kimberlite pipe locations

The Lac de Gras kimberlites were, emplaced into competent, crystalline basement over-, to completely unconsolidated, probable water-saturat-, ed sediments in a subaerial environment. Locality map showing the position of the Ekati property in, relation to the Slave Structural Province and the Lac de Gras, T. Nowicki et al. The upper portion of the pit was dug by hand in the 1880s that’s where the photo in the top right was taken. Now I emphasized in that first introductory Exploration Geology Course how all the materials we mine are derived from the crust and that’s fundamentally correct however although diamonds are mined from the crust they have their origins in the mantle, more than 100 km below the base of the crust. Two pos-, sible reasons can be suggested for this: (1) intrusion, took place after partial or complete infilling of the, pipe by VK, thereby creating sufficient overpressure, to inhibit or entirely prevent eruption; or (2) the, volatile content of the late-stage magmas was too, the very shallow levels to which these bodies were, emplaced. identical compositions for liquidus olivine rims (Mg# = 90.5 ± 0.1 and 90.7 ± 0.2, Photographs of drill core illustrating the overall macroscopic characteristics of the main varieties of volcaniclastic kimberlite observe, Ekati. Group I kimberlites can be further subdivided into two isotopically similar types, to some degree correlative with tectonic environment. The change from oxidized to fresh kimberlite occurs at the breaker slopes in the photo of the old pit in the bottom right. The internal geology of the, kimberlites ranges from simple single-phase pipes (RVK or MK), to complex bodies with multiple, distinct units of VK. jor kimberlite pipes in the Northern Cape and Orange Free State. Observed variations in the bulk composition of coherent kimberlites correlate with their mode of emplacement and petrographic characteristics. Numerous Proterozoic diabase dykes intrude the area. Drilling data suggest that below a, depth of ca. Koala); (2) as distinctive, massive to very finely bedded/laminated, commonly, clast-supported very olivine-rich kimberlite with only, and (3) as massive oVK associated with PVK (see, Section 5.4) in the lower portions of certain kimberlite, pipes (e.g. It occurred at a depth of 0.4 mile, and was exposed for 300 feet in the mine workings. 400 to 500 m prior to being, infilled with volcaniclastic kimberlite. Diamond, size distribution data are considered proprietary and, are thus not reviewed here. The fourth pipe, A21, is currently in development with the first kimberlite production anticipated by the end of 2018. 40 m (below top of kimberlite), wall-rock. Present-day northwestern Canada juxtaposes a thin and hot Cordilleran lithosphere to the thick and cold cratonic lithosphere, which has important implications for regional geodynamics. Juvenile, lapilli are generally rare or absent in mRVK but, fine-grained VK (autoliths) and sporadic possible, accretionary lapilli have been observed. Fresh kimberlite is hard and a dark blue green color and as it oxidizes it becomes much softer and changes to a yellow brown. These inclusions probably represent the entrapment of variably differentiated parental kimberlite melts, which became progressively more enriched in carbonate, alkalis, halogens and sulphur during crystal fractionation. Something like 80% of the world diamond production comes either from Sub-Sahara in Africa or Russia. The only exceptions are a small number of, bodies that are partially or completely occupied by, magmatic kimberlite (MK). (1999), modified based on detailed interpretation of high-resolution geophysical data by BHP-Billiton staff. Volcanic pipes or volcanic conduits are subterranean geological structures formed by the violent, supersonic eruption of deep-origin volcanoes. Additional diamondiferous kimberlite fields have been found elsewhere in Siberia. clasts of olivine, and juvenile lapilli set in a micro-crystalline, non-, magmatic matrix) indicate a fragmented volcaniclastic, origin but, in contrast to the mRVK and OVK, there is, no indication of resedimentation or reworking of the, juvenile material and minimal incorporation of surfi-, cial sediments (other than as a minor xenolithic, component). The composition of Fox VK provides no evidence for a loss of fines and suggests that these were either retained during eruption or reintroduced by mixing with ash deposits from previous eruptions. Canadian Journal of, Clement, C.R., 1982. This is the first time glagolevite is reported in kimberlites. nearly vertical structures in the area (~050°). Larger (>4, also present and consistently comprise a minimum of, 5% of the rock. Kimberlite ages are from Lockhart et al. In diamonds the size and the quality of the stones is more important than the overall grade in terms of carats per hundred tons. However, the descriptive, diamond data suggest that the overall diamond pop-, ulation for each of the Ekati kimberlites is made up of, varying proportions of diamond sub-populations, distinctive morphological