The Hall Lake (Cretin) occurrence is located immediately northeast of Hall Lake, approximately 34 kilometres west-southwest of Kimberley.
Regionally, the area is underlain by undivided sedimentary rocks of the Mesoproterozoic Creston Formation and argillite, greywacke, wacke and conglomerate turbidites of the Mesoproterozoic Aldridge Formation, both of the Purcell Supergroup, that have been intruded, contemporaneously, by gabbro-diorite sills and dikes. Porphyritic quartz monzonite/granodiorite stocks intruded the package during the Upper Cretaceous. Structurally the area is cut by the Hall Lake fault, a west-dipping thrust fault with some north strike-slip movement. The area is cored by a zone of phylonitic/mylonitic metamorphism that is likely related to the Hall Lake fault.
The occurrence area is dominated by a 2.5 by 3.5 kilometre Upper Cretaceous porphyritic granitoid pluton that intrudes the conformable contact between moderately-dipping Middle and Upper Aldridge rocks to the east and overlying Creston Formation rocks to the west. The pluton also appears to crosscut north-south–trending, subvertical, regional-scale thrust faults.
Locally, a roughly 7-metre wide, northwest-striking, subvertical felsic dike that crosscuts the main intrusive body and can be traced for more than 1.5 kilometres. The light-grey to rusty-orange–weathering dike is very fine-grained to aphanitic with rare 0.5-millimetre quartz eyes. The texture of the dike is massive.
Sulphide mineralization in and around the dike, and common along fracture surfaces, consists of rare millimetre-scale euhedral pyrite cubes; minor disseminated, medium-grained arsenopyrite prisms and needles; and medium-grained euhedral arsenopyrite needles to fine-grained, massive, arsenopyrite. Arsenopyrite-bearing, light- to dark-grey, sugary quartz veins that average 0.5 centimetre in width crosscut the dike. Larger 3- to 10-centimetre, medium- to coarse-grained, rusty quartz veins intrude the host metasedimentary rocks; veins can contain muscovite and form minor stockworks. Sulphide mineralization includes coarse-grained euhedral galena, coarse-grained euhedral pyrite cubes and limonite, and fine-grained disseminated arsenopyrite.
Work History
In 2003 and 2004, Eagle Plains claimed the area surrounding the occurrence to conduct a rock geochemical survey on the region. Anomalous gold values were found in samples from a large dike in the sediments of the Creston Formation. Highlighted samples include sample H-16, which yielded 2.39 grams per tonne gold and greater than 1 per cent arsenic; sample H-02, which yielded 42 grams per tonne silver and 1.64 per cent lead; and sample H-18, which yielded 1.77 grams per tonne gold and greater than 1 per cent arsenic (Kenwood, S. (2011-11-30): 2011 Technical Report for the Hall Lake Property). Sampling was mostly undertaken around the Cretin occurrence. Rock sampling in 2004 assayed up to 0.187 per cent lead, 0.310 per cent zinc and greater than 1.00 gram per tonne gold (Assessment Report 27694).
In 2005, Eagle Plains conducted a soil sampling and rock geochemical sampling program near Hall Lake, the region closest to the Cretin occurrence. Results showed insignificant values of gold, although multiple mineralized outcrops were not sampled due to hazardous conditions during the field program.
In 2011, Bethpage Capital Corp. conducted an airborne geophysical survey of the Hall Lake area including the occurrence. The survey identified five anomalous features. It was hypothesized that the first two zones could be the extension of the felsic dike that hosts the mineralization found at the Cretin occurrence.
In 2013, Eagle Plains Resources Ltd. conducted a program of geological mapping and geochemical (rock, silt and soil) sampling on the Hall Lake property. Two grab samples (AHHLR014 and AHHLR019) of felsite, located on the ridge to the west-southwest of the occurrence, yielded values of up to 0.19 per cent lead, 0.83 per cent arsenic, 0.26 gram per tonne gold and greater than 0.20 per cent antimony (Assessment Report 34463).
