The Bonanza occurrence is located approximately 4 kilometres south-southwest of the Klappan River and McEwan Creek confluence, about 21 kilometres southeast of the village of Iskut. The property lies in the high rolling terrain of the Tanzilla Plateau.
The property lies within the Stikine Terrane of the Intermontane Belt and regional geology is dominated by the Stikine arch which is bounded to the south by the Bowser Basin. Exposed along the southern flank of the Stikine arch are Permian or older sediments, metasediments, metavolcanics, and intrusions. Unconformably overlying the Paleozoic rocks are volcanic arc-related extrusive rocks and sediments ranging in age from Middle Triassic (Tsaybahe Group) to Middle Jurassic (unnamed units). The Bowser Lake Group, a megacycle succession of fine to coarse clastic sediments representing a prograding delta, was deposited in the Bowser Basin from the Middle Jurassic to Lower Cretaceous. Unconformably overlying the eastern margin of the Bowser Lake Group are medium to coarse-grained clastic, nonmarine sediments of the Lower to Upper Cretaceous Sustut Group. The bulk of plutonic rocks in the region belong to the Hotailuh batholith which ranges in age from Late Triassic to Late Jurassic and intrudes all units older than the Bowser Lake Group. The intrusions are predominantly hornblende monzodiorites, granodiorites and diorites but include rare quartz monzonite and syenite systems. The northwest trending folds and contraction faults found in the Bowser Basin contrast with the dominantly east-west faulting found along the southern flank of the Stikine arch. Rock units older than the Bowser Lake Group have undergone at least one phase of regional metamorphism.
Underlying the prospect area are 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. Locally intruding the above units are quartz feldspar porphyritic dikes and a feldspar porphyritic subvolcanic intrusion believed to be related to the mineralizing event. The showing lies near the axial trace of a north trending upright syncline.
Surrounding rocks 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. Three diamond-drill holes tested the mineralization and gave an average grade of 0.02 to 0.08 per cent copper, 0.04 to 0.16 gram per tonne gold and 0.001 to 0.002 per cent molybdenum. However, assays up to 0.213 per cent copper, 0.79 gram per tonne gold, and 0.0132 per cent molybdenum were encountered over a 3 metre intersection (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 1976-77, Texasgulf conducted soil geochemical, geological, ground magnetometer and induced polarization (IP) surveys and a small amount of hand trenching. In 1979-80, 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 induced polarization and total field magnetometer, and collected 276 soils and one rock sample.
In 2012, Colorado Resources Ltd. optioned the Eldorado property (including the Bonanza area) from Sunrise Resources Ltd. and completed a 28.6 line-kilometre induced polarization 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 tonnes 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).
