The Canadian Mineralogist最新文献

{"title":"Genesis of the Jinbaoshan PGE-(Cu)-(Ni) deposit: Distribution of chalcophile elements and platinum-group minerals","authors":"Yiguan Lu, C. Lesher, Li‐Qiang Yang, M. Leybourne, Wen-yan He, Ming-Gang Yuan, Zhen Yang, Xue Gao","doi":"10.3749/canmin.2100056","DOIUrl":"https://doi.org/10.3749/canmin.2100056","url":null,"abstract":"\u0000 The Jinbaoshan platinum group element-(Cu)-(Ni) deposit in southwest China is a sulfide-poor magmatic platinum-group element deposit that experienced multiple phases of post-magmatic modification. The sulfide assemblages of most magmatic Ni-Cu-platinum-group element deposits in China and elsewhere in the world are dominated by pentlandite-pyrrhotite-chalcopyrite with lesser magnetite and minor platinum-group minerals. However, Jinbaoshan is characterized by (1) hypogene violarite-pyrite 1-millerite-chalcopyrite and (2) supergene violarite-(polydymite)-pyrite 2-chalcopyrite assemblages. The platinum-group minerals are small (0.5–10 μm diameter) and include moncheite Pt(Te,Bi)2, mertieite-I Pd11(Sb,As)4, the atokite Pd3Sn – rustenburgite Pt3Sn solid solution, irarsite IrAsS, and sperrylite PtAs2 hosted mainly by violarite, silicates (primarily serpentine), and millerite. The platinum-group minerals occur in two sulfide assemblages: (1) mertieite-I-dominant (with irarsite, palladium, and Pd-alloy) in the hypogene assemblage and (2) moncheite-dominant (with irarsite, sperrylite, and atokite) in the supergene assemblage. Palladium and intermediate platinum-group elements (Os, Ir, Ru) are concentrated mainly in violarite, polydymite, and pyrite 2. Platinum is seldom hosted by base metal sulfides and occurs mainly as discrete platinum-group minerals, such as moncheite, sperrylite, and merenskyite. Violarite and polydymite in the Jinbaoshan deposit contain more Pb-Ag than pentlandite and pyrrhotite in the Great Dyke and Lac des Iles deposit. The formation of the sulfide assemblages in Jinbaoshan can be interpreted to have occurred in three stages: (1) a magmatic Fe-Ni-Cu sulfide melt crystallized Fe-Ni monosulfide and Cu-rich intermediate solid solutions, which inverted to a primary pyrrhotite-pentlandite-chalcopyrite-magnetite assemblage; (2) an early-secondary hypogene voilarite-millterite-pyrite 1-chalcopyrite assemblage formed by interaction with a lower-temperature magmatic-hydrothermal deuteric fluid; and (3) a late-secondary supergene violarite-polydymite-pyrite 2-chalcopyrite assemblage formed during weathering. Late-magmatic-hydrothermal fluids enriched the mineralization in Pb-Ag-Cd-Zn, which are incompatible in monosulfide solid solution, added Co-Pt into violarite, and expelled Pd to the margins of hypogene violarite and millerite, which caused Pd depletion in the hypogene violarite and the formation of mertieite-I. Supergene violarite inherited Pd and intermediate platinum-group elements from primary pentlandite. Thus, the unusual sulfide assemblages in the Jinbaoshan platinum-group element-(Cu)-(Ni) deposit results from multiple overprinted post-magmatic processes, but they did not significantly change the chalcophile element contents of the mineralization, which is interpreted to have formed at high magma:sulfide ratios (R factors) through interaction of crustally derived sulfide and a hybrid picritic-ferropicritic magma derived from sub","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"20 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121233437","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Preface part I: Dedication","authors":"Michael Lesher, L. Cabri, A. McDonald","doi":"10.3749/canmin.int011","DOIUrl":"https://doi.org/10.3749/canmin.int011","url":null,"abstract":"","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-11-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115121400","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"The Paleoproterozoic Kombolgie Subgroup (1.8 Ga), McArthur Basin, Australia: Sequence stratigraphy, basin evolution, and unconformity-related uranium deposits following the Great Oxidation Event","authors":"E. Hiatt, T. Kyser, P. Polito, J. Marlatt, P. Pufahl","doi":"10.3749/canmin.2000102","DOIUrl":"https://doi.org/10.3749/canmin.2000102","url":null,"abstract":"\u0000 Proterozoic continental sedimentary basins contain a unique record of the evolving Earth in their sedimentology and stratigraphy and in the large-scale, redox-sensitive mineral deposits they host. The Paleoproterozoic (Stratherian) Kombolgie Basin, located on the Arnhem Land Plateau, Northern Territory, is an exceptionally well preserved, early part of the larger McArthur Basin in northern Australia. This intracratonic basin is filled with 1 to 2 km-thick, relatively undeformed, nearly flat-lying, siliciclastic rocks of the Kombolgie Subgroup. Numerous drill cores and outcrop exposures from across the basin allow sedimentary fabrics, structures, and stratigraphic relationships to be studied in great detail, providing an extensive stratigraphic framework and record of basin development and evolution.