Summary Repor t The Lentiira Diamond Prospect, Eastern Finland Contents Summary 1 Introduction 2 General Diamond exploration in Finlan d The Lentiira Prospect 5 Location and Access 5 Physical features 5 Titles 5 Geological Outline 8 Bedrock Geology 8 Quaternary Geology 1 0 Sampling and Processing 1 0 Results 1 1 Conclusions and Recommendations 1 6 Reports and publications relevant to the Lentiira region 1 8 List of Appendices 20 SUMMARY The Lentiira Diamond Prospect is located in eastern Finland, 50 km north of the town o f Kuhmo, in an area of ready access and good infrastructure . The prospect consists of several claim reservations totalling up to about 80 km2 . The local bedrock comprises Late Archean plutonic rocks, some remnants of greenschists, and abundant Paleoproterozoic hypabyssal mafi c dikes . Quaternary cover includes one till bed up to a few metres thick and locally glacial outwash, sand and gravel . The area has low relief and between drumlins and moraine hillock s the ground may be swampy. Climate is continental with a mean temperature of +1 °C . Winters are rather cold and snow cover may exceed one metre . Snow cover stays in open areas some 190 days per year and frost may penetrate the till down to nearly 2 metres . The Geological Survey of Finland (GTK) has been carrying out regional heavy minerals studies on Quaternary sediments since 1992. The Lentiira Prospect is the first discovery site of kimberlitic indicator minerals from this regional study where a more detailed till sampling ha s been completed. The detailed investigation comprises some 50 surficial and basal till samples . Sample size was 80 kg of -20 mm material of which the -2 .0 mm fraction was taken for sampl e processing using methods and techniques developed at GTK . The investigation revealed kimberlitic indicator mineral fans covering an area of 4 km by 14 km oriented along the younger glacial transport direction . The transport distances of glacial detritus are considered to b e relatively short . In addition, two vertical olivine lamproite dikes about one metre wide wer e discovered in the middle of the study area . Diamond and kimberlitic indicator minerals, chrome pyrope, chromite and picroilmenite were found at 17 sampling sites . Both the dikes and till contained indicator minerals , although G9 and G10 garnets and picroilmenites are known only from till samples . It is typical of the study area that most indicator minerals were found in the fine fraction (0 .25-0.50 mm) of the nonmagnetic heavy mineral concentrate, whilst the coarser fraction contained only a few, if any, indicator minerals . In this investigation a recently developed method for the processing fine fractions was applied . This cost effective processing is based on excellent, near-complete indicator mineral recovery and identification of fine graine d slightly heavy minerals in till samples . The Kuhmo region has been the site of active diamond prospecting for many years, and severa l exploration companies currently hold diamond claims in the region of the study area . However, GTK is not directly involved in prospecting for diamonds but rather has concentrated on regiona l heavy mineral studies and research and development work . This summary report and the tendering procedure is in accordance with the government policy of releasing results to th e private sector at an early stage of exploration . GTK has comprehensive geological and geophysical data available on the region, including regional geological maps, geochemical an d low altitude geophysical surveys . Additionally there are a number of reports and scientifi c articles bearing on different aspects of the area. -1- INTRODUCTIO N General The Geological Survey of Finland is a government funded agency under the auspices of th e Ministry of Trade and Industry of the Republic of Finland. One of the major roles of GTK is i n promoting exploration and mining in Finland . Therefore it is active in performing grass-roo t exploration for industrial minerals and metals and in providing basic geological data, provisiona l deposit modelling and evaluation, and consulting services for mining companies . There is no direct involvement in mining activities by either the Finnish Government or GTK. The Survey headquarters which includes the southern Finland regional office and the R&D section is based in Espoo, 10 km east of Helsinki . Regional offices are located in Kuopio and Rovaniemi. The permanent staff is some 700 persons, including nearly 300 geoscientists and chemists . The Geological Survey of Finland has been carrying out regional heavy mineral studies in northern and eastern Finland since 1992 . The original objectives of this survey were to search fo r kimberlitic indicator minerals that might reveal areas with potential for diamond exploration an d to develop cost effective techniques to process and identify indicator minerals . At the beginning of 1994, with the entrance of Finland into the European Economic Area, Finnish territory wa s for the first time open to international exploration . Since then GTK has successfully processe d several thousand quaternary sediment samples on a contract basis for several external clients. In addition the Survey has continued with its own regional studies, and at present some 2,00 0 samples have been processed into heavy mineral concentrates . The study of these concentrate s is still underway. With respect to sample processing, GTK began the regional survey using an off-the-shel f Knelson Concentrator for preconcentration in the field camps . As the Knelson Concentrator was originally intended for concentrating gold, recoveries for the slightly heavy minerals remaine d low. Therefore GTK modified the concentrator initially to improve the recovery of the coarse r grained indicators using a manual feed . Subsequently a semiautomatic pulp feeder for the Knelson Concentrator was designed . Using this assemblage the recoveries for the finer graine d (down to 0.25 mm) indicators improved drastically, up to some 90% . As the feeder itself acts as a preconcentrator, only a partial drive of the sample was needed which resulted in substantia l savings of time, manpower and water . Additionally, at the end of last year the development of a module to make picking of finer grained indicators cost effective was completed . The Lentiira Diamond Prospect is the breakthrough of this R&D work and it can be expected that severa l other prospects will be reported in the near future . The indicator mineral data bank of GTK was developed as a part of the R&D work on diamon d investigations . The data bank currently include thousands of in house microprobe analyses o n Finnish, Russian, South-African and Namibian samples . Diamond exploration in Finland Diamond exploration was initiated in Finland in the 1980's by a small Finnish copper mining company, Malmikaivos Oy after discovering a train of kimberlite glacial boulders . Malmikaivos -2- Oy established a joint venture with the Australian company Ashton Mining Ltd . in 1986 and in 1994 Malmikaivos Oy became fully owned by Ashton . Ashton's countrywide regional sampling program has identified several separate and distinct areas in Finland from which kimberlite indicator minerals are sourced . Ashton has discovered intrusions of 24 kimberlites and related rocks in Finland and 16 of these are diamond bearing . Two kimberlite clusters are known, one located in Kaavi and the other close to the city o f Kuopio in eastern Finland (Figure 1). Mini-bulk samples have been taken from five of the diamond bearing pipes . At least two of the more closely studied pipes contain substantia l quantities of clear and colourless diamonds . A 23 tonne sample from a pipe of approximatel y two hectares in surface area yielded some 26 carats of +0.8 mm diamonds per 100 tonnes, mos t of which were of good quality. Another pipe, slightly over one hectare in size, contained 13 t o 26 carats per hundred tonnes, based on a 9 .4 tonne sample . Dia Met Minerals Ltd. (AMEX, TSE, VSE), which has been operating in Finland through Oy Alwima Ltd., announced in February 11, 1998 that in addition to continuing exploration on its 100-per-cent-owned Finland project, an agreement has been reached to enter into a joint ventur e with Australian company Ashton Mining Limited on Ashton's Finland diamond project . The joint venture covers two areas in eastern Finland, one of 38,475 km 2 and the other of 40,750 km2. Follow-up sampling has identified indicator mineral trains in these areas, in addition t o those that Dia Met had already discovered. Other companies involved in diamond exploration in Finland include RTZ Mining & Exploration Ltd, Finsearch Oy (De Beers), Glenmore Highlands Inc. (ASE), North Star Diamonds A.S . (Poplar Resources Inc., VSE) and Baltic Minerals Finland Oy. These companies have not released any information concerning their success . The Geological Survey of Finlan d is not engaged in diamond exploration but does offer sampling, sample processing and othe r exploration services for diamond exploration companies, and undertakes regional heavy mineral surveys. By analogy with other shield areas, the potential exists for further and significant diamon d discoveries in Finland. Furthermore, the late Archean terrane comprising much of eastern and northern Finland is contiguous with the Karelia and Kola cratons in Russia, which contain th e major Archangelsk kimberlite province, at the easternmost edge of the shield, and diamond - bearing lamproites at Kostamuksha, near the Finnish border (Figure 1) . Finland offers many advantages for exploration companies . Over 80% of Finland has been flown by GTK airborne geophysical surveys, with raw and processed magnetic, EM an d radiometric data readily available, based on survey line spacings of 200 m and a terrain clearance of 30-40 m. Bedrock and surficial geological mapping also covers a large part of the country a t scales of 1 :100 000 or better, and most data are available in numerical form .
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