Rogers Creek Project, British Columbia Canada
The Rogers Creek property straddles the Lower Lillooet River valley, approximately 90 km northeast of Vancouver, and 28 km south of Pemberton (Figure 1). It consists of 108 contiguous claims aggregating 484.92 km2. Carube Copper is 100% owner of the property subject to a net smelter royalty. The Rogers Creek property was staked on the basis of a logging road discovery in 2007 and now consists of four significant target areas including a minimum 6 x 2 km area of anomalous soil geochemistry, multiple untested IP anomalies and significant surface exposures of copper, gold and silver mineralization.
Road access to and within the Rogers Creek valley is good due to substantial logging operations in and around the property. The BC Rail line passes through Pemberton 28 kilometres to the north and there is a high tension power line, which extends through the western side of the property following the Lower Lillooet River. A power sub-station was constructed at kilometre 43 of the In-SHUCK-ch Forest Service Road at the foot of Rogers Creek valley in 2011.
The property (Figure 2) is centred on the Miocene-aged Rogers Creek Intrusive Complex (16.7+/-2.7 Ma), which intrudes overlying and coeval Miocene-age Crevasse Crag volcanic flows and pyroclastics and older metamorphosed Jurassic and Cretaceous host rocks. Although the Rogers Creek Pluton is dominantly granodioritic, the western contact of the pluton comprises a porphyritic, intermediate contact phase, and discrete feldspar-, biotite-, and hornblende-phyric syenitic bodies. Syenite, diorite, porphyritic granodiorite, and monzonite phases have also been mapped.
After securing an option agreement on the Rogers Creek property in 2008, the company conducted a major field program including a 1,506 line-km airborne magnetic survey, which was flown over the northern two-thirds of the property (Figure 2). In 2010, an airborne magnetic and radiometric survey was flown over the southerly Fire Mountain claim block. Results of the two airborne surveys, and field work consisting of stream sediment and soil sampling, and prospecting and mapping in 2008 and 2009 defined four target areas. Two of these (Targets I and II) lie within a 6 x 2 kilometre area on the north side of the Rogers Creek valley, which is the locus of anomalous silt, soil and rock sample geochemistry (Figure 3a). Both Target areas I and II are centred on two ~1.6 kilometre diameter magnetic lows (Figure 3b). A 28 line-kilometre IP survey completed over Targets I and II in 2009 and helped to focus an initial three-hole drill program on the western margin of Target I that was completed in the fall of 2009.
Streams draining Targets I and II (Figure 3a) returned silt samples containing up to 800 ppb gold, 835 ppb silver and 73 ppm copper versus background values of approximately 2.5 ppb gold, 20 ppb silver and 15 ppm copper. Quartz-sulphide veins on the periphery and cutting Target I breccia returned gold and silver values up to 23.1 grams per tonne gold, 232 grams per tonne silver, 0.69% copper and 81.4 ppm molybdenum. The strong stream and rock geochemistry is reflected in the broad distribution of gold (>25 ppb Au) and copper (>100 ppm Cu) soil anomalies within the 6 x 2 kilometre area encompassing Targets I and II and to a lesser extent Target III, which has a dominant gold signature.
Carube Copper's interpretation of the magnetic signature (Figure 3b) in the northern half of the property is that it has imaged an oval-shaped eroded caldera cored mainly by various dioritic to granodioritic intrusives and cut by multiple generations of arc-parallel and related conjugate fault sets. These faults are interpreted to have focused the emplacement of a post-mineral intrusive breccia at the core of Target I and likely gave rise to the formation of the magnetic low at the core of Target II. The formation of these faults also directly controlled multiple stages of copper-gold +/- molybdenum mineralization across at least the northern half of the property especially in and around the margins of Targets I and II magnetic lows (Figure 4, Figure 5 and Figure 6).
Figure 5 and Figure 6 present an interpretation of geology, mineralization and alteration along section D-D' (Figure 4) whereas Figure 7 and Figure 8 present these interpretations along orthogonal section J-J'.
