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Gold/Mining/Energy : ASHTON MINING OF CANADA (ACA) -- Ignore unavailable to you. Want to Upgrade?

To: violetta martinez who wrote (3970)	2/20/1998 2:22:00 PM
From: Jesse	Respond to of 7966

All: I have the esteemed privilege of sharing this excellent report from APEX Geoscience Ltd. This is a summary of the paper given by Mike Dufresne at the Toronto Geological Discussion Group presentation, as discussed on this thread. It's lengthy for this forum, but I am posting it for its invaluable information. WELL worth the read! Here it is (hope there's few errors), in three parts (sorry for formatting): ------------------------------------Part 1------------------- APEX Geoscience Ltd. Edmonton Office: Toronto Office: Suite 200, 9797 - 45th Avenue Suite 218, 920 Yonge Street Edmonton, Alberta T6E 5V8 Toronto, Ontario, M4W 3C7 Email: apexgeo@compusmart.ab.ca Email: Apexto@istar.ca Tel: 403-439-5380 Tel: 416-923-8254 Fax: 403-433-1336 Fax: 416-923-8304 ALBERTA DIAMONDS - AN UPDATE ON THE NEWLY EMERGING DIAMONDIFEROUS KIMBERLITE FIELD IN WESTERN CANADA By APEX Geoscience Ltd. Dr. R.A. Olson, P. Geol., President and Senior Consultant, APEX Toronto office Mr. M.B. Dufresne, P. Geol., Principal and Consultant, APEX Edmonton office EXTENDED ABSTRACT Summary At least 15 kimberlite deposits have been discovered to date in northern Alberta, and there are also reports of kimberlites or diamonds in a few places in central and southern Alberta, Many, if not most, of the northern Alberta kimberlites are diamondiferous, and a few have carats per 100 tonne grades, micro diamond and macro diamond counts, and stone qualities, that are similar to those reported during the early phases of exploration of the economically important diamondiferous kimberlites which exist near Lac de Gras, N.W.T. In contrast to most of the N.W.T. diamondiferous kimberlite pipes, at least some of the pipes and related pyroclastic aprons in Alberta are quite large; in some cases, reportedly up to 15 to 20 ha in areal extent. Thus the potential exists for a diamondiferous deposit in Alberta to have substantial tonnages, which could impact favourably on the economics of any discoveries, even if the carats per tonne or quality of stones turns out to be somewhat less than that found in the N.W.T. The economic and regulatory aspects of diamond exploration and development in Alberta also are highly favourable because there is excellent infrastructure in most areas, including power, water and access via summer and winter roads and cut seismic lines, and many of the aboriginal land claims in Alberta have already been settled. As a result, the capital development and operating costs for a diamond mine in Alberta may be one-third to one-half the cost of such in the N.W.T. In conclusion, the exploration for diamondiferous kimberlites is at an early stage in Alberta, and the potential is high for discovery of an economically important diamond deposit. ---------------------------- -Continued... (2 more parts) ...

