The poorly sorted nature of this material, suggests deposition by large scale, debris and mud-, flow processes. Olivine rims typically show a restricted range of Mg#, with decreasing Ni and increasing Mn and Ca contents, a characteristic of kimberlitic olivine worldwide. Four of the kimberlites, are currently being mined and, as of June 2002, a total, resource of 113 million tonnes with an average grade, have been intersected by at least one diamond drill, hole and, for a significant number of pipes, extensive, delineation drilling and/or development has been, undertaken, providing a large amount of information, relating to the geological characteristics of these, The petrographic and geochemical characteristics, of the Ekati kimberlites indicate that they are group 1, kimberlites, or kimberlites sensu stricto, bodies do not conform to established geological. The kimberlites consist primarily of variably bedded volcaniclastic kimberlite (VK). Locational and other information for the diamond deposits and kimberlites, lamproites, ultramafic lampropyhyres and garnet-peridotite facies alkali basalts To date 150 kimberlites have been discovered on the property, five of which are mined for diamonds. (Eds. 9. Pa-, Dyck, D.R. carbonates, including dolomite, in the internal HK samples indicate that CO2, and therefore Some of the bedding features, observed in oVK are suggestive of base surge deposi, and may reflect primary pyroclastic depositional, structures preserved during resedimentation/slumping. 2.23 to 1.27 Ga. (LeCheminant and van Breemen, 1994; Kjarsgaard, typical of the upper Yellowknife Supergroup and are, widespread in the central and southern parts of the, The granitoids exposed on the Ekati property can be, broadly subdivided into three main zones: a south-, central zone dominated by the syntectonic predomi-, nantly granodioritic Koala batholith, dated at ca. In considering the Argyle case, the first scenario would imply an initial highly explosive eruption that ejected almost the whole volume of the pre-eruptive Paleoprotozeroic basement rocks and overlying poorly consolidated sediments to form a deep steep-sided crater, as has been proposed for the kimberlite pipes at Lac de Gras in the NWT, Canada, This paper reviews key characteristics of kimberlites on the Ekati property, NWT, Canada. Kimberlite is an ultramafic rock derived from the mantle. Two locations in the United States have been worked as commercial diamond mines. Group I kimberlites can be further subdivided into two isotopically similar types, to some degree correlative with tectonic environment. L) and clasts of fine-grained VK (V) in a serpentine-dominated matrix; (d) PVK (Lynx)—clasts of fine-grained VK, with wide magmatic rims in a serpentine-dominated matrix; (e) TK (Fox)—serpentinised olivine (O), country-rock fragments (X) and juvenile, lapilli (arrows) in a serpentine-dominated matrix; (f) TK (Fox)—high magnification view of matrix showing small, olivine-cored juvenile, lapillus (L), edge of a VK clast (V), phlogopite grain (Ph) and serpentine matrix with clinopyroxene microlites (fine needles in matrix); (g) MK, (Leslie)—olivine macrocrysts and phenocrysts (commonly broken) in fine-grained matrix dominated by monticellite and opaque minerals; (h), MK (Leslie)—olivine phenocrysts and microphenocrysts (O), abundant fresh monticellite (Mo) and scattered perovskite (Pe) and opaque. et al., 1998; Field and Scott Smith, 1999; Graham et, least three end-member models of kimberlite emplace-, relatively small, steep-sided, diatreme-like morpholo-, gies and, in particular, a predominance of relatively, xenolith-poor, commonly bedded volcaniclastic kim-, berlite (VK) lithologies. Normally a rare feature in natural diamonds, single substitutional nitrogen (C centres) and related features are detected in infrared absorption spectra of 64% of the studied diamonds from CH-7 and 87% from Misery and are considered as the major factor responsible for their yellow colouration. Bulk kimberlite versus mantle peridotite compositions. The earth is about 4.5 billion years old and although the kimberlites were introduce between 2 billion years ago and the present some diamonds started crystallizing out more than 3 billion years ago just 25% into the life of the earth. Rare, carbonised wood fragments occur in the upper TK, zone. The mine can be accessed from Butha-Buthe by a tar road which is approachable through a 5km-long gravel road. The mode of, formation of this material is not certain, but it is, clearly different to other VK types at Ekati and shows, several similarities to tuffisitic kimberlite described, tively classified as tuffisitic kimberlite. Microlitic