An independent evaluation of a potential bulk-tonnage target in the Cow Mountain area of the Cariboo gold property, near Wells, B.C., not only concludes that the mineral inventory is about half as large as previously reported by
At the request of the Canadian Venture Exchange, International Wayside brought in consultant Ronald Simpson, president of GeoSim Services, to audit, at arm’s-length, an in-house “measured, indicated and inferred” resource calculation of 1.1 million oz. Wayside had used the estimate to promote its Cariboo property. The earlier uncut estimate of 10.1 million tonnes grading 3.36 grams gold per tonne had been prepared in January 1999 by an individual who was, at the time, a shareholder of Wayside. The resource estimate was lowered to 9.3 million tonnes grading 2.33 grams, equivalent to 693,000 contained ounces, by cutting higher-grade assays to 17.1 grams. The resource is contained in an open-pit target covering the Sanders, Pinkerton and Rainbow zones of the historic Cariboo Gold Quartz mine on the flank of Cow Mountain.
In April of this year, Wayside announced it had submitted a conceptual plan to the British Columbia Environmental Assessment Office outlining the proposed development of a 3,000-tonne-per-day combined open-pit and underground mine on the basis of its early resource work.
The company’s most recent press release, dated June 2, acknowledges that the “disclosure of earlier estimates by the company was inappropriate and the estimates should not be relied upon since they were calculated by in-house personnel who are not independent of the company.”
Using a drill database of 376 holes totalling 18,209 metres (including 273 surface and underground percussion holes, plus 70 surface and 17 underground diamond drill holes), Simpson estimated an inferred mineral resource of 515,000 oz. contained in 7.9 million tonnes grading 2.03 grams gold, capped at 17 grams. Simpson states that, owing to uncertainty in the reliability of conventional percussion drilling and the lack of density measurements, measured and indicated categories cannot be assigned.
Simpson’s evaluation is lower both in grade and tonnage than Wayside’s cut resource estimate. The difference in grade is likely attributable to the “add-back” method used in the earlier estimate to assign the high uncut values back to the blocks that they occupy. The difference in estimated tonnage is attributed to a lower tonnage factor, block orientation, anisotropic search parameters and the fact that a minimum of two composites is required to interpolate a block grade.
The Cariboo project centres on the past-producing Cariboo Gold Quartz, Island Mountain and Mosquito Creek gold mines, all of which are in an 13-by-5-km area. The Barkerville-Wells area is famed for the Cariboo gold rush of the 1860s, and for lode mining that began in the 1930s. Historic production from the area is recorded as being 3.9 million oz., of which 2.6 million oz. came from placer mining.
Underground hard rock mining began in earnest in 1934 with the opening of the Cariboo Gold Quartz mine and, soon afterwards, the Island Mountain mine. Cariboo Gold Quartz finally closed in 1959, while Island Mountain lasted until 1967. The third major producer, Mosquito Creek, operated from 1980 to 1987.
Approximately 70% of the historic gold was mined from individual quartz veins and narrow zones of quartz stockworks in units of dark-grey metasediments at an average grade of 0.38 oz. per ton (13 grams per tonne). The remainder of the gold was mined from pyritic replacement-type bodies in a unit of bleached marble, marking the Baker-Rainbow contact. The replacement bodies averaged a much higher grade of 0.63 oz. (21.6 grams) and occurred as rod-like shoots or pancake-like lenses in the plane of the limestone unit.
The Cariboo Gold Quartz mine consists of 58 km of underground development on 13 levels between elevations of 4,800 and 3,350 ft. (1,460 and 1,020 metres).
Wharf Resources targeted the open-pit potential of the Cariboo Quartz mine in 1980-1981, carrying out a surface percussion drill program centred mainly over the Sanders zone. Simpson was unable to find any information on the sampling procedures or check analyses used in this program. The precise location of these holes with respect to the current survey grid has not been firmly established, as subsequent trenching programs have destroyed most of the old drillhole collars in the Sanders zone. An accurate tie-in to the current survey grid must be made if these data are to be used for further resource evaluation, says Simpson, who also points out that the primary drilling direction of the Wharf percussion holes was sub-parallel to one of the major vein directions, a cause for concern.
