An integrated geochemical and isotopic study of the Prieska Province kimberlites from the Republic of South Africa
Date
1994
Authors
Clark, Trevor, Charles
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Abstract
Rb-Sr emplacement ages of nineteen kimberlites from the Prieska Province
vary from 74 to 174 Ma, Their isotopic, whole-rock geochemical signatures
and perovskite REE distributions were also determined.
Non-micaceous and micaceous kimberlites from the area show similar
petrographic, geochemical and isotopic compositions relative to cratonic
kimberlites, indicating similar sub-continental mantle source compositions
in the two tectonic environments. Transitional varieties of kimberlite,
which can be defined petrographically, geochemically and isotopically are
also recognised from the area, but are not prevalent in the cratonic
environment. The Prieska Province kimberlites are possibly derived by
partial melting processes within a subcontinental reservoir characterised by
a spectrum of compositions from time-averaged depleted (HllMU) to
enriched (Group II).
The occurrence of these components in both on- and off-craton settings
indicates that the kimberlite source area is not strictly linked to the
suberatonic lithosphere. Mantle' plume sources are not favoured because of
the variable source compositions and distribution of emplacement ages
within the Province. Transitional kimberlites were derived from a source
component with mixed character, not yet noted from within the Kaapvaal
Craton. This is the first documented example of isotopically transitional
kimberlites from southern Africa.
Description
A research project submitted to the Faculty of Science, University of the
Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the
degree of Master of Science.
Keywords
Kimberlite -- South Africa., Isotopes., Geochemistry -- South Africa.