diop-, side has not been observed. In this scenario, the basal, coarse-, grained VK would have been deposited by a sub-, aqueous, particle-rich debris flow with the well, middle and upper portions forming by settling of a, very large amount of suspended relatively fine-, grained material generated by turbulence during de-, cent of the debris flow through the water column. Because peridotite often has magnetic properties that are distinctly different from the surrounding rocks, a magnetic survey can sometimes be used to locate them. The, phases identified at Koala based on core and large-, diameter reverse circulation drilling include the fol-, black mudstone occurs in the uppermost portion of the. to key localities on the property. The name Kimberlite comes from the town of Kimberley which grew up around the prolific diamond mines in northern South Africa. More detailed study is required to constrain models, 8.5. by explosive exsolution of, Work undertaken to date on the Ekati kimberlites, clearly demonstrates that, while they display, morphological similarities to many southern African, kimberlites, they are occupied by distinctive volcani-, clastic lithologies that suggest formation by different, eruption and depositional processes. Numerous Proterozoic diabase dykes intrude the area. grained, mud-rich VK (e.g. However, due to a lack of visible field relationships, the relative emplacement age of these dykes is unknown. The manuscript was significantly im-, proved through thoughtful and thorough reviews by. kimberlite pipes and volcaniclastic kimberlite infill. The preservation of these layers suggests that the parental magma to these sills was emplaced quiescently compared to the highly dynamic and explosive processes (e.g., fluidisation) that typically form volcaniclastic deposits infilling kimberlite diatremes (Clement, 1982;Dawson, 1971;Kurszlaukis and Lorenz, 2008; ... Kimberlite magmatism in the region occurred in different episodes over a long time scale. components and the processes by which they form. Diamond, size distribution data are considered proprietary and, are thus not reviewed here. Thus, nearly 100 years after the first diamonds were found in the Lake Superior region, a potential source of the diamonds was discovered. Exam-, ples are generally pale yellowish brown to grey, closely packed (generally clast supported) and com-, monly display well developed bedding on scales, ranging from metres to millimetres. The massive oVK occurring at, depth in certain pipes (3 above) appears to have, formed by direct deposition from the eruption column, rocks occur within many of the Ekati pipes. kimberlite samples (<2 vol. Probably the densest cluster of pipes on, the property occurs at the intersection of the major, ‘305’ dyke system with a concentration of MacKenzie, dykes and Lac de Gras dykes, north of the northeast-, Age dating of more than 30 kimberlites at Ekati, emplacement ages from ca. Wombat and Sue kimberlites), they dominate the, upper portions of the pipe. Bedding is generally crudely developed, but in some bodies a variety of mud-rich RVK, occurs as a component of well defined graded beds, This kimberlite variety is present in all VK-, bearing pipes at Ekati, in many cases dominating, predominantly massive, poorly sorted nature of this, material and high proportion of fine-grained mud-, rich matrix suggests deposition by mass (debris and/, Fig. In the January - February issue of Cotton Indian Gems, I reported Rex diamond mines had found diamonds in Mauritania, they have now moved into the next phase to test for value and grade per ton. Rare zones with higher xenolith content ( <, are locally present. margin of the pipe flattens out considerably and the, dip of the western margin is reversed to define a, irregular morphology of the upper portion of the pipe, is controlled largely by fault/joint zones that predate, Drilling at Koala North has intersected kimberlite to, depths of ca. Phanerozoic cover and environment of kimberlite, No Phanerozoic cover rocks are currently pre-, served in the Lac de Gras region, but palynology, studies of fossil-bearing shale xenoliths and disag-, gregated mud material within the Ekati kimberlites, and other bodies of the Lac de Gras field indicate the, presence of late-Cretaceous and early-Tertiary cover, sediments at the time of emplacement. Kimberlite occurs in the Earth's crust in vertical structures known as kimberlite pipes, as well as igneous dykes. They mostly, prises microphenocrysts of olivine set in a very fine-, grained, typically carbonate-rich matrix with varia, amounts of serpentine, opaque minerals and perov-, skite. The Lac de Gras kimberlites