The Invermay occurrence is on Silverdaisy Mountain, approximately 4 kilometres south east of the junction of Silverdaisy Creek and the Skagit River.
The area is underlain by steeply dipping and tightly folded rocks of the Lower and Middle Jurassic Ladner Group. The northwest- trending Hozameen fault is to the immediate west and separates the Ladner rocks from mafic volcanics and lesser sediments of the Permian-Jurassic Hozameen Complex, to the west.
The Ladner Group rocks in the area of interest are mainly argillites and siltstones with minor greywacke and felsic tuff. Intruding this package is the Invermay stock, a medium-grained diorite to granodiorite body thought to be Oligocene. Numerous dikes and sills ranging from diorite to pyroxenite also intrude.
An area of brecciated quartz diorite within the stock is reported to be the host for mineralization; three types of mineralization are indicated. Underground development explored a strong, relatively tight shear zone that strikes northeast with a near-vertical dip. Along this shear, a narrow mineralized zone contains quartz, galena, sphalerite and minor chalcopyrite. The width of this zone ranges from several centimetres up to 60 centimetres. Diamond drilling from the drifts revealed a second type of mineralization in a breccia consisting of fine disseminated chalcopyrite that assayed uniformly low- grade values in copper. A third type of mineralization consists of scattered pockets of jamesonite, pyrite, arsenopyrite and chalcopyrite in tourmaline-rich banded quartz diorite at the A and B adits.
Another mineralized breccia zone, referred to as the Tramline zone, is located approximately 2 kilometres to the northwest. It is described as a north east elongate zone of brecciated diorite with pyroxene dikes and weak copper mineralization.
Between 1933 and 1938, 5 short adits were driven and 23 tonnes of ore were mined in 1936 and 1937. Later, between 1941 and 1946, two additional adits were driven. Records show that a further 67 tonnes were mined in 1941 and 4 tonnes in 1947. Total production from the property was 94 tonnes from which 313,020 grams of silver, 716 grams of gold, 9654 kilograms of lead and 10, 619 kilograms of zinc were recovered.
In 1980, a diamond drill hole (79-4), located 17 metres south of the No.4 adit portal, yielded up to 39.9 grams per tonne silver, 0.6 gram per tonne gold, 0.59 per cent copper, 0.012 per cent molybdenum, 0.06 per cent lead and 0.18 per cent zinc over 3.0 metres; while another section yielded 2.0 grams per tonne gold, 11.2 grams per tonne silver and 0.15 per cent copper over 3.0 metres (Assessment Report 7823).
In 1996, diamond drilling yielded significant results including 0.322 grams per tonne gold, 41.7 grams per tonne silver, 0.308 per cent copper and 0.217 per cent zinc over 55.5 metres from drill hole GSC 96-3 (Assessment Report 24986). While two, other holes were completed to test the north extension of the zone: hole GSC 96-11 yielded 1.803 grams per tonne gold, 32.7 grams per tonne silver, 0.164 per cent copper and 0.921 per cent zinc over 14.85 metres and hole GCS 96-13 yielded 0.489 gram per tonne gold, 68.2 grams per tonne silver, 0.759 per cent copper and 0.479 per cent zinc over 16.35 metres (Assessment Report 24986).
A geological resource for the Invermay is reported as 15.4 million tonnes grading 0.21 per cent copper, 0.38 gram per tonne gold and 7.92 grams per tonne silver (1997 Cordilleran Roundup Abstracts, page 24 and WWW).
The Giant Copper property originally consisted of two properties; the AM (MINFILE 092HSW001), discovered in 1930 by Consolidated Mining and Smelting Company and the Invermay, discovered in 1933 by Invermay Annex Mining Company. On the Invermay, between 1933 and 1946, seven short adits had been driven: five adits approximately in line down the hillside and two adits, designated A and B, just to the south. By the 1950s, greater than 600 metres of underground development had occurred. The two properties were consolidated in 1956 by Canam Mining Corp. Between 1955 and 1963, several companies optioned the property and carried out exploration and development programs. After a two year option, Giant Mascot Mines Ltd. purchased all of Canam's assets in 1966. Giant Mascot Mines Ltd. continued work between 1966 and 1972. By the end of 1980, a total of 6017 metres of underground drifts and raises, and 14,078 metres of diamond drilling had been completed on the combined properties. The property lay dormant again until 1988, when Bethlehem Resources Corp. acquired it from Campbell Resources Inc. (formerly Giant Mascot Mines Ltd.). Between 1988 and 1990, a comprehensive exploration and evaluation program was carried out. In 1996, Imperial Metals completed a program of soil and rock sampling, diamond drilling (16 holes, totalling 3457 metres), 658.8 line-kilometres of airborne geophysical surveys and a 11.2 line-kilometre ground induced polarization survey on the area with the aim of establishing a second open-pit resource on its Giant Copper property (MINFILE 092HSW001). The company believes it is testing a porphyry-to-transitional-type deposit with mineralization contained within a tourmaline breccia. No further exploration work is reported until 2015, when a program of soil and rock sampling was completed.
