Lac des Iles Mine
|Lac des Iles Palladium Mine|
Location: Toronto, Canada.
Products: PGE Deposits.
By product: Gold. Platinum, silver, nickel, and copper.
Owner: North American Palladium Ltd.
GEOLOGICAL SETTING AND MINERALIZATION
The Property is underlain by mafic to ultramafic rocks of the Lac des Iles Intrusive Complex in the Wabigoon Subprovince of the Canadian Shield. The LDI-IC is an irregularly-shaped Neoarchean-age mafic-ultramafic intrusive body having maximum dimensions of approximately 9 km in the north-south direction and approximately 4 km in the east-west direction. The complex incorporates three discrete intrusive bodies viz.:
The North Lac des Iles Intrusion (NLDI) characterized by a series of relatively flatlying and nested ultramafic bodies with subordinate mafic rocks.
The Mine Block Intrusion (MBI), host to all of the stated Lac des Iles mineral reserves and resources (refer to Sections 14.0 and 15.0).
The South Lac des Iles Intrusion (SLDI), a predominantly mafic (gabbroic) intrusion having many similarities to the MBI in terms of rock types and textures. To date, NAP’s exploration activities have been focused on the MBI. The MBI is a small, teardrop-shaped mafic complex with maximum dimensions of 3 km by 1.5 km and having an elongation in an east-northeast direction. The MBI consists of gabbroic (noritic) rocks having highly-variable plagioclase: pyroxene proportions, textures, and structures. The MBI was emplaced into predominantly intermediate composition orthogneiss basement rocks. The MBI is intersected by a series of brittle to ductile faults and shear zones, some of which appear to control the distribution of higher-grade palladium mineralization. A major north-trending shear zone appears to have cut the western end of the MBI and is spatially associated with the development of high-grade palladium mineralization. Textural and mineralogical variability is greatest in the outer margins of the MBI, especially along the well documented western and northern margins that host most of the known palladium resources. Commonly observed textures in the noritic marginal units of the MBI include equigranular, fine- to coarse-grained (seriate textured), porphyritic, pegmatitic, and varitextured. Platinum-group element and copper-nickel sulphide mineralization in the MBI is found in a variety of structural and geological settings but in general is characterized by the presence of small amounts (e.g., typically less than 2%) of fine- to medium-grained disseminated iron-copper-nickel sulphides within broadly stratabound zones of platinum group elements (PGE) and gold enrichment.
The mineralization is commonly associated with varitextured gabbroic rocks; coarse-grained noritic rocks; and local, intensive zones of amphibolitization, chloritization and shearing. An important, distinguishing characteristic of the MBI mineralization relative to other PGE deposits is the consistently high palladium:platinum ratio, commonly averaging 10:1 or higher. Sulphide mineral assemblages are dominated by pyrite with lesser pyrrhotite, chalcopyrite, pentlandite, and millerite.
MINERAL RESERVE ESTIMATE
The mineral reserves were estimated by applying wireframe models depicting stope and pillar shapes to the underground geological block models provided by NAP. NAP aslo provided a separate, more historical geological block model for open pit evaluations, as well as RGO stockpile resource information that was used to estimate the amount of the stockpiled resource material that would be recovered during the LOM time period and accordingly be brought into the reserves. For the underground models, a mineral resource envelope was established with a 1.0 g/t palladium resource grade and a block size of 5 m by 5 m by 5 m. For the open pit block model, NAP used a 2003 block model that had a block size for pit evaluations of 15 m by 15 m by 8 m. Tetra Tech’s senior geologist reviewed and validated each of NAPs submitted block models, prior to use.
|Mineral Reserves at the Cut‐off Grades|
The Diavik Diamond Mine
Location: Lac de Gras, Northwest Territories, Canada.Products: Diamonds.
Owner: Dominion Diamond Corporation and Diavik Diamond Mines Inc.
Ore Type: The mine consists of three kimberlite pipes.