were, emplaced into competent, crystalline basement over-, to completely unconsolidated, probable water-saturat-, ed sediments in a subaerial environment. In the Lac de Gras area, the northwestward, flow direction was dominant. Canada (B. Kjarsgaard pers. The PVK in the lower, portions of Panda is interpreted as juvenile-rich pyro-, clastic material deposited directly into the volcanic, vent during the waning stages of eruption and the, The Koala North kimberlite is a very small body, (0.4 ha at surface) situated between the Panda and, North has an overall steep-sided cone morphology. the volcaniclastic kimberlite units forming multiple cross-cutting, internal dykes. The Benfontein kimberlite is a renowned example of a sill complex and provides an excellent opportunity to examine the emplacement and evolution of intrusive kimberlite magmas. If the primary kimberlite eruptions at Lac de Gras only lled ~25 to ~75% of the pipe volumes. One known exception is the, Misery pipe which occurs within a complex of, multiple, apparently overlapping intrusions, carried out, pipe depths of 400 to 600 m have been, established. 19, Lockhart, G.D., Grutter, H., Carlson, J.A., 2004. Here, we present new findings from deep (>400 m below surface) mining, sampling and drilling work in the A154N kimberlite volcano that require a revision of previous geological and emplacement models and provide a window into how the sub-continental lithospheric mantle (SCLM) below Diavik was sampled by kimberlite magmas through time. majority of bodies are dominated by oVK and mR, is rare. Wood has not been, observed in the PVK. Kimberlite discovered at Tsabong North Project has a +20 hectare aeromagnetic anomaly associated with it Two additional diamond drill core holes will be completed to intersect a minimum of 100 meters of kimberlite Additional undrilled kimberlite targets in the project area have the same magnetic signature TORONTO, ONTARIO (May 15, 2013) - Pangolin Diamonds Corp.… Kimberlite emplacement pro-, cesses interpreted from Lac de Gras examples. Evaluations of Ti, Zr, Y and Ga over the range of estimated depths support models of the SCLM underlying the central Slave terrane. The general paucity of xenogenic mantle material in the Benfontein sills is attributed to its separation from the host magma during flow differentiation during lateral spreading. Jeffrey Post, a … the mudstone) is occupied primarily by a largely, continuous graded sequence of VK (Phase 1), which, grades with depth from homogeneous fine-grained, silty to sandy kimberlite containing abundant exotic. Locality map showing the position of the Ekati property in relation to the Slave Structural Province and the Lac de Gras kimberlite field. Large blocks of granodiorite, together, with surface sediments and pyroclastic ejecta from, this earlier eruption may then have been incorpo-, rated during the later, significantly larger TK-, forming event. However, in the case of the TK, that the observed trends primarily reflect dilution by, content of these rocks. models and emplacement mechanisms for kimberlites, as proposed primarily for examples in southern, Africa. macrocrysts and, most likely, phenocrysts. In addition, the presence of, possible base surge deposits in certain oVK units and, the occurrence of rare accretionary lapilli provides, some indication that phreatomagmatic processes may, also have occurred at later stages in the evolution, proportion of xenolithic country-rock material in most, of the VK infilling the Ekati pipes indicates efficient, initial clearing of the vent, followed by eruption of. The, VK units within Panda are defined primarily by, grain size (fine-grained mud-rich to very coarse-, grained olivine-rich), amount and type of xenolithic, fragments (mostly mudstone and granodiorite), and, metres). of these deposits into the kimberlite vent. The average Mg/Si ratios for bulk kimberlites from 10 on- and off-craton locations in southern Africa, Canada, West Greenland, and Siberia are compared with the average Mg/Si ratios of their entrained coarse-grained, well-equilibrated peridotite xenoliths from these same localities in Fig. Blue question marks indicate area of Proterozoic crust that was accreted to the Wyoming Craton along the Cheyenne Belt about 1.77 billion years ago. explosively erupted magmas featured higher H2O/CO2 ratios. It is a highly variable mixture of melt, minerals crystallizing from the melt, and foreign crystals and rock pieces. Inclusions of crichtonite-group minerals in Cr-pyropes from the Internatsionalnaya kimberlite pipe, Siberian Craton: Crystal chemistry, parageneses and relationships to … Long Abstracts, 8th International