Targets I and II (Figure 3 to Figure 8) are defined by moderately to intensely altered granodiorite, hornblende diorite and intrusive breccia, and related alteration, mineralization and geophysical (magnetic and induced polarization [IP]) responses. Host Rogers Creek granodiorite and intrusive breccia are cross-cut by several generations of copper-gold-silver-mineralized quartz-sulphide vein types but otherwise are largely barren. In contrast, hornblende diorite at both Targets I and II is associated with hypogene (disseminated) as well as vein-related copper-gold-silver +/- molybdenum mineralization.
Figures 4 to 6 illustrate the interpreted distribution of rock units, and alteration and mineralization facies across the 6 x 2 kilometre area containing Targets I and II (Figure 3b). The figures show there is a close relationship between hornblende diorite with porphyry-style alteration and copper-gold mineralization that has been discovered on surface and in drill holes, particularly on the western flank of Target I. Copper-gold mineralization in these areas typically occurs in narrow sulphide veins and as sulphide disseminations and therefore gives a good IP response as shown on Figure 4 at Target I.
Figure 4, a plan map at the 450 metre elevation, shows an elevated >30 mV/V, roughly circular, IP chargeability response which is centred on the hornblende diorite. Drilling in the western lobe of the hornblende diorite yielded interesting porphyry-related gold-copper-molybdenum mineralization including 150.9 m of 380 ppm Cu in MRC-007 and 120 metres of 0.2 g/t Au in WRC-002. In the same area, WRC-001 returned sporadic vein-hosted Cu-Au-Mo mineralization over a 178 metre interval. The style and distribution of alteration and mineralization associated with Targets I and II, and in particular the hornblende diorite unit are consistent with a porphyry copper-gold environment.
The interpretation of Figures 4-8 is that MRC-006 and MRC-007 have intersected the outer weakly mineralized pyritic halo (Figure 8) of a porphyry alteration and mineralization system, which has been intersected at depth where it has cut gold +/- copper (WRC-002) and copper-gold +/- molybdenum (WRC-001) mineralization closer to the core of the system near the top (?) of a zone of potassically altered hornblende diorite (Figure 8).
Alteration and mineralization patterns (Figure 4 to Figure 8) as interpreted from surface mapping, drilling and geophysics strongly suggest drilling to date has largely been in the pyritic halo of a large, buried hydrothermal system. Although drill intercepts to date have not been of economic grade, they demonstrate the system was capable of producing long mineralized intercepts as seen in WRC-002 and MRC-007 and will be used to focus exploration into the core of the system.
Target I was shown by field work to largely coincide with a recessively weathering, 1.6 km diameter magnetic low centred immediately to the north of Rogers Creek at the intersection of a number of regional-scale and subordinate fault sets (Figure 2). Based on outcrop exposures along logging road networks, the magnetic low was shown to be occupied by a polymictic breccia pipe similar to other porphyry deposits world-wide (Figure 4 to Figure 6). The breccia pipe is largely clast-supported with a marginal phase of in-situ brecciated Rogers Creek granodiorite. The marginal phase is transitional into a hydrothermally altered clast- and locally matrix-supported breccia dominated by feldspar-phyric rock clasts in a rock flour matrix with rare malachite-stained (i.e. Cu mineralized) rock clasts. Alteration within the breccias is zoned from weak to moderately developed chlorite-pyrite +/- carbonate assemblages in the contact breccias inward to strong pervasive clay-carbonate +/- silica alteration toward the pipe interior. Zones of intense argillic (clay) alteration are centred on vertical faults.
Propylitic (pyrite, carbonate, chlorite and epidote) alteration extends up to 1,000 metres beyond the margins of the magnetic low and breccia pipe, and may contain up to several percent pyrite ± chalcopyrite mineralization. Intense phyllic (quartz, sericite, pyrite) alteration is confined to the extent of the magnetic low and overprints an earlier phase of potassic (K-feldspar, biotite) alteration (Figures 6). Mineralization on local to regional vein sets (020o, 340o) is zoned outwards from the interpreted core of the hydrothermal system. Inner vein sets comprise gold- and silver-rich poly-metallic (quartz-sulphide; pyrite, chalcopyrite, galena, sphalerite and tetrahedrite) and sulphide-sulphate vein assemblages that are present mainly within the phyllic alteration zone; these grade outwards through precious metal-rich assemblages and then iron-sulphide assemblages that are present well out into the surrounding propylitic alteration zone.
