This barite-lead-zinc prospect is located in the Rough number 4 claim, 27 kilometres southeast of the confluence of Through Creek and Gataga River, 16.5 kilometres east-northeast of Mount New in the mountainous Muskwa Ranges of the Northern Rocky Mountains (Assessment Report 10693, Figure 3b).
The occurrence is in the northwest of the Gataga mineral district, in a belt of Paleozoic basinal-facies sedimentary strata known as the Kechika Trough, part of Ancestral North America (Exploration and Mining Geology, Volume 1; Geological Survey of Canada Map 1713A). The Gataga mineral deposits are characterized by stratiform sedimentary-exhalative barite-sulphide mineralization. The most important deposit in the area is the Driftpile Creek developed prospect (094K 066), 24 kilometres along strike to the southeast of the Rough prospect.
Like the rest of the region, the Rough claims are underlain by Cambrian to Mississippian rock units which have been deformed into tight to isoclinal, northeasterly-overturned anticlines and synclines, and imbricated by thrust faults. The regional strike is northwest. The oldest rocks present are quartzite and limestone of an unnamed Middle to Upper Cambrian unit. Stratigraphically above this are shale of the Cambro-Ordovician Kechika Group; calcareous and non-calcareous siltstone and shale, and limestone of the Ordovician to Lower Devonian Road River Group; and finally the Devonian to Mississippian Earn Group (Geological Survey of Canada Map 1712A).
The Middle to Upper Devonian Gunsteel Formation (informal name) of the Earn Group hosts barite-lead-zinc mineralization at the Driftpile Creek deposit, and can be traced along the strike of a synclinorium into the Rough property (Preliminary Map 38; Geological Survey of Canada Paper 88-1E). Here, it is composed of bluish-grey weathering carbonaceous shale, siliceous shale and cherty mudstone, siltstone and minor limestone. Locally the shale contains horizons of nodular barite or bedded, highly siliceous barite; a strong lead soil anomaly is clearly associated with these baritic bands but no substantial sulphide mineralization has been found (Assessment Reports 6997, 8169). The outcrop of the baritic shale and that of the Gunsteel Formation in general is quite irregular due to the complexity and plunge reversals of the folds, and to truncation by faults and thrusts, and this lack of continuity may limit the economic potential of the unit (Assessment Report 10693).
These Devonian baritic shales also outcrop along strike in the Sic 1 claim, 3 kilometres to the southeast of the Rough 4 claim. Here, too, they are associated with lead and zinc soil anomalies, but without obvious sulphides (Assessment Report 10083).
Although some of the exploration at the Rough was focussed on the baritic facies of the Gunsteel Formation, the initial and principal interest in this area was actually on a zone, lower in the stratigraphy, of disseminated to massive sphalerite-pyrite-galena mineralization in cherty shale and breccia at the partially thrust-faulted contact between Cambrian limestone and younger shales, centred on the "Waterfall showings". This horizon was judged to be on the faulted, overturned (southwestern) limb of a syncline (Assessment Report 10693). It strikes approximately 310 degrees and dips about 50 degrees southwest. The shale has been interpreted as Kechika Group (Assessment Report 6997) or alternatively, Road River Group (Assessment Report 8169).
This mineralized zone is generally about 10 metres thick but may reach 30 metres, and has been traced for 3.9 kilometres. However, high grade mineralization is erratic (Assessment Report 6997). The sphalerite is pink-red or yellow, and fine grained and appears to have both syngenetic and epigenetic characteristics, the latter shown by veining, and replacement and recrystallization textures (Assessment Reports 6454; 6997, pages 9, 18). Galena is subordinate; small amounts of gypsum have been found. A sample of black cherty shale from trench 77-2 assayed 4.4 per cent combined lead-zinc over 10 metres (Assessment Report 6997). Individual samples range up to 8.9 per cent zinc.
This stratabound mineralization has been remobilized by faulting and hydrothermal activity, as indicated by quartz veins containing coarse sphalerite, and stringers of pyrite (Assessment Report 6997). In addition, quartz veins containing calcite and barite occur locally in the Road River Formation (Assessment Reports 6997, 10693). Very minor chalcopyrite, tetrahedrite and azurite are present locally in veins (Assessment Reports 6997, 10693).