinia breakup suture zone zambezi belt geothermometer evolution zimbabwe garnet crust calibration subduction phengite mantle
Research affiliation: Kiel University
DOI etc.: 10.1130/0091-7613(2003)031<0243:efanoi>2.0.co;2
ISSN: 0091-7613
Date Deposited: 24 Jan 2012 05:43
Last Modified: 08 Oct 2012 10:35
URI: http://eprints.uni-kiel.de/id/eprint/16198

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