61
ognition of uranium provinces, 305-335. Vienna: Interna tential of the Motzfeldt Centre, South Greenland. Rapp. tional Atomic Energy Agency. Grønlands geol. Unders. 145, 66-73. Steenfelt, A. & Kunzendorf, H. 1979: Geochemical methods Tukiainen, T. 1988: Niobium-tantalum mineralisation in the in uranium exploration in northern East Greenland. In Watt Motzfeldt Centre of the Igaliko Nepheline Syenite Complex, erson, J. R. & Theobald, P. K. (ed.) Geochemical explora South Greenland. In Boissonnas, J. & Omenetto, P. (ed.) tion 1978, 429-442. Rexdale, Ontario: Association of Explo Mineral deposits within the European Community, 230-246. ration Geochemists. Berlin: Springer Verlag. Taylor, S. R. & McLennan, S. M. 1985: The continental crust: its composition and evolution, 312 pp. Oxford: Blackwell Scientific Publications. Thomassen, B. 1989: Evaluation of the niobium-tantalum po- A. S. & T. T., Geological Survey of Greenland, Copenhagen.
Registration of kimberlites and other potentially diamond-bearing rocks in Greenland
Lotte Melchior Larsen
Kimberlites are potentially diamondiferous rocks. Some information about occurrences of kimberlites They have been found at a number of localities in and related rocks in Greenland is published, as cited Greenland (Fig. l), notably in the Holsteinsborg-Sar above. However, much unpublished information re fart6q region and south of Frederikshåb (Andrews & sides in the Geological Survey of Greenland (GGU) in a Emeleus, 1971, 1975, 1976; Larsen, 1980; Scott, 1977, variety of forms ranging from Ph.D. and other theses 1979, 1981; Thy et al., 1987). Prospecting for diamonds through internal reports from scientists and mining and kimberlites was carried out by several mining com companies to scattered field notes and samples from panies in West Greenland in the years 1970-1988. many mapping teams. All mining company reports rele In recent years it has been realised that other rocks vant in this connection are now available to the public. than kimberlites may carry diarnonds. Some lamproites In order to provide interested parties with more easy are now known to carry significant amounts of dia access to this very heterogeneous information source, a monds (Scott-Smith & Skinner, 1984; review by Berg computer-based registration system has been estab man, 1987), and also ultramafic lamprophyres some lished at GGU, covering all the currently known occur times contain a few diamonds (Rock, 1986; Hamilton & rences of kimberlite, lamproite and ultramafic lampro Rock, 1990). Such rocks are also known from various phyre. localities in Greenland. The potentially diamondiferous rocks kimberlite, Registration lamproite and ultramafic lamprophyre are all of very deep-seated origin, hence the diamonds which are only Each known locality has been given a number. The stable at more than 150 km depth. They are all volatile first part of the number is that of the Kort- og Matrikel rich and strongly potassic, and distinction between the styreisen (KMS, formerly Geodetic Institute) 1:250000 three groups involves a complex set of mineralogical topographical map sheet on which the locality is sit and geochemical criteria. They occur mostly as thin uated, while the second part is a consecutive number. dykes and sometimes as narrow vo1canic pipes. The This allows the number of localities within a given map rocks weather easily and tend to be covered by soil and sheet to increase with time as necessary. For each local vegetation. Because of this they are very elusive rocks, itYexisting information is compiled in a standard form, and it is difficult to establish a true picture of their as shown by the example in Table 1. In some instances distribution in a region. the information available amounts only to a locality and
Rapp. Grønlands geol. Unders. 152, 61-65 (1991) © GGU, Capenhagen. 1991 62 TaiJIe I. Examp/e af detai/ed information 72" registered for a /oea/ity K Kimberlite
L Lamproite Locality no: 65V1.2 C:oordin;ltes: 65.392 -52.400 U Ullramafic Plaee namc: Alanguarssuk, Søndre Isortoq south lamprophyre COiJst Rock lype: Kirnberlitc 70" Field dcs<:riplion: Dykl' 0.6-2 rn thick. orient
·Coorflinales': Latitudc and longi{udc in dccimi:ll dcgrecs. Thc 66" minus sign indiC,ltc:s western longitude. 'Primary !ocaliti: Originallocality nurnbcr from field notes or thesis given for case of access to thc original souree.
