The PPK is located in the central to north-eastern portion of the Star Kimberlite and, in the northeast, is deposited directly on Pense sandstone and, locally, on Pense mudstone. Towards the central area, PPK material rests directly on the Cantuar Formation, indicating either scouring into the older Cantuar sediments and/or prior erosion/denudation of Pense sandstone. The PPK consists of pyroclastic kimberlite that is generally bedded up to a 15 metre scale.
The EJF is volumetrically the most important eruptive phase. This phase is spatially widespread, with the thickest intersections towards the western portion of the Star Kimberlite. Distal deposits of the kimberlite sit directly on Lower Joli Fou shale (Spinney Hill Member) and are interpreted as Joli Fou-age equivalent. This kimberlite is also observed resting directly on older PPK and CPK.
The younger, cross-cutting MJF eruptive phase is restricted to the western portion of the Star Kimberlite. MJF has erupted through the older EJF. The youngest kimberlite eruptive event, the LJF, is confined to the northern and north-eastern portion of the Star Kimberlite and generally forms a thin veneer, deposited on older EJF and MJF.
The Star Kimberlite is dominated by crater facies rocks, which include well-defined pyroclastic flows that radiate away from the crater. The sheet-like CPK and the PPK are kimberlites deposited from pyroclastic flows from nearby kimberlite volcanoes. The EJF is a combination of vent filling pyroclastics and pyroclastic flows away from the crater. MJF and LJF are a crater facies vent-filling pyroclastic kimberlite.
On October 17, 2006, Shore produced a preliminary three dimensional (3-D) geological model of the Star Kimberlite. The model was compiled from surface and underground drilling information combined with 1,050 in-situ bulk density measurements that were performed on lengths of complete drill core by Shore during its advanced exploration work program. The model was constructed for all kimberlite phases above an elevation of 71 metres above sea level, which corresponds to a depth of approximately 350 metres below the existing land surface.
In November, 2007, Shore produced an updated 3-D geological model utilizing an additional 157 surface and underground holes. Many of the additional holes were infill holes. Some of the holes were drilled along the edge of, and angled into, a north–northwest trending ravine which cross- cuts the Star property to recover geological information from a previously inaccessible area. Also included was an additional 1,635 in-situ bulk density measurements. The updated geological model estimated that the Star Kimberlite contained a total of 278 million tonnes of kimberlite. The geological models for kimberlite and country rock were finalized by Shore and AMEC on January 23, 2008 and are used by P&E in their updated Resource Estimate.
Sampling and Sample Processing
In order to bulk sample the various kimberlite phases for diamond grade estimation and diamond valuation purposes, Shore sank a 250 metre shaft with a drill station at 175 metres and a working level at 235 metres. Shaft sinking began in January, 2003 and was completed in May, 2004. Phase 1 of lateral drift development and underground bulk sampling began in May, 2004 upon
P&E Mining Consultants NI 43-101 Technical Report No 159 Shore Gold - Star Diamond Project