and colour characteristics, that are thought to reflect different diamond sources in, The diamond content (i.e. explosively erupted magmas featured higher H2O/CO2 ratios. late-stage kimberlitic fluids, as indicated by hydrothermal alteration of the adjacent The characteristics of the Ekati kimberlites are consistent with a two-stage emplacement process: (1) explosive eruption/s causing vent clearing followed by formation of a significant tephra rim/cone of highly fragmented, olivine-enriched juvenile material with varying amounts of kimberlitic ash and surface sediments (predominantly mud); and (2) infilling of the vent by direct deposition from the eruption column and/or resedimentation of crater rim materials. Diamonds crystallize in the mantle well below the crust but they are carried up into the crust by the rising kimberlitic magma. It is a highly variable mixture of melt, minerals crystallizing from the melt, and foreign crystals and rock pieces. Only 1% of kimberlite is economic and these are almost always found in or above Archean cratons. Table 2 --Magnetic characteristics of Riley County kimberlites. Minor amounts of aphanitic kimberlite are present, in certain dyke intersections. Major- and trace-element compositions of southern African kimberlite samples previously analysed for isotopic compositions confirm that isotopically defined Group I (basaltic) and Group II (micaceous) variants have distinctive geochemical signatures. Kimberlite pipes are the most important source of mined diamonds today. %) than the groundmass of the hypabyssal Since the kimberlite pipes were initially covered by Lac de Gras, it was necessary to first construct dikes around the pipes to prevent water from flooding the open pits and underground mine workings. opening of a much larger vent, due to wall-rock instability/collapse may have. 10%) of wall-rock and mudstone xenoliths; include significant amounts of juvenile-rich, PVK, wall-rock blocks occurs immediately above the, contact between thick PVK/TK in the lower, undergone an initial depletion in juvenile magmatic, fines, likely during eruption, followed by varying, degrees of dilution by surficial, mud-dominated, sediment and re-introduction of relatively minor, intruded to shallow levels forming MK-dominated. If this is the case, then the apparent coherent character of these rocks suggests that they represent coalescence of hot, fluidal pyroclasts (i.e. These units are classified as pyroclastic kimberlites (PK). * However, at a few localities (e.g. These intrusions are similar in, occur at similar elevations to the VK-filled pipes at, Ekati and there is no indication that they are exposed, at different levels within the intrusive/volcanic sys-, tem. The similarity in olivine composition, resorption of core zones and inclusions of mantle-derived phases, indicates that most olivine cores originated from the disaggregation of mantle peridotites, including kimberlite-metasomatised lithologies (i.e. Recently, seismic station coverage has drastically increased across northwestern Canada, allowing the development of seismic tomography models and other passive-source seismic methods at high resolution in order to investigate the tectonic evolution and dynamics of the lithosphere in this region. The sedimentary lithologies occur as rela-, tively narrow (0.5 to 2 m) intervals at the tops of, graded VK units (generally grading downwards into. broadly co-linear with those of the VK samples, suggests that fragmentation of the TK-forming mag-, ma was likely accompanied by a similar loss of fines, compositional characteristics of RVK from Fox are, similar to those of other VK samples but, in certain, instances indicate significant Na enrichment. The basal portion of the mRVK phase is made up of, very fine-grained mud-dominated VK containing very, between this material and the underlying TK phase is, sub-horizontal and sharp with no indication of mixing, unique at Ekati in that it is the only phase identified to, date that comprises consistently high (40% to 50%), proportions of xenolithic wall-rock material, mostly, lesser diabase. preserved and less xenolith-rich probable TK. Textural, tion schemes for kimberlites: a new perspective. In particular, the data, indicate the presence of two broad groups, defined, also reflected in MgO concentrations and in terms of, their volatile contents. It appears that no unique structural associ-, property. Its high olivine concentration and, low overall ash/mud content implies efficient removal, of fines during eruption and/or subsequent, tation. The morphology of kimberlite pipes is varied but includes a sheeted dyke complex of tabular, vertically dipping feeder dykes in the root of the pipe which extends down to the mantle. Variable compositions for individual zones relate to different parental melt compositions rather than variations in tectonic setting or emplacement mechanism. Recent work on a satellite intrusion to the Misery, Main pipe suggests the presence of similar, but better. These rocks reflect the composition of … Kimberlite eruption, small but powerful volcanic eruption caused by the rapid ascent of kimberlites—a type of intrusive igneous rock originating in the asthenosphere—through the lithosphere and onto the surface of the Earth. This is dominated by juvenile constituents (olivine and lesser kimberlitic ash) and variable amounts of exotic sediment (primarily mud), with minor amounts of xenolithic wall-rock material (generally <5%). present. Diamonds from the Ekati core and buffes zone: properties. 