Universität zu Köln

Cutts, Kathryn A., Stevens, Gary ORCID: 0000-0003-1593-9419, Hoffmann, J. Elis ORCID: 0000-0001-6670-1393, Buick, Ian S., Frei, Dirk ORCID: 0000-0002-3734-737X and Muenker, Carsten (2014). Paleo- to Mesoarchean polymetamorphism in the Barberton Granite-Greenstone Belt, South Africa: Constraints from U-Pb monazite and Lu-Hf garnet geochronology on the tectonic processes that shaped the belt. Geol. Soc. Am. Bull., 126 (3-4). S. 251 - 271. BOULDER: GEOLOGICAL SOC AMER, INC. ISSN 1943-2674

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Abstract

The Barberton Granite-Greenstone Belt (BGGB) of South Africa is an exceptionally well preserved Meso-Paleoarchean metamorphic supracrustal belt, one of only a few in the world. Studies of metamorphism in the BGGB have considerable potential to advance our understanding of tectonic processes in the Archean crust. Two current hypotheses persist to explain the origin of amphibolite-facies metamorphism in the southern BGGB. The first interprets these rocks to be the consequence of accretionary tectonics, while the second proposes a domeand-keel vertical tectonic process driven by sinking of greenstone layers and the doming of the underlying granitoid crust. In this study, metamorphic pressure-temperature (P-T) analysis has been combined with garnet Lu-Hf and monazite U-Pb geochronology to directly date the amphibolite-facies metamorphism within the Stolzburg terrane of the BGGB. A garnet-biotite-chlorite-bearing sample yields a Lu-Hf garnet age of 3233 +/- 17 Ma and a garnet-staurolite-kyanite-bearing sample produces a U-Pb monazite age of 3191 +/- 9 Ma, whereas an andalusite-kyanite-bearing sample produces a U-Pb monazite age of 3436 +/- 18 Ma. Phase diagrams and garnet compositional modeling produce a clockwise P-T evolution, with rocks reaching peak P-T conditions of 8.5 kbar and 640 degrees C for the ca. 3200 Ma event and minimum peak P-T conditions of similar to 4.5 kbar and 550 degrees C for the ca. 3435 Ma event. The duration of metamorphism for the ca. 3200 Ma event is estimated to be similar to 50-20 m.y. based on differences in age between U-Pb and Lu-Hf systems and durations needed to fit models of diffusionally modified garnet chemical zoning. Similarly shaped P-T paths over the Stolzburg terrane indicate that the metamorphism occurred in response to crustal thickening due to an accretionary tectonic process. Thus, the Stolzburg terrane constitutes an orogenic core, exhumed along the Komati fault.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Cutts, Kathryn A. UNSPECIFIED UNSPECIFIED UNSPECIFIED Stevens, Gary UNSPECIFIED orcid.org/0000-0003-1593-9419 UNSPECIFIED Hoffmann, J. Elis UNSPECIFIED orcid.org/0000-0001-6670-1393 UNSPECIFIED Buick, Ian S. UNSPECIFIED UNSPECIFIED UNSPECIFIED Frei, Dirk UNSPECIFIED orcid.org/0000-0002-3734-737X UNSPECIFIED Muenker, Carsten UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-443663
DOI:	10.1130/B30807.1
Journal or Publication Title:	Geol. Soc. Am. Bull.
Volume:	126
Number:	3-4
Page Range:	S. 251 - 271
Date:	2014
Publisher:	GEOLOGICAL SOC AMER, INC
Place of Publication:	BOULDER
ISSN:	1943-2674
Language:	English
Faculty:	Unspecified
Divisions:	Unspecified
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language PROGRADE METAMORPHIC REACTIONS; MOUNTAIN LAND; STRUCTURAL EVOLUTION; FACIES METAMORPHISM; PELITIC SCHISTS; TERRANE SOUTH; MOODIES GROUP; CORE-COMPLEX; GROWTH; RATES Multiple languages Geosciences, Multidisciplinary Multiple languages
URI:	http://kups.ub.uni-koeln.de/id/eprint/44366