To: violetta martinez who wrote (3970)	2/20/1998 2:22:00 PM
From: Jesse	Respond to of 7966

APEX Geoscience Ltd, Alberta Diamond Update continued (Part 2): By APEX Geoscience Ltd. Edmonton Office: Toronto Office: Suite 200, 9797 - 45th Avenue Suite 218, 920 Yonge Street Edmonton, Alberta T6E 5V8 Toronto, Ontario, M4W 3C7 Email: apexgeo@compusmart.ab.ca Email: Apexto@istar.ca Tel: 403-439-5380 Tel: 416-923-8254 Fax: 403-433-1336 Fax: 416-923-8304 ------------ Introduction Diamonds were first reported in Alberta in 1958 (the "Ophdal diamond" near Evansburg in west-central Alberta). In the early 1990's, a kimberlitic diatreme and related pyroclastic facies were discovered near Peace River, about 75 km northeast of Grande Prairie, Alberta (the "Mountain Lake diatreme"). More recently, during 1997, the Ashton Mining of Canada Ltd. - Pure Gold Ltd. - Alberta Energy Company Ltd. joint venture have reported the discovery of 14 kimberlitic diatremes, at least 10 of which are diamondiferous, in the Buffalo Head Hills area of north-central Alberta. At present there exist many untested aeromagnetic anomalies and diamond indicator mineral anomalies in both northern and southern Alberta. Therefore, because exploration for diamondiferous kimberlites in Alberta is at a very early stage, these positive early results indicate the probability for discovery of other important diamondiferous kimberlites in other areas of Alberta, is high. Regional Geology and Structure The regional geology of Alberta is both diverse and complex (see attached list of Selected References). In southern and north-central Alberta the Precambrian Basement is thick (>40 km to the Moho), In southern Alberta the basement age is Archean, whereas in north-central Alberta the basement may be re-worked Archean or accreted Early Proterozoic (Aphebian) terranes or, perhaps in places, comprise Proterozoic terranes overthrust onto Archean blocks. In any case, the basement is thick and old, hence favourable for the formation and preservation of diamonds in the mantle. Overlying the Precambrian rocks in Alberta is a westerly thickening wedge of Phanerozoic strata that ranges in age from early Paleozoic to Early Tertiary, which is up to 5 km or more total thickness in the deep basin adjacent to the Rocky Mountain Fold and Thrust belt in westernmost Alberta. Present within the Phanerozoic succession there is evidence for at least four episodes of volcanism or kimberlitic activity or both, which from oldest to youngest are: (a) uppermost Devonian (Exshaw Fm. bentonites - about 360 Ma); (2) mid Cretaceous (Viking and Shaftesbury bentonites, Crowsnest Volcanics, and Buffalo Head Hills kimberlites - ranging from about 100 to 85 Ma); (3) late Cretaceous (Horseshoe Canyon, Belly River and Kneehills Tuff bentonites, and the Mountain Lake kimberlitic diatreme - ranging from about 80 to 65 Ma); and lastly (4) early Tertiary (Sweetgrass Intrusions - about 54 to 49 Ma). In the past, all the bentonites in Alberta were considered to be altered windblown volcanic debris that was entirely derived from outside Alberta from volcanic centers active in British Columbia or the northwestern USA. However, there is some recent evidence, including locally anomalously thick bentonites, markedly increased number of bentonites in north- central versus east-central Alberta, and anomalous geochemical REE signatures that indicate at least some bentonites are or may be derived from more local volcanic centers, including possible kimberlitic diatreme activity. With respect to the regional and more local structures in Alberta, although the Plains region is generally considered to be much less deformed than the Rocky Mountain Fold and Thrust Belt, and the easterly adjacent Foothills region of Alberta, nonetheless there exists evidence for long-lived tectonic activity that has affected the Phanerozoic strata in the Plains region of the Western Canada Sedimentary Basin. That is, there has been a long history of periodic re-activation of regional structures such as (a) the Great Slave Lake Shear Zone and the Peace River Arch in northern Alberta; (b) the Snowbird Tectonic Zone, Thorsby Low, Western Alberta and Caroline Arches, and Alberta Syncline in central and west-central Alberta; and (c) the Southern Alberta Rift, and Sweetgrass and Bow Island Arches in southern Alberta. Evidence exists for re-activation of many of these structures periodically throughout the Phanerozoic, into possibly as late as the early Tertiary or later. It is probable that such regional and local structures would have played an important role in the emplacement of diamondiferous kimberlitic magmas that