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AGE AND FIELD RELATIONSHIPS OF MAHAMBA ORTHOGNEISSES AND MKHONDO VALLEY METAMORPHIC SUITE PARAGNEISSES FROM THE MKHONDO RIVER, ANCIENT GNEISS COMPLEX, SWAZILAND.

2012; Geological Society of South Africa; Volume: 115; Issue: 3 Linguagem: Inglês

10.2113/gssajg.115.3.369

1996-8590

J. Taylor, Gary Stevens, Cristiano Lana,

Geological formations and processes

Research Article| September 01, 2012 AGE AND FIELD RELATIONSHIPS OF MAHAMBA ORTHOGNEISSES AND MKHONDO VALLEY METAMORPHIC SUITE PARAGNEISSES FROM THE MKHONDO RIVER, ANCIENT GNEISS COMPLEX, SWAZILAND. J. TAYLOR; J. TAYLOR Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa, e-mail: jtaylor@sun.ac.za; gs@sun.ac.za Search for other works by this author on: GSW Google Scholar G. STEVENS; G. STEVENS Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa, e-mail: jtaylor@sun.ac.za; gs@sun.ac.za Search for other works by this author on: GSW Google Scholar C. LANA C. LANA Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa, Present address: Departamento de Geologia (DEGEO), Universidade Federal de Ouro Preto, Ouro preto, Minas Gerais 35400000, Brazil. e-mail: cristianodeclana@gmail.com Search for other works by this author on: GSW Google Scholar Author and Article Information J. TAYLOR Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa, e-mail: jtaylor@sun.ac.za; gs@sun.ac.za G. STEVENS Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa, e-mail: jtaylor@sun.ac.za; gs@sun.ac.za C. LANA Centre for Crustal Petrology, Department of Earth Sciences, Stellenbosch University, Private Bag X1, Matieland 7602, South Africa, Present address: Departamento de Geologia (DEGEO), Universidade Federal de Ouro Preto, Ouro preto, Minas Gerais 35400000, Brazil. e-mail: cristianodeclana@gmail.com Publisher: Geological Society of South Africa First Online: 09 Mar 2017 Online ISSN: 1996-8590 Print ISSN: 1012-0750 © 2012 Geological Society of South Africa South African Journal of Geology (2012) 115 (3): 369–384. https://doi.org/10.2113/gssajg.115.3.369 Article history First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation J. TAYLOR, G. STEVENS, C. LANA; AGE AND FIELD RELATIONSHIPS OF MAHAMBA ORTHOGNEISSES AND MKHONDO VALLEY METAMORPHIC SUITE PARAGNEISSES FROM THE MKHONDO RIVER, ANCIENT GNEISS COMPLEX, SWAZILAND.. South African Journal of Geology 2012;; 115 (3): 369–384. doi: https://doi.org/10.2113/gssajg.115.3.369 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 SocietySouth African Journal of Geology Search Advanced Search Abstract This study documents for the first time the ages and structural field relationships of banded orthogneisses, and associated high-grade paragneisses, from the Mkhondo River in the Ancient Gneiss Complex of Swaziland, whose age and regional context has been disputed. LA-ICP-MS U-Pb zircon dating shows that the orthogneiss unit mapped as Mahamba gneiss is composed of a 3215 ± 12 Ma granodiorite phase that was intruded by a 3162 ± 11 Ma felsic granitic phase. A hornblende-bearing tonalite dated at 2889 ± 13 Ma, which occurs structurally beneath the Mkhondo Valley Metamorphic Suite (MVMS) metasediments, experienced a metamorphic overprint at 2735 ± 11 Ma that coincided with granulite facies metamorphism and partial melting in the MVMS (Taylor et al., 2010). Both the MVMS and the Mahamba gneisses are characterised by north-northwest aligned, syn-peak-metamorphic deformation structures, indicating a period of west-southwest to east-northeast directed crustal shortening. Neither the Mahamba gneisses, nor the hornblende tonalite are intrusive into the structurally overlying MVMS sediments. This suggests that: (1) the Mahamba gneisses form part of the exposed basement in the area; and (2) the MVMS is a relatively young, late Archaean sedimentary succession that is unrelated to ≥ 3.23 Ga high-grade paragneiss units documented to the east and northeast of the MVMS (Taylor et al., 2012). You do not have access to this content, please speak to your institutional administrator if you feel you should have access.