The Eldorado occurrence (Assessment Report 9132) is located approximately 4.4 kilometres south-southwest of the Klappan River and McEwan Creek confluence. Refer to the Bonanza prospect (104H 013) for work history and regional geology.
The area is underlain by lower greenschist metamorphosed augite trachyandesite, porphyritic basalt and dacite with minor interbeds of volcaniclastic wacke, sandstone and siltstone mapped by the Geological Survey of Canada (Open File 2241) as the Upper Volcanic Unit of the Middle Triassic Tsaybahe Group.
Outcrops are pervasively altered to a chlorite-carbonate-pyrite assemblage and locally to epidote-chlorite. Narrow sections of intense hostrock alteration to sericite-carbonate-pyrite with minor biotite occur along a stockwork system of quartz-carbonate veinlets containing chalcopyrite-pyrite with minor galena-sphalerite and associated magnetite-hematite-specularite. Drillhole 80-4, collared on weak copper mineralization, intersected pyritic (5 to 10 per cent disseminated) andesite breccia and flows near the surface. A barren augite trachyandesite-basalt porphyry occurs in the middle section and pyritic (1 to 8 per cent disseminated) feldspar porphyry breccia and feldspar porphyry occur at the base of the hole.
Samples of drill core assayed greater than 0.229 per cent copper, 0.42 gram per tonne gold and 0.01 per cent molybdenum in various 3 metre intersections (Assessment Report 9132). Assays ranged from 0.02 to 0.04 per cent copper, 0.04 to 0.1 gram per tonne gold and 0.001 to 0.002 per cent molybdenum (Assessment Report 9132).
In 1975, Texasgulf Canada Limited conducted the initial exploration work on the property. The original Eldorado (104H 026) and Bonanza claims were staked after anomalous copper results were obtained in regional silt samples from area creeks. In 1976 and 1977, Texasgulf conducted soil geochemical, geological, ground magnetometer and induced polarization (IP) surveys and a small amount of hand trenching. In 1979 and 1980, Esso Resources Canada optioned the property and further soil sampling, geophysics, trenching and diamond drilling programs were completed.
In 1995, additional soil sampling, silt sampling, rock sampling, and geologic mapping were carried out on the property by the then current owners, Homestake Canada Inc. and Falconbridge Limited.
In 2003, A.R. Travis staked the area and in 2004 Amarc Resources Ltd. brushed out 16.6 kilometres of grid line and 2.1 kilometres of baseline, surveyed 16.6 kilometres of IP and total field magnetometer, and collected 276 soils and one rock sample.
In 2012, Colorado Resources Ltd. optioned the Eldorado property from Sunrise Resources Ltd. and completed a 28.6-line kilometre IP survey. In 2013, a 44-line kilometre ground magnetometer geophysical survey was completed over the 2012 grid and additional areas. Five drillholes totalling 1435 metres were completed in the southern portion of Block D, of which only three successfully reached bedrock. Drilling intersected units of basalt, local volcanic-derived sedimentary units, as well as numerous feldspar/hornblende porphyritic monzonitic to dioritic intrusions. The drill program identified significant intervals of low grade copper and gold mineralization, including 91.6 metres grading 0.12 per cent copper and 0.28 gram per tonne gold in drillhole EL13-004 (Assessment report 34277). In 2014, Colorado Resources conducted a 4.5-line kilometre ground magnetometer geophysical survey to infill lines surveyed in 2013. Four drillholes totalling 891.6 metres were completed in 2014 to extend the mineralization encountered the previous year. Drillhole EL14-008 intersected 196.5 metres grading 0.06 per cent copper, 0.19 gram per tonne gold, and 0.005 per cent molybdenum over the entire length of the drillhole (Assessment Report 35324).
In November 2019, Roughrider Exploration Ltd. acquired 100 per cent interest in the Gin, Eldorado and Bonanza properties from Cazador Resources Ltd. (Press Release - Roughrider Exploration Ltd., November 8, 2019).