\u0000 Tectonic events controlled the internal stratigraphic architecture of the basin and led to the formation of three unconformity-bounded sequences that are punctuated by volcanic events. The first sequence records the onset of basin formation and is comprised of coarse-grained sandstone and polymict lithic conglomerate deposited in proximal braided rivers that transported sediment away from basin margins and intra-basin paleohighs associated with major uranium mineralization. Paleo-currents in the upper half of this lower sequence, as well as those of overlying sequences, are directed southward and indicate that the major intra-basin topographic highs no longer existed. The middle sequence has a similar pattern of coarse-grained fluvial facies, followed by distal fluvial facies, and finally interbedded marine and eolian facies. An interval marked by mud-rich, fine-grained sandstones and mud-cracked siltstones representing tidal deposition tops this sequence. The uppermost sequence is dominated by distal fluvial and marine facies that contain halite casts, gypsum nodules, stromatolites, phosphate, and “glauconite” (a blue-green mica group mineral), indicating a marine transgression. The repeating pattern of stratigraphic sequences initiated by regional tectonic events produced well-defined coarse-grained diagenetic aquifers capped by intensely cemented distal fluvial, shoreface, eolian, and even volcanic units, and led to a well-defined heterogenous hydrostratigraphy. Basinal brines migrated within this hydrostratigraphy and, combined with paleotopography, dolerite intrusion, faulting, and intense burial diagenesis, led to the economically important uranium deposits the Kombolgie Basin hosts.\u0000 Proterozoic sedimentary basins host many of Earth's largest high-grade iron and uranium deposits that formed in response to the initial oxygenation of the hydrosphere and atmosphere following the Great Oxygenation Event. Unconformity-related uranium mineralization like that found in the Kombolgie Basin highlights the interconnected role that oxygenation of the Earth, sedimentology, stratigraphy, and diagenesis played in creating these deposits.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"63 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125841931","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paragenesis of gold mineralization at the Kiyuk Lake Project, Kivalliq Region, Nunavut, Canada","authors":"Stacie Jones, K. Kyser, M. Leybourne, R. Mackie, A. Fleming, D. Layton-Matthews","doi":"10.3749/canmin.2000058","DOIUrl":"https://doi.org/10.3749/canmin.2000058","url":null,"abstract":"\u0000 Exploration for gold in Nunavut has been primarily focused on Archean greenstone belts in the north and coastal regions of the territory, resulting in large areas of underexplored terrain in the south. The Kiyuk Lake property is located in the underexplored southwest corner of the Kivalliq Region of Nunavut within the Hearne domain of the ∼1.9 Ga western Churchill Province. The property is hosted by Proterozoic calc-silicate and clastic sedimentary units of the Hurwitz Group (<2.4–1.9 Ga) and the unconformably overlying Kiyuk Group (1.9–1.83 Ga). Gold mineralization in Proterozoic sedimentary rocks is rare in the Canadian Shield, so the Rusty Zone at Kiyuk Lake presents a unique opportunity to study the enigmatic gold mineralization hosted in such sedimentary rocks. Mineralization at the Rusty Zone is hosted by an immature lithic wacke cut by thin intermediate dikes that are associated with hydrothermal breccias composed of Fe-carbonate, calcite, calcic-amphibole, Fe-sulfide, Fe-oxide minerals, and gold. Textural and timing relationships suggest that the gold mineralization is post-sedimentary and syn- to post-intrusion of intermediate dikes. Stable isotope thermometry suggests that mineralization took place between 450 and 600 °C, and geochronological studies indicate that the intrusion and mineralization occurred before or about 1.83 Ga. Using basement breaching thrusts faults as conduits to the surface, over-pressurization along a later normal fault is thought to be the primary cause for the localized breccia pipe that controls gold mineralization. The hydrothermal fluids are postulated to be volatile-rich aqueous solutions exsolved from a source of cooling magmas at depth. Although sub-economic at present, the occurrence of high-grade gold in a Paleoproterozoic basin such as Kiyuk Lake could signal a new opportunity for exploration for gold in the Canadian Shield.