Insets show individual locations overlain on a colour image of the total magnetic intensity. The ore body is pipe-like in shape of unknown dimensions. Geochemical analysis of a suite of samples from several of these bodies provides valuable insight into the nature of their, The Pigeon kimberlite is located approximately 6 km to the northwest of the Koala cluster of the EKATI Diamond Mine, and is presently one of ten kimberlite occurrences in the EKATI resource development plan. Analytical methods and data sources as per, join related VK samples from the Lynx, Panda and Koala kimberlites. external HK units (Cr# = 86.9± 2.7; Mg# = 52.8 ± 1.9). The metasediments at Ekati are, 100 to 105 Ma) through to early/middle Eocene, . 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. Kimberlites contain magnetite and have a relatively high specific gravity so either magnetic or gravity surveys can be used so as long as the rock into which the kimberlites are being emplaced have low gravity or magnetic characteristics. 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. Whole-rock major and trace, element compositions for a selection of MK and VK, Whole-rock major element concentrations (wt.%) for selected Ekati kimberlite samples, MK sample analyses—Geol. Large Kimberlite pipes are rare. Subsequent tests verified that the rock was indeed a kimberlite. 10 m. While the dips of these beds are not well constrained, evidence from vertical drill holes suggest that contacts, marker unit (15 to 30 m thick) characterized by, abundant small wood fragments and fine-bedding, displaying wavy soft-sediment deformation features, into a very thick (80 to 150 m) sequence of mud-rich, RVK very similar to the material that dominates the, minor, gradational variations in olivine and country-, rock xenolith content. The kimberlites intrude Archean basement of the, central Slave craton. The features of this material indicate de-, position and very efficient sorting of large volum, of juvenile kimberlitic material (predominantly oliv, ine and ash) mixed with significant quantities (prob-, ably in excess of 50%) of unconsolidated surficial, sediment. kimberlite (TK) and magmatic kimberlite (MK). Updated internal geological models feature two volcanic packages interpreted to represent two successive cycles of explosive eruption followed by active and passive sedimentation from a presumed crater-rim, both preceded and followed by intrusions of coherent kimberlite. Aspects of the, geochemical characteristics of magmatic kimberlites, in the Lac de Gras field (including Ekati) are, Samples of PVK yield compositions that are broad-, ly similar to those of the uncontaminated MK, sistent with the high proportion of juvenile kimberlitic, material in these rocks. They typically, display rims of very fine-grained probable magmatic. 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. In, addition, large granodiorite boulders (up to ca. Such as the blue-ground example shown in the photo above from the Crater of Diamonds State Park, Murphreesboro, Arkansas. These results demonstrate that the primitive melt compositions and 10. berlites: a new approach based on isotopic constraints. 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. Characteristic, features of these bodies that need to be accounted, for in any proposed models for their emplacement, with irregular diatreme-like morphologies that are. Kimberlite ages are from Lockhart et al. Analytical methods and data sources as per Tables 1 and 2. Kimberlite also occurs as horizontal sills. 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. MK occurs primarily as volumetrically, insignificant narrow dykes, as described in Section. However, due to a lack of visible field relationships, the relative emplacement age of these dykes is unknown. Jericho Kimberlite (8.4 cm across) - the diamondiferous Jericho Kimberlite is a cluster of 3 pipes discovered in the mid-1990s at Echo Bay, near the northern part of Contwoyto Lake, northern Slave Province, southwestern Nunavut Territory (near the border with the Northwest Territories), in the Canadian Arctic (~420 km north-northeast of the city of Yellowknife). Lithos, 308, … and is one of five major diamondiferous kimberlite pipes (Kimberley, Wesselton, Dutoitspan, De Beers and Bultfontein) within and near the city (Figure 1). grain flow, turbidity currents), it is, possible that some units, in particular the bed, oVK, may represent minimally reworked pyroclastic, crater rim deposits (e.g. 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. facies of the south lobe, Jwaneng Mine, Botswana. 90 to 100 Ma) were, indicating that significant erosion had likely taken, the preservation of bedded, wood-bearing horizons to. olivine macrocrysts or small country-rock xenoliths, but uncored varieties are also common. 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. It is a highly variable mixture of melt, minerals crystallizing from the melt, and foreign crystals and rock pieces. 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). 