International Wayside optioned the Cariboo group of claims from
From 1995 to 1998, Wayside completed 71 surface and 17 underground diamond drill holes, as well as 135 underground percussion holes in the Cow Mountain area. Comparisons of mineralized intervals from the different drill programs show a significant difference between percussion and diamond drilling results, which Simpson says may be due in part to recovery problems, but the statistics show that the underground percussion accounts for a disproportionate percentage of the total resource, particularly in the Rainbow and Pinkerton zones. Virtually all of the resource in the Sanders zone is based on surface and underground percussion drilling.
In the Rainbow zone, the percussion drilling accounts for 13% of the total drilled footage but more than 40% of the total ounces. Simpson says this suggests either that the underground percussion drilling was targeted primarily at mineralized structures or that up-hole contamination from vein material took place. An extreme example is percussion hole UP97-21, which yielded 30.5 metres averaging 4.7 grams. Surface diamond drill holes in the vicinity (for example, hole SD97-23) show no comparable intersections.
“The bias toward the underground percussion drilling data throws considerable doubt on the reliability of any mineral resource estimation,” Simpson states in his report. “Results from diamond drilling alone have not confirmed the presence of a bulk-tonnage deposit.
“In order to upgrade the classification from inferred to measured and indicated, a program of diamond drilling, possibly accompanied by reverse-circulation drilling, is required to validate the grades and widths of mineralized intervals intersected by the previous drill programs . . . Twinning some of the percussion holes may give sufficient confidence to allow their inclusion in further resource evaluation. A program of underground sampling in accessible areas would also help to validate the extent and grade of mineralization indicated by resource modeling.”
Wayside has been halted by the Canadian Venture Exchange since May 11, pending an operational audit of exploration procedures. The company has come under scrutiny since March 23, when it announced the discovery of a previously unrecognized style of high-grade gold mineralization in the footwall of the BC quartz vein. Several analysts who visited the property in mid-April expressed concerns over the company’s sampling protocol, including the lack of quality-control. Also, analysts learned that whole core analyses had been conducted on selected sections of the mineralized intervals. (Normal industry practice is to split the mineralized core and send half in for analysis, leaving the remaining half as a permanent record. The interval can then be visually inspected and re-analyzed, if warranted, at some future date. Analyzing the whole core makes it impossible to perform an accurate check on the assay value of the intersection.)
The company has said whole core sampling was conducted mainly in friable or broken intervals, and that it was difficult to cut or split. Holes 1 through 17 of the 2000 drilling program were drilled with BQ-size core (36.5 mm core diameter). Starting with hole 18, Wayside has switched to the larger-diameter NQ (47.6 mm core diameter) to improve core recovery and sample size.
The BC vein was a secondary drilling target at the Cariboo property, 3 km south of the open-pit prospect in the Cow Mountain area. The BC vein dips 70 to the northeast on the flank of Barkerville Mountain near the headwaters of Lowhee Creek and Stouts Gulch. In 1940-1941, the 1,500-level adit at the Cariboo Gold Quartz mine was extended 1,677 metres and intersected the BC vein 262 metres below surface. A 68 inclined shaft was deepened in 1941 to 290 metres to intersect the end of the adit.
With the exception of three highly productive stopes in the hangingwall of the Goldfinch fault, little exploration, development or mining were carried out in this drift extension. Wayside first drill-tested the BC vein in 1998, completing 13 initial diamond drill holes along a 183-metre-long portion northwest of the BC shaft to the Goldfinch fault. By the end of 1999, the junior had sunk a total of 31 diamond drill holes into the vein. Twenty-five holes had tested a 275-metre section along strike northwest of the BC shaft, while six holes tested 213 metres of strike length southeast of the shaft.
Wayside resumed drilling this spring by stepping farther out on the southeastern extension of the BC vein. The company says it literally stumbled on to the new pyritic zone of mineralization, dubbed “Bonanza Ledge,” after hole BC2K-3 was left to drill deeper into the footwall area of the vein. Hole 2, collared at an angle of minus 45, intersected 6.1 metres averaging 6.21 grams starting at a down-hole depth of 38.1 metres. This was followed by a 7.5-metre intercept averaging 9.41 grams, beginning at 64 metres of depth. Hole 4 was steepened to minus 66 from the same pad as hole 3 and encountered 8.5 metres averaging 10.12 grams at a down-hole depth of 43.3 metres. Holes 3 and 4 were collared 427 metres south of the BC shaft.