Geological notes of Diamond and The Diavik Mine:
Our knowledge of the primary sources of diamonds in the lithospheric upper mantle is mainly derived from the studies of mantle xenoliths in kimberlites and of mineral inclusions in diamonds themselves. Inclusions in diamonds preserve evidence of the physical and chemical environment at the time of diamond formation, presumed to have occurred early in Earth’s history (e.g. Richardson et al. 1984). Mantle xenoliths, in contrast, integrate a more protracted history that may have involved multiple stages of melt extraction, and thermal re-equilibration in response to short lived thermal pulses or secular cooling, and metasomatic re-enrichment. Rare diamond-bearing peridotite xenoliths provide unique opportunities to study the principal source of diamonds in the Earth’s mantle directly and to obtain information on the evolution of cratonic lithosphere, spanning the time from diamond formation to kimberlite eruption. Based on inclusion studies, peridotitic diamonds largely formed in depleted harzburgitic sources (Gurney and Switzer 1973; Gurney 1984). Evidence for changes in the composition of peridotitic subcratonic lithospheric mantle over time, involving a decreasing ratio of harzburgite to lherzolite (Griffin et al. 2003), raises the possibility that diamonds are stored in mantle rocks that are compositionally quite distinct from the environment of diamond formation. This would have important implications for diamond exploration, because indicator mineral assessment, evaluating the state of mantle lithosphere at the time of kimberlite eruption, is strongly based on chemical criteria derived from inclusion studies depicting the environment of diamond formation. One of the key questions for our study of diamondiferous peridotite xenoliths from Diavik, therefore, is verifying the extent to which the originally highly depleted signature at the time of diamond formation has been preserved or modified during subsequent metasomatic events.
Based on the composition of xenoliths and garnet xenocrysts, Griffin et al. (1999a) inferred that the mantle beneath the Lac de Gras area is chemically and thermally stratified. They suggested that an ‘‘ultradepleted’’, predominantly harzburgitic layer overlies a less depleted, predominantly lherzolitic layer with the transition being located at *145 km depth. Griffin et al. (1999a) proposed the shallower ‘‘ultradepleted’’ layer to represent Mesoarchean oceanic or sub-arc mantle lithosphere and the lower layer to be the frozen head of a Neoarchean plume derived from the lower mantle. Aulbach et al. (2007) suggested that the deeper portions of the lower layer experienced secondary re-enrichment in FeO (Aulbach et al. 2007). An alternative model for the formation of subcratonic lithospheric mantle involves stacking of highly depleted Archean oceanic lithospheric mantle beneath early continents (e.g. Schulze 1986; Helmstaedt and Schulze 1989; Bulatov et al. 1991; de Wit 1998; Stachel et al. 1998). In this model, the observed increase in fertility with depth in the central Slave craton may relate to metasomatism by infiltrating fluids/melts ascending from the asthenosphere (Stachel et al. 2003).
Aulbach S, Griffin WL, Pearson NJ, O’Reilly SY, Doyle BJ (2007)
Lithosphere formation in the central Slave Craton (Canada):
plume subcretion or lithosphere accretion. Contrib Mineral
Bernstein S, Kelemen PB, Hanghøj K (2007) Consistent olivine Mg#
in cratonic mantle reflects Archean mantle melting to the
exhaustion of orthopyroxene. Geology 35:459–462
Bleeker W, Davis WJ (1999) The 1991–1996 NATMAP Slave
province project: introduction. Can J Earth Sci 36:1033–1042
Boyd SR, Kiflawi I, Woods GS (1994) The relationship between
infrared absorption and the A defect concentration in diamond.
Philos Mag B 69:1149–1153
Boyd SR, Kiflawi I, Woods GS (1995) Infrared absorption by the B
nitrogen aggregate in diamond. Philos Mag B 72:351–361
Griffin WL, Cousens DR, Ryan CG, Sie SH, Suter GF (1998) Ni in
chrome pyrope garnets: a new geothermometer. Contrib Mineral
Kidd Creek Mine
It is the world's deepest copper/zinc mine.
Products: Copper & Zinc.
Owner: Xstrata Copper.