resulted in diatremes and related pyroclastic facies deposits in Alberta. Prior Geoscientific and Exploration Work During the mid 1990's, a compilation of scientific studies conducted prior to and under the Canada - Alberta Mineral Development Agreement, and in some exploration assessment reports, identified a number of geochemically favourable diamond indicator trends in Alberta (Dufresne et al., 1994, 1886). Subsequent exploration by the Ashton joint venture, and by others, has discovered to end 1997: (a) at least 14 kimberlitic diatremes in the Buffalo Head Hills region in north-central Alberta, at least 10 of which are diamondiferous; (b) the Mountain Lake kimberlite near Peace River in northwest Alberta, which is reportedly weakly diamondiferous; and (c) diamonds in alluvium near Hinton in west-central Alberta, near Edmonton and near Legend in southern Alberta. The inferred ages of the currently known kimberlitic diatremes, based on stratigraphic evidence, indicate that the Buffalo Head Hills kimberlites may be early Turonian (i.e., about 90 to 85 Ma, existing within the Second White Specks or Dunvegan Fm or equivalents), whereas the Mountain Lake kimberlite is somewhat younger, late Campanian (i.e., about 75 Ma, existing within the Wapiti Fm.). These ages are somewhat younger than the diamondiferous kimberlites which exist at the Fort a la Corne area, Saskatchewan (age about 101 to 94 Ma), and age equivalent to somewhat older than those at the Lac de Gras region in the Slave Structural Province, N.W.T. (age about 74 to 52 Ma). Current Successful Exploration Methods for Diamonds in Alberta Exploration methods which to date have been successfully used in Alberta include: (a) detailed to semi-detailed airborne magnetometer surveys; (b) diamond indicator mineral sampling of selected surficial materials (mainly stream sediment and till heavy mineral concentrates); (c) interpretation of aerial photography and Landsat imagery to search for 'circular' topographic or vegetation features; (d) more recently, digital elevation modelling of topographic data and re-interpretation of old and new seismic data have been used with success in some places; and, finally, (e) diamond drill testing of selected targets. The Ashton - Pure Gold - Alberta Energy joint venture, for example, initially discovered a total of 11 kimberlites by the drill testing of 10 selected, subtle, but definite, aeromagnetic anomalies (1 of the kimberlites was discovered during caterpillar tractor work while digging a drill sump). Nonetheless, exploration in Alberta is still in its infancy, and some exploration techniques or methodologies that have been used elsewhere may not be applicable, or may have to be modified for the Alberta situation, For example, thick drift occurs in many places in northern Alberta, and this will effect both the interpretation of airborne and ground geophysical survey results, but also the diamond indicator mineral sampling methods and interpretation of results. That is, even weak geophysical anomalies or a few anomalous indicator mineral grains may be important in the Alberta situation, particularly if they correlate with a 'roughly circular' topographic or vegetation anomaly. Interestingly, one difference between the topographic expression of kimberlites in the Lac de Gras region, N.W.T, and Alberta, is that in Alberta several of the diatremes which have been found to date comprise low, but distinct positive topographic features, which is contrast to the majority of the Lac de Gras kimberlites that typically occur beneath lakes or in similar, covered depressions. The reason for this probably is that in the N.W.T. situation, the kimberlites are less resistant to glacial erosion compared to the surrounding Precambrian rocks, whereas in Alberta the kimberlites are more resistant in comparison to the typically surrounding Mesozoic shales and other thin-bedded sedimentary rocks. As well, another difference may be the types and chemical signatures of indicator grains in Alberta. For example, although pyropic garnets have been found in several places in Alberta, G10 pyropic garnets are, to date, relatively rare; the reason for this is uncertain. Some of the indicator minerals which have been found to be useful in Alberta to indicate kimberlitic or other ultramafic diatremes, and particularly those that are potentially diamondiferous, include: chrome diopsides, eclogitic and pyropic garnets, omphacitic pyroxenes, chrome-rich picro chromites, picro ilmenites and chromian olivines. In short, the diamond indicator mineral chemistry data that currently are in the public domain are largely derived from South