Cronin Mine (Cronin), Omineca Mining Division, British Columbia, Canadai

Regional Level Types
Cronin Mine (Cronin)	Mine
Omineca Mining Division	Mining Division
British Columbia	Province
Canada	Country

27 kilometres north east of Smithers, British Columbia; Omineca Mining Division.
The following quotes are from B.C. Government site “Minfile”- Minfile No. 093L 127:
“The geology at the Cronin mine is very complex, however three major rock types host the mineralized structures: the Middle to Upper Jurassic Bowser Lake Group (Ashman Formation), and two Late Cretaceous to Tertiary rhyolitic sub-volcanic intrusives. The Bowser Lake Group is in fault contact with Lower-Upper Cretaceous volcanic rocks of the Kasalka Group immediately west of the showings.
The sedimentary unit is comprised of a bedded clastic sequence of argillite, grits and minor pebble conglomerate. Sericite schist has developed at the contact with rhyolite. Sedimentary structures include graded bedding, crossbedding and slump structures. Tight folds were observed in the argillites and overturned beds indicate intense folding. Locally, the argillite is graphitic and hosts moderate to intense quartz veining, 1 to 4 millimetres in width, with minor galena. Interbedded mudstone, sandstone, intraformational pebble conglomerate and ash tuffs are also part of the sedimentary unit.
A grey, massive, medium to fine-grained rhyolite porphyry is the most prominent part of the intrusive complex. It is comprised of an aphanitic groundmass of quartz, sericite, calcite, zoisite, and chlorite with laths of albite. No appreciable chill margin was mapped at the contact with the sedimentary unit. A quartz stockwork exists within the rhyolite porphyry and this has been intruded by another porphyry which has in turn been cut by a second phase of quartz veining. The quartz veins average 4 to 20 millimetres in width and host sphalerite and galena.
Silicification adjacent to the quartz veining is the only alteration associated with this unit other than low grade regional metamorphism.
An altered, white to pale yellow rhyolitic stock intrudes the porphyry. Pyrite, sphalerite, and galena occur along fractures within the stock rather than in a quartz stockwork. A set of post-mineral, quartz diorite and dioritic lamprophyre dikes crosscut the host rocks.
The main exploration targets at Cronin are massive sulphide and quartz veins that contain argentiferous galena and sphalerite with minor pyrite and chalcopyrite. Boulangerite, freibergite and arsenopyrite have also been identified.
Sulphide mineralization occurs in quartz stockworks, quartz infilling in faults, along fractures or as disseminations in the intrusive. The mineralized veins are results of two sinuous faults which strike northeasterly and dip moderately westward. The quartz veins exposed in the workings range in width from 0.3 to 1.0 metres, striking northeast and dipping 45 to 65 degrees to the northwest. Mineralization occurs as pods up to 40 metres long by 6 metres wide within the main fault system. There is a distinct zoning of minerals within the pods; galena, boulangerite and tetrahedrite are concentrated near the fault plane with the sphalerite spread out into the altered and brecciated wallrock. Pyrite and chalcopyrite occur erratically throughout the vein system.”
“Production from 1917 to 1974 totalled 25,838 tonnes yielding 8,169,918 grams of silver, 8,772 grams of gold, 18,012 kilograms of cadmium, 10,394 kilograms of copper, 1,367,178 kilograms of lead and 1,517,881 kilograms of zinc.”
Robinson (1953) reported that both bournonite and meneghinite were X-ray confirmed by Dr. R. M. Thompson at the University of British Columbia. The Pacific Museum of Earth at UBC has a polished section with bournonite – catalogue number 3662 – reported to be from the Babine Range, near Smithers, British Columbia.

Giles Peatfield
BASc. (Geological Engineering) University of British Columbia 1966.
PhD Queen's University at Kingston 1978.
Worked for Texas Gulf Sulphur / Texasgulf Inc. / Kidd Creek Mines - 1966 to 1985.
Vancouver based consultant 1982 to retirement in 2016

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Link to British Columbia Minfile:	093L++127

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References