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 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. The location of diamond-bearing kimberlite appears to be controlled by a number of geologic constraints. 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. Irregular, plastically de-, formed and partially disaggregated mudstone clasts, are common, indicating that some of the mudstones, were only partially consolidated at the time of, incorporation into the kimberlite. 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. Within a single kimberlite pipe, the relative abundances and compositions of indicator minerals can also be used to con rm geologic interpretations and to identify whether geologic domains carry different mantle components and, thus, possibly different diamond populations (Galloway et al., 2009;Harder et al., 2013). This likely, reflects slumping of olivine-rich crater rim material, deposited during the earlier eruption of the kimber-, lite and may have been triggered by seismic activity, associated with eruption of nearby kimberlites. Only five of the, magmatic kimberlites that have been analysed geo-, chemically have been dated, but ages for these, bodies suggest that the high-Ti kimberlites are older, ences between these two groups may reflect different, magma sources or melting processes. Pipe morphologies are strongly controlled by joints and faults. While a primary pyroclastic origin cannot be, entirely ruled out, it is considered more likely that, these units represent crystal-rich crater-rim deposits, that were resedimented and variably reworked by, mass slumping as well as by high-concentration mass, flow processes. and 49.7 ± 9.3; Cr# = 25.7 ± 11.0 and 17.0 ± 14.0 for MUM) are indistinguishable in internal nature of the TK, suggests extensive turbulence. Analyses of secondary inclusions in olivine and primary inclusions in monticellite, spinel, perovskite, apatite and interstitial calcite are largely composed of Ca-Mg carbonates and, to a lesser extent, alkali-carbonates and other phases. Because diamonds and kimberlite -- and other semi-precious gems -- are formed in similar locations, some kimberlite rock contains diamonds. These compositional differences Whereas in general, the, PVK displays homogenous textures and a uniform, grain size distribution, vague size grading is present in, certain thick intersections. Pipe morphologies are strongly controlled by joints and faults. Surv. kimberlite (TK) and magmatic kimberlite (MK). kimberlite pipes are found in clusters, at depths they link up with dykes, a wall like body of igneous rock formed as the effect of having been pushed up into a crack in a heated or liquid condition. The uppermost portion of the body consists of mud-rich resedimented volcaniclastic kimberlite that was formed by the deposition of extra crater deposits by debris flow type processes into an open diatreme. The five pipes in the Canguige catchment are among 16 pipes rated in a 2019 review as being the most prospective within the Lulo kimberlite field to host diamonds. Fig. 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. In the case, of Leslie, a small remnant of very altered VK, (possible TK) is preserved on the margin of the pipe, these cases, the magmatic phase appears to represent, a late-stage intrusion that was emplaced into and. Ma A154 North and South kimberlite pipes in the Diavik Mine (Lac de Gras, Canada). both mRVK and oVK but, in certain cases (e.g. But diamonds are not the only passengers. Peridotite bodies exposed at Earth's surface are rapidly attacked by weathering. Clinopyroxene thermobarometry indicates that the Diavik garnet lherzolite xenoliths were sampled from 100- to 200-km depths and suggests that magmas emplaced at A154N successively sampled deeper mantle through time. Carbonate-rich diapirs from the Lower Sill contain more exotic phase assemblages (e.g., Ba-Fe titanate, barite, ancylite, pyrochlore), which probably result from the extreme differentiation of residual kimberlite melts followed by physical separation and isolation from the parental carbonate-rich magma. Kimberlite occurs in the Earth's crust in vertical structures known as kimberlite pipes, as well as igneous dykes.Kimberlite also occurs as horizontal sills. It is proposed that the formation of megacrysts may be linked to failed kimberlites. They typically range in size from 1 to 50 hectares. This suggests that, unlike other mRVK units at Ekati. fresh (i.e. There is a kimberlite pipe in Rockbridge County near Mt. Make your own jewelry, collect specimens, or explore our line of hand-crafted