Mary Porphyry Root Zone
Between Mary and Cliff porphyry centres is a large untested resistivity anomaly coupled with flanking chargeability high domains which are coincident with low magnetism. This geophysical signature is considered to be the idealized deep level porphyry response. The resistivity body (>850 Ωm) is interpreted to reflect a potassic-altered porphyry root zone and measures 600 x 600 m in plan view and measures 800 m vertical starting from 200 m, open at termination of the 3D inversion.
District-scale vertical metal zonation from high gold values on ridges to highest copper in valleys is present throughout. A conceptual root zone is inferred to have high relative copper compared Mary due to the deeper level. The geophysical anomaly indicates that the root zone target is larger in vertical and lateral scale than Mary. The presence of low angle metal patterns at Mary suggest that the copper-rich root zone may lie lateral to the deposit, as opposed to directly below.
A comparable system at KSM (Mitchell and Snowfield deposits) grades from low copper at upper levels (Snowfield deposit), into high relative copper grades at the root zone levels at depth (Mitchell deposit). In this example, economic gold is present throughout the ~1.5 km vertical extent of the system without significant zonation in grade. Bornite zones are commonly located at depth in porphyry systems, and at Mitchell-Snowfield the highest gold and copper body is located at depth with bornite. The absence of bornite at Mary coupled with unusually high gold:copper ratios indicate significant exploration potential for a copper-rich porphyry at depths below and flanking the Mary deposit.
The Cliff gossan is part of a ~4 km-long Cu-Au-Ag-Mo soil anomaly on trend with the Mary deposit. Mapping identified a significant porphyry alteration footprint flanking an outcrop of potassic-altered stockwork. Although terrane limitations have hindered characterization of the trend, the continuation of the gossan can be observed several hundred meters from the stockwork outcrop.
The Cliff target was tested by a single hole in 2006 that drilled parallel to the inferred dip of the altered body. This hole bottomed in 62.5 m of 0.11% Cu from 134.7 m.
South of the Mary and Cliff porphyries, separated by a glacially eroded valley, is the ME porphyry target (Minfile 104G 042). Historical work mapped a large area of disseminated sulfide in outcrop, and in 2019 a very high tenor Au-Ag-Mo-Cu soil anomaly was identified below treeline. The soil anomaly is highlighted by 11 soils with greater than 0.5 g/t Au.
Two historical holes targeted the ME porphyry below the mapped disseminated sulfide outcrops and at a much lower level than the 2019 soil anomaly. The ME porphyry alteration and soil geochemistry patterns reflect a tabular geometry, comparable to the low angle metal patterns at Mary. Drill targeting will delineate the core of the soil anomaly, upslope of previous drilling.
The gold-rich quartz breccia and stockwork were discovered at Rainbow, or ‘Rainbow North,’ (Minfile 104G 255) in the early 2000s. The first-ever drill hole intersected 0.76 g/t Au over 91.4 m from surface in 2011. The outcrop showing is surrounded by broad gossan and anomalous Cu-Au geochem. This early-stage discovery has a drill footprint of only ~250 x 50 m. Future drill targets at Rainbow require ground geophysical surveys to target below widespread glacial till cover rock.
The Ridge target (Minfile 104G 256) is on trend and south of Rainbow, defined by a Cu-Au-Mo-Ag soil geochem anomaly that measures 1800 x 2000 m and is open to the north, east, southeast and northwest. Significant soil sampling gaps limit interpretation of lateral scale of the target. Surface grab samples grade up to 59.3 g/t Au. The Ridge anomaly was tested on the western margin of the soil anomaly, west and away from the soil anomaly in 2011.
Further surface geological work and soil sampling will outline the large-scale zonation patterns required for drill targeting.
Rojo Grande Gold
The Rojo Grande Au-Ag gossan (Minfile 104G 107) is a large alteration area host to quartz-alunite-dickite-pyrite, part of a high sulfidation-type gold system. High sulfidation deposit-types form at upper levels of the porphyry-epithermal system and can be situated vertically above porphyry systems at depth. A 500 x 900 m zone of anomalous arsenic and mercury in soils was identified in the 1990s, indicative of the highest levels of the hydrothermal system. The target represents significant vertical exploration potential for both epithermal and porphyry type mineralization.
Regional Porphyry Targets
Numerous regional targets are identified by large soil geochemical anomalies that are coincident with mountain-scale gossans, or colour anomalies. Gossan is commonly a product of the exposure of sulfide minerals widespread in porphyry-epithermal systems to air and water. The widespread presence of gossan is interpreted to roughly reflect the alteration footprint of target areas.
Ground geophysical surveys have identified new untested anomalies flanking the Williams deposit and south of the Hank deposit (unnamed target 5 and 9).
Airborne magnetic surveys flown in 2014 and 2018 identified ~600 m diameter circular magnetic anomalies that coincide with magnetite-bearing potassic-altered rock in outcrop at both Mary and Williams porphyry deposits. Several new porphyry targets have been identified with a comparable circular magnetic signature: unnamed targets 1, 2, 3, 4, 5, 6, 7 and 8.
The SW Copper Trend is a significant 5 x 2 km copper-molybdenum-silver soil anomaly to the southwest of the Mary porphyry system and the Hank-Rainbow epithermal gold trend. The large-scale anomaly is located only 2 km west of the Hank deposit and 3 km west of Williams. Infill soil sampling and prospecting is required to outline causative mineral centres.