Growth focused Western Australian nickel company St George Mining (ASX: SGQ) today announced exciting exploration results at its flagship Mt Alexander nickel-copper sulphide project, located in the north-eastern Goldfields of WA.
Two very strong off-hole electromagnetic (EM) conductors – modelled with conductivity of 49,000 and 16,200 Siemens respectively – have been identified by the downhole EM (DHEM) survey in MAD184.
The new EM conductors were detected approximately 475m downhole in MAD184 and represent the deepest conductors ever identified at Mt Alexander.
MAD184 was drilled at the West End Prospect, in an area with no prior drilling and more than 800m north-west of known massive sulphides in the Cathedrals Belt.
The electrical signature of the new conductors is consistent with a massive sulphide source.
All other EM conductors with similar characteristics in the Cathedrals Belt have been confirmed by drilling to be massive sulphides with high grades of nickel, copper, cobalt and PGEs.
Modelling of the DHEM survey data for MAD184 has defined two discrete EM plates for drill testing with the EM anomalism open in all directions and further drilling required to fully test the scale of the potential massive sulphide source.
Drilling of the new EM conductors is scheduled to commence early next week with outstanding potential to make a new discovery of massive sulphide mineralisation.
New EM conductors further confirm the camp-scale potential of the +16km long Cathedrals Belt with four shallow high-grade nickel-copper sulphide deposits already discovered and new high priority targets being established.
DHEM surveys in other recently completed drill holes have also identified additional EM anomalies which are being assessed and prioritised for drill testing.
Significant EM conductors identified
The current drill programme at Mt Alexander is focused on deeper drilling to test conductive features identified by a number of geophysical surveys completed by St George across the Cathedrals Belt. The drill targets are located below and down-dip from the shallow high-grade deposits already discovered in the Belt.
DHEM surveys on the completed drill holes are being used to identify discrete EM conductors for follow-up drilling.
MAD184 was completed to a downhole depth of 497.8m to test a broad single component (Z) EM anomaly identified by the surface SQUID MLEM survey carried out earlier this year. The drill hole intersected a 23.2m thick mafic-ultramafic unit from 444.5m downhole. This was highly encouraging because these types of intrusive rocks are known to host massive sulphide deposits in other parts of the Cathedrals Belt.
More significantly, the drill hole intersected 5m of disseminated and blebby nickel-copper sulphides from 462.7m downhole. These disseminated and blebby sulphides can represent the halo around proximal massive sulphide mineralisation and support the potential for the presence of higher-grade mineralisation nearby.
The DHEM survey in MAD184 recorded a very strong off-hole anomalous response to the east and down dip at 475m downhole. The response was seen in the mid to late times with a modelled conductivity of 49,000 Siemens, which is consistent with a massive sulphide source. A second anomaly was detected to the northwest of the drill hole and has a modelled conductivity of 16,200 Siemens.
Importantly, given the large distance of MAD184 from other drill holes, any potential high-grade mineralisation at this location is open in the direction beyond the anomalies.
The modelled plates for these new EM conductors are interpreted to represent the strongest part of the anomalous EM responses and are a reliable targeting tool to test for the presence of massive sulphides. Modelling cannot accurately predict the geometry of any massive sulphide deposit that may be present and is not a definitive measure of the scale of all potential mineralisation.
The new DHEM conductors provide potential to significantly increase the footprint of known high-grade mineralisation in the large mineral system at the Cathedrals Belt.
John Prineas, St George Mining’s Executive Chairman, said: “Our deep drill programme is delivering excellent results with thick intrusive-style rocks and nickel-copper sulphide mineralisation intersected at depths not previously explored.
“The downhole EM surveys have delivered the breakthrough moment with two new exceptional conductors identified from MAD184 that are both interpreted to represent massive nickel-copper sulphides.
“The MAD184 conductors are particularly exciting as they are the deepest conductors ever identified in the Cathedrals Belt and located 800m to the west of previously intersected massive sulphides on the Cathedrals Belt.
“The potential discovery of massive sulphides at these new conductors could be our most important discovery to date as it would confirm the continuity of the high-grade mineralisation at depth and upgrade the western extension of the Cathedrals Belt – which coversthe 2.5km long West End Prospect that straddles the major Ida Fault – as a fertile and highly prospective area for further mineralisation.
“The Cathedrals Belt is interpreted to dip to the north-west at about 40 degrees so, from a geological perspective, the MAD184 conductors are in an ideal location for the presence of massive sulphide mineralisation down-dip from the high-grade mineralisation already discovered near surface.
“With a 100% success rate in testing these kinds of conductors in the Cathedrals Belt, we are confident that our next significant discovery of massive nickel-copper sulphides is imminent.”