|Blackstone Range Project|
|Ownership:||Farm-in Agreement with Resource Mining Corporation (ASX: RMC)|
|Exploration licences:||69/2108, 69/2109|
The Blackstone Range Project covers an area of 338 km2 approximately 25km east of the BHP-Billiton Babel and Nebo Ni-Cu-PGE discoveries. High-resolution aeromagnetic surveys identified the 12 km diameter elliptical ring complex named the Saturn Complex, interpreted to be a mafic cone-shaped feeder of Giles Intrusive Complex. This intrusion, and associated mafic complex cuts through the large layered mafic intrusions of the Blackstone and Cavanaugh Ranges and it is along these intrusive boundaries that the Halleys and Halleys NW Ni-Cu-PGE trend occurs. These magmatic boundaries are proving to be highly complex, containing multiple intrusions including fractionated magnetite-bearing layered intrusions rich in PGE mineralization, and pipe-like bodies such as the Halleys Cu-PGE-Ni body.
The Halleys target was first drilled with RAB and shallow RC in 2007. At this time a 100+m thick mineralized zone was defined which yielded a peak intercept of 74m of 0.33% Cu and 0.24g/t PGE+Au including 20m @ 0.56% Cu, 0.14% Ni and 0.32g/t PGE+Au (from 16m).
Split results were received for RAB drill hole BSB058 at Halleys which drilled 3m into the hanging wall of the mineralized zone. Significantly, assays include 1m @ 1.1g/t PGE + Au, 0.32% Ni and 0.25% Cu from 61m (total hole depth 63m), demonstrating higher grades of PGE and Ni are present in the system. Reinterpretation of the drill results for the adjacent holes highlighted a high grade zone in the hangingwall grading 10m @ 0.75% Cu, 0.18% Ni and 0.28g/t PGE (BSC003 from 22m).
A second round of drilling was conducted in April 2008. This second round of shallow vertical RAB drilling at the Halleys prospect was undertaken to determine the limits of the Halleys pipe-like body and to clearly define the geometry of the mineralized system in preparation for deeper drilling.
Halleys Cu-Ni-PGE Prospect peak RAB drill intercepts May 2008 program. PGE results calculated geochemically, Ni and Cu results calculated from XRF sampling of pulps
This drilling has better defined the geometry of the Halleys Ni-Cu-PGE body. Disseminated sulphides with significant copper-PGE grades (>0.1%Cu and 200ppb PGE) occur in an ovoid shaped pipe 300m x 230m in size. The pipe is coincident with an elongate magnetic high defined by ground magnetics. A large EM anomaly occurs from the pipe to the northwest, and the EM anomaly is thought to be related to deeper regolith cover (conductive overburden). However, it is possible that the EM anomaly reflects a shallow NW plunging pipe, similar to Babel Nebo. Drilling has indicated a minimum dip of 40º to the NE for the body, however a steeper dip is implied in several areas and the actual dip might be highly variable if a plunging pipe is present. The body is zoned, with a central core of Cu-PGE and an outer zone richer in Ni with Cu and PGE. Table 1 highlights significant intercepts from RAB drilling in 2008.
RAB drilling intercepts from the second drill phase (1m split samples) include:
- 9m @ 0.67% Cu, 0.1% Ni and 0.76 g/t PGE (BSB0512) along the eastern margin from an overall intercept of 43m @ 0.31% Cu, 0.06% Ni and 0.30 g/t PGE + Au;
- 16m @ 0.50% Cu, 0.11% Ni and 0.53 g/t g/t PGE + Au; and
- Along the western margin 11m @ 0.56% Cu, 0.25% Ni and 0.16 g/t PGE from an overall intercept of 35m @ 0.29% Cu, 0.12% Ni and 0.16g/t PGE + Au (BSB0536).
Deeper exploratory drilling is planned to follow up the thick intercepts of mineralisation, in order to test the down-dip and down-plunge position at Halleys prospect.
Halleys NW PGE and Last Frontier
Regional surface geochemical sampling previously defined an 11km long PGE anomaly on the SW margin of the Saturn Intrusive Complex to the northwest of the Halleys Prospect. Reconnaissance RAB drilling in 2007 was aimed at broadly testing the southern part of the surface geochemical anomaly at 400 to 800m line centres with shallow holes 50m apart. Peak intercepts in the RAB include 7m @ 0.29g/t PGE + Au. Infill geochemical sampling has defined a discrete 1km long PGE reef-type target which was drilled in 2008 with angled overlapping holes. The setting and host to the PGE mineralisation is now better understood after detailed ground magnetics and lithogeochemical ratio work has identified a distinct fertile intrusion which is highly prospective for PGE type mineralisation. This strongly supports the exploration model for PGEs in the West Musgrave region based on a flow-through model for the Platreef in South Africa.
At least 4 PGE reefs were defined over 1km strike by RAB drilling. Three separate 1m intercepts are greater than 0.45g/t PGE + Au indicating the presence of narrow PGE reefs (i.e. possibility of 20cm reefs @ 2.5g/t PGE + Au). The true width of the PGE anomalous zone is 26 to 40m width at >0.1g/t PGE + Au. The lower reef generally contains anomalous copper (500ppm) with a peak result of 0.18% Cu. The upper reef is devoid of copper and generally higher grade. Drilling did not provide 100% overlap as hoped as the reefs dip more steeply than the surrounding stratigraphy. The zone of PGEs go under significant cover to the NW and surface sampling in this area is deemed to be ineffective.
One line of RAB drill holes was drilled at Last Frontier 4.5km NW of the Halleys NW PGE reefs. The drilling intercepted thick zones of anomalous PGEs (average 70ppb PGE + Au) with peak results including 5m @ 0.21g/t PGE + Au (BSB0645) and 5m @ 0.19g/t PGE + Au (BSB0641). Drilling here is very broad spaced, showing that the PGE rich intrusion has narrow low grade reefs over at least 5.5km.
More drilling is required to test over 6km of fertile PGE-rich intrusion.