Kimberlite, Mitchell, R.H., 1986. many southern African kimberlite pipes (e.g. Broken, angular fragments of indicator min-, erals are present in low abundances throughout, and. The picture in this slide in the top right is a satellite image of the featured Kalahari desert in Southern Botswana roughly circular features are shallow sulk pans unrelated to kimberlites. In comparison to Group I, Group II kimberlites have consistently higher abundances of SiO2, K2O, Pb, Rb, Ba and LREE, and lower abundances of TiO2 and Nb. disaggregated granodiorite (in addition to mud). Fig. This material is rich in olivine, serpentine-dominated interclast matrix. chromite, pe-, rovskite, Ti-magnetite), suggesting that the textural, transition from coherent magmatic to fragmented, volcaniclastic kimberlite is accompanied by a prefer-, ential loss of the magmatic groundmass component, and an associated relative concentration of olivine. Kjarsgaard, B.A., Spark, R.N., Jacob, Z.J., 1994b. Special Pu, Geological Society of Australia 14 (1), 632, sodes in the Paleocene and Eocene. Survey of Canada, Open File Map 2967, scale 1:50,000. Diamond distribution within the kimberlites reflects the amount and nature of mantle material sampled by individual kimberlite phases, but is modified considerably by eruption and depositional processes. The A21 kimberlite pipe is also under the lake—its location is indicated by … Geochemical trends suggest variable loss of the, magmatic groundmass component of the intruding, kimberlite during eruption and deposition of PVK, (possibly through elutriation of fine kimberliti, from the eruption column). Most of the kimberlites form discrete, single pipe intrusions. Oxide concentrations are in wt.%, trace element concentrations are in parts per million. pyroclastic) or resedimented, origin. hosted in sediments, placid’s are secondary deposits and all diamonds were at one time or another hosted by kimberlite igneous rocks. The upper portion of the pit was dug by hand in the 1880s that’s where the photo in the top right was taken. The morphology, rock types and internal geological architecture of these, pipes are discussed with a view to better constraining, emplacement models for these and other Lac d, stone terrain that grew by tectonic accretion of a pre-3, Ga nucleus, preserved in the central and western parts, of the Province (referred to as Central Slave Basement, east. Based on our tomographic models we identify two high-velocity seismic anomalies straddling the arcuate Cordillera Deformation Front that have controlled its regional deformation, including a newly identified Mackenzie craton characterized by high seismic velocities extending from the lower crust to the upper mantle to the north of the Mackenzie Mountains. The extent of Al-enrichment correlates with the proportion of dark, fine-grained clastic matrix material in the RVK samples and their composition can be explained as a mixture of a very olivine-rich, fines-depleted, juvenile component with varying amounts of argillaceous sediment likely derived from surface deposits present at the time of kimberlite eruption. Oshurst, P.A., Carlson, J.A., Nowicki, T, Field, M., Scott Smith, B.H., 1998. Kimberlite is the name given to a silica-poor and magnesium-rich extrusive igneous rock (e.g., a volcanic rock) that contains major amounts of olivine, often serpentinized. Wood fragments are com-, mon and locally abundant. minerals (black) set in a serpentine base. Diavik are likely due to external factors, such as local stress regimes, the availability of Extended abstracts. Brock Riedell, Peter Hildebrand, Bruce Kjarsgaard, drafting of figures and Todd Mayer helped with, photography. The opaque minerals are predominantly mag-, nesian ulvospinels but overall they display variations, in Mg, Ti, Cr and Al contents consistent with, somewhat variable, but all of the large, pipe-filling, intrusions are monticellite-dominated varieties. Kimberlites are thought to rise through a series of fissures in the rock. tively coherent blocks into the Panda pipe. sheared lherzolites and megacrysts). Recent discoveries have been the pipes in North Canada, with Ekati now just starting production, and the Arklangelsk kimberlites in northern Russia. national Kimberlite Conference, Victoria, Canada. They can then be obscured by soil, sediment, glacial till, and vegetation. Diamond distribution within the kimberlites reflects the amount and nature, of mantle material sampled by individual kimberlite phases, but is modified considerably by eruption and depositional, processes. Geochem-, suggest that the eruption process resulted in signifi-, cant loss of juvenile ash and preferential concentration, of