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129775972","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleoredox conditions, hydrothermal history, and target vectoring in the MacMillan Pass base-metal district, Yukon, Canada: 1 – Lithogeochemistry of proximal and distal shales","authors":"C. Leighton, M. Leybourne, D. Layton-Matthews, J. Peter, M. Gadd, A. Voinot","doi":"10.3749/canmin.2000075","DOIUrl":"https://doi.org/10.3749/canmin.2000075","url":null,"abstract":"\u0000 The MacMillan Pass District in Yukon, Canada, hosts the Tom and Jason clastic sediment-hosted Zn-Pb-Ag-(Ba) deposits. Bulk geochemical paleoredox proxies (Eu/Eu*, Ce/Ce*, Mo, Re/Mo, and Ni/Co) indicate anoxic–dysoxic water column and sulfidic porewater conditions persisted during the Late Devonian deposition of the Lower Earn Group host rocks. Positive Eu/Eu* anomalies (up to 3.31) in sulfide mineralization at the Tom deposit are consistent with relatively high temperature (probably >250 °C), reducing, acidic hydrothermal fluids that infiltrated laterally through unconsolidated sediments proximal to the hydrothermal upflow zone and/or exhaled at the seafloor as moderate- to high-density brines. Molybdenum and U enrichment factors (relative to upper continental crust) and Mo/organic C values are consistent with a moderately restricted basin; Mo/C values fall between those of the Black Sea (highly restricted) and the Framvaren Inlet (moderately restricted). A Ba-rich shale was identified in rocks that are distal and time-equivalent units to the Pb-Zn mineralization; based on the bulk chemical compositions and on previous S and Sr isotope studies, we interpret the baryte in this unit to be largely hydrothermal in origin and perhaps remobilized and reprecipitated during hydrothermal base-metal mineralization.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"39 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128364307","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleoredox conditions, hydrothermal history, and target vectoring in the Macmillan Pass base-metal district, Yukon, Canada: 2 – Pyrite paragenesis and mineral chemistry","authors":"C. Leighton, D. Layton-Matthews, J. Peter, M. Gadd, A. Voinot, M. Leybourne","doi":"10.3749/canmin.2000077","DOIUrl":"https://doi.org/10.3749/canmin.2000077","url":null,"abstract":"\u0000 The MacMillan Pass district in Yukon, Canada, hosts the Tom and Jason clastic sediment-hosted Zn-Pb-Ag-(Ba) deposits. Pyrite-bearing drill core samples were collected from seven drill holes that intersected sulfide mineralization and time-stratigraphically equivalent rocks at varied spatial distances extending up to 3 km away from the deposits to assess the relative timing of pyrite mineralization and the chemistry of pyrite paragenesis. There are four pyrite morphologies: framboids and polyframboids (Py1), subhedral to euhedral inclusion-free crystals (Py2a), silicate inclusion-bearing nodules with serrated edges (Py2b), and euhedral idiomorphic overgrowths on preexisting pyrite morphologies (Py3). These morphological varieties correspond in time from syngenetic to earliest diagenetic growth (Py1), early to late diagenetic growth (Py2a, Py2b), and metamorphic crystallization and/or recrystallization of previous textural varieties (Py3). A representative subset of pyrite grains was analyzed for trace element contents and distributions by laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS). Analyses by LA-ICP-MS reveal that each textural variety of pyrite has a distinct trace element composition that also varies depending on stratigraphic unit. A suite of clastic sediment-hosted sulfide mineralization-related elements was incorporated into Py2 within sulfide mineralized units at greater abundances than that in unmineralized units (e.g., Zn, As, Pb, Tl, Bi). Lead abundances and Pb/Se and As/Mo values in pyrite are the most robust vectoring tools documented. The timing for clastic sediment-hosted Zn-Pb mineralization was syn and/or post late diagenesis (Py2b).\u0000 A Ba-enriched horizon was identified in rocks and this is interpreted to be the distal time-stratigraphic equivalent unit to Zn-Pb mineralization. The Ba-enriched horizon contains Py2 with anomalous metal (Tl, Co, Mn, Cd, Zn, Sb) contents and abundant macroscopic baryte, and it is interpreted to represent the distal expression of sulfide mineralization-forming hydrothermal activity. Four genetic models for mineralization are reviewed; however, the only model that is consistent with our whole rock and pyrite geochemistry involves venting of buoyant hydrothermal fluid, mixing with ambient seawater, and remaining or sinking into unconsolidated sediments, with lateral migration up to 2–3 km from the vent source.