The Tan - Main zone occurrence is located south west of Tamihi Creek at an elevation of 1050 metres, approximately 5.5 kilometres south of its junction with the Chilliwack River.
The area is underlain by a series of volcanic rocks and associated sediments and volcaniclastics of the Devonian to Permian Chilliwack Group. The volcanics range from basaltic to rhyodacite in composition and the sediments range from siltstone to conglomerate. The volcanic pile is dominated by amygdaloidal flows (of probable andesitic to basaltic composition) which contain minor interbeds of felsic ash and lapilli tuffs and lesser pyroclastic breccias. Breaks in the volcanism are indicated by sequences of carbonate, pyroclastics and clastics. Overall bedding appears to have a gentle easterly dip on the order 10 degrees, however, local fault-rotated blocks have steep northwest dips.
Two styles of mineralization are reported. The first and most common type of mineralization is that associated with intense quartz vein stock-works, vein breccias and associated "replacements". Minerals include abundant pyrite, lesser amounts of chalcopyrite and sphalerite, and rare galena. The quartz vein/replacement zones often appear to be zoned, with an outer zone of broad quartz veining. Quartz veining increases dramatically towards silicified or "replaced" zones and with it the country rock becomes increasingly silicified, often losing primary textures. These "replacement" zones commonly have associated strong brecciation with quartz vein events both prior to and following brecciation. The "replacement" zones are described as massive, siliceous, complete replacements along bedding or fracture zones and are followed by hairline, black quartz veining and/or white quartz veining. These "replacement" zones are usually less than tens of metres in length. Silicification of this type has been observed for over 100 metres but do not have the sulphides or quartz-sulphide veining of the smaller zones.
A grab sample from a zone of siliceous breccia with black quartz yielded 0.2 per cent copper, 5.2 grams per tonne silver and greater than 0.4 per cent zinc (Assessment Report 6113).
The second type of mineralization on the property is syngenetic, consisting of pyrite occurring in dark siltstone. Fine disseminated pyrite forms weak or discontinuous bands paralleling bedding planes.
Narrow veins of chalcopyrite and sphalerite, up to 15 centimetres wide, are also reported to occur on the north side of Tamihi Creek.
In 1972, Cominco completed a program of geological mapping, and soil and stream silt sampling on the area as the Tan property. During 1974 through 1977, Great Plains Development completed airborne and ground electromagnetic and induced polarization surveys, geological mapping and seven diamond drill holes, totalling 397.0 metres, on the area. In 1981, Lornex Mining Corporation completed a program of VLF-EM and total field magnetometer surveys on the area. In 1984, Aberford Resources completed a program of rock sampling and geological mapping.
