The Banbury Porphyry prospect occurs on the south bank of the Similkameen River, just west of Henri Creek, 3.5 to 4 kilometres west of Hedley. Gold-bearing veins and shear zones of the Banbury prospect (092HSE046) outcrop to the south.
In the area, north-striking, steeply-dipping sediments and volcanics of the Upper Triassic Stemwinder Mountain and Whistle Creek formations (Nicola Group) are cut by leucocratic quartz diorite and gabbro/diorite sills, dykes and stocks of the Early Jurassic Hedley Intrusions.
The Banbury stock (Hedley Intrusions), an elongate west-trending body, 400 metres wide by 1.5 kilometres long, interfingers with limestone, siltstone, argillite, conglomerate and andesitic tuff, marked by a hornfelsed contact aureole. The stock is composed of the following two phases: a medium to coarse-grained dark green hornblende diorite occurring along the southern margin, and a medium to fine-grained light grey quartz diorite along the northern margin. The quartz diorite is locally intensely skarn altered with coarse garnet and clinopyroxene.
Low-grade, near-surface, porphyry-type gold mineralization is hosted in diorite of the Banbury stock and in argillite and minor limestone of the Stemwinder Mountain Formation, adjacent to the stock's northern contact. This mineralization is contained in two zones, the 86 and 87 zones. The 86 zone is comprised of 3 steeply southeast-dipping, roughly tabular, en echelon bodies straddling the diorite-sediment contact. Two of the bodies are in quartz diorite, and the third occurs in sediments. The 86 zone has a composite strike length of 100 metres, a composite dip length of 250 metres and an overall thickness of 50 metres.
The 87 zone is a roughly tabular body in quartz diorite that is subparallel to the diorite-sedimemt contact. The zone's subvertical footwall lies 40 to 90 metres from the sediments. The body has a strike length of 185 metres, dip length of 150 metres and a 30 metre thickness.
Gold mineralization occurs in a quartz-carbonate stockwork and in slightly altered quartz diorite in the two zones. Minor pyrite and pyrrhotite and traces of arsenopyrite and chalcopyrite are associated with gold values. Several small nuggets and flakes of native gold have been observed in the 86 zone. Inferred reserves are as follows (Assessment Report 17631, page 11):
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Tonnes Au (g/t)
86 Zone 1,530,000 1.90
87 Zone 2,080,000 1.33
Total 3,610,000 1.57
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This deposit was discovered in 1986, while exploring for gold- bearing skarn zones adjacent to the Banbury stock, similar to that hosting the producing Nickel Plate mine (092HSE038), 7 kilometres to the east. Noranda Inc. drilled a total of 2753 metres in 12 holes during 1986 and 1987 while optioning the property from Banbury Gold Mines Ltd.