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127905484","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Diagenesis of paleodrainages in Lake Way and Lake Maitland, Western Australia, and the role of authigenic Mg-clays and dolomite in the genesis of channel and playa uranium deposits","authors":"Justin B. R. Drummond, T. K. Kyser, Robert R. Bowell, N. James, D. Layton-Matthews","doi":"10.3749/canmin.2000053","DOIUrl":"https://doi.org/10.3749/canmin.2000053","url":null,"abstract":"\u0000 This study integrates mineralogical and hydrogeochemical analysis of channel and playa uranium deposits to characterize aquifer evolution and the physico-chemical mechanisms that result in the accumulation of uranium into potentially economic deposits. This subset of surficial U deposits occur in Tertiary to Recent calcrete and dolomitic, clay-rich fluvial paleochannel and palustrine sediments, wherein uranium is largely bound in the potassium-uranyl-vanadate mineral carnotite [K2(UO2)2(VO4)2·3H2O].\u0000 Scanning electron microanalysis indicates that the carnotite mineralization is part of a late-diagenetic mineral assemblage that critically includes Mg-clays (sepiolite and stevensite), amorphous magnesium silicate, and synsedimentary dolomite. This authigenic mineral assemblage is observed concentrated in fractures and pores in groundwater calcrete and silty salt marsh “palustrine” sediments. Drill-hole gamma ray and conductivity data from the Centipede-Millipede uranium deposit indicate that the locus of uranium mineralization occurs near the present-day water table where oxidizing fresh-to-brackish groundwater interacts with playa brine, forming a hypopycnal groundwater estuary beneath the clay pan and salt marsh. It is interpreted that effective U fixing occurs in areas where groundwater, near-saturated with respect to carnotite, is hydrologically focused upward and into the zone of evaporation. The appreciable precipitation deficit in the Northern Yilgarn is interpreted to produce an evaporation-driven positive feedback mechanism that results in the co-precipitation of Mg-clays, dolomite, and carnotite. The presence of vanadium-rich Mn-oxide phases in high-grade U ore zones indicates that Mn-redox cycling may serve an important role in increasing the local activity of V, and thus carnotite saturation. Mineralogical comparison of other channel and playa uranium deposits throughout Western Australia and Namibia have identified a similar mineral association and paragenetic trend, suggesting that contemporaneous evaporative precipitation of Mg-clays and dolomite are integral in achieving carnotite saturation and precipitation.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"23 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126440648","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Carbon and oxygen isotopic composition of fluid inclusion CO2 and CH4 within the Archean Junction gold deposit, Kambalda, Western Australia","authors":"P. Polito, T. Kyser, A. Vuletich, Y. Bone","doi":"10.3749/canmin.2000027","DOIUrl":"https://doi.org/10.3749/canmin.2000027","url":null,"abstract":"\u0000 The Junction orogenic gold deposit in the St Ives district of Western Australia is characterized by a syn-gold mineral assemblage dominated by quartz-calcite-albite-biotite-chlorite-pyrrhotite. The deposit had a light hydrocarbon,CO2, and O2 soil-gas signature above known mineralization prior to mining and it has been proposed that the source of the light hydrocarbon gases in the soil was gas-rich fluid inclusions trapped in gold-related alteration minerals, particularly calcite, albite, quartz, and pyrrhotite. Linking the soil gases with those in the deposit is extremely difficult. However, establishing that the gases in the soil are indeed present within the deposit and that those gases are related to the syn-Au alteration minerals is achievable through stable-isotope studies. Carbon and O stable-isotope compositions of pre-gold, syn-gold, and post-gold quartz veins; syn-gold and post-gold calcite; and CO2 and CH4 in the fluid inclusions that each of these minerals host were investigated to establish if the various mineral and fluid-gas species in the deposit are in isotopic equilibrium with each other, an important first step to relate syn-ore minerals with the relevant gases.