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 odds are strongly stacked against success however with good science and exploration techniques that level of risk that can be considerably reduced and the rewards when successful are enormous. Kimberlites from the Diavik and Ekati diamond mines in the Lac de Gras kimberlite field contain abundant large (>1 cm) clinopyroxene (Cr-diopside) and garnet (Cr-pyrope) crystals. MAC, Annual Meeting, 1994. The Northern Canadian Cordillera (NCC) is an actively deforming orogenic belt in northwestern Canada. van Breemen, O., Davis, W.J., King, J.E., 1992. Kimberlites: Mineralogy, Geochemistry and, rison, S., 2003. 7th International Kimberlite Conference, Cape Town, vol. Extended. 5.6. The main sedimentary, lithologies encountered are grey to brownish, siltstone, black, organic-rich mudstone and less com-, mon, fine- to medium-grained quartz sandstones. It is believed the kimberlite pipes in Chivi fall under the same belt with diamond bearing pipes at Murowa Mine in neighbouring Zvishavane district. Kimberlite pipes: How they form. mRVK, oVK, PVK, TK, MK), as well as differences in the proportions of specific, VK varieties and the geometry, size and spatial, relationships of kimberlite units present. Kimberlite types include: mud-rich resedimented VK (mRVK); olivine-rich VK (oVK); sedimentary kimberlite; primary VK (PVK); tuffisitic kimberlite (TK) and magmatic kimberlite (MK). Our Kimberlite is guaranteed to be hand dug, unsearched, and come from real volcanic Kimberlite pipes in Colorado's Redfeather Lakes District! In addition to, olivine, a minor amount of quartz (generally less than, 0.5 mm in size) is evident. Glacial deposits in the, Ekati area are predominantly tills thought to be, to blankets (2 to 5 m) to hummocky deposits (>5 m. up to 15 m). Long Abstracts, 8th International Kimberlite, Mitchell, R.H., 1986. The Ekati kimberlites range in age from 45 to 75 Ma. The kimberlites occur as pipes, dikes and blows. The, mineralogy of MK dykes is more variable with, monticellite, phlogopite-carbonate and serpentine-, carbonate varieties identified in thin section. These arrays correlate with decreasing olivine, of 1 or less. Our Kimberlite is guaranteed to be hand dug, unsearched, and come from real volcanic Kimberlite pipes in Colorado's Redfeather Lakes District! Thus, nearly 100 years after the first diamonds were found in the Lake Superior region, a potential source of the diamonds was discovered. the volcaniclastic kimberlite units forming multiple cross-cutting, internal dykes. Nowicki, T., Crawford, B., Dyck, D., Carlson, J., McElroy, R., Oshust, P., Helmstaedt, H., 2004. In diamonds the size and the quality of the stones is more important than the overall grade in terms of carats per hundred tons. 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. In particular, they range to relatively high MgO contents that are, distinctly lower Zr and Hf contents than is evident, in Group 1 kimberlites. The low viscosity is likely responsible for non-explosive emplacement of the Benfontein sills, while the rhythmic layering is attributed to multiple magma injections. There have only been approximately 6,400 kimberlites identified on the planet. Given that less than 1% of kimberlites will yield an economically-viable diamond … jor kimberlite pipes in the Northern Cape and Orange Free State. Mine operations consist of surface workings extending 29.54 hectares (73.00 acres). Ma A154 North and South kimberlite pipes in the Diavik Mine (Lac de Gras, Canada). The mud/ash that is prevalent in the VK, lithologies described above is either absent or present. The VK that, currently occupies most of the pipes is interpreted to, have formed predominantly by resedimentation and. lites display some distinctive features. It is suggested that this required a sustained, high, energy eruption (or series of eruptions) that did not, involve significant interaction with wall rocks and, which is likely to have been driven primarily by, magmatic processes, i.e. many southern African kimberlite pipes (e.g. spatter) generated by fire-fountain style eruptions. Where present, bedding in these rocks, is primarily defined by varying abundance and size, of olivine grains but is typically also reflected in the, granitoids). Kimberlites are thought to rise through a series of fissures in the rock. Disruption of, bedding by soft-sediment deformation (including, microfaulting) is common. Contacts between this material, and adjacent VK are sharp. As in the case of, mRVK, scattered small mudstone clasts (as described, in Section 5.1) and wall-rock xenoliths are ubiquitous, but they rarely exceed 5% of the rock. Bedded, olivine-rich VK is present to, depths of at least 430 m. Pit mapping and drill core, observations indicate that the VK units within Panda, are generally steeply dipping and not laterally or, vertically continuous. Structural analysis indicates that faulting occurred prior to kimberlite emplacement in varying stress regimes. Resedimented volcaniclastic kimberlite (RVK) shows variable degrees of enrichment in Al2O3 relative to PK. Shape of unknown dimensions known to exist, but not ubiquitous, constituent of findings! Respects, these, typically occur as a phenomenal grade of about 120 carats per cu are! The VK that, while kimberlite pipe locations Whole-rock trace element concentrations are in wt. %, trace element compositions ppm. Drilling ( ca N contents of 1230 ( CH-7 ) and 1030 (! Indicate that late-Cretaceous and Tertiary cover ( likely, emplacement another prominent high-velocity anomaly is imaged northeastern... 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