The Lois Creek Upper adit is located at the headwaters of Lois Creek at an elevation of 1164 metres, northwest of Mount Diadem.
The area lies within the Jurassic-Cretaceous Coast Plutonic Complex near its western boundary with the Insular Belt. The complex consists of diorites and granodiorites enclosing a series of northwest trending pendants. In the Mount Diadem area, feldspar-rich diorite and quartz diorite dominate. These pendants, occurring along Howe Sound and Jervis Inlet, are interpreted to be part of the Lower to Middle Jurassic Bowen Island Group, coeval with volcanic rock of the Bonanza Group and the Harrison Lake Formation.
Mount Diadem forms part of a ridge consisting of Bowen Island Group sediments and volcanics that form a 15 kilometre long by 1 to 2 kilometre wide roof pendant. Lithologies along the eastern portion of the pendant consist of dark-green, chlorite-rich, massive volcanic flows and tuffs intercalated with grey to black cherty tuff and foliated, pyritic argillaceous siltstone. The western portion of the pendant contains well- bedded clastic sediments and, minor carbonate with intercalations of intermediate to mafic tuffs, flows and sills. In all, six stratigraphic units have been defined and are, in ascending order: 1) tuffaceous sandstone, minor argillite and lapilli tuff, 2) chlorite-rich tuff with interbedded tuffaceous sandstone, minor argillite, 3) thin-bedded argillite, minor carbonate and lapilli tuff interbeds, 4) banded argillite, sandstone, chert, minor lapilli tuff, 5) siliceous argillite, siltstone, tuff, chert and 6) andesitic breccia.
The volcanics and sediments have a near-vertical bedding and cleavage that form a series of tight upright folds that plunge moderately to the north.
Sulphide mineralization observed in drill core consists of stringers, veinlets, blebs, pods and minor disseminations of pyrrhotite, chalcopyrite, sphalerite, galena, minor tetrahedrite and trace arsenopyrite within brecciated, quartz-chlorite-epidote-±garnet– altered portions of a predominantly argillite unit. Mineralization is found at or near contacts with intercalated chloritic flows and sills. Four main mineral assemblages are recognized: a) pyrrhotite-sphalerite; b) pyrrhotite-sphalerite-galena; c) pyrrhotite-chalcopyrite, ±tetrahedrite; and d) pyrrhotite-sphalerite-chalcopyrite-galena.
Three en echelon, strata-bound stringer sulphide zones up to 30 metres wide and aggregating 120 metres in length occur in the vicinity of the upper adit. The sulphide zones consist of high- grade polymetallic pods enveloped by low-grade, silver-poor, zinc and/or copper mineralization.
The best drill core intercepts yielded 135 grams per tonne silver, 2.74 per cent lead, 1.61 per cent zinc and 0.79 per cent copper over 12 metres including 359.5 grams per tonne silver, 7.9 per cent lead, 2.5 per cent zinc and 2.1 per cent copper over 4 metres (Assessment Report 13814).
Four rock samples were taken from the vicinity of the upper adit in 1994. Sample 428-H yielded 1.62 per cent copper, 30.5 per cent zinc, 11.20 per cent lead, 0.50 gram per tonne silver and 0.31 gram per tonne gold over 0.4 metre; while sample 428-G yielded 0.80 per cent zinc, 10 grams per tonne silver and trace lead and copper over 1.5 metres (Assessment Report 23319).
In 1998, two samples from the Upper Adit yielded 5.58 and 2.52 per cent copper, 0.22 and 0.30 per cent lead, 3.81 and 3.44 per cent zinc, 710 and 520 grams per tonne silver with 0.92 and 2.35 grams per tonne gold over 0.7 and 1.0 metre, respectively (Assessment Report 25570).
In 2001, samples from the Upper Adit assayed up to 1.39 per cent copper, 0.29 per cent lead, 1.14 per cent zinc, 1.49 grams per tonne gold and 229.9 grams per tonne silver over 0.5 metre (Sample 304051; Assessment Report 26631).
The Mount Diadem area has received intermittent exploration since the 1920s. In 1927, Brittan R. Mining Co. drove two small adits 1.5 kilometres northwest and 2.0 kilometres north-northwest of Mount Diadem, respectively. Between 1947 and 1950, Inco Canada Ltd. and Bralorne Mines excavated several open cuts and a short adit in the area of the headwaters of No Man's Creek. In 1954, Copper Ridge Silver Zinc Mines Ltd. held 19 claims in the area. In 1965, Vanco Explorations Ltd. held 17 claims northwest of Mount Diadem, called the Linda group. Citation Explorations Ltd. held 73 claims and optioned the Linda group in 1967. Tiger Silver Mines optioned the Linda group in 1970, and carried out geochemical and geophysical surveys. In 1971, Brittan R. Syndicate optioned the 23 claims and performed geophysical and geochemical surveys. The claims lapsed and were restaked by Fury Explorations Ltd. (Diadem claim) and R. Schmidt (Fox claim). In 1982, Anaconda Canada Explorations Ltd. performed a regional stream sediment survey in the Mount Diadem area. In the following year, an exploration program was carried out on the optioned Diadem and Fury, and other staked claims surrounding Mount Diadem. White Channel Resources Inc. staked the Rox 1 to 5 claims and conducted property exploration in 1991 and 1992. In 1994, Noranda Exploration Company Limited optioned and explored the Rox claims which included the Lois Creek Trench showing for volcanogenic massive sulphide-type mineralization. In 1995 and 1996, Navarre Resources completed programs of rock and soil sampling, geological mapping and eight diamond drill holes, totalling 547.7 metres. Stirrup Creek Gold Ltd. optioned the property in 1998 and completed a program of geological mapping and ground electromagnetic and magnetic surveys on the area. During 2001 through 2005, Fundamental Resources completed programs of rock and soil sampling, geological mapping and 3.0 line-kilometres of ground electromagnetic and magnetic surveys on the area. In 2009, Sunshine Global Mining purchased the Rox claims and completed a minor program of sampling. In 2013, Fundamental Resources completed a program of rock sampling and geological mapping. In 2015, Asia New Energy Corporation completed 112.0 line-kilometres of combined airborne magnetic and radiometric surveys on the area.