J refercnce. while Jt the other cxtreme a whole thesis 64" may be written ovcr one loeality. Fæ"ngehavn U~" :L ~ A t prescnt tilc total numbcr of localities rcgistcrecl is ---""l,~ "o around .s00. The detailed information about localities, "\ as shown in Table l. will bl' available as computer o ~i," \ printOLHs on rcqucsl. A summar)' list has been compi1cd Frederikshåb UU~ \ Isblmk ( ,U-, \ giving only numher. coordinates and rock type, as ~S '..., \ shown by the cxamplc in Table 2. This list, togethcrwith FrederikShåb"~K--" \ distribution maps and c1escriptiolls af the main rock U«~ K ~ groups. will hc availahle as Open File Series 9112. ~~t-'"~, ,,~!u " • ~I U I Information about the kimbcrlitc localities is planned Ivigtut e;;,> ~ \ r;7. Ci6U l,,) to bc inc!lIcicci in the Greenland Mineralis;Jtion Data C\> Qoo" L Bank. GREENMIN.
60" 52" 48" Distribution Fig. I. Distribution ol' kimberlites, larnproitcs and ultramafic The localities are very unevcnly distribllted, depend larnprophyres in western Greenland. ing Url the faet Lh.Jt the rocks uften occur in swarms. and un lhe degrcc ol' detail with which an area has becrl invesligatecl. Figurc l shows the location ol' the main land, and as two uHramafic lamprophyre c1ykes of Tcrti swarms. The distribution of localities Oll the 1:250 000 ary age from Scoresby Sund, East Greenland. (Occur topographic map shects in \Vest Greenland is shown in renees of carbotlatites and more s,-lIic lamprophyres are Table 3. Occurrenees of the rocks in queshoJl ,nc ex not includccl in the compilatiorl.) Thc large numbcr of trcmcly scarce elsewhere in Greenland; they are knowll kimberlite occurrcnccs registcrcd on map shcet 66V2 ollly from the Caledonian ultramafic, ultrapotassie S0ndrc Strømfjord is due to a combination af tile two Batbjerg complex from Kangcrdlllgssllaq, Eas1 Grccn- facts Illcntioncd above: there is a large kimberlite 63 Table 2. Summary list af localities with kimberlite and related rocks in the Sukkertoppen district (map sheets 65Vl and 65V2)
Loc. no. Lal. (N) Long. (W) Rock type
65Vl 1 65.4588 -52.7078 Mica-rich ultramafic lamprophyre 65Vl 2 65.392 -52.400 Kimberlite 65Vl 3 65.35833 -51.8843 Kimberlite 65Vl 4 65.30751 -52.3008 Kimberlite 65Vl 5 65.303 -52.267 Kimberlite, alkali basalt 65Vl 6 65.26129 -51.7824 Kimberlite 65Vl 7 65.22633 -51.9873 Kimberlite 65Vl 8 65.21247 -52.1980 Kimberlite 65Vl 9 65.18161 -52.2965 Kimberlite 65Vl 10 65.08441 -52.1794 Kimberlite 65Vl 11 65.08306 -52.0328 Kimberlite 65Vl 12 65.45 -52.80 Carbonatitic lamprophyre (kimberlite?) 65V2 1 65.40225 -51.7013 Micaceous lamprophyre 65V2 2 65.37000 -51.5518 Micaceous lamprophyre 65V2 3 65.37560 -51.5381 Micaceous lamprophyre 65V2 4 65.38238 -51.5185 Micaceous lamprophyre 65V2 5 65.32469 -51.6905 Kimberlite 65V2 6 65.30165 -51.6460 Kimberlite 65V2 7 65.29249 -51.7114 Kimberlite 65V2 8 65.19748 -51.5421 Kimberlite 65V2 9 65.19843 -51.5286 Kimberlite 65V2 10 65.19373 -51.5198 Kimberlite 65V2 11 65.08149 -51.7148 Kimberlite 65V2 12 65.37806 -51.5319 Micaceous lamprophyre
