The Storm Copper Project is located on Somerset Island, Nunavut, approximately 20 kilometres from tidewater at Aston Bay. Storm Copper is a strata-bound and structurally-hosted copper zone of mineralization, hosted in dolomitic sediments of the Allen Bay Formation. Hypogene copper mineralization is present at surface and identified to a depth of at least 100 metres in the form of chalcocite, bornite, covellite and chalcopyrite. Malachite and azurite are common oxide coatings. The geologic setting, mineralogy and zonation suggest affinities to sediment-hosted copper deposits.
Storm Copper has been explored intermittently since the 1960s; however, most of the historic work on the property was undertaken by Cominco Ltd. (now Teck Resources Ltd).
Sixty-seven holes (9,032.5 metres) were drilled at Storm between 1996 and 2000. These efforts defined four separate zones of copper mineralization — 2200N, 2750N, 3500N, and 4100N Zones — all of which remain open both laterally and vertically.
Highlights from the historic drilling at Storm Copper include:
In addition to the historical drill results, a 3,970 line-kilometre Versatile Time Domain Electromagnetic (VTEM) airborne survey was completed over the property in 2011. The spatial correlation of conductance anomalies with mineralized intercepts in the historic drilling suggests that the near-surface copper mineralized zones of the Storm copper property can be accurately mapped and modeled with electromagnetic techniques. Three of the twelve holes drilled by BHP Billiton in 2016 targeted VTEM anomalies; all three intersected copper mineralization, including:
Aston Bay believes the Storm Copper project holds significant potential for further development, and is also indicates the potential for other mineralized zones concealed in the subsurface elsewhere on the property.
Aston Bay’s 2017 Geophysical Program
A property-wide Falcon Plus Airborne Gravity Gradiometry survey was conducted by CGG Multi-Physics. The new high-resolution survey was completed over two large blocks within the Nunavut Property area and acquired a total of 15,327 line-kilometres of data at a line spacing of 200m (Figure 1). The Property is underlain mainly by very shallow-dipping Paleozoic carbonate strata. The survey was designed to detect horst-graben features indicative of potentially favourable “structural plumbing” for stratiform base metal mineralization, as well as detection of blind, sub-surface mineralization within the carbonate strata.
Key areas covered by the survey include the Storm Copper prospect and Seal Zinc deposit in the northern block, and the Typhoon Zinc prospect and nearby target areas in the south. All three areas returned strong gravity responses that were evaluated in detail by the Company’s geological and geophysical team prior to selection of diamond drill targets for the 2018 summer field program currently underway.
The Storm Copper prospect and Seal Zinc deposit occur with the northern survey block, characterized by a mainly east-west structural-stratigraphic grain. The Storm prospect comprises four high-grade, dominantly chalcocite occurrences associated with an east-west graben, partially delineated by prior diamond drilling (Figure 2). Copper-silver mineralization occurs both in close association with steeply dipping graben-bounding faults and as broadly stratiform mineralization lateral to the faults. The gravity survey returned strong responses along and within the graben, including three anomalies spatially associated with the 4100N, 2750N and 2200N occurrences; these anomalies extend well beyond the current drilling and are potential drill targets.
A fourth composite gravity anomaly occurs along the eastern extension of the Storm graben and is spatially associated with the Tornado copper occurrence, which to date has seen only two diamond drill holes. The gravity data suggest the presence of a second-order graben on the northern flank of the main structure, to date untested. A fifth gravity anomaly occurs along the northern flank of the Storm graben, west along strike from the large 4100N occurrence, and is also poorly tested to date.
The southern, relatively poorly known, part of the Nunavut Property is underlain by north-south trending Paleozoic carbonate and Precambrian basement strata, with several base metal showings and areas of geological complexity of interest to Aston Bay. The central part of this area was covered by the new survey, which outlined a strong north-south pattern of alternating gravity highs and lows, possibly indicative of favourable horst-and-graben structures. Further refinement of the geology and survey results will be completed to guide ongoing exploration.
VTEM and gravity gradiometry delineate copper mineralization at Storm
At Storm, hole AB18-09 targeted a 200 by 200 metre VTEM anomaly coincident with the western flank of a gravity anomaly, ~2.2 kilometres along strike from the 2750N zone (Figures 4 and 5). An historical drill hole, ST97-15, was drilled northwards to intersect local copper mineralisation (3m grading 1.5% Cu) on what Aston Bay’s modelling interpreted as the flank of the VTEM anomaly. Drill hole AB18-09 was drilled southwards and intersected significant copper in variably brecciated dolomudstone of the Allen Bay Formation from 39 to 83 metres downhole, primarily as fracture-controlled chalcocite with lesser to minor chalcopyrite, native copper and cuprite. Significant results within the 44m copper mineralized zone include:
These results demonstrate the continued effectiveness of VTEM, in conjunction with modelled gravity gradiometry, in detecting shallow copper sulphides. The remaining holes at Storm intersected local pyrite mineralisation, primarily in Allen Bay dolomudstones (Figures 5 and 6). The origin of these targeted gravity gradiometry anomalies remains unclear: variations in bulk rock density, topography and depth to target are possible explanations being investigated in advance of targeting and drill planning for the 2019 season. Density data obtained from this year’s core drilling will be instrumental in improving the targeting. Numerous gravity targets in the vicinity of the ~5km-long Storm graben remain untested, and drilling to date has been shallow relative to the prospectivity for stratiform mineralisation at depth.
Aston Bay’s 2018 Drill Program
Aston Bay’s 2018 drill program consisted of 3,135 metres of drilling over a total of nine drill holes targeting high-grade copper mineralization in the vicinity of Storm Copper and adjacent prospects, as well as targeting Polaris-type zinc mineralization at the Seal Zinc deposit and the Seal South prospect. The program comprised seven holes at the Storm copper prospect and two along strike from the Seal zinc deposit. Targets were based primarily on interpreted gravity gradiometry anomalies proximal to known mineralisation at Storm and Seal. Unusually challenging weather reduced the planned meterage for this drill season and several anomalies remain untested. The majority of the drill holes were relatively shallow at approximately 300m or less.