Drilling in the fall of 2009 (Figure 4 to Figure 8) focused on testing IP and geological targets on the western margin of Target I magnetic low. These targets are related to copper-gold mineralization exposed along Copper Road and in deeply incised stream valleys, which has produced anomalous soil and stream sediment results. This initial program of drilling consisted of three holes for a total of 2,123 metres of NQ core and demonstrated that Target I was underlain by mineralization and alteration consistent with porphyry Cu-Au-Mo deposits being explored world-wide.
Highlights values from WRC-002 drilled in 2009 included a 120 m of 0.2 g/t Au from 598.0 m to 718.0 m down-hole. Values within this zone included:
0.53 g/t Au over 16 m from 613.0 m to 629.0 m,
- including 4.24 g/t Au over 1.5 m from 627.5 m to 629.0 m,
1.05 g/t Au, 0.0.093% Cu, and 12 g/t Ag over 13.5 m from 704.5 m to 718 m,
- including 4.37 g/t Au, 0.130% Cu, and 20.0 g/t Ag over 1.5 m from 710.5 m
to 712.0 m.
Hole WRC-001 intersected scattered intercepts of copper-gold +/- molybdenum mineralization and porphyry-style alteration over 178.5m including 0.105% Cu over 7.0 m.
In 2011, MRC-006 and MRC-007, aggregating 1,130.86 meters, were drilled to test IP anomalies in the area north of the mineralization encountered in drill holes WRC-001 and WRC-002 (Figure 4 to Figure 8). MRC-006 and MRC-007 both intersected elevated copper and gold values along substantial core lengths (up to 150 metres) within sparsely disseminated, porphyry-style pyrite-chalcopyrite mineralization and alteration (propylitic and chloritic/argillic). As with WRC-001 and WRC-002, alteration assemblages and the intensity of Cu-Au mineralization are consistent with intersections in the outer pyritic halo of a buried porphyry system.
The most interesting mineralization observed in 2011 was in MRC-007, which intersected 380 ppm Cu over 150.9 metres from 345.60 to 496.50 metres, including:
- 0.071% Cu over 3.0 metres from 200.4 to 203.7 metres
- 0.089% Cu over 8.0 metres from 222.0 to 230.0 metres
- 0.05% Cu over 16.7 metres from 363.0 to 379.7 metres
- 0.172% Cu over 12.3 metres from 422.2 to 434.2 metres
- 0.067% Cu over 6.0 metres from 447.0 to 453.0 metres
These drill hole intercepts and related alteration confirmed the presence of structurally controlled copper-gold mineralization, indicative of the upper levels of a porphyry copper-gold system.
Target II is cored by a second magnetic low (~1.5 km diameter) and located about four kilometres to the south-west of Target I (Figure 2, Figure 3a and Figure 3b). Outcrop is very scarce within the core of the magnetic low with only a few scattered hornblende granodiorite outcrops exposed north of Rogers Creek.
Soil sampling defined multiple gold- and copper-in-soil geochemical anomalies (> 25 ppb Au, >100 ppm Cu, respectively) particularly along the western (values up to 0.242 g/t Au) and northern margins (values up to 0.542 g/t Au) of the magnetic low. Several chalcopyrite occurrences also were found on the northern margin on the magnetic low. Soil sampling in 2011 delineated an open-ended, NNW-trending soil anomaly (Figure 3a) over a 200 x 1,200 metre area, defined by gold-in-soil values of between 25 and 542 ppb gold and copper-in-soil values between 100 and 1,115 ppm copper at the northern end of Target II.
Mapping, prospecting and surface sampling within this soil geochemical anomaly located gold/copper mineralization within an 80 x 100 metre area. The mineralization, hosted by silica-chlorite altered hornblende diorite, consisted of up to several percent disseminated chalcopyrite and lesser pyrite with rare chalcopyrite and pyrite veins up to 1 cm wide. An initial 10 grab samples, excluding one cross-cut by a pyrite-chalcopyrite vein which returned 3.72% Cu, 15.75 g/t Au and 91.9 g/t Ag, averaged 1.372 g/t Au, 0.53% Cu and 11.97 g/t Ag. Highlight samples included:
Sample K881055: 3.72% Cu, 15.75 g/t Au and 91.9 g/t Ag
Sample K881054: 0.72% Cu, 4.91 g/t Au and 25.8 g/t Ag
Sample K881053: 0.79% Cu, 2.19 g/t Au and 21.6 g/t Ag
Sample K880323: 0.82% Cu, 0.836 g/t Au and 8.95 g/t Ag
Channel sampling of the surface mineralization returned 9.12 metres of 1.958 g/t gold ("Au"), 0.573% copper ("Cu") and 13.7 g/t silver ("Ag") confirming the results of the grab samples.