Coordinates (latitude and longitude) are given in decimal degrees. The minus sign indicates western longitude. swarm, and the rocks have been systematically searched margin of the Archaean craton (map sheets 61V1, for (Larsen, 1980). The lack of reported occurrences 62V1); these are c. 220 million years old. References from the map sheets 67V2, 68V1 and 68V2, covering are cited above in the introduction. Kimberlite dykes eastern Nordre Strømfjord and the Egedesminde and have also been reported from Ingia, at 72°N (Smith, Christianshåb districts, may be due more to a lack of 1981), but little is known about this occurrence. detailed work than to an absence of occurrences - this is A few microdiamonds were found in bulk rock sam not known at present. On the other hand the absence of ples from the Pyramidefjeld and Midternæs kimberlites reported occurrences in the very well investigated Godt (Geisler, 1972), and two microdiamonds were reco håbsfjord region (map sheets MV1 and MV2) must vered from large stream sediment samples from the reflect a real absence of occurrences there. SarfartOq region (Brunet, 1974, 1976). The Sukkertop pen kimberlites have not been investigated for dia monds. Kimberlites Kimberlites occur in three major 'swarms' in West Lamproites Greenland: (1) In the Holsteinsborg-Sarfartoq region at the northern margin of the Archaean craton (map Lamproites were intruded into shear zones in the sheets 66V1, 66V2, 67V1); they are c. 600 million years Proterozoic continental collision zone north of the Ar old. (2) In the Sukkertoppen region in the central part chaean craton around 1230 million years ago (Scott, of the Archaean craton (map sheets 65V1, 65V2); these 1979, 1981; Thy et al., 1987; map sheets 66V1, 67V1); are also c. 600 million years old. (3) In the Pyramide they are mostly leucite lamproites, a type which nor fjeld-Midternæs-Nigerdlikasik region at the southern mally does not carry diamonds. A smalllamproite pipe 64 Table 3. Number af lacalities with kimberlite, 1981, 1984), and in the Sukkertoppen region in associ lamproite and ultramafie lamprophyre in western ation with the Qaqarssuk carbonatite complex (Larsen Greenland et al., 1983; unpublished data). A few dyke occurrences near Færingehavn (map sheet 63V1), of which one is a possibie kimberlite, are also Mesozoic. KMS ultramafic Ultramafic lamprophyres only contain diamonds in 1:250 000 map sheet kimberlite lamproite lamprophyre total very rare instances; these melts are usually generated at lower pressure than kimberiites, well outside the stabil 60V I 1ulianehåb 12 12 itYfield of diamond. 60V2 Nanortalik 4 4 61Vllvigtut 26 40 66 61 V3 Narssarssuaq 40 40 Conciusions 62VI Frh. Isb!. 1 36 37 63VI Færingehavn 1? 5 6 A computer-based registration system for potentially 65V1 Sukkertoppen 10 2 12 diamondiferous rocks in Greenland has been estab 65V2 Majorqaq 7 5 12 66VI Holsteinsborg 37 24 5 103 lished at GGU, thereby providing interested parties 66V2 Sdr. Strf. ø 115 11 128 with easy access to the existing, very heterogeneous 67Vl Ndr. Strf. V 5 6 11 body of information about occurrences of such rocks. 