|dc.description.abstract||A petrographical and geochemical study of the acid phase of the Bushveld
Complex, north of Pretoria, was undertaken with the aim to identify the
different rock units, to determine their interrelationships and to classify
the rocks as well as describing their geochemistry.
The oldest geological formation in the area is the Rooiberg Group which is
subdivided into two units, namely the Kwaggasnek (lower) and Schrikkloof
(upper) Formations. Petrographical, mineralogical and geochemical data
are submitted for the different units. From the data it can be deduced
that these units formed as products of a single parental magma, while statistical
manipulation of the geochemical data indicates that these formations
differ significantly from the Damwal Formation farther to the east. The
gradational contact relationships between the felsites and underlying granophyre
are described and explained in the text.
The various granophyre occurrences of .the Rashoop Granophyre Suite are
classifiedand described. The mineralogical, petrographical and geochemical
data indicate a limited differentiation trend from the felsites into the granophyre.
This may indicate that the granophyre in part resulted from
. the rapid crystallization of the parental magma of the Rooiberg Group.
A model for the origin and formation of the Rashoop Granophyre Suite,
based on petrographical and-qeochernical evidence, is proposed.
The granites are subdivided according to age and field relationships, as well
as mineralogical, petrographical and geochemical characteristics into the
Sekhukhuni, Verena, Makhutso, Klipvoor and Klipkloof granites. The mode
of intrusion as well as the mineralogical, petrological and geochemical composition
of each type are discussed. A petrochemical investigation of the
granites indicate that the various granites, with the exception of the Klipkloof
granite, represent the differentiation products of a single parental
magma. A similar study on the Makhutso and.Verena granites indicates that
leptite assimilation influenced the final differentiation trend in these granites,
causing enrichment in certain elements and depletion in others.||en_ZA