TMC

Prospect, Active

Commodities and mineralogy

Main commodities Ag; Au; Cu; Fe; Pb; Sb; Zn
Ore minerals arsenopyrite; chalcopyrite; galena; gold; pyrite; pyrrhotite; stibnite; sphalerite
Gangue minerals ankerite; quartz

Geographic location

Quadrangle map, 1:250,000-scale HE
Quadrangle map, 1:63,360-scale A-1
Latitude 63.1786
Longitude -147.2483
Nearby scientific data Find additional scientific data near this location
Location and accuracy This prospect is about 0.5 mile south of the top of Lucky Hill between Roosevelt Creek and White Creek south of upper Valdez Creek.. The prospect is about 0.2 mile south of the center of section 18, T. 20 S., R. 3 E., of the Fairbanks Meridian. The location is accurate.

Geologic setting

Geologic description

The TMC prospect is one of four deposits that was explored by CanAlaska Resources Ltd. from 1983 to at least 1996 as the Rainbow Hill project. It and the nearby Gold Hill (HE209), Lucky Top (HE210), and Lucky Saddle (HE215) prospects share a similar origin and general characteristics. The Rainbow Hill project is described in considerable detail by Adams (1996) and Freeman (2002) and most of what follows is based on their work.
The rocks in the area consist of folded Jurassic to Cretaceous argillite, graywacke, siltstone, and mafic tuff that were intruded by small stocks and dikes of Tertiary and Cretaceous gabbro and diorite. The rocks underwent lower-greenschist- to amphibolite-grade metamorphism in the Cretaceous and early Tertiary. Airborne geophysical data suggest that the Gold Hill/Lucky Top area that roughly coincides with the Rainbow project is underlain by a shallow, structurally deformed meta-igneous complex. The regional structure is dominated by a set of east-trending thrust faults and cross-cutting high-angle faults. A set of northwest-trending, high-angle faults and dikes associated with the mineralization is offset by northwest- and northeast-trending faults.
The mineralization in the Rainbow project consists of zones of stacked, sulfide-bearing, ankerite-quartz veins and stockworks that strike east and dip variably to the north and south. The sulfides in the veins and stockworks are mainly pyrite and arsenopyrite; minor amounts of pyrrhotite, chalcopyrite, galena, stibnite, and sphalerite occur widely, as does visible gold. Abundant sulfides usually indicate high gold values. The auriferous zones typically have a central area of intense silicification, sericitization, and carbonatization, that weakens outward. Sericite from the veins has been dated at 57.6 to 63.1 Ma by argon-argon methods.
Although there had been some earlier work on the gold veins in the Gold Hill/Lucky Top area (Moffit, 1912; Ross, 1933; Tuck, 1938), the first extensive exploration in the area was in 1983 when CanAlaska began a program of surface mapping, outcrop sampling, soil geochemical surveys, trenching, and ground geophysical surveys. The TMC zone was discovered a few years later. In 1989, CanAlaska drilled 7 holes on it that totaled 1,507 feet, and in 1990 they drilled 45 holes that totaled 14,772 feet. The drilling defined a series of stacked gold-bearing zones that were intersected over a vertical distance 600 feet. The drilling indicated that the mineralization continued along strike for about 1,000 feet, to a depth of 200 feet. They estimated that the total 'drill-inferred gold resource in 5 blocks of the TMC zone contained an estimated 90,285 ounces of gold with an average grade of 0.21 ounce of gold per ton' (at a cut-off grade of 0.03 ounce of gold per ton). The average true width of the mineralization is 17 feet; segments up to 70 feet in length averaged 0.475 ounce of gold per ton. Geophysical evidence suggests that the mineralization continues for another 1,000 feet along strike and at least 500 feet down dip.
Geologic map unit (-147.25055854266, 63.1781535465489)
Mineral deposit model Low-sulfide Au-quartz veins (Cox and Singer, 1986; model 36a).
Mineral deposit model number 36a
Age of mineralization About 60 Ma based on the age of sericite from the quartz veins.
Alteration of deposit The mineralization is associate with pervasive sericite-carbonate-quartz alteration; local hornfelsing and tourmalinization.

Production and reserves

Workings or exploration Although there had been some earlier work on the gold veins in the Gold Hill/Lucky Top area ( Moffit, 1912; Ross, 1933; Tuck, 1938), the first extensive exploration in the area was in 1983 when CanAlaska began a program of surface mapping, outcrop sampling, soil geochemical surveys, trenching, and ground geophysical surveys. The TMC zone was discovered a few years later. In 1989, they drilled 7 holes on it that totaled 1507 feet; in 1990, they drilled 45 holes that totaled 14,772 feet.
Indication of production None
Reserve estimates Based on 52 drill holes and considerable surface exploration, CanAlaska estimated that the total 'drill-inferred gold resource in 5 blocks of the TMC zone contained an estimated 90,285 ounces of gold with an average grade of 0.21 ounce of gold per ton' (at a cut-off grade of 0.03 ounce of gold per ton. The average true width of the mineralization is 17 feet; segments up to 70 feet long averaged 0.475 ounce of gold per ton.

References