69V2 lakobshavn 1 56 57 The few microdiamonds yielded by the kimberiites at 71 VI Svartenhuk H. 4 2 6 the northern and southern margins of the Archaean Total 206 31 218 494 craton show that the lithosphere beneath Greenland is capable of yielding diamondiferous rocks, provided that KMS: Kort- og MatrikelstyreIsen (formerly Geodetic Institute). their origin is sufficiently deep. The best prospect for The total number of localities on a map sheet is in some cases larger future investigations is considered to be the kimberiites than the sum of kimberlites, lamproites and ultramafic lamprophyres, because for some localities the rock cannot be properly identified. from the Sukkertoppen region, in the central part of the The name 'ultramafic lamprophyre' is used sensu lato and encom Archaean block. However, whereas dykes are known, passes a rather large variety of rock types. no pipes have been found in this area (Lappalainen, On the map sheets not listed there are no registered localities. For 1972). Another prospect is the lamproite in the Disko western Greenland these comprise 59Vl, 61V2, 63V2, MVl, MV2, Bugt area; the known pipe is very small, but there may 67V2, 68Vl, 68V2. 69Vl, 70Vl, 70V2, 71V2 and all sheets north of 73°N. be other, as yet undiscovered occurrences. The swarm of ultramafic lamprophyres in the same region, and of the same age, may perhaps have some diamond poten of mid-Proterozoic age occurs in the lakobshavn region tial, because the rocks show affinities to diamondiferous (L. Skjernaa, unpublished data; map sheet 69V2); its olivine lamproites. geochemistry seems akin to the diamondiferous lam proites of Bergman (1987). References
Ultramafic lamprophyres Andrews, J. R. & Emeleus, C. H. 1971: Preliminary accountof kimberlite intrusions from the Frederikshåb district, South Ultramafic lamprophyres occur in a number of dyke West Greenland. Rapp. Grønlands geol. Unders. 31, 26 pp. swarms. One swarm in the lakobshavn region (map Andrews, J. R. & Emeleus, C. H. 1975: Structural aspects of sheet 69V2) is mid-Proterozoic, c. 1650-1750 million kimberlite dyke and sheet intrusion in south-west Green years old (Marker & Knudsen, 1989; unpublished data). land. In Ahrens, L. H., Dawson, J. B., Duncan, A. R. & A number of occurrences in South Greenland forrned Erlank, A. J. (ed.) Physics and chemistry of the Earth 9, part of the widespread Gardar igneous activity 1100 43-50. 1300 million years ago (e.g. Upton & Emeleus, 1987; Andrews, J. R. & Emeleus, C. H. 1976: Kimberlites of West map sheet 60V1, 60V2, 61V1, 61V3). At least three, Greenland. In Escher, A. & Watt, W. S. (ed.) Geology of and probably four, swarms were emplaced into the Ar Greenland, 574-581. Copenhagen: Geological Survey of Greenland. chaean craton during the Mesozoic period when rifting Bergman, S. C. 1987: Lamproites and other potassium-rich and crustal thinning in the Davis Strait took place in the igneous rocks: a review of their occurrence, mineralogy and first phase of the prolonged continental break-up proc geochemistry. In Fitton, J. G. & Vpton, B. G. J. (ed.) ess. These swarms occur south of Frederikshåb (map Alkaline igneous rocks. Spec. Pub!' geol. Soc. Lond. 30, sheet 61V1; Walton & Arnold, 1970), around Frede 103-190. rikshåb Isblink (map sheet 62V1; Hansen, 1979, 1980, Brunet, J. 1974: Concessions granted to Charter Consolidated 65