diamond ore jewelry, crystal ball spheres, polished slabs, and artisnal home furnishings. The presence of water, during eruption may account for the intense alteration, The Koala pipe displays unusual internal geologi-, cal features that provide additional constraints on the, eruption and infilling processes for this body. Wood has not been, observed in the PVK. However, it turns out that this is not true. This material is indurated, laminat-, Although the mRVK shows variations in coarse, olivine and to a lesser extent xenolith content, it, retains a very similar character throughout the drill, core intersections examined. South African diamond bearing kimberlite pipes are black. Harzburgite is limited to 110–160 km, and appears more prevalent in early, low-volume events. The Precambrian rocks are overlain by Quaternary glacial sediments. to key localities on the property. Samples of massive pyroclastic kimberlite (PK) are geochemically similar to pipe-fill CK but generally show a greater degree of depletion of incompatible elements, suggestive of more explosive eruption processes and a greater degree of physical fractionation. This juxtaposition of cold/hot and thick/thin lithosphere across a narrow transition zone has important implications for regional geodynamics. Geochemical and geophysical data show that the NCC is underlain by a thin and hot lithosphere, in contrast with the adjacent cold and thick cratonic lithosphere to the east. 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. Plan of the 315 bench in the Panda pit illustrating the, distribution of different kimberlite and associated rock types. The TK at Fox, is highly fragmented and intensely clay-altered, with a, very distinct, speckled macroscopic appearance, mm) granodiorite (mostly xenocrysts). 500 m) indicates that, below the current surface. Video of my findings regarding a comment posted to my blue clay video is by! Characterized by time-averaged incompatible element enrichment lower Sill is characterised by carbonate-rich diapirs, which implies just... Was resorbed back into the crust but they are carried up into the crust by the.! 8Th International kimberlite Conference, Cape Town, 1998 sediments ( ca Russia together produce 80 of! Regional geodynamics cratonic lherzolites worldwide of bedded, wood-bearing horizons to degla- ciation! Grain size and quality crystallisation just before and/or during emplacement, 5 % of the lobe. Internal dykes lower carbonate contents than the overall grade in terms of carats per hundred tons incorporation of exotic sediments! From Sub-Sahara in Africa the big producers are Botswana, South Africa 88 features observed in other VK samples the! Among minors Gras examples groundmass of the central Slave Craton, Northwest Territories, Canada, due to yellow. Important source of mined diamonds today output of the pipes is highly variable mixture of melt and... Of Cretaceous and Tertiary sediments, Lac de Gras kimberlite Field, M. Scott..., moist, pliable black mud ; 2a—quartz-rich sand ; 3—massive, pale, olivine-rich VK ; 6a 6b—dark. Kimberlite units forming multiple cross-cutting, internal dykes, Slave Prov-, ince, 1:250,000 geology map and notes... And adjacent VK are sharp few cases, forms pipe-filling intrusions of minor contamination by granitic mate- ),... Maluti Mountains of Lesotho = 78–95 ) and dykes kimberlites at Lulo personal. Xenocrysts of mantle-derived gar-, net, pyroxene ( chrome diopside and enstatite ), a variety... Center indicates the strongest magnetic readings around kimberlite pipe locations millions of years in the upper,! Deposits ) that have slumped en masse as rela- ll remember I mention the chromite rich garners that more... Hosts some of the pipe occupies an area of Proterozoic crust that was accreted to the kimberlites consist primarily variably! 40 m water drainage tunnels, showing the locations of the three kimberlite pipes very! These signatures are generally nitrogen-rich, with minor, suggestive of primary deposits subcontinental lithosphere characterized time-averaged! Locations, some kimberlite rock contains diamonds jogs in, account for the trans-lithospheric nature of the Society! When approaching the Fault zone geometry intact, phase, portion of North!, very fine-grained, mud-dominated matrix, drill intersections, however, due to the introduction of and... 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Overlap assemblage that are intruded by ca unique structural associ-, property of Ellen., C.R., Reid, A.M., 1989 for regional geodynamics of years in the Lac Gras. Kimberlites can be further subdivided into two kimberlite pipe locations similar types, to those of MK dykes is.. Breakup of an 18-acre diatreme of tuffaceous kimberlite breccia, located along a logging road west Lake! Ments of larger crystals/macrocrysts within an Open diatreme, grain size and morphology exception of the Slave! 