The region of the GR occurrence is largely underlain by late Tertiary and younger flows of the Mount Edziza eruptions. These rocks range from basalts to rhyolite in composition. A thick sequence of Upper Triassic sedimentary and volcanic rock underlies the Cenozoic volcanics. These sediments are up to 900 metres thick and consist of volcanic agglomerate, greywacke, grit and chert breccia interbedded with tuffaceous siltstones. The Triassic volcanics overlie the sediments and consist of about 1200 metres of green, purple and grey andesite and derived volcaniclastics. The volcanics are cut by diorite dykes and sills, and irregular subvolcanic intrusive bodies. Small diorite and granodiorite intrusive bodies of Juro-Cretaceous Age cut all the Triassic rocks. The Upper Triassic rocks are warped into open folds with east-west axes. These are cut into blocks by north-south, east-west, northwest and northeast faults.
In 1981 Northcal Resources reported that this showing consisted of two narrow quartz veins 10 metres apart, occurring in basaltic volcaniclastics of Upper Triassic Age. These veins strike from 10 to 20 degrees and dip 50 to 80 degrees west. The east vein is up to 35 centimetres wide and exposed along its length for 3 metres. The west vein is 20 to 30 centimetres wide and is exposed along a creek for some 40 metres. Both veins contain pyrite, sphalerite, galena, arsenopyrite and a little chalcopyrite. The east vein assayed 4.05 grams per tonne gold, 33.26 grams per tonne silver and 4.78 per cent zinc across 35 centimetres (Assessment Report 10117). The west vein, sampled in three small trenches, had an average assay of 5.11 grams per tonne gold, 838.64 grams per tonne silver, 5.72 per cent lead and 12.61 per cent zinc over an average width of 23.3 centimetres (Assessment Report 10117).
Veinlets carrying pyrite and chalcopyrite occur in a bleached zone within andesitic volcaniclastics about 500 metres west-northwest of the above veins. Two showings, 25 metres apart, with a north trend were sampled. A sample with a combined width of 2 metres returned an assay of 6.21 grams per tonne gold, 54.17 grams per tonne silver, 2.12 per cent copper, 0.09 per cent lead and 0.17 per cent zinc (Assessment Report 10117).
Sampling was conducted in 1990 by Columbia Gold Mines and on the nearby WC showing, about 450 metres northwest of the GR occurrence. Samples 24060-062, with 1.95 to 5.4 grams per tonne gold were taken from the WC showing (Assessment Report 20861). Most rock samples of altered and mineralized volcanics found on GR and West Creeks (WC) within a soil gold anomaly yielded gold values greater than 0.1 gram per tonne gold and five were over 3.4 grams per tonne gold (Assessment Report 20861).
In 2015, prospecting, grab and rock chip samples were collected by Skeena Resources Ltd over a 50 by 30 metre area. Forty-four grab and rock samples were collected in total. One of the chip samples (Sample S792246) graded 4.88 grams per tonne gold, 260 grams per tonne silver, 0.135 per cent copper, 2.68 per cent lead and 0.49 per cent zinc over 0.4 metre (Assessment Report 36675). Initial mapping suggests a more northerly orientation to this mineralization. Due to poor exposure, the lateral extent of these mineralized structural zones is unknown as is the continuity between the West Creek and GR showings; however, a band of elevated Cu in soil values does suggest a possible continuity.
Refer to the Spectrum occurrence (104G 122) for details of a common work history.
