The Tree River property is centred at 670 08’ N 1120 09’ W on NTS 86 P01, 155 kilometres southeast of Kugluktuk in the Kitikmeot Region of Nunavut. The property consists of three Prospecting Permits covering 39,250 hectares and is accessible by float plane or helicopter from Kugluktuk or Yellowknife.
Gold mineralization was discovered in the general area by BHP Billiton (BHP) during reconnaissance work in the early 1990’s. Claims were staked in the property area by BHP in 1993 for both diamonds and gold. BHP’s prospecting subsequently located gold in structurally controlled veins, gabbro and within an extensive “siliceous horizon”. The latter quickly became the focus of their efforts when grab samples up to 142 g/t Au were collected near Cracker Lake. They eventually concluded that the gold-bearing horizon was too extensive to be an exhalate bed, collecting numerous samples greater than 1 g/t Au along a western horizon in addition to the high-grade samples returned from an eastern horizon. BHP conducted additional prospecting and sampling on the property until 1997. The property was restaked by 4763 NWT Ltd. in 2002 and optioned to Strongbow Exploration Inc. Strongbow conducted airborne horizontal aeromagnetic surveys over the property in the winter and spring of 2002 and made a single visit to the property on August 20, 2002. They collected 7 samples; two of which returned 102.64 g/t Au and 2.357 g/t Au. Subsequent work focused on the uppermost of two conglomerate horizons in a metasedimentary rock unit which Strongbow identified as hosting mineralization similar in style to that found in the Witwatersrand of South Africa. Strongbow conducted geologic mapping, petrographic studies and channel sampling on the property but subsequently allowed it to lapse when they failed to located a large zone of higher grade gold mineralization. The property was acquired by Silver Range Resources in February 2018 and is held under three Prospecting Permits covering 39,250 hectares.
The Tree River property is at the north end of the Anialik Greenstone Belt and is underlain by mafic volcanic rocks overlain by clastic marine sediments, subsequently metamorphosed to greenschist facies. The sedimentary rocks are dated at between 2940 and 2700 Ma based on detrital zircons. A monomictic, clast-supported quartz pebble conglomerate (QPC) from 15 to 20 metres thick, lies approximately 80 m stratigraphically up-section from the volcanic / sedimentary contact. This laterally extensive unit has been traced for kilometres and is particularly enriched in gold, with background values in excess of 100 ppb Au, numerous grab samples in excess of 1 g/t Au and local occurrences of high grade gold. The most significant high-grade showing is in the eastern portion of the property where, in addition to high grade grab samples, a channel sample returned 0.35 m @ 63.15 g/t Au.
The QPC contains abundant pyrite within the matrix, carrying 1-2% in background and up to 25% in localized pods. Arsenopyrite, stibnite and sphalerite together with a green mica identified as fuchsite also occur in the matrix. The pyrite is detrital with grains described as rounded to “muffin-shaped”. In addition, the matrix contains up to 5% carbonaceous material in layers parallel to bedding.
Mineralization in the QPC at the Tree River property is similar in setting and style to gold mineralization recently discovered in the Pilbara district of Australia and fits currently proposed models for Witwatersrand-style gold mineralization:
- Gold is hosted in a regionally extensive, fluvial to shallow marine conglomerate.
- Pods of high grade gold mineralization are present within a much larger envelope of lower grade material.
- Primary carbonaceous material is present.
- Pyrite is abundant and a significant proportion is reported to be rounded and detrital in origin
- The QPC is dated between 2,940 to 2,700 Ma, placing it in the favourable time window for the Great Gold Deposition Event (Hennigh, 2016).
Silver Range intends to conduct systematic sampling, geological mapping and focused prospecting at Tree River in the coming season, building on the solid technical data collected by Strongbow and incorporating the latest insights into the developing Witwatersrand 2.0 deposit model.