Bryson Burke Diamond Corporation: Diamond Exploration and Mining in Canada

8.0 INTERPRETATION

8.1 Geochemistry

Given the nature of the gneisses in the area, consideration must be given to the utility of the indicator minerals as being uniquely indicative of a potential kimberlite or lamproite source-rock. Both chrome diopside and ilmenite can be expected to occur as normal constituents of some portion of the Grenville gneisses. Garnet also occurs in the gneisses in prodigious amounts, red-brown and pink garnets are most common, although garnets with a range of other colors, including orange, are also abundant. In the absence of chemical analyses, visual identification of pyrope garnets must be considered uncertain.

Two minerals that occur in the indicator-mineral suite that cannot reasonably be attributed to the gneisses in the region are chrome spinel and olivine. As well, the glass and magnetic balls are unusual in the extreme and taken together, the presence of these four indicators is considered to substantiate the validity of the indicator-mineral suite as being potentially indicative of the presence of kimberlite or lamproite source-rocks. Further substantiation is derived from the fact that all indicator-minerals have very similar distributions.

About 12 percent of all samples collected to date within the area of the Properties contain indicator minerals, including microdiamonds. The majority of these anomalous samples was collected in the area immediately south of Bryson Lake, and southeast of Lamb Lake. The most logical explanation of these restricted distributions and the prevailing occurrence of multiple indicators at any one sample site is that the source or sources, are located up-ice of the anomalous sample sites. The probable up-ice direction in both cases is northerly or northeasterly. Sampling to the north, east, and west of Bryson Lake resulted in the discovery of few, or no, indicator-minerals. It is therefore reasonable to infer that the probable source of the indicator-minerals, microdiamonds, and macrodiamonds found on the south side of Bryson Lake is beneath the lake itself.

A similar inference can be drawn for the anomalies south and southeast of Lamb Lake. Although the area to the north and west of Lamb Lake has not been sampled so as to eliminate this area as a possible source of the indicator-minerals, the most probable source is on the southeast shore or within the immediate vicinity of the lake itself.

The indicator-minerals and microdiamonds that have been found on the bank of the Coulonge River, where it is intersected by the paleo-drainage from Bryson Lake are inferred to have been transported there from Bryson Lake. The anomalous samples that were obtained from the north shore of Duval Lake may have been transported to that location from Bryson Lake which is situated about five kilometers directly to the north.

Most other samples that contained indicator-minerals are single-point anomalies. Although they may be indicative of an up-ice diamondiferous source, their scattered and isolated distribution does not permit a meaningful interpretation of their significance.

One possible exception is a two-sample anomaly on the north shore of Gerland Lake about 10 kilometers northwest of the large cluster of anomalous samples on the south shore of Bryson Lake. Both contain pyrope garnet and chrome spinel, but one (A1268) also contains olivine and magnetic balls. Given that all the other samples that contained magnetic balls are closely grouped at the south end of Bryson Lake, this outlier may be important. Two samples (A1243 and A1244) collected relatively nearby, to the south of Gerland Lake, may be related. Both contained abundant indicator minerals that the laboratory notes in the attached database describe as "pyrope-like" garnets. As well, sample A1243 contained a "few chrome diposides and ilmenites". Sample A1244 contained "hundreds of apple-green chrome diposides, ilmenites and one chromite". These samples were collected near the locations of mafic to ultramafic rock noted by Ressources Dianor, and near the circular magnetic low feature described in Section 7.0.

Several aspects of the indicator-mineral suite collected in the area of the Properties warrant discussion. The indicator-mineral suite collected in the Coulonge River area differs in two major respects in comparison with those from sampling programs in other areas of glaciated terrain in Canada (e.g.LeCheminant et al, 1996):

The number of indicator-minerals recovered from all the sample media in the Coulonge River area is extremely low, amounting to probably fewer than one thousand grains from over 700 samples. Overburden-sampling programs in areas of kimberlite occurrences elsewhere in Canada have recovered thousands to tens of thousands of indicator minerals. This difference may be attributable to the nature of the source rock. Kimberlites typically contain abundant xenoliths and xenocrysts, the sources of the resultant indicator minerals. Lamproites are xenolith and xenocryst-poor and therefore contain few indicator-minerals. The paucity of indicator-minerals in the Coulonge River area may be attributable to a lamproitic source rock.