Deposit Type: The Kidd deposit is one of the largest volcanogenic massive sulfide ore deposits in the world, and one of the world's largest base metal deposits.
Ore Geology: Kidd Creek is based on a rich, steeply dipping volcanogenic sulphide deposit located in the Archaean Abitibi greenstone belt. There are two major orebodies, with associated smaller lenses. The ore is hosted in felsic rocks of the Kidd Volcanic Complex and is cut by mafic sills and dykes. Structural deformation resulting from several phases of folding and faulting affects the distribution of sulphide lenses.
Three ore types predominate: massive, banded and bedded (MBB) ores (pyrite, sphalerite, chalcopyrite, galena and pyrrhotite); breccia ores containing fragments of the MBB ores; and stringer ores consisting of irregular chalcopyrite stringers cutting a siliceous volcaniclastic host.
Geological setting & Stratigraphic section of the mine:
The Kidd Creek Volcanic Complex is interpreted to have formed within a proto-arc geodynamic setting, with the high silica FIII rhyolites a product of crustal extension during rifting and melting of the lithosphere (Wyman et al., 1999; Prior et al., 1999). A graben interpreted to contain the Kidd VMS deposit is consistent with this geodynamic setting and a recent volcanic reconstruction of the North Rhyolite by DeWolfe et al. (2003), suggest a minimum graben width of 5 to 7 km (Gibson and Kerr, 1993; Bleeker, 1999). Fissures that controlled the eruption and emplacement of the Footwall and QP rhyolites may be graben-parallel structures (Prior, 1996).
The simplified stratigraphic column in Figure 3 provides a general overview of the Kidd Mine stratigraphy and location of massive sulfide deposits. Komatiitic flows and intrusions constitute the base of the known stratigraphic sequence and likely formed a broad, low-relief lava plain upon which the Kidd Creek rhyolitic dome and ridge complex was constructed. The minimum thickness of the komatiitic unit is estimated at 500 metres.
Figure 2. Kidd Mine ore-bodies looking east from surface to 10,200 ft
Mining operation and reserves :
The mine started production in 1966 from an open pit. The orebody is now mined at depth through three shafts as the No.1, No.2 and No.3 Mines. Phase 2 of No.3 Mine is currently being developed. Mine D will extend Kidd Creek below No 3, from a depth of 2,100m to 3,100m.
Blasthole stoping with cemented backfill is used to extract the ore underground, Kidd Creek being the world’s second-largest user of cemented backfill (after Mt Isa in Australia). Blastholes are drilled using Ingersoll Rand, Mission and Cubex drills and broken ore is hauled underground by Tamrock load-haul-dump units. The hoisting shafts are equipped with an ABB Hoist Automation System, which has significantly increased the efficiency of raising ore from depth.
At the end of 2005, Kidd Creek’s proven and probable reserves were stated as being 19Mt grading 1.8% copper, 5.5% zinc, 0.18% lead and 53g/t silver. Measured and indicated resources totalled 2.6Mt at 2.2% copper, 6.3% zinc, 0.2% lead and 48 g/t silver, with a further 11.9Mt in inferred resources at 2.7% copper, 4.8% zinc, 0.3% lead and 81g/t silver.
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Abitibi Subprovince, Canada: In Hannington, M.D., and
Barrie, C.T., eds. The Giant Kidd Creek Volcanogenic Massive
Sulfide Deposit, Western Abitibi Subprovince, Canada. Economic
Geology, Monograph 10, p. 143-162.
Beaty, D.W., Taylor, H.P., & Coad, P.R., 1988. An oxygen
isotope study of the Kidd Creek, Ontario, volcanogenic massive
sulfide deposit: Evidence for high heat 18O ore fluid. Economic
Geology, v. 83, p. 1-18.
Bleeker, W., 1999. Structure, stratigraphy, and primary setting
of the late Archean Kidd Creek Volcanogenic massive sulfide
deposit: A semi-quantitative reconstruction: In Hannington,
M.D., and Barrie, C.T., eds.