Lithostratigraphy of the Mesoproterozoic Twakputs Gneiss
| dc.contributor.author | Doggart, S | |
| dc.contributor.author | Macey, P | |
| dc.contributor.author | Frei, D | |
| dc.date.accessioned | 2022-08-04T19:29:42Z | |
| dc.date.available | 2022-08-04T19:29:42Z | |
| dc.date.issued | 2021 | |
| dc.description.abstract | The Twakputs Gneiss is a garnetiferous, K-feldspar megacrystic, biotite granite-granodiorite orthogneiss. It represents a major unit in the Kakamas Domain of the Mesoproterozoic Namaqua-Natal Metamorphic Province extending about 250 km between Riemvasmaak in South Africa and Grünau in southern Namibia. The Twakputs Gneiss occurs as foliation-parallel, sheet-like bodies tightly infolded together with granulite-facies paragneisses into which it intrudes along with a variety of other pre-tectonic granite and leucogranite orthogneisses. These rocks were subsequently intruded by late-tectonic garnet-leucogranites, granites and charnockites. The Twakputs Gneiss is a distinctive unit characterised by large ovoid to elongate megacrysts of twinned perthitic K-feldspar, set in a coarse-grained matrix of garnet, biotite, quartz and feldspar. It contains a penetrative foliation defined by the alignment of K-feldspars and streaks of biotite that developed during the main phase D2 of the Namaqua Orogeny (~1.2 to 1.1 Ga). The foliation and an accompanying elongation lineation are more intensely developed along lithological contacts, especially at the margins of the mega-scale F3 domes and basins that refold the regional fabrics. U-Pb zircon dating of the Twakputs Gneiss has yielded concordia ages of between ~1192 and 1208 Ma. Wholerock geochemistry shows consistent major, trace and REE elemental trends, and thus reflect chemical variability from a single fractionating magma. The Twakputs Gneiss has a granitic to granodiorite composition and is strongly peraluminous. The geochemistry and the ubiquitous presence of garnet and pelitic xenoliths indicate an S-type granite protolith. The Twakputs Gneiss is the most voluminous and widespread member of the Eendoorn Suite which comprises seven textural variants of garnetiferous, K-feldspar-megacrystic granitoid orthogneiss of the same age. | en_US |
| dc.identifier.citation | Doggart, S, P. H Macey, and D Frei. “Lithostratigraphy of the Mesoproterozoic Twakputs Gneiss.” South African journal of geology 124.3 (2021): 783–794. Web. | en_US |
| dc.identifier.issn | 1012-0750 | |
| dc.identifier.uri | DOI: 10.25131/sajg.124.0041 | |
| dc.identifier.uri | http://hdl.handle.net/10566/7692 | |
| dc.language.iso | en | en_US |
| dc.publisher | Bureau for Scientific Publications | en_US |
| dc.subject | Twakputs Gneiss | en_US |
| dc.subject | Lithostratigraphy | en_US |
| dc.subject | biotite granite-granodiorite orthogneiss | en_US |
| dc.title | Lithostratigraphy of the Mesoproterozoic Twakputs Gneiss | en_US |
| dc.type | Article | en_US |