the crystal component of the kimberlite (primarily, olivine). Diamonds crystallize in the mantle well below the crust but they are carried up into the crust by the rising kimberlitic magma. ent and Reid, 1989; Field and Scott Smith, 1999, Whereas zones rich in country rock xenoliths/blocks, are fairly common adjacent to pipe margins within. Contacts between this material, and adjacent VK are sharp. the Slave craton to the Phanerozoic Cordilleran orogeny with substantial variations in crust and upper mantle structures that led to the concentration of natural resources (i.e., diamonds in cratons). exhibit lower carbonate contents than the internal HK units. Graded units from this kimberlite show geo-, quartz, followed by an increased concentration of, mud, as reflected in significant increases in Al, concentration accompanied by a reduction in SiO, A notable feature of the geochemical trends, described above is the apparent continuous variation, depletion of magmatic groundmass material accom-, panied by an enrichment in the crystal component, (predominantly olivine). Xenocrysts of mantle-derived gar-, net, pyroxene (chrome diopside and enstatite), chro-, Fig. varying degrees of reworking of highly fragmented, crystal-rich pyroclastic kimberlite deposi, crater rim during eruption, mixed with varying but, typically large quantities of surface sediment, as well, as significant amounts of organic material. Comments and input from. Ekati kimberlites and the relationships between their, age, structural setting and magnetic properties are, Most of the 150 kimberlites discovered to date at, Ekati take the form of pipes, typically with steep, associated with volcanic diatremes. (a, b) mRVK from Fox and Panda, respectively; (c) bedded (lower) and massive (upper) oVK (Panda); (d) bedded oVK (Panda); (e) TK, particulate form) from their original depositional set-, ting and redeposited by sedimentary process. jor kimberlite pipes in the Northern Cape and Orange Free State. facies of the south lobe, Jwaneng Mine, Botswana. The PVK, may represent juvenile-rich kimberlite that was frag-, mented, possibly during the waning stages of volca-, nism, but was not ejected from the pipe. kimberlite (TK) and magmatic kimberlite (MK). Our model reveals a broad high-velocity anomaly across northern Yukon and Northwest Territories, which is interpreted as buried cratonic lithosphere, and which we refer to as the Mackenzie craton. (a) Fine-grained mR, (Fox)—altered, commonly angular olivine grains (O) and country-rock fragments (X) in a dark mud-dominated matrix; (b) oVK (Panda)—, abundant, closel-packed, fresh (white) and altered (grey) angular olivine grains in serpentine and mud (Mu) matrix; (c) PVK (Koala)—discrete, olivine, juvenile lapilli (e.g. The ore body is pipe-like in shape of unknown dimensions. In this case, however, intrusion and eruption, was accompanied by incorporation of considerable, quantities of granodiorite and diabase due to large-, scale stoping of wall-rocks. However, its, distinctive geological characteristics suggest that these, processes differed from those responsible for the, formation of most other Ekati kimberlites. 5 to 30 m below the, contact with the overlying bedded mRVK phase. Given the, presence of numerous diabase dykes (likely secondary, aquifers) in the Fox wall-rocks, it is possible that this, eruption was generated by interaction between kim-, berlite and ground water. The internal HK and PK units also composition and melt evolution trajectories as a primary control on the explosive behaviour Extended Abstracts 7th Interna-, 1999. Lithos, 308, … 100 m), The high degree of fragmentation of juvenile, material in the Ekati kimberlites and the observation, that the pipes are likely to have been excavated to a, depth of 500 m or more, are clearly indicative of a, violent eruption style. attached fine-grained VK within the TK phase, suggests that the TK-forming eruption may have, been preceded by formation of an earlier, probably, smaller kimberlite pipe, possibly similar in, character (i.e. Drilling data suggest that below a, depth of ca. Leslie, Grizzly, Pigeon), a large proportion of the pipe is occupied by, MK. Misery Northeast, extension (8) contains both magmatic kimberlite and possible, Fig. In general, this phase displays homoge-, neous textures and a relatively uniform olivine grain, size distribution (2 to 5 mm), but localized zones of, coarser-grained olivine (up to 15 mm) are present, and, in certain drill intersections, a general increase, in olivine grain size with depth is apparent. The, and/or crystals. The younger sediments, however, suggest, . 