Thomas Creek Copper-Gold Project
The Thomas Creek Copper-Gold Prospect shows strong porphyry affinities and has dimensions indicating it could support a world-class sized copper accumulation in excess of 1 million tonnes of contained copper. The prospect is a significant occurrence of copper and gold anomalism occurring in surface soils and associated with hydrothermal alteration of an andesitic to dioritic intrusive-volcanic complex. Sulphide mineralisation occurs over a large area in excess of 2 km2 and is associated with intense brecciation, veining and ‘porphyry’-style potassic feldspar-silica and magnetite-chlorite alteration. Limited shallow reconnaissance drilling undertaken by Plutonic Operations in 1996 over one portion highlighted the extensive nature of the alteration and mineralisation.
A major demagnetised zone with an ovoid magnetic rim clearly visible in the regional aeromagnetic data defines the area of mineralisation. Such demagnetised zones are often characteristic of porphyry copper-gold deposits. The aeromagnetic and regional gravity data also highlight major intersecting crustal faults interpreted to provide openings for magmatic activity and associated mineralisation.
Soil sampling undertaken by previous explorers defined a copper and gold anomaly approximately 1000 metres long and 700 metres wide using a 100 ppm copper cut off, roughly coincident with the eastern side of the demagnetised zone. A second new zone of high copper anomalism has been recently identified on the western side too and will be followed up. Exceptional copper and gold assays have been returned, with several zones in excess of 0.1% Cu in soil and include one area which returned a soil sample of 7% copper with 3 g/t gold and an adjacent sample of 2% copper and 1 g/t gold.
Aeromagnetic image showing classic “Porphyry” magnetic signature of the Thomas Creek Target
In 1996 Plutonic undertook a limited drill campaign at Thomas Creek, drilling8 narrow-diameter diamond drill holes utilizing a small light weight rig. Holes were angled 45 degrees to the south and ranged between 88m and 127m drill depth. Vertical penetration is calculated to be 63 to 90m, however given the narrow diameter of the holes there is a reasonable likelihood of some drill hole lift occurring, and vertical penetration could be less than calculated. Down-hole drill orientation surveys were not undertaken by Plutonic.
Thomas Creek copper-in-soils contours overlying aeromagnetic image
Recovered drill core was commonly highly broken with significant core loss evident, particularly in some clay alteration rich zones. Plutonic commented that effect of this loss upon the grades from some intervals had not been fully assessed, but could be significant if appreciable chalcopyrite was introduced with the clay-rich vein phase. The drilling returned widespread low grade copper mineralisation, such as 58 m @ 0.08% Cu from 40 m in TCD2 and 15m @ 0.17% Cu from 32m in TCD5. The core shows intense potassic feldspar–silica, pyrite, chlorite, actinolite, magnetite, hematite, pyrite and chalcopyrite with late tourmaline, pyrite, smectite, and epidote alteration.
The drill core is notable for broad zones of stockwork hematite veining and pervasive chloritic alteration, which appear to be associated with brecciation and faulting. It is postulated the hematite stockwork may be after primary sulphide and the shallow drilling has only tested the leached zone of the mineralised system.
Thomas Creek Core - Stockwork hematite veining and strong pervasive chlorite-silica alteration of diorite porphyry.
Drill-Ready Target |Large untested geophysical anomaly
In early 2014 Sherlock undertook pole-dipole induced polarisation (IP) surveys at Thomas Creek in order to identify potential zones of disseminated sulphide mineralisation within the broader alteration system. 7.3 line-km of surveys were taken on four traverses.
This work defined a distinct chargeability anomaly of significant dimensions. The anomaly is visible on three of the four survey lines completed and is at least 300m W-E by 500m N-S. Modelling of the IP data indicates that the top of this large chargeability feature lies at depths of between 100 and 200m below surface and has not been tested by previous drilling.
A second separate chargeable feature has also been partly identified from the IP and is associated with a second zone of copper soil anomalism on the north-western edge of magnetic ring feature offering further potential and warrants further follow-up.
3D modelling of the target highlights the spatial relationship between the chargeability anomaly within the demagnetised zone and lying beneath the surface geochemical copper anomaly. This target warrants immediate drill testing.