Africa or Australian kimberlitic or lamproitic diamondiferous diatreme fields, and these data may or may not be directly applicable to the Alberta situation, or there may exist some differences with respect to mineral grain chemistries in Alberta that still are favourably indicative of diamondiferous eclogitic or peridotitic mantle and kimberlitic or lamproitic diatremes. Economic and Regulatory Considerations One comparison of interest is the number of micro and macro diamonds which have been reported to have been discovered to date in Alberta, compared with some of the preliminary early-stage data from pipes discovered at the Lac de Gras region. That is, for the initial 10 pipes which were discovered at Lac de Gras, 6 pipes had micro diamond counts of 25 or more {ranging from 28 to 132 micro diamonds) in core samples ranging from 23.2 kg to 161.4 kg in weight, and macro diamond counts ranging from 8 to 55 stones. In Alberta, of the first 14 pipes discovered by the Ashton joint venture, 10 are diamondiferous, and of these the initial recoveries from core samples include at least 4 pipes with micro diamond counts ranging from 31 to 270 stones, and macro diamond counts ranging up to 90 stones, although both counts include some broken stones. In short, the initial Alberta micro and macro diamond counts compare favourably with the initial results from the Lac de Gras region. Another difference between Alberta and the N.W.T, is that the initial Lac de Gras discoveries resulted from initial drilling of targets with favourable diamond indicator mineral chemistries that followed the culmination of years of indicator mineral sampling by Mr. Fipke and others. In contrast, the Alberta discoveries resulted from the initial recognition of unusual, relatively low amplitude, circular magnetic anomalies in wide-spaced fixed-wing aeromagnetic data flown essentially for oil and gas exploration purposes in northern Alberta, followed by drill testing of targets that had not been further prioritized by use of diamond indicator mineral sampling. The size of the currently known Alberta diamondiferous kimberlitic diatremes compares very favourably with those in the N.W.T. In the N.W.T. because of erosion of the upper parts of the N.W.T. diamondiferous diatremes, both BHP/Diamet and Aber/Kennecott have to put 4 or 5 higher grade pipes together in order to get sufficient tonnes of economically viable kimberlite. In contrast, in Alberta many of the diatremes have a diamondiferous crater pyroclastic facies preserved, and some of the Alberta pipes encompass an areal extent of 15 ha to 20+ ha. Hence, the tonnage potential of some of the diamondiferous kimberlites in Alberta is huge, even if the diamond grades and quantities turn out to be less than those in the N.W.T. Lastly, turning to the economic and regulatory aspects of diamond exploration and development in Alberta, these are also favourable. For example, during the 1980's and early 1990's the government of Alberta promulgated significantly revised staking, exploitation and environmental regulatory regimes that compare favourably to other provincial and territorial jurisdictions of Canada. As well, many of the aboriginal land claims have been settled in Alberta. Finally, in most parts of Alberta there is excellent infrastructure, including power, water, and communities for logistical support, and there is good all-year access via summer and winter roads and cut seismic lines. As a result, the exploration for and capital development and operating costs for a diamond mine in Alberta may be one-third to one-half the cost of such in the N.W.T. ----------------------- ...continued (one more part)...

To: violetta martinez who wrote (3970)	2/20/1998 2:22:00 PM
From: Jesse	Read Replies (4) \| Respond to of 7966

APEX Geoscience Ltd, Alberta Diamond Update, conclusion (Part 3): By APEX Geoscience Ltd. Edmonton Office: Toronto Office: Suite 200, 9797 - 45th Avenue Suite 218, 920 Yonge Street Edmonton, Alberta T6E 5V8 Toronto, Ontario, M4W 3C7 Email: apexgeo@compusmart.ab.ca Email: Apexto@istar.ca Tel: 403-439-5380 Tel: 416-923-8254 Fax: 403-433-1336 Fax: 416-923-8304 ---------- Conclusion In conclusion, there are several reasons for believing Alberta is geologically favourable for the existence of important diamondiferous kimberlitic diatremes, including: (1) thick Precambrian continental crust is present in both north-central and southern Alberta; (2) a complex regional and local structural setting exists in places in both the southern and northern parts of the province, which include numerous long-lived faults and faulted zones that may have facilitated access of