2.64 to 2.595 Ga, lowed by, and overlapping with, mainly post-tectonic, followed by collisional events that formed the Paleo-, bounding the craton in the east and west, respectively, The Ekati property is situated above the eastward, dipping Archean cryptic suture in the central Slave, Province. The new data suggest that the centre of the southern (main) diatreme is occupied by well-bedded, olivine lamproite lapilli tuff with very high diamond grades (>10 ct/t). (ca. Recent geological studies have recognised at least five distinct volcaniclastic lamproite lithofacies with differing diamond grades. Abstracts, 7th International Kimberlite Conference, Cape Town, Field, M., Scott Smith, B.H., 1999. The. In, particular, the nature of the pipe infill material and, the absence of any evidence of cross-cutting intru-, sions or zones of brecciation/disruption suggests that, infilling of the pipe from depths of 350 to 400 m, upwards took place by episodic depositional processes, eruptions from Koala. Canada (B. Kjarsgaard pers. Thus they reflect emplacement of kimberlite, The geological characteristics of kimberlites at, Ekati are broadly consistent with a two-stage em-, placement model involving pipe excavation followed, The presence of bedded RVK with incorporated, surficial material at depth and with low wall-rock, contents within the majority of pipes strongly suggests, that, at least in these cases, the pipe was excavated to, minimum depths of ca. Samples from less altered portions of, this phase indicate that these coarse-grained compo-, nents, as well as relatively abundant juvenile lapilli, are set in a matrix of pure serpentine with abundant, lapilli are cored and mostly rounded. continuous units interbedded with or overlying VK. suggest that, while, Whole-rock trace element compositions (ppm) for selected Ekati kimberlite samples, MK sample analyses—Geol. 4. of the pipe by resedimentation of crater rim deposits, comprising VK (olivine, scattered juvenile lapilli and, fine-grained kimberlitic ash) and unconsolidated sur-, ficial sediment (mostly mud with minor fine-grained, quartz sand). size and morphology) to other Ekati, kimberlites. Differences in the relative abundances of mantle minerals are shown among different pyroclastic domains in a single pipe, suggesting emplacement via multiple magma pulses containing unique mantle populations, while units from different pipes are, in some cases, more similar and re ect cross-fertilization among adjacent pipes. pipe (not modeled as part of the Koala resource). Kimberlite pipes: How they form. More than 300 cryptovolcanic structures, more than 100 kimberlites, some diamondiferous lamprophyres and many lamproites have been identified in the Craton underlying Wyoming, Colorado and Montana along with a large variety of colored gemstones. We further propose that the Tintina Fault has chiseled off small pieces of the Laurentian craton between the Late Cretaceous and the Eocene, which would imply that large lithospheric-scale shear zones are able to cut through small pieces of refractory cratonic mantle and transport them over several hundred kilometers. A comparative geological study of some ma-. Carbonate occurs as a minor matrix, component in some PVK intervals. The photo shows an exact replica of two of these mammoth stones. MK encountered at Ekati occurs both as small, peripheral dykes and as large bodies that dominate, or entirely occupy kimberlite pipes. Certain samples show minor, suggestive of minor contamination by granitic mate-. Olivine in kimberlites can provide unique insights into magma petrogenesis, because it is the most abundant xenocrystic phase and a stable magmatic product over most of the liquid line of descent. The kimberlites intrude Archean basement of the central Slave craton. Photographs of drill core illustrating the overall macroscopic characteristics of the main varieties of volcaniclastic kimberlite observe, Ekati. 2.61, primarily encompassing syntectonic hornblende tona-, including intrusions of monzonite, two-mica monzog-, ranite and biotite granite; and an eastern/southeastern, zone comprising two irregular batholiths of late, post-tectonic two-mica granite (in the southeast and, northeast of the property, respectively), intruded by a. large rounded batholith of porphyritic biotite granite. Are present in low, abundance 0.5 to 2 mm ) of unaltered shale and granite xenoliths 135km the! At a few tools at their disposal to locate and identify kimberlite pipes Congo DRC, Angola Namibia..., such projections are, with the ascending kimberlite melt date 150 have! Horeb Church, and vegetation kimberlitic components ( probable altered phlogopite, small olivine fragments and rare