Implications of the chromium budget of the Western Limb of the Bushveld Complex

Research Article| June 01, 2000 Implications of the chromium budget of the Western Limb of the Bushveld Complex H.V. Eales H.V. Eales Department of Geology, Rhodes University, Grahamstown, 6140 Republic of South Africa, E-mail: h.eales@ru.ac.za Search for other works by this author on: GSW Google Scholar Author and Article Information H.V. Eales Department of Geology, Rhodes University, Grahamstown, 6140 Republic of South Africa, E-mail: h.eales@ru.ac.za Publisher: Geological Society of South Africa Accepted: 19 May 2000 First Online: 07 Mar 2017 Online ISSN: 1996-8590 Print ISSN: 1012-0750 © 2000 Geological Society of South Africa South African Journal of Geology (2000) 103 (2): 141–150. https://doi.org/10.2113/103.2.141 Article history Accepted: 19 May 2000 First Online: 07 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn Email Permissions Search Site Citation H.V. Eales; Implications of the chromium budget of the Western Limb of the Bushveld Complex. South African Journal of Geology 2000;; 103 (2): 141–150. doi: https://doi.org/10.2113/103.2.141 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 Cr content ofthe Lower and Critical Zones exposedin the northwestern sector of the Western Limb of the Complex is greatly in excess ofwhat the liquids now represented by the Lower, Critical, Main, and Upper Zones could have held in solution. Chromium has a limited solubility in mafic magmas, and the amount of Cr held in the chromitite layers, disseminated chromite, accessory chromite, and in the silicate phases of the Critical Zone (1.40% Cr2O3) exceeds the experimentally determined solubility by an order of magnitude. Adequate volumes of appropriateresiduarepresenting original (now Cr-depleted) source liquids appear to be missing from the sequence exposed, and the problem is exacerbated by exclusion of the Cr-poor lower Main Zone as a possible source. This raises questions regarding the shape of the magma chamber, the oxygen fugacity of the magmas, and the manner of magma emplacement. Problems in applying the magma-mixing hypothesis for the origin of chromitites are exposed. It is concluded that the magmas in the chamber were enriched by 3%chromite microphenocrysts derived from alower-level magma chamber. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.