The Coulonge River-area samples contain abundant microdiamonds relative to the number of other indicator-minerals. Although microdiamonds have been unofficially reported to have been found in heavy-mineral samples from the Slave Province, they are unquestionably rare. Microdiamonds did, however, occur in sufficient abundance in heavy-mineral samples collected during the pre-discovery phase of exploration in the Argyle area of northwest Australia to be a useful compon

The abundance of microdiamonds in the heavy-mineral suite found in the Coulonge River area may therefore also be indicative of diamond-rich lamproitic source rocks. The validity of either hypothesis cannot, at this time, be assessed as neither lamproites nor other diamond-bearing rocks are known to exist within the area.

A notable aspect of the Coulonge River microdiamonds is the absence of any whole crystals, which clearly implies that the source diamonds were larger than the fragments recovered. All the documented microdiamonds were identified by Russian geoscientists and it was standard practice for them to crush samples prior to analysis. (D. Burke, personal communication) It is therefore possible that destruction of whole diamonds occurred during crushing, however, fragmentation as a result of glacial transport is a more reasonable possibility.

Four of the five macrodiamonds recovered my Mr.Burke are whole and euhedral octagons which suggests that whole diamonds do exist in the overburden in the Coulonge River area, and therefore that glacial transport did not necessarily destroy all diamonds that became entrained in the glacial material. A possible explanation of the absence of whole microdiamonds and the presence of whole macrodiamonds may reside in the sampling process: The preferred sample grain-size for indicator-mineral analysis was the 0.25 to 0.5 millimeter fraction. (D.Burke personal communication) As described above, the whole macrodiamonds were found in the greater-than-one-millimeter fraction. If the source diamonds are generally or exclusively of a size in excess of 0.5 millimeters, it would be unreasonable to expect that whole microdiamonds would have been recovered from the smaller size fraction. To the writer's knowledge, no analysis of the potential original size of the parent crystals of the microdiamond fragments has been undertaken, and therefore the reasonableness of this putative explanation cannot be assessed.

The presence of rounded coesite grains (glass balls) has been mentioned above in the context of such grains having also been found in the lamproitic Argyle deposit. The presence of these grains in the Coulonge River area heavy-mineral suite constitutes further permissive evidence of the presence of a lamproitic source-rock in this area. Coesite is also a constituent of eclogitic rocks (Berman, R.G. in LeCheminant et al, page 177). Therefore, in addition to being possibly indicative of the presence of lamproite, the presence of coesite in the Coulonge River area heavy-mineral suite may also be suggestive of the near-surface presence of rocks, other than lamproite, that formed at a depth within the diamond-stability field.

8.2 Geophysics

Meaningful geophysical data for the area of the Properties is restricted to 1:250,000-scale airborne magnetic survey mapping conducted by the Geological Survey of Canada. Other than by fortuitous coincidence, the 800-meter flightline-spacing of this survey is too coarse to identify potentially diamondiferous intrusives that can be expected to have dimensions on the order of several hundred meters. However, several features of the regional magnetic pattern are considered to reinforce the potential indicated by the indicator-mineral distributions.

The possibility that the area of high magnetic intensity coincident with Bryson Lake may be indicative of a buried mafic intrusive is entirely inferential but the magnetic high does, at a minimum, suggest that this area is anomalous with respect to the surrounding area. Further, the northerly trend of the regional magnetic high that includes the Bryson Lake anomaly is suggestive of a major structure. The intersection of this trend with the northwest-trending Murtagh Creek Fault in the vicinity of Bryson Lake is interpreted as permissive evidence of a tectonic setting that may have facilitated the emplacement of deep-seated intrusive bodies.