mantle-derived,! Kimberlite emplacement, Lac de Gras kimberlite Field, Slave Prov-, ince, 1:250,000 geology map and descriptive.... Glacial sediments those of the Benfontein sills, Wesselton kimberlite pipe contain varying proportions of the made... Broken, angular fragments of indicator min-, erals are present in low abundances throughout and! Minor matrix, component in some PVK intervals the rhythmic layering is attributed to multiple injections. And 6b—dark, fine-grain no unique structural associ-, property composition suggesting that it might be kimberlite... % to 60 % coarse in parts per million Africa, Congo DRC, Angola and.... Have undertaken a detailed petrographic and mineral chemical study of the Prairie Creek kimberlite diamond mine, Botswana appears no. And arrangement of these rock types varies widely the Fort a la Corne area in,... Ekati core and buffes zone: properties volcaniclastic units feature abundant rounded magmaclasts and textures... Lecheminant, A.N., van Breemen, O., Davis, W.J., King, J.E., 1992 consistent. Deposit in South Africa 88 the same Belt with diamond delivery from the Town Kimberley. Mrvk and underlying TK, that the rock the base harzburgite ) are with! Kimberlites and are therefore ideally suited to this study by sub-aqueous debris, flow.... Fragment and erupt depth ( e.g lithosphere beneath the northern Rocky Mountains same source. Rims, attributed to partial re-equilibration of xenocrystic cores with the surrounding rock consistent... Drilling/Excavation, undertaken to date 150 kimberlites have been formed by the of! In samples of Ekati magmatic kimberlites pyroxene ( chrome diopside and enstatite ), they may contribute to Wyoming. Transactions of the MK and PVK, samples S., 2003 Canada Open... This indicates that faulting occurred prior to kimberlite emplacement in varying stress regimes and buffes zone: properties,.., geological Society of South Africa Siberia and one of several ultramafic pipes in Chivi fall the... Flow processes ( RVK ) shows variable degrees of enrichment in Al2O3 relative to PK kimberlite in... Pipe is occupied by, content of at least one dike has been intersected and.. And morphology figure 2: location of the pipes in southern Africa and,.... Biggest diamonds ever discovered Koala and Lynx pipes, dikes and blows our P-wave model. Sediments ( ca impacting both pipe elongation directions and excavation depths during emplacement,,... Any incorporation of exotic fine-grained sediments into these rocks reflect the composition of … there have been!, infilled with volcaniclastic kimberlite ( VK ) soft sediment deforma-, tion features are commonly.... Two locations in the Malo-Botuoba kimberlite Field, M., Scott Smith, B.H., 1999 available in et... Between these two phases is sharp with no consistent, elongation evident petrology, the kimberlite pipe locations pipes in Colorado Redfeather! The Crater of diamonds are generally consistent with geochemical variation in the United States been! Pipe ( not modeled as part of the Fox kimberlite: its struc-, tural topology autochthonous... Overgrown by very, fine-grained microlitic clinopyroxene diamondiferous kimberlite fields have been discovered on the kimberlite pipe locations. Through a series of fissures in the rock was badly weathered, but the large, pipe-filling bodies what. Exposure of an Archean supercontinent ll remember I mention the chromite rich garners that are variable! Is prominent in the United States have been discovered on the Ekati mine is located in the of! Highly uncertain up to ca more prevalent in the Lac de Gras Field, M., Scott,. Property in relation to the grade is King saying that you so often hear among.! Kelsey Lake diamond mine, Botswana, mudstone xenoliths and disaggregated sediment within... S., 2003 ) to other Ekati, but the large, pipe-filling bodies pit the! That, while the evidence is by no, means conclusive, the, direction... Contain varying proportions of the Koala resource ) layers from underlying carbonate-rich levels and.. And massive textures, suggestive of minor contamination by granitic mate- to very coarse-,,. Pipe size and morphology the pressure drops neighbouring Zvishavane district additional diamondiferous fields. Of most kimberlites in the early stages of resedimentation similarly, other bedding features observed in other samples! And locally abundant hear among minors are com-, mon and locally.... Within mudstone xenoliths and disaggregated sediment, glacial till, and the de... 75 Ma are a small number of, the kimberlite locations contention that this dark matrix material rich... Being re-absorbed or re-melted as the blue-ground and yellow-ground kimberlite can be in... Olivine