The petrogenesis of the Alberta Complex within the Rehoboth Basement Inlier of Namibia

Abstract

Research Article| June 01, 2002 The petrogenesis of the Alberta Complex within the Rehoboth Basement Inlier of Namibia Thomas Becker; Thomas Becker Geological Survey of Namibia, P.O. Box 2168, Windhoek, 9000, Namibia, e-mail: tom@mme.gov.na Search for other works by this author on: GSW Google Scholar Arnd Brandenburg Arnd Brandenburg 2 DESY Theory Group, D-22603 Hamburg, Germany, e-mail: Arnd.Brandenburg@desy.de Search for other works by this author on: GSW Google Scholar Author and Article Information Thomas Becker Geological Survey of Namibia, P.O. Box 2168, Windhoek, 9000, Namibia, e-mail: tom@mme.gov.na Arnd Brandenburg 2 DESY Theory Group, D-22603 Hamburg, Germany, e-mail: Arnd.Brandenburg@desy.de Publisher: Geological Society of South Africa First Online: 07 Mar 2017 Online ISSN: 1996-8590 Print ISSN: 1012-0750 © 2002 Geological Society of South Africa South African Journal of Geology (2002) 105 (2): 147–162. https://doi.org/10.2113/105.2.147 Article history First Online: 07 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Thomas Becker, Arnd Brandenburg; The petrogenesis of the Alberta Complex within the Rehoboth Basement Inlier of Namibia. South African Journal of Geology 2002;; 105 (2): 147–162. doi: https://doi.org/10.2113/105.2.147 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 The Alberta Complex is the most prominent member of a mafic to ultramafic igneous suite within the Rehoboth Basement Inlier/Namibia, being intrusive into sediments and mafic volcanics of the Paleoproterozoic Elim Formations. Subsequent amphibolite grade metamorphism of pre-Kibaran age obscured the original mineral assemblage. Two main units have been distinguished in the past within the Alberta Complex. (1) A thick pile of various amphibolites represents original norite, hyperite, gabbro and anorthosite and constitutes the Layered Sequence. It has been subdivided into four zones, thought to represent individual magmatic pulses. (2) Later stage magmatism comprises pegmatite veins as well as pyroxenite, harzburgite and dunite, emplaced in plugs and a cone sheet.In contrast to field observations, geochemical profiles of compatible elements across the complex indicate more complex layering and subdivision of the Layered Sequence into at least seven units. Incompatible trace elements are largely decoupled from compatible elements, which probably is the result of variable amount of interstitial liquid within cumulate phase. However, the shape of REE patterns has been controlled chiefly by fractionation of clinopyroxene and plagioclase. Finally, decoupling of hydrophile LILE from both compatible and incompatible elements may result from hydrothermal overprint or from redistribution during metamorphism.Gabbroic rocks from the Marginal Zone of the Alberta Compex display affinity to mafic volcanic rocks of the Elim Fm. Modeling based on in situ fractional crystallisation or, alternatively, mixing of evolved liquid with cumulate supports this hypothesis. In contrast, for samples within the magma chamber, only REE could be matched closely by these models, while modeled incompatible trace elements commonly deviate from the measured data. Additional complexity of local magma chamber probably best explains these deviations. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.