situated approximately 160 metres below ground level (“BGL”). The Mannville Group and Palaeozoic interface lies approximately 340 metres BGL as interpreted from Shore drill holes.
6.3.1 GEOLOGY OF THE STAR KIMBERLITE
Based on the historical and current surface core drilling and underground mapping of the various kimberlite phases encountered from Shore’s underground bulk sampling program, the Star Kimberlite consists of two distinct types of kimberlite: 1) eruptive kimberlite phases; and 2) kimberlitic sediments. The eruptive kimberlite deposits at Star are sub-divided into five main kimberlite phases, each with distinct physical and chemical properties which enable their mapping and stratigraphic correlation in three dimensions (Harvey et al., 2006) (Figure 6.3).
Late-Joli Fou Kimberlite (LJF)
Mid-Joli Fou Kimberlite (MJF)
Early-Joli Fou Kimberlite (EJF)
Pense Kimberlite (PPK)
Cantuar Kimberlite (CPK)
These kimberlite phases are well constrained within the Cretaceous stratigraphy in which they were deposited. For example, those kimberlites deposited during Cantuar Formation time (part of the Mannville Group) are considered to be Cantuar age-equivalent kimberlite and are termed Cantuar Kimberlite. Similarly, kimberlite deposited during early Joli Fou Formation time (part of the Lower Colorado Group) is Early Joli Fou age-equivalent kimberlite and are termed Early Joli Fou Kimberlite. It is important to note that the stratigraphic age-equivalence nomenclature is also used in other kimberlite of the FALC area (e.g. Orion South) and that two stratigraphically equivalent kimberlite packages (e.g. Pense Kimberlite on Star and Orion South) may not have any genetic relationship and each may have very different diamond grade and price characteristics.
Eruptive Kimberlite Phases – Star Kimberlite
The oldest kimberlite phases within the Star Kimberlite are those termed Cantuar-aged kimberlites (“CPK”), which are hosted by sandstone, siltstone and mudstone units of the Cantuar Formation. These CPK deposits are typically restricted to thin sheet-like deposits that generally vary in width from 20 metres to 40 metres (see Figure 6.3). There are two end-member types of CPK: matrix-supported pyroclastic kimberlite, which primarily occurs to the north and a clast- supported pyroclastic kimberlite and kimberlite breccia variety that occurs to the south. The CPK is typified by the ubiquitous presence of small (1-4 mm) clinopyroxene xenocrysts and relatively common mantle xenoliths. The kimberlite is variably fine- to medium-grained and is bedded at the 1-5 metre scale although massive beds do occur. Rare fine-grained reworked equivalents are present and locally display cross-bedding features.
Restricted to the south of the Star Kimberlite is a younger, potential Cantuar-aged kimberlite, known as JLRPK (juvenile lapilli-rich pyroclastic kimberlite), that occurs as two spatially restricted feeder vents which have shapes similar to the classic South African model carrot- shaped pipes and cross-cut older CPK. The main vertical feeder vents are less than 150 m in width with edges bounded by the Cantuar Formation sediments and at depth the Devonian-age carbonates (dolomites). Near the margins of the vent, common Cantuar Formation xenoliths with highly variable bedding angles are present. The unit is clast-supported and is dominated by
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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