The Borealis Project

CAS

In 1992, Placer Dome completed a comprehensive exploration program at the Cas area, combining induced polarization (IP), ground magnetometer, VLF-EM surveys, and soil and rock geochemistry.
The surveys defined two strong IP chargeability highs (up to 73 msec) with coincident low resistivity in zones of pyritic clay alteration along the margin of a monzonite stock. Ground magnetics showed elevated responses over the intrusion and surrounding alteration, suggesting extensions beneath cover and outlining subtle magnetic highs that follow pyritic zones.
Geochemical sampling returned encouraging results with soils grading up to 138 ppm Cu and 970 ppb Au, and rock samples returning up to 2.3% Cu and 695 ppb Au. Within this system, the Cas 3-9 area hosts multi-stage quartz veins in lapilli tuff, including a sample that assayed 106 g/t Ag.
Taken together, the datasets point to a potential sulphide-bearing alteration system at an intrusive margin. Geochemical analysis suggests that gold-silver-copper anomalies are near-source, while elevated molybdenum values may indicate broader dispersion from a porphyry-style source at depth.

Toodoggone Mining District

FIRESTEEL

The Firesteel area lies along a limestone–volcanic contact, where carbonate-reactive rocks have focused fluids and heat to create a replacement/skarn-style system with associated silver-bearing veins.
Historic work has reported strong mineralized intervals, including:
  • 11.5% Zn, 0.50% Cu, and 54.0 g/t Ag over 4.8 m
  • 2.3% Zn, 0.3% Pb, and 106.0 g/t Ag over 2.1 m (Trench 57)
  • 0.80% Zn, 1.2% Cu, and 177.8 g/t Ag over 0.9 m (Trench 101)
Additional surface sampling has outlined very high-grade potential:
  • Freibergite-bearing quartz veins up to 11,163 g/t Ag over 0.46 m
  • Selective samples with 12–44% Zn, 0.25–0.74% Cu, and 2.7–195 g/t Ag
  • A chip sample grading 10.5% Zn over 1.0 m
A historical resource estimate was also reported, underscoring the exploration significance of Firesteel as a potential high-grade polymetallic system.

BREN

The Bren target hosts silver-rich polymetallic veins and breccias localized within structurally prepared zones. Historic drilling returned strong silver and gold values, including:
  • 349.7 g/t Ag & 0.68 g/t Au over 0.09 m (Hole G-6)
  • 140.2 g/t Ag & 0.68 g/t Au over 0.60 m (Hole G-3)
  • 123.1 g/t Ag & 0.34 g/t Au over 0.60 m (Hole G-7)
Surface sampling further outlined the high-grade nature of the system, with results up to 11,135.5 g/t Ag over 0.45 m and 801.3 g/t Ag over 1.35 m. A representative grab sample also returned 0.695 g/t Au, 40 g/t Ag, 0.85% Zn, 1.16% Pb, and 2.3% Cu.