D2 Shear Research Articles

Tectonic implications of new geochronologic data from the Limpopo belt at Pikwe, Botswana, southern Africa

Research Article| October 01, 1975 Tectonic implications of new geochronologic data from the Limpopo belt at Pikwe, Botswana, southern Africa MARTHA H. HICKMAN; MARTHA H. HICKMAN 1Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, England Search for other works by this author on: GSW Google Scholar JOHN WAKEFIELD JOHN WAKEFIELD 1Department of Earth Sciences, University of Leeds, Leeds LS2 9JT, England2Present address: Mindeco Noranda, Box 4370, Lusaka, Zambia. Search for other works by this author on: GSW Google Scholar GSA Bulletin (1975) 86 (10): 1468–1472. https://doi.org/10.1130/0016-7606(1975)86<1468:TIONGD>2.0.CO;2 Article history first online: 01 Jun 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation MARTHA H. HICKMAN, JOHN WAKEFIELD; Tectonic implications of new geochronologic data from the Limpopo belt at Pikwe, Botswana, southern Africa. GSA Bulletin 1975;; 86 (10): 1468–1472. doi: https://doi.org/10.1130/0016-7606(1975)86<1468:TIONGD>2.0.CO;2 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 A Rb-Sr isotope study of gneiss units in the Limpopo orogenic belt at Pikwe, Botswana, southern Africa, confirms two previously established isotopic events in the belt at 2,700 and 2,000 m.y. B.P. The new data make it possible to relate these ages to specific events in the tectonometamorphic history of the Pikwe area and to show that some deformation took place substantially later than the emplacement of the satellite extensions of the Great Dyke (2,600 ±120 m.y. ago), which cut Limpopo belt gneiss units to the north in Rhodesia.In the first recognizable tectonometamorphic event affecting the Pikwe area, the formation of regional gneissic foliation was accompanied by granulite facies conditions and extensive partial melting. This metamorphism has a Rb-Sr whole-rock isochron age of 2,660 ± 40 m.y. (2σ) and resulted in the complete isotopic homogenization of Sr across distances of at least 350 m in the gneissic succession.Upright folds were superimposed on recumbent folds in a late polyphase event 2,100 to 2,000 m.y. ago. Minor structures in a late D3 shear zone show a transition from ductile to brittle deformation, and from early D2 to late D3, metamorphic conditions fell from upper amphibolite to greenschist facies. Upper amphibolite facies conditions caused near-complete isotopic rehomogenization of Sr on a scale of 7 cm; isotopic mixing was restricted to less than 25 cm. First Page Preview Close Modal You do not have access to this content, please speak to your institutional administrator if you feel you should have access.