Shallow drilling (MRC-003, 004 and 005), aggregating 933.4 meters, beneath the surface mineralization intersected only weakly anomalous gold and copper values but did demonstrate that the altered and mineralized host rock of the surface showing and related structures continued to the north beneath the northern extent of the copper and gold soil geochemical anomaly.
Numerous occurrences of copper and gold mineralization have been found along a logging road between Targets I and II, where chalcopyrite and bornite mineralization is exposed in narrow "A" and "D" vein assemblages, along fault planes, within chloritic hydro-fractures and a fluid exsolution pipe. Selective grab samples returned up to 6,850 ppm copper with weakly to moderately anomalous gold and silver values.
At Target III, a 200 m diameter zone of hematite and clay/sericite/tourmaline-altered breccia was located in an area of anomalous Au-in-silt values (up to 2.3 g/t Au) and zones of intense silica and potassic alteration (Figure 3). Stream sediment samples with anomalous gold (Figure 3a) were recovered from streams that drain roughly east-west and north-northeast-trending structures. These host zones of intense quartz-sericite-pyrite alteration up to 5 metres wide that have returned up to 0.82 g/t Au.
Target IV was discovered on the Fire Mountain claim block in the south-western part of the property during prospecting along newly built logging roads in 2009. Two new showings were located with significant molybdenite, chalcopyrite, and malachite (Figure 9a, Figure 9b and Figure 9c) mineralization occurring along north-northwest trending veinlets and fractures.
Work to date has advanced the property from a small showing discovered on a logging road in 2007 to an advanced exploration stage property, with evidence for a large mineralized system. This has validated the initial working hypothesis that there is considerable potential to discover significant mineralization within the Miocene age intrusions of the Cascade Magmatic Arc in southwestern BC, which have seen very little modern exploration.
Work to date has been focused in Area 1. The last hole drilled in Area 1, MRC-007, was drilled north of the limit of the IP and soil geochemical coverage and intersected 158 metres of 380 ppm Cu in MRC-007, including 12.3 metres of 0.172% Cu, confirming that the mineralized system is open to the north beyond the limits of current geophysical and geochemical coverage. To date the mineralization intersected by drilling is consistent with that from the periphery of a mineralized system. Interpretation is complicated by the presence of a large post-mineral breccia pipe. Mineralized clasts noted within this pipe indicate it has passed through mineralization at depth. Further work is required to fully define the extent and geometry of what appears to be a very large mineralized system, in order to define the location of the potassic core of the system which would be expected to produce higher grade intercepts.
Work in Area 2, has identified copper-gold mineralization associated with chlorite-sericite altered hornblende granodiorite. The large magnetic low at the centre of Area 2 remains unexplained.
Little work has been carried out in Areas 3 and 4. Potential in Area 3 appears to be for high level epithermal gold mineralization, while Area 4 is a copper-molybdenum target. Both of these areas are currently ranked to be of lower priority to Targets 1 and 2. Sufficient work has been filed to keep Target 3 until December 31, 2021 and Target 4 until December 31, 2018. Because these areas are contiguous with Targets 1 and 2, any work completed on these targets can be applied to retain Targets 3 and 4 for future exploration.
Objectives of the currently proposed work program are to follow-up on the results from MRC-007 and define the northern limits of the mineralized system as well as to get better definition of the internal geometry and metal zonation within the system in order to optimize drill targeting for the next phase of drilling.
IP and soil geochemistry will be extended north of the area of the current coverage, to define the northern limits of the system. A total of 12 kilometres of IP surveying and soil sampling is proposed.
Proposed work includes a re-examination of the existing core from Area 1, as well as the collection of physical property data, both magnetic susceptibility and chargeability measurements from this core. This data will then be used to produce constrained 3D inversions of the geophysical data, (currently only unconstrained models are available) which will be merged with the geology data to produce an integrated 3D model of the mineralized system.