contribution to the overall mineralogy from each source varies widely and significantly influences the petrographic character of the rocks. Consequently, Group 1 kimberlites comprise a petrological clan of rocks that exhibit wide differences in appearance and mineralogy as a consequence of the above variation, coupled with differentiation and diverse styles of emplacement of the magma (Mitchell, 1986).
Figure 7.1 illustrates an idealized South African kimberlite magmatic system, showing the relationships between effusive rocks, diatremes and hypabyssal rocks. Currently, three textural- genetic groups of kimberlite are recognized, each being associated with a particular style of magmatic activity in such a system. These are:
diatreme facies; and
Rocks belonging to each facies differ in their petrology and primary mineralogy, but may contain similar xenocrystal and megacrystal assemblages (Mitchell, 1986).
With a few exceptions, such as the Finsch Kimberlite Mine in South Africa and the Dokolwayo Kimberlite Mine in Swaziland, most of the well known diamondiferous kimberlites in South Africa and elsewhere are Group 1 kimberlites.
FORT À LA CORNE KIMBERLITE MODEL
Unlike the idealized South African kimberlite model, the majority of the FALC kimberlites are mainly shallow champagne-glass shaped kimberlite pipes which have kimberlite footprints ranging up to 2,000 m wide and occur at depths from approximately 100 m to greater than 700 m.
At depth, however, FALC kimberlites may resemble the idealized South African model. The limited deep drilling precludes interpretation of the shape of the kimberlites below about 350 metres below the current ground surface.
FALC kimberlites were emplaced into poorly consolidated Cretaceous-age clastic and marine sedimentary rocks. The FALC kimberlites are generally interpreted to be in the form of stacked, sub-horizontal lenses or shallow zones of crater facies kimberlite with associated pyroclastic flow and fall deposits of large lateral extent. The kimberlite phases were originally classified entirely as crater-facies pyroclastic kimberlite, though a number of kimberlitic phases may be distinguished according to grain size, style of emplacement, primary and chemical alteration and the abundance and presence of olivine macrocrysts.
P&E Mining Consultants Inc. NI 43-101 Technical Report No 159 Shore Gold Inc. - Star Diamond Project Resource Estimate Update
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