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

Abstract

Research Article| March 01, 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 Kathryn A. Cutts; Kathryn A. Cutts † 1Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa †E-mail: [e-mail] Search for other works by this author on: GSW Google Scholar Gary Stevens; Gary Stevens 1Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa Search for other works by this author on: GSW Google Scholar J. Elis Hoffmann; J. Elis Hoffmann 2Universität zu Köln, Institut für Geologie und Mineralogie, Zülpicher Str. 49b, 50674 Köln, Germany Search for other works by this author on: GSW Google Scholar Ian S. Buick; Ian S. Buick 1Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa Search for other works by this author on: GSW Google Scholar Dirk Frei; Dirk Frei 1Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa Search for other works by this author on: GSW Google Scholar Carsten Münker Carsten Münker 2Universität zu Köln, Institut für Geologie und Mineralogie, Zülpicher Str. 49b, 50674 Köln, Germany Search for other works by this author on: GSW Google Scholar Author and Article Information Kathryn A. Cutts † 1Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa Gary Stevens 1Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa J. Elis Hoffmann 2Universität zu Köln, Institut für Geologie und Mineralogie, Zülpicher Str. 49b, 50674 Köln, Germany Ian S. Buick 1Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa Dirk Frei 1Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa Carsten Münker 2Universität zu Köln, Institut für Geologie und Mineralogie, Zülpicher Str. 49b, 50674 Köln, Germany †E-mail: [e-mail] Publisher: Geological Society of America Received: 09 Oct 2012 Revision Received: 09 Jul 2013 Accepted: 23 Sep 2013 First Online: 08 Mar 2017 Online ISSN: 1943-2674 Print ISSN: 0016-7606 © 2013 Geological Society of America GSA Bulletin (2014) 126 (3-4): 251–270. https://doi.org/10.1130/B30807.1 Article history Received: 09 Oct 2012 Revision Received: 09 Jul 2013 Accepted: 23 Sep 2013 First Online: 08 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation Kathryn A. Cutts, Gary Stevens, J. Elis Hoffmann, Ian S. Buick, Dirk Frei, Carsten Münker; 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. GSA Bulletin 2014;; 126 (3-4): 251–270. doi: https://doi.org/10.1130/B30807.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGSA Bulletin Search Advanced Search 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 "dome-and-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 °C for the ca. 3200 Ma event and minimum peak P-T conditions of ∼4.5 kbar and 550 °C for the ca. 3435 Ma event. The duration of metamorphism for the ca. 3200 Ma event is estimated to be ∼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. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.