The Vickers Target is located in the west-trending Pistol Bay Corridor in the central part of the property. The Vickers Target host rocks are a sequence of quartz-sericite-carbonate schists and proto-mylonites which resemble the host rocks at the Sako Target which is approximately 6 kilometres east of the Vickers Target. The schistose rocks at Vickers and Sako are locally known as “pipeline rocks” because they have pronounced, penetrative schistosity reaching proto-mylonite and extreme secondary sericite and carbonate alteration. The pipeline rocks define the Pistol Bay Corridor. Because of the fabric and secondary hydrothermal alteration superimposed on the pipeline rocks it is difficult to ascertain their protolith(s), however, our contention is that they are derived from a parent rock of felsic composition, and possibly part of a felsic volcanic or volcaniclastic sequence derived from rhyolite, ryhyolitic pyroclastic rocks, and quartz-feldspar porphyries.
The mineralized zone of the Vickers Target is in the contact of a gabbro-diorite intrusion. The nature of the intrusion is difficult to define because there are no unaltered primary rocks. Secondary, chlorite, white mica, rutile, and carbonate are ubiquitous and in thin section, the plagioclase grains have mortar texture caused by extreme strain. The least altered rocks in the western part of the intrusion have retained some remnant magnetism and nominally have a relict gabbro texture with plagioclase grains surrounded by a matrix of chlorite and rutile pseudomorphs presumably after clinopyroxene. In addition, the nominally “gabbroic” rocks are intruded with abundant dikes and pipe-like bodies varying in composition from diorite to granite. Petrographic examination of the rocks in thin section indicate that there is no primary clinopyroxene, which may be attributed to alteration, and that the composition of plagioclase grains interpreted as remnant primary grains are not more calcic than Ab50An50 and therefore cannot be derived from gabbro. Accordingly, the intrusion is either an albitized gabbro with no surviving primary chemistry, or the intrusion is an intermediate to felsic composition such as diorite or granite. Because of the mortar texture of plagioclase, interpreted as primary grains, our contention is that the intrusion is not gabbroic but dioritic.
The contact of the intrusion with the pipeline rocks trends approximately 295 degrees and dips approximately 60 to 70 degrees to the south. The intrusion is elliptical and approximately 1 kilometre in length based on mapped contacts with the surrounding rocks which are mature quartz arenite. On the east contact of the intrusion, the quartz arenite sequence is a mature, cross-bedded sequence of highly variable attitude caused by complex folding. Bed forms of the quartz arenite sometimes dip north and away from the intrusion, i.e. the opposite dip of the intrusion and footwall contact. Bedding of the quartz arenite is not in the same orientation the as the schistose planar fabric of the intrusion and footwall contact and secondary, hydrothermal alteration and secondary hydrothermal minerals in fractures in the quartz arenite are virtually absent. There are also no intrusions of gabbro or diorite in the quartz arenite, no veining of any kind, and no gold concentrated in the quartz arenite. Accordingly, it is our contention that the quartz arenite surrounding the Vickers diorite intrusion, and altered footwall rocks, is younger than the Vickers intrusion, rests unconformably upon the intrusion and footwall, and is part of the Paleoproterozoic Hurwitz Group (2.45 Ga), which is common in outliers throughout the region. Hence, the Vickers intrusion and host rocks, which are Archean in age, do not intrude the quartz arenite but rather, they are unconformably overlain by it and partly concealed.
Further evidence of the relationship of the quartz arenite to the Vickers intrusion and footwall is found on Section 8700 W where INCO drilled hole 63744 in 1988. Drill hole 63744 was collared in quartz arenite and drilled towards the north. At a vertical depth of about 25 metres, the drill hole intersected 5.91 metres of pebble conglomerate which we interpret as the base of the Hurwitz Group. Interestingly, the conglomerate intersection had a 0.95 metre interval in drill core containing 8.03 grams gold per tonne. Hence, either alluvial gold is concentrated on the unconformity, or gold was concentrated on the unconformity by hydrothermal alteration.
The Vickers intrusion is a magnetic anomaly with two parts; i) a moderate magnetic anomaly in the west part of the intrusion, which is remnantly magnetic presumably because there is minor primary, disseminated magnetite, and ii) no magnetic anomaly in the east part of the intrusion which is demagnetized by magnetite-destructive hydrothermal alteration attendant with the gold concentration. The east part of the intrusion has the same magnetic intensity as the surrounding rocks, and because of this, and the relationship of the Hurwitz cover sequence, we do not currently know the location and nature of the east contact of the intrusion.
In August, 2013, an induced polarization (IP) and resistivity survey was completed on a 16.3 line-kilometre grid covering the mineralized zone in the east part of the intrusion and an area to the east to determine what, if any, IP and resistivity anomaly is associated with the gold bearing rocks. A very clearly defined and strong IP anomaly starts at about 8950 W and is coincident with gold-bearing drilling intersections from that section to the east at least as far as section 8800 W, where our easternmost drill hole is located. East of section 8800 W, the IP anomaly continues for at least another 200 metres, which is the limit of the current IP survey area, and in that area the anomaly is concealed by the Hurwitz Group. Another strong IP anomaly on the east edge of the grid, 150 metres east of the V2 Zone, is concealed by the Hurwitz Group and untested by drilling. The resistivity survey highlights the resistive quartz arenites of the Hurwitz Group and does not provide much definition of the variably resistive gold bearing rocks.
