Minnie Moore occurrence, Wilgress Lake, Summit Camp, Greenwood Mining Division, British Columbia, Canadai

Regional Level Types
Minnie Moore occurrence	Occurrence
Wilgress Lake	- not defined -
Summit Camp	Mining Area
Greenwood Mining Division	Division
British Columbia	Province
Canada	Country

The Minnie Moore epithermal precious-metal occurrence lies about 14 kilometres north-west of the city of Grand Forks, on the northward continuation of the Emma mine structure, immediately north of the Jumbo occurrence. For more information on the area, refer to Mindat postings for “Emma Mine, Summit Camp, Eholt, Greenwood Mining Division, British Columbia, Canada” and for “Jumbo occurrence, Summit Camp, Greenwood Mining Division, British Columbia, Canada”
Giles Peatfield comments:
The property lies within the Triassic conglomerate/limestone/skarn package that has been called the Brooklyn Formation by all workers in the area, up until 1986, when Church (1986), without offering any explanation, changed it to the Brooklyn Group. No justification was offered for this change, and indeed Fyles (1990) declined to accept it and continued to use Brooklyn Formation, as have other workers up to the present. Refer to Mindat “Cyclops zinc deposit, Summit Camp, Greenwood Mining Division, British Columbia, Canada” for a more detailed discussion of this point.
This property, although not of any direct economic importance, is of geological interest because it contains a well exposed zone of epithermal quartz veining with elevated precious metal values. British Columbia “Minfile” reported that “Locally, there is a zone of faulting, diking and veining that measures, on the surface, up to 15 metres in width. Trenching has exposed a vein, ranging up to 8.5 metres in width, bounded on the east and west by strong, north-northeast trending, vertical to steeply west dipping faults. Eocene dikes within the wider fault zone are strongly argillic altered and locally cut by chalcedonic quartz veins.” Caron (2008) reported on channel sampling across this fault-bounded vein segment; the best interval was 6.2 metres grading 1,044 grams/tonne silver and 2.71 grams/tonne gold. This occurrence provides good evidence for an Eocene epithermal Ag>Au overprint on the Triassic copper (and locally zinc)-rich mineralization in the area.