\u0000 Pre-ore Mo-type quartz veins contain CO2 (δ13Cgas = –1‰) and CH4 (δ13Cgas = ca. –33‰) in fluid inclusions at a ratio of ca. 93:7. The paucity of Mo-type quartz veins in the deposit suggests that these veins were not the main source of the soil-gas signature. Syn-gold alteration post-dates the Mo-type quartz veins. Quartz and co-existing calcite in the Au-bearing Junction shear zone have δ18Omineral values around 12.0 and 10.5‰, respectively. Multiple co-existing quartz-calcite pairs indicate that gold deposition occurred at ∼400 °C. This temperature agrees with mineral equilibria temperature estimates, the entrapment temperatures of fluid inclusions, and temperature modelling of solid-solution mineral phases. The temperature dictates that the quartz and calcite are in isotopic equilibrium with each other.\u0000 The calcite in the Junction shear zone has δ13Cmineral values from –7.4 to –2.5‰, indicating that the CO2-rich ore fluid had a δ13Cfluid value of –3.7 ± 0.9‰. CO2 and CH4 released from quartz-hosted fluid inclusions have δ13Cgas values from –4.3 to +3.5‰ (mean = –1.5 ± 1.9‰) and –50.5 to –35.2‰, respectively. The isotopic composition of the fluid inclusion CO2 is in disequilibrium with co-existing CH4 that was co-released from the same quartz vein and the calculated δ13Cfluid value from co-existing calcite. Isotopic mass balance calculations using the two co-released gases show that the CO2 was initially in equilibrium with the syn-ore calcite but has since re-equilibrated with CH4 at temperatures below 200 °C. The abundance of CH4 in some quartz veins suggests that the syn-gold vein assemblage could be the source for the soil-gas anomaly.\u0000 Post-gold veins contain quartz and calcite that have δ18Omineral values of ca. 11.0 and 10.0‰, respectively. Individual mineral","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"72 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133109600","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Geometallurgical ore characterization of the high-grade polymetallic unconformity-related uranium deposit","authors":"Andrew J. Kaczowka, T. K. Kyser, T. Kotzer, M. Leybourne, D. Layton-Matthews","doi":"10.3749/canmin.2000050","DOIUrl":"https://doi.org/10.3749/canmin.2000050","url":null,"abstract":"\u0000 Cigar Lake is a polymetallic, unconformity-related uranium deposit with complex geochemistry and mineralogy located in the eastern Athabasca Basin of northern Saskatchewan, Canada. Variable concentrations and spatial distributions of elements of concern, such as As, Mo, Ni, Co, Se, and Zr, associated with the high-grade tetravalent uranium ores [UO2+x; U(SiO4)1–x(OH)4x] present unique mining, metallurgical, and environmental challenges. Sulfide and arsenide minerals have significant control over As, Mo, Ni, Co, and Se abundances and have properties that affect element of concern mobility, thus requiring consideration during mineral processing, mine-effluent water treatment, and long-term tailings management.\u0000 The U-bearing (uraninite, coffinite) and metallic arsenide (nickeline, often called “niccolite” in the past), sulfarsenide (gersdorffite, cobaltite), and sulfide (chalcopyrite, pyrite, galena, bornite, chalcocite, sphalerite, pyrrhotite) minerals provide the main controls on the distributions of the elements of concern. Arsenic, Ni, and Co occur primarily in a reduced state as 1:1 molar ratio, Ni-Co:As, arsenide, and sulfarsenide minerals such as gersdorffite, nickeline, and cobaltite. Molybdenum occurs within molybdenite and uraninite. Selenium occurs within coffinite, sulfide, and sulfarsenide minerals. Zirconium is found within detrital zircon and coffinite.\u0000 The spatial distribution and paragenesis of U-, As-, and S-bearing minerals are a result of the elemental composition, pH, and redox conditions of early formational and later meteoric fluids that formed and have modified the deposit through access along lithostratigraphic permeability and tectonic structures. Using the holistic geometallurgical paradigm presented here, the geochemistry and mineral chemistry at Cigar Lake can be used to optimize and reduce risk during long-term mine and mill planning.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"3 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128399940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Dendrogeochemistry and soil geochemistry applied to exploration for alkalic Cu-Au porphyry mineralization under cover at the Racecourse prospect, NSW, Australia","authors":"Cole McGill, D. Layton-Matthews, T. K. Kyser, M. Leybourne, P. Polito, E. Leduc","doi":"10.3749/canmin.2000065","DOIUrl":"https://doi.org/10.3749/canmin.2000065","url":null,"abstract":"\u0000 The Racecourse Cu-Au porphyry prospