Post by
diabase1 on Dec 21, 2022 10:44am
McQuibban5
Referring to the OGS Map 82811, Total Field Residual Magnetic Map, it will be noted that just off the west end of the RTM's McQuibban property, it clearly shows a large, oval-shaped, ring-type magnetic feature with 2 or 3 separate, shorter magnetic trends flaring off from it, perpendicular to the near circular magnetic feature. I'll call this larger anomaly the 'Ring of Skarn'. The eastern most part of this larger magnetic circle is the magnetic anomaly that lies just outside of the western end of RTM's property (west end of Lake Shore Gold's airborne magnetic and VLF survey, OGS Assessment File 20000002703/20004201).
This large oval-shaped magnetic feature is believed not to be an oxide iron formation, but thought to be due rather to a band of metamorphosed rocks, thus the skarn. The western end of the oxide iron formation on RTM's property seems to terminate at the contact with this fenitic zone. The latter also tends to conform with the outer edges of the near circular southern bay of Pierre Lake. Interesting!!
Could the core inside this magnetic anomaly be a syenite, with the magnetic feature being related to a skarn formation around the outer contact of the syenite? Skarns may form a magnetic high due to large concentrations of magnetite or other magnetic minerals such as pyrrhotite. With so many Ni/Cu indicator minerals, if these are from the core, then what would be the source rocks?
In 2001, the Ontario Geological Survey carried out an alluvium sampling survey in the Smooth Rock Falls region (Open File Report 6044). The study was to determine the number of VMS, Skarn and Nickel/Copper indicator minerals. No samples were taken in the immediate area of the McQuibban property oxide iron formation. However, just south of the 'Ring of Skarn', 3 samples were taken. Two samples are on the south shore of Pierre Lake, with the 3rd sample a few kilometres further south. The results of these 3 samples are as follows:
2312: 3 VMS indicator minerals, 2 cpy grains
2 Skarn indicator minerals
139 Ni/Cu indicator minerals
26 chromite grains
0 gold grains
2313: 12 Ni/Cu indicator minerals
15 chromite grains
0 gold grains
2358: 2 VMS indicator minerals, 2 cpy grains
2 Skarn indicator minerals
36 chromite grains
0 gold grains
There's much more info in this report that may be of interest to follow up, because of the high number of Ni/Cu indicator minerals.
Merry Christmas to everyone and all the Best in 2023.