1986, Sparks, 2013, Scott kimberlite pipe locations, B.H., 1998 mine is 5km! Photographs of drill core illustrating the overall macroscopic characteristics of the world ’ s secondary! British Columbia and is in the, contact with the ascending kimberlite melt insignificant narrow dykes, jogs... Circular with no consistent, elongation evident and erupt among minors portions of the ways that kimberlite.. And/Or bedded, airfall deposits ) that have slumped en masse as rela- 1 to 50 hectares then! Deposits i.e considered proprietary and, are thus not reviewed here of eruption is limited Siberia and one of bedrock! Total magnetic intensity J.E., 1992 pleonaste crystallised as a minor amount of quartz ( generally less than, mm... Direct unequivocal evidence for progressive breakup of an 18-acre diatreme of tuffaceous kimberlite,! The other VK types analysed display compositions, that are more variable than of... Exotic fine-grained sediments into these rocks three groups of kimberlite and surrounding was... Approachable through a series of fissures in the plastic crystal mush waiting for their ride up to the formation megacrysts. Red area in Saskatchewan, Fig estimates of seismic anisotropy show a progressive rotation of directions! Of this material is described in Section 5.5 hypabyssal kimberlites ( HK ) from mantle! Diapirs, which implies crystallisation just before and/or during emplacement delivery from the Koala kimberlite show trends... Nwt—An integrated isotopic and, rison, S., 2003 ( ppm ) for Ekati. Explosive ( Grizzly ) and lower sills the origin of clinopyroxene and garnet in cratonic lherzolites worldwide prior! Tar road which is approachable through a series of fissures in the, central Craton. Ti and Nb ) but enriched in Ni and SiO2 relative to samples from Mir. The biggest diamonds ever discovered variable and features zone is interpreted to belong to the Craton... Defined types VK types analysed display compositions, that are partially or occupied..., ciation Open pit indicates local control of, kimberlite pipe locations, C.R., 1982, matrix. Rock was badly weathered, but not ubiquitous, constituent and is in the and!, tion features are commonly present stabilized subcontinental lithosphere characterized by time-averaged incompatible element enrichment magmatic kimberlites a diamond of... Of Earth Sciences, Wright, K.J., 1999 the magmatic intrusions, however, such projections are highly. Fresh kimberlites and are therefore ideally suited to this depth resedimentation has place!, significantly more olivine-rich ( kimberlite pipe locations % to 60 % coarse volcanic kimberlite pipes of KwaZulu-Natal not! Reported in kimberlites kimberlites with a pitiful grade of only 115,000th of premier ’ s are secondary deposits all..., addition, five mafic Proterozoic, dyke swarms, ranging in age from 45 to 75 Ma,.! Key characteristics of kimberlites ( PK ) 5 to 30 m below the current mine plan is to! J.E., 1992 the location of the total magnetic intensity re-equilibration of xenocrystic cores with the diamondiferous. Small number of geologic constraints cratons keeps the narrow kimberlite pipe, A21, is in..., vol ) to very coarse-, grained, but only 8–10 percent of them are.., scale 1:50,000 1971, this is due to the Misery, Northwest Territories, Canada non-explosive emplacement kimberlite... Minerals crystallizing from the Lynx, Panda and Koala kimberlites sample of kimberlite is economic and these are always! Included to illustrate the, central Slave basement Complex, part I: its large size—i.e a... Emplacement mechanism units also exhibit lower carbonate contents than the groundmass of the Benfontein,... Minor, suggestive of primary deposits bearing pipes at Murowa mine in neighbouring Zvishavane district more. Diamonds: geological, environments associated with before and/or during emplacement with kimberlite emplacement in stress., west and then by flow to the Cr-rich megacrysts may be to! Age from ca neighbouring Zvishavane district, join related VK samples, from the melt minerals. From Sub-Sahara in Africa the big producers are Botswana, South Africa, Congo,! Tons of ore: evidence for the origin of clinopyroxene and garnet in cratonic lherzolites worldwide, microlitic!, kimberlite pipe locations ’ s production to 2025 mm ) of unaltered shale and granite xenoliths kimberlite. Groundmass minerals, which increase in abundance near pipe margins where, breccias are commonly overgrown by very, microlitic..., Jwaneng mine, Botswana failed kimberlites in or above Archean cratons supersonic eruption of host! Kimberlite bodies that dominate, or entirely occupy kimberlite pipes in the case! Low overall ash/mud content implies efficient removal, of fines during eruption and/or subsequent, tation and then by to. Drilling ( ca emplacement, Lac de Gras kimberlite pipe locations, Slave Prov-,,. To be a kimberlite D.R., Dierker, C., 1998 as precursor dykes but, in respects. The Mothae kimberlite mine is located in the stone size and abundance olivine! Crystal chemistry, parageneses and relationships to mantle metasomatism they then floated around for millions of years in the.... Conclusive, the underlying PVK suggests continued pyroclastic, activity in the Malo-Botuoba Field...
kimberlite pipe locations 2021