To date, assay results have been reported for nine holes that tested the Bonanza Ledge discovery over a strike length of just 122 metres. The best of these was hole 10, which cut 25.8 metres averaging 24.6 grams, including a 13.6-metre interval averaging 42.9 grams, starting at a down-hole depth of 48.2 metres. However, hole 11, which undercut hole 10, encountered only 4.8 metres grading 4.65 grams, starting at 55.5 metres down-hole.
The mineralized intercepts, beginning with the most northwesterly drilled hole in Bonanza Ledge, are highlighted in the table below. Assay results for holes 15 through 18 are pending.
In mid-April, in a bid to alleviate sampling and security concerns, Wayside hired independent consultants David Rhys and Katherina Ross of Panterra Geoservices to review core-handling and sampling techniques, as well as to verify sampling results and conduct petrographic analysis on the newly discovered Bonanza Ledge mineralization.
The most startling find was that the practice of whole core sampling had been conducted on some or all sampling intervals in holes 3, 4, 8, 9, 10, 11, 13 and 14, and that no sample tags had previously been placed in core boxes to mark sample intervals. More than 50% of sample intervals have been whole core sampled in holes 3, 4, 8, 9 and 13. None of the sample intervals in hole 12, and less than a quarter of those in holes 10 and 11, were whole-core sampled.
But in their report, Rhys and Ross state that many well-mineralized intervals grading in excess of 5 grams gold are preserved, even in drill holes where significant whole-core sampling was practised, allowing verification of the style and distribution of the gold. Unfortunately, visitors to the site who examined the drill core after logging and sampling frequently collected samples from mineralized intervals, leaving gaps in some high-grade intervals.
To verify the results of previous sampling, 16 intervals from several drill holes were selected for re-sampling. The previously reported gold grades ranged from undetectable to a high-grade 87.1 grams across 2.65 metres. Samples were selected from intact split intervals where no specimen collection was evident, which limited the intervals available in high-grade sections.
Core was quartered and sent to ASL Chemex Labs of Vancouver for gold analysis by fire-assay with gravimetric finish. “The re-sampling results correspond positively with the previously reported results and confirm both the presence and grade of gold in the earlier samples,” state Rhys and Ross. “The consistent results from this and previous check-sampling work suggest that nugget effect is not a significant factor in this zone.”
Based on re-logging of the core and petrographic analysis, the consultants conclude that the newly discovered Bonanza Ledge zone is hosted by an overturned, northeasterly dipping sequence of clastic metasedimentary rocks made up of upper laminated, carbonaceous pelitic phyllite and lower metaturbiditic rocks in the structural footwall of the BC vein. Mineralized zones occur in a broad area of muscovite-carbonate alteration. The alteration is zoned from an upper area of intense muscovite alteration containing auriferous pyrite mineralization with grey-blue quartz-dolomite-ankerite stringers, to a lower zone of weak muscovite-chlorite-albite alteration with siderite-magnesite stringers. Pyrite mineralization occurs in both zones, but is best developed in discrete areas locally more than 100 ft. thick in the upper zone, where it comprises 10-70% of the rock as stringers, concordant laminations and massive bands.
Gold mineralization is confined to the upper zone. Petrographic analysis of high-grade intervals in holes 10, 12 and 13 indicates that the gold is native, in grains 2.5 to 60 microns in size, on micro-fractures or grain boundaries of pyrite, often with chalcopyrite and galena. To a lesser extent, fine gold grains are encapsulated in pyrite.
Drilling to date shows a discontinuity of mineralized zones, lithologies and alteration within and between sections, and the consultants conclude that the presence of numerous minor D2 folds in drill core indicates that the area is structurally complicated. Rhys and Ross believe the area ultimately will have to be drilled on 12-to-15-metre centres in order to delineate the mineralization, owing to its structural complexity.
They also conclude that the structural, textural and mineralogical style of mineralization and associated alteration mineralogy of the Bonanza Ledge zone are similar to pyrite replacement styles of mineralization historically mined at the Island Mountain and Mosquito mines.
Rhys has made 13 recommendations based on his review of core-handling and sampling procedures at Cariboo. Wayside says it is in the process of implementing these recommendations. In particular, the practice of whole-core sampling has been stopped, all holes are now of NQ-size, and a fenced, secure handling and logging facility is under construction, with one trailer on site, and a second to be delivered shortly.
In related news,
Be the first to comment on "Independent evaluation calls Wayside estimates into question"