Comments on the Minerals Reported:
It is important to note that this list includes “minerals reported”, not in all cases minerals identified through detailed analytical methods.
Amphibole group: Caron (2008) reported ‘hornblende’; Leitch (2007b) reported ‘amphibole’, varieties actinolite and tremolite. There are no precise mineral data available.
Apatite: Leitch (2007b) reported, in thin sections, numerous examples of trace amounts of tiny apatite crystals, notably in dacite and latite porphyries.
Calcite: Calcite is a common late-stage mineral, generally in veinlets. Leitch (2007a) remarked that in some cases it may be Fe-rich.
Chalcopyrite: Commonly reported, but not in large quantities.
Chlorite group: Leitch (2007a, 2007b) reported ‘chlorite’ in thin section, but gave no specific data. Caron (2008) reported chlorite alteration of pyroxene in drill core logging.
Clinopyroxene: Leitch (2007b) reported clinopyroxene, in many cases as a major constituent, in intrusive, skarn and hornfels thin sections; in some cases suggesting hedenbergite, but with no detailed analyses.
Clinozoisite: Leitch (2007b) reported numerous examples of the epidote group minerals clinozoisite and zoisite in thin sections.
Covellite: Leitch (2007a) described a breccia where “. . . chalcopyrite also locally shows minor replacement by covellite as minute flakes <15 microns in size.”
Epidote group: Caron (2007, 2008) reported ‘epidote’ in skarn. See also notes for clinozoisite and zoisite.
Feldspar group: Caron (2008) reported ‘K-spar’ and plagioclase. Leitch (2007b) reported ‘K-spar’ as well as albite and oligoclase-andesine in thin sections.
Fluorite: Caron (2008), in logging core from an epithermal vein zone, noted “. . . minor local green fluorite.”
Galena: Leitch (2007a) noted small amounts of galena in polished sections of quartz-rich breccia, in many cases associated with pyrite, chalcopyrite and sphalerite.
Garnet group: Caron (2007, 2008) reported ‘garnet skarn’. Leitch (2007b) reported ‘garnet’ in thin section. There are no analytical data; regional information suggests that the mineral is somewhere in the grossular-andradite field.
Gold?: Leitch (2007a) showed a polished section of a quartz-rich breccia with pyrite and base metal sulfides “. . . all partly replaced by limonite (lm) that contains a single rounded 20 micron grain of possible native gold (Au?).” Caron (2008) reported a possible trace of native gold in the epithermal vein zone.
Hematite: Caron (2007, 2008) reported hematite in skarn.
Hydrobiotite?: Leitch (2007b) noted numerous examples of what he called “hydrobiotite” or possibly Fe-rich chlorite.
Ilmenite: Leitch (2007b) noted numerous examples, in thin sections, of traces if ilmenite.
Limonite: Limonite is common, generally after pyrite or other sulfides.
Magnetite: Leitch (2007b) noted numerous examples of small amounts of magnetite in sections of dacite, latite and hornfels.
Malachite: Caron (2008) noted a trace of malachite with pyrite in skarn exposed in trenching.
Marcasite: Leitch (2007b), described a polished thin section of an altered rock of uncertain derivation, writing that “Sulfides are mostly pyrrhotite (subhedra to 0.1 mm, rarely aggregating to 0.25 mm where it is partly replaced by marcasite euhedra to 70 microns), locally intergrown with a little pyrite (sub/euhedra <25 microns in size) and traces of chalcopyrite <10 microns in size, . . . .”
Mica group: Caron (2008) reported biotite and sericite in core logging. Leitch (2007b) found biotite, sericite and muscovite in thin sections.
Prehnite: Leitch (2007b) described numerous examples in thin section of deuteric prehnite.
Pyrite: This is ubiquitous, but seldom in large quantities.
Pyroxene group: Caron (2008) reported pyroxene skarn.
Pyrrhotite: See note above for marcasite.
Quartz: This is common here. Caron (2008) described it in some areas as vuggy and in part chalcedonic.
Rutile: Leitch (2007a, 2007b) noted that rutile is a common trace constituent of most of the rock types.
Sphalerite: Leitch (2007a) identified several examples of sphalerite in polished sections, with other sulfides and sulfosalts. In some cases the sphalerite was reddish, suggesting a moderate Fe content, in other cases (see note below for wurtzite?) the sphalerite was pale yellow, suggesting a lower Fe content.
Talc?: Caron (2008) reported numerous examples of ‘talc (or clay)’ during drill core logging. There are no analytical data for this material, and the identification should be regarded as tentative.
Tetrahedrite group?: Leitch (2007a) reported possible ‘tetrahedrite’ in polished sections; these are very small grains (c. 50 microns) and there are no analytical details.
Titanite: Leitch (2007b) reported numerous examples of ‘sphene’ in various rock types. It appears to be a common accessory mineral here.
Wurtzite?: Leitch (2007a), describing a breccia with base metal sulfides and sulfosalts, wrote that “Minor sphalerite forming subhedra to 0.4 mm is pale yellow coloured, indicating low Fe content (rarely intergrown with anisotropic, clear wurtzite?); the zinc sulfides are associated with lesser chalcopyrite as ragged subhedra to 0.5 mm, commonly oxidized to limonite along fractures and at rims.”
Zoisite: See note above for clinozoisite.
Comments on the rock types Reported:
Breccia: Caron (2008) noted, in core logging, numerous examples of breccia, generally limestone breccia with varying textures.
Chert: Caron (2008), in core logging, described numerous examples of ‘cherty’ sediments. An example is “Pale grey-green siliceous siltstone, typically very hard and non-calcareous, with minor interbedded pale grey lst[limestone]/limey sst[siltstone] and dark grey chert.”
Conglomerate: Caron (2008) logged several conglomerates, the most abundant being the so-called ‘sharpstone’ conglomerate. The ‘sharpstone’ conglomerate is a major member of the Brooklyn Formation on a regional basis. The unit was originally named by Seraphim (1956) in the Phoenix Mine area to the west, as “. . . a conglomerate formed from stones predominantly angular.” There has been much discussion over the years regarding the composition and origin of this stratigraphic unit (Peatfield, 1978). It is now generally accepted that the rock is of sedimentary origin rather than formed by hydrothermal processes – further discussion is beyond the terms of this review. Another conglomerate mentioned by Caron (2008) is her ‘jelly bean’ conglomerate, described as “Typical "jelly bean" conglomerate with 70% 2 mm - 1 cm sized subround[ed] grey to grey-green chert pebbles supported in a pale grey-green-white highly siliceous g[round]mass.” This is probably a silicified version of the ‘peanut-brittle limestone’ of Seraphim (1956) or ‘aeolian’ limestone of Reinsbakken (1970). The conglomerates of the Brooklyn Formation are a complex story, beyond the scope of this review.
Dacite: Leitch (2007b) reviewing the results of thin section examination, wrote that “The 17 samples [studied], however, appear more likely to represent skarn alteration . . . or rarely hornfels . . . developed in brecciated limestone host rocks . . . in and around hypabyssal intrusions of latite . . . or dacite . . . porphyry.” The ellipses in the above quote represent sample numbers, which are irrelevant in this context.
Hornfels: See note above for dacite.
Latite: See note above for dacite and below for monzodiorite.
Limestone: This is a major unit on the property, part of the Brooklyn Formation.
Marble: Leitch (2007b) noted that in many cases the limestone is re-crystallized to form marble.
Monzodiorite: Caron (2008) noted numerous examples of intrusive rock that she called ‘monzodior[ite]’. This may be what Leitch (2007b) termed ‘latite’.
Siltstone: Caron (2007, 2008) reported numerous examples of siltstone as part of the stratigraphic package, in most cases described as ‘siliceous’. In some cases, the rock was described as volcanic siltstone.
Skarn: Many of the limey sediments have been altered to skarn.
Syenite: Caron (2008) described Eocene syenite dykes; an example was a “Typical massive, homogeneous, fresh, pinkish-brown medium grained Kspar megacrystic syenite dyke.”
Research by Giles Peatfield, Courtenay, British Columbia.
edited by Doug Scott, Ottawa
Posting prepared 07 March, 2025.

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Link to British Columbia Minfile:	082ESE106

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References