Northquest has completed a total of 5,616 metres of drilling in 24 drill holes at the Vickers Target. The Vickers Zone has been intersected over a strike length of 200 metres. The width of the mineralized zone as defined both by alteration facies and gold mineralization varies in width from approximately 50 to 160 metres. Three drill holes (PB-12-11, PB-12-21, and PB-13-02) have intersected the zone at a vertical depth of approximately 300 metres; however, most of the drill holes tested relatively shallow depths of approximately 150 metres or less. In the west, evidence from a single outcrop and the recently completed induced polarization (IP) and resistivity survey, suggests that the west edge of the mineralized zone subcrops in the vicinity of Section 9100 W and has a steep, south-easterly plunge. In the east, PB-13-10 intersected robust mineralization and alteration on Section 8800 W (44.00 metres grading 3.44 grams gold per tonne) and an IP anomaly on Section 8800 W continues for at least 200 metres to the east of that section. Hence, the Vickers Zone has a minimum strike length of 200 metres, a minimum vertical depth 300 metres, and it is open along strike to the east and at depth.
In the west, the mineralized zone appears to be more prevalent in the intrusion and in the east; the mineralized zone is more prevalent within the footwall rocks. Within the intrusion, the mineralized zone is dark to light grey/green, fine to medium-grained, variably siliceous, carbonaceous and chloritic, and contains variable concentrations of pyrite, rutile, arsenopyrite and gold. The rocks are very fractured and sometimes very brecciated. Relicts of altered rock resembling diorite or granite without much continuity between drill holes, are prominent in the more mineralized sections. Within the footwall rocks, the mineralized zone consists of light yellow to buff coloured, banded, variably siliceous, sericitic, and brecciated rocks with variable concentrations of pyrite, arsenopyrite and gold. A planar fabric of sericite and quartz-rich bands is prominent and interpreted as parallel to the intrusion-footwall contact. Near the intrusion contact dioritic or granitic bodies resembling those in the intrusion are prominent. In brief, there seems to be a positive correlation between gold, diorite dikes, and breccia of diorite and sandstone. The width of the mineralized zone within the footwall rocks and the gold distribution are illustrated on the sections and in the drill log files.
One of the characteristics of the mineralized zone, in both the intrusion and its footwall rocks, is that rocks grading over one gram gold per tonne are in some instances interspersed with intervals of low gold concentration (sometimes below the detection limit of 0.05 ppm) up to several metres thick, even though the silicate alteration is the same. The intervals with low gold concentration generally have less diorite and are less brecciated. An interpretation is that these intervals are less permeable domains and therefore somewhat less mineralized, or alternatively, the less altered rocks may possibly be mega breccia fragments that contain less gold. The lower grade intervals are included in the weighted average gold concentration calculation because they are an inseparable part of the contact zone between the intrusion and its footwall. Moreover, there are some intervals, up to a few metres in core length, with grains of visible gold with local silicic alteration with or without attendant sulphide minerals.
In general, although there are sections of the mineralized zone that have several per cent pyrite and arsenopyrite over several metres, the overall sulphide concentration of the mineralized zone is probably less than 2%. The abundance of silica and paucity of carbonate indicate that the mineralized zone is on a high silica fluid cooling path. The paucity of quartz veins and abundance of large volumes of silicic rock, including chalcedony matrix in some of the breccias, without a dominant structural fabric, suggests that the Vickers Zone is an epizonal concentration of silica and gold.
The drilling sections from east to west are set out in the attached pdf file and a summary of the drilling results is listed in the following table.
Summary of weighted average grade of gold in all of the drill holes from the Vickers Target to date, completed in 2012 and 2013, including all continuous intervals of variable average grade.
Note: Intersection lengths are core lengths and do not necessarily represent the true width of the mineralized zone. Weighted average grades are calculated from assays of drill core with nominal sample lengths of 1.0 metres. The detection limit of the assay method is 0.05 ppm gold. Some of the samples within the intersected lengths reported in the table are below the detection limit and the assay value for those samples used in the weighted average grade calculation is zero.
Plan of future exploration work
The goal of future exploration will be to extend the strike length and depth of the mineralized zone. The IP and resistivity survey anomalies extend for at least another 200 metres to the east and the goal of the next drilling phase will be to test the geophysical anomalies for at least 200 metres east of section 8800 W. Subsequent to, and contingent upon, the results of that work, it might be appropriate to complete an initial resource estimation in order to establish the nature, grade, and geometry of the gold zone in order to optimize a follow up drilling campaign, if warranted.
Gold occurrences and magnetic anomalies (TMI) of the Pistol Bay Project
Vickers Target and environment including the Colt and Kimber Targets nearby targets on TMI
Vickers Target drill holes on geology plan map illustrating the contact of the gold zone
Vickers Target compilation with magnetic contours, outcrops, drill holes, topography, and gold zone contact on chargeability
Vickers Target compilation with magnetic contours, outcrops, drill holes, topography, and gold zone contact on resistivity
Vickers Target Cross Sections - click on the image for all of the sections in pdf format -