kimberlitic magmas from the deep mantle to the surface; (3) there are stratigraphically and geochemically anomalous bentonites which may be derived from local volcanic or kimberlitic extrusive centers; (4) there are several areas within Alberta which have been identified by widely spaced sampling to contain anomalous diamond indicator grains that in some places include micro or macro diamonds that have not, as yet, been traced to a bedrock source; and most importantly, (5) there are at least 15 kimberlitic diatremes in north-central and northwest Alberta, of which 10 are known to be diamondiferous and several are reported to have micro diamond and macro diamond counts which are similar to the early phases of sampling of the diamondiferous kimberlites which exist at the economically important Lac de Gras region, N.W.T. In short, we conclude that, at present, ALBERTA IS INADEQUATELY EXPLORED FOR DIAMONDIFEROUS DEPOSITS. ------------------- SELECTED REFERENCES Dufresne, M.B., Leckie, D.A. and Eccles, D.R., In Press. Study of the geochemical and stratigraphic setting of the Shaftesbury Formation in northern Alberta and its potential to host ore deposits; Geological Survey of Canada Open File Report. Dufresne, M.B., Eccles, D.R., McKinstry, B., Schmitt, D.R., Fenton, M.M., Pawlowicz, J.G. and Edwards, W.A.D., 1996. The Diamond Potential of Alberta; Alberta Geological Survey Bulletin No. 63, 158 p. Dufresne, M.B., Olson, R.A., Schmitt, D.R., McKinstry, B., Eccles, D.R., Fenton, M.M., Pawlowicz, J.G., Edwards, W.A.D. and Richardson, R.J.H., 1994. The Diamond Potential of Alberta: A regional synthesis of the structural and stratigraphic setting, and other preliminary indications of diamond potential; Alberta Research Council Open File Report, 1994-10, 349 p. Dufresne, M.B., Henderson, B.A.,Fenton, M.M., Pawlowicz, J.G. and Richardson, R.J.H., 1994. The mineral deposits potential of the Marguerite River and Fort McKay areas, Northeast Alberta; Alberta Research Council Open File Report, 1994-9, 67 p. Eccles, D.R., Dufresne, M.B. and Kjarsgaard, B.A., 1997. Heavy mineral geochemical analysis of the Mountain Lake Diatreme; In Geology of a Late Cretaceous possible kimberlite at Mountain Lake, Alberta - chemistry, petrology, indicator minerals, aeromagnetic signature, age, stratigraphic position and setting; Geological Survey of Canada Open File 3441, p. 159-174. Eccles, D.R., Dufresne, M.B. and Lywood, P., In Press. Reconnaissance study of diamond and metallic mineral potential for the Kakwa/Wapiti area, west-central Alberta; Alberta Geological Survey Open File 1997-04. Fenton, M.M., Pawlowicz. J.G., Andriashek, L.O., Dufresne, M.B., Chao, D., Price, M. and Goulet, D., In Press. Wapiti Map Sheet 83L: Quaternary geology, till mineralogy and geochemistry, preliminary report; Alberta Geological Survey Open File Report. Fenton, M.M., Pawlowicz, J.G. and Dufresne, M.B., 1994. Reconnaissance mineral and geochemical survey with emphasis on northern Alberta; MDA Project M92-04-006, year 2; Alberta Research Council Open File Report 1994-21. Fenton, M.M., Pawlowicz, J.G. and Dufresne, M.B., 1996. Reconnaissance mineral and geochemical survey with emphasis on northern Alberta: project final report: MDA Project M92-04-006; Alberta Geological Survey Open File Report 1996-07. Hamilton, W.N. and Olson, R.A. 1994. Mineral resources of the Western Canada Sedimentary Basin; in G.M. Mossop and I. Shetsen (eds.), Atlas of the Western Canada Sedimentary Basin, Alberta Geological Survey of the Alberta Research Council, and Canadian Society of Petroleum Geologists, pp. 483-501. Olson, R.A. on behalf of the Alberta Chamber of Resources, 1987. Alberta - Opportunities for Metallic Minerals; a document jointly prepared by Trigg, Woollett, Olson Consulting Ltd., and the Alberta Geological Survey of the Alberta Research Council, and subsequently published and distributed by the Alberta Chamber of Resources. Olson, R.A., Dufresne, M.B., Freeman, M.E., Richardson, R.J.H. and Eccles, R.E. 1994. Regional metallogenic evaluation of Alberta; Alberta Research Council Open File Report 1994-8. Olson, R.A., Iannelli, T.R., and Gilmour, W.R., 1994. Regional Stratigraphic Study, Orientation Heavy Mineral Stream Sediment Study, Southern Alberta Rift, Southwest Alberta (Canada -Alberta MDA Project M93-04-034); Alberta Geological Survey, Alberta Research Council Open File Report 1994-7. Williamson, J., Dufresne, M.B. and Olson, R.A., 1993. The Southern Alberta Rift in southwest Alberta, Program to Identify Targets for Metallic Mineral Exploration; Alberta Research Council Open File Report 1993-13A and 13B. ------------------------ --END! -j :>