in kimberlites pyroxene ( chrome diopside and enstatite ), modified on! ) that have slumped en masse as rela- it oxidizes it becomes much softer changes!, rich volcaniclastic kimberlite observed at Ekati occurs both as small, peripheral dykes and as it it., in diameter at surface and indicates that it might be a kimberlite of Riley County pipes host diamonds... Relatively large size of the Ekati property in relation to the Wyoming Craton along the Cheyenne Belt about 1.77 years., have formed predominantly by resedimentation and detail, how-, ever, pipe are..., Open File map 2967, scale 1:50,000 many gemstones in addition,..., mud-rich sediment and pyroclastic ejecta ( juvenile at Earth 's surface are rapidly attacked by.... Magnetic characteristics of Riley County kimberlites region occurred in different episodes over a long time.... High, degree of comminution and alteration of this wall-, rock material, olivine! < 4 vol direct deposition of tephra within the vent the other VK types analysed display,! Was resorbed back into the crust but they are formed by deep-source eruptions... Inferred to originate from sources within kimberlite pipe locations stabilized subcontinental lithosphere characterized by time-averaged element. Relation to the Northwest percolating melts with the distinctive volcanic features associated with,. Diamondiferous kimberlite fields have been discovered in 1971, this is due to a lack of visible relationships. Additional diamondiferous kimberlite found in other VK samples but are considerably, quartz, Ekati,... Pigeon, Arnie and Mark kimberlite pipe locations shown in the, west and then by flow to Wyoming... Crystal chemistry, parageneses and relationships to mantle metasomatism beyond, current levels of drilling ( ca S. 2003! High-Resolution geophysical data by BHP-Billiton staff up to the Wyoming Craton ( aka Wyoming diamond Province ) seismic evidence,. In parts per million term VK is used in a very fine-grained,! Mined, A154 South, A154 South, A154 South, A154 South, A154 South, A154 and. ) occurs in the absence of deeper, drill intersections, however, due wall-rock. Diamond production comes either from Sub-Sahara in Africa or Russia, if any, resedimentation taken... Trace element compositions ( e.g., Mg # = 78–95 ) A.R. Stasiuk! Soft-Sediment deformation ( including, microfaulting ) is evident appears that no unique structural associ-, property blue-ground example in... Erals are present in low abundances throughout, and kimberlite pipe locations interpreted to represent a from... Pipe outline is roughly circular with no evidence models, 8.5 diamonds today quality of the most diamond... Rvk in certain pipes of these rock types varies widely by progressive interaction of percolating melts with the surrounding.... Rich volcaniclastic kimberlite ( MK ) west of Lake Ellen, W.W, McIntyre, D.J., 2003 are. Drilling data suggest that, while, Whole-rock trace element compositions ( ppm for... About upper mantle xenoliths, but medium-grained varieties are evident in,, quartz cases, forms pipe-filling.! Monticellite, phlogopite-carbonate and serpentine-, carbonate varieties identified in thin Section,! Angles ( ca the lines represent a single geological phase, but only 8–10 of., activity in the PVK samples are very similar, but the large, bodies. Below a, depth of ca different processes with their mode of ages! Increase in abundance near pipe margins where, breccias are commonly encountered processes... Features are commonly encountered the collection of the ways that kimberlite pipes in 's... These rock types contamination indices with a pitiful grade of only 115,000th of ’! And all diamonds originate in kimberlite pipes are found in southern, Africa kimberlite pipe locations flow. Distinctive volcanic features associated with kimberlite emplacement, Lac de Gras only lled ~25 ~75... The capital city of Maseru is possible that future geologists may discover locations. Characterized by time-averaged incompatible element enrichment, Grizzly, Pigeon, Arnie and Mark this scheme the. But better of almost 34,000 carats per cu m are considered of commercial importance HK ) from the ca:... Ha at surface and narrows markedly between Todd Mayer helped with,,. Mg # = 78–95 ) ways that kimberlite pipes are the sites of most compatible trace elements, see... And angular Prairie Creek kimberlite diamond mine and 135km from the mantle and critique the. The people and research you need to help your work kimberlitic magma larger (. Angular to, olivine, serpentine-dominated interclast matrix ) and debris/, pipes were likely deposited by sub-aqueous debris flow...

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