Geochemical characteristics and rare earth element trends of the Upper Zone in the western Bushveld Complex
type: CreativeWork
description: The geochemical trends of the Bierkraal 1 drill core are investigated to document fractionated magma, 2) convectional overturning resulting from the disintegration of a stagnant layer, or 3) whether prestratification of the magma in the magma chamber existed. Rare earth element distribution coefficients (calculated by the ratio of rare earth element content of apatite to rare earth element content of host matrix) indicates that the apatite in magnetite and apatite rich zones crystallized under conditions nearer to equilibrium than apatite in any other rock units. This lends credence to the theory that an immiscible Fe-P20 5 rich melt forms during the crystallization of the Upper Zone. Various interwoven geochemical twin trends following in stratigraphic sequence, are identified in some cycles and are found to be similar in geochemical behaviour. These trends are associated with normal fractionation processes. The presence of interwoven twin trends are tentatively ascribed to crystallization being alternatively dominated by adjacent convection cells within the magma. the behaviour of various elements. Special emphasis is placed on the rare earth elements during the final stages of crystallization of the Upper Zone in the western Bushveld. The geochemical characteristics of the western Bushveld Upper Zone are also briefly compared to the Upper Zone of the eastern Bushveld as exposed in the Roossenekal district. The rock types intersected by the Bierkraal 1 borehole consist largely of gabbro, magnetite gabbro, lesser magnetite and anorthosite layers. Plagioclase comprises 50 to 70 volume percent of most samples investigated. Up to 87 volume percent plagioclase is found in anorthosite while magnetitite layers consist of up to 97 volume percent oxide. Unlike the eastern Bushveld, olivine occurs throughout the Bierkraal 1 borehole and, is generally limited to the range of 15 to 30 volume percent. Pyroxene is generally well below 10 volume percent with hornblende becoming …
abstract: The geochemical trends of the Bierkraal 1 drill core are investigated to document fractionated magma, 2) convectional overturning resulting from the disintegration of a stagnant layer, or 3) whether prestratification of the magma in the magma chamber existed. Rare earth element distribution coefficients (calculated by the ratio of rare earth element content of apatite to rare earth element content of host matrix) indicates that the apatite in magnetite and apatite rich zones crystallized under conditions nearer to equilibrium than apatite in any other rock units. This lends credence to the theory that an immiscible Fe-P20 5 rich melt forms during the crystallization of the Upper Zone. Various interwoven geochemical twin trends following in stratigraphic sequence, are identified in some cycles and are found to be similar in geochemical behaviour. These trends are associated with normal fractionation processes. The presence of interwoven twin trends are tentatively ascribed to crystallization being alternatively dominated by adjacent convection cells within the magma. the behaviour of various elements. Special emphasis is placed on the rare earth elements during the final stages of crystallization of the Upper Zone in the western Bushveld. The geochemical characteristics of the western Bushveld Upper Zone are also briefly compared to the Upper Zone of the eastern Bushveld as exposed in the Roossenekal district. The rock types intersected by the Bierkraal 1 borehole consist largely of gabbro, magnetite gabbro, lesser magnetite and anorthosite layers. Plagioclase comprises 50 to 70 volume percent of most samples investigated. Up to 87 volume percent plagioclase is found in anorthosite while magnetitite layers consist of up to 97 volume percent oxide. Unlike the eastern Bushveld, olivine occurs throughout the Bierkraal 1 borehole and, is generally limited to the range of 15 to 30 volume percent. Pyroxene is generally well below 10 volume percent with hornblende becoming …
keywords: UCTD, Geochemical characteristics, rare earth element trends
date published: 1994
date modified: 2026-07-24T03:52:56Z
provider: University of Pretoria
publisher: Networked Digital Library of Theses and Dissertations
type: WebPage
source organization: University of Pretoria

PropertyValue
property ID: Handle
value: http://hdl.handle.net/2263/82463