Post by
diabase1 on Jul 14, 2023 7:47am
Nordica
Discovery
"The Windward PGE--Cr showing, which is part of the Nordica mafic/ultramafic intrusion, is located in northwestern Nordica Township. It was discovered by prospectors Gary Edwards and Garry Windsor in late 1997. Surface grab samples assayed 0.3% Cu, 0.3% Ni, 1.1 ppm Pd. The property was subsequently optioned by Band--Ore Resources Ltd. Overburden stripping, line cutting, airborne and ground geophysics surveys, and diamond drilling was completed in 1998. Drill hole NW98--1 assayed 1 ppm combined Pd and Pt over 7 m (Band--Ore Resources Press Releases March 9, April 9, and April 28, 1998). For further information see Windward PGE--Cr Showing under property visits in this report" (OFR 5991).
Geology
The Nordica intrusion is a mafic and ultramafic layered intrusion located at the south-west margin of the Kasba Lake granodioritic pluton in northern Nordica Township. This mafic-ultramafic suite is intrusive into the volcanic rocks of the Kinojevis assemblage and is clearly cut by the granodiorites of the Kasba Lake pluton .
Trenches excavated by Band-Ore Resources Limited revealed several distinct lithologies in this intrusion. The most abundant unit exposed consists of troctolite, which is either coarse-grained or pegmatitic. It is locally intruded by very coarse hornblendite. A cumulate olivine gabbronorite located on the west side of the exposure is interpreted to represent the basal portion of the intrusion. A small chromitite layer (1m - 3m in thickness) is also present within the gabbronorite portion of the exposed area of the intrusion (OFR 6102). The cumulate texture of the troctolite and olivine gabbronorite is reasonably well preserved but the primary mineralogy is completely transformed (OFR 6042). This unit is very strongly magnetic.
Abundant pegmatitic units are interlayered with the previously described troctolites. Although the size of the plagioclase and mafic minerals is much larger, they are chemically similar to the troctolites. Some of the elevated platinum-group element values reported by Band-Ore Resources Limited come from these units.
Very coarse-grained hornblendite locally intrudes the troctolites. The hornblendites locally contain up to 8% sulphides. The thickness of the chromitite unit observed in the outcrop varies from 1 m to less than 3 m. It is massive with a dark gray to brownish color and is composed of over 50% chromite.
Disseminated pyrite, pyrrhotite and local chalcopyrite are present in all the different units of the intrusion, but are commonly more abundant in the hornblendites (up to around 8%) and pegmatitic troctolites (up to around 3%).
Because the PGE are very strongly compatible with the sulphides (more so than Ni and Cu), it means that the mafic magma did not suffer sulphide removal, and thus PGE removal, prior to its emplacement in the crust. It also indicates that the sulphides have concentrated the PGEs. Therefore, any conductor, regardless of strength, deserves to be looked at.
To date, no massive sulphides were discovered and it is possible that sulphide accumulation did not take place in this specific area. However, since the study supports all other criteria of the model, the potential to find Ni-Cu-PGE mineralisation elsewhere in this intrusion or in a similar one remains very high.
This intrusion contains lithologies holding large amounts of magnetite, which should be perceivable on a magnetic geophysical survey.
The Nordica Intrusion has been classified as a stratified reef type intrusion of tholeiitic affinity, with examples such as the Chrome-Puddy Lake Intrusion (near Thunder Bay) and the Mann Intrusion (near Timmins).
Map P3421 shows a rough outline of the Nordica Intrusion, which has been mapped as a gabbro. The boundaries of this intrusion will change, as we will see a little later. Towards the extreme southeastern edge of the Nordica Intrusion (Windward Discovery Area) is where Band-Ore Resources carried out a 2 hole sectional drilling program, in order to get an idea of the lithology of the mafic/ultramafic intrusive. More on that later.