Limited in the areas of Holsteinsborg and Frederikshåb in mafic lamprophyre dykes in the Archaean of the Ata area, western Greenland. Report on exploration. Charter Consol central West Greenland. Rapp. Grønlands geo/. Unders. idated Ltd. intern. rep., 12 pp. 145,23-28. Brunet, J. 1976: Report on the investigation of the Holsteins Rock, N. M. S. 1986: The nature and origin of ultramafic borg concession, western Greenland. Charter Consolidated lamprophyres: aln6ites and related rocks. J. Petrology 27, Ltd. intern. rep., 25 pp. 155-196. Geisler, R. A. 1972: Investigations on the Renzy Mines Lim Scott, B. H. 1977: Petrogenesis of kimberlites and associated ited Frederikshåb concession, Greenland, to June 15, 1972. potassie lamprophyres from central West Greenland. Un Renzy Mines Ltd. intern. rep., 6 pp. published Ph.D. thesis, Univ. Edinburgh, 133 pp. Goff, S. P. 1973: The mineralogy and geochemistry of a kim Scott, B. H. 1979: Petrogenesis of kimberlites and associated berlite dyke from Søndre Isortoq fjord, South-West Green potassie lamprophyres from central west Greenland. In land. Unpublished M.Ph. thesis, Leicester Univ. Boyd, F. R. & Meyer, H. O. A. (ed.) Kimberlites, dia Hamilton, R. & Rock, N. M. S. 1990: Geochemistry, mineral tremes, and diarnonds: their geology, petrology, and geo ogy and petrology of a new find of ultramafic lamprophyres chernistry. Proc. 2nd int. kimberlite con/. 1, 190-205. Wash from Bulljah Pool, Nabberu Basin, Yilgarn Craton, Western ington: Arner. geophys. Uno Australia. Lithos 24, 275-290. Scott, B. H. 1981: Kimberlite and lamproite dykes from Hol Hansen, K. 1979: Lamprofyrgange fra Frederikshåbs Isblink, steinsborg, West Greenland. Meddr Grønland Geosci. 4, 24 syd vest Grønland. Unpublished thesis, Univ. Copenhagen, pp. 83 pp. Scott-Smith, B. H. & Skinner, E. M. W. 1984: Diamondif Hansen, K. 1980: Lamprophyres and carbonatitic lampro erous lamproites. J. Geology 92, 433-438. phyres related to rifting in the Labrador Sea. Lithos 13, Smith, B. H. S. 1981: Report on the laboratory investigation of 145-152. rock samples from western Greenland. Charter Consoli Hansen, K. 1981: Systematic Sr-isotopic variation in alkaline dated Ltd. intern. rep., 14 pp. rocks from West Greenland. Lithos 14, 183-188. Thy, P., Stecher, O. & Korstgård, J. A. 1987: Mineral chem Hansen, K. 1984: Rare earth abundances in Mesozoic under istry and crystallization sequences in kimberlite and lam saturated alkaline rocks from West Greenland. Lithos 17, proite dikes from the Sisimiut area, central West Greenland. 77-85. Lithos 20,391-417. Lappalainen, P. 1972: Magnetic surveys of kimberlites and Upton, B. G. J. & Emeleus, C. H. 1987: Mid-Proterozoic e1ectromagnetic surveys in Fox Valley and Ulamertoq. Kryo alkaline magmatism in southern Greenland: the Gardar litselskabet Øresund AJS intern. rep. 127, 2 pp. + app. province. In Fitton, J. G. & Upton, B. G. J. (ed.) Alkaline Larsen, L. M. 1980: Lamprophyric and kimberlitic dykes asso igneous rocks. Spec. Publ. geol. Soc. Lond. 30, 449-471. ciated with the Sarfart6q carbonatite complex, southern Walton, B. J. & Arnold, A. R. 1970: Plutonic nodules in West Greenland. Rapp. Grønlands geol. Unders. 100,65-69. lamprophyric carbonatite dykes near Frederikshåb, South Larsen, L. M., Rex, D. C. & Secher, K. 1983: The age of West Greenland. Bul/. Grønlands geol. Unders. 91, 26 pp. carbonatites, kimberlites and lamprophyres from southern (also Meddr Grønland 190(5)). West Greenland: recurrent alkaline magmatism during 2500 million years. Lithos 16, 215-221. Marker, M. & Knudsen, C. 1989: Middle Proterozoic ultra- L. M. L., Geological Survey of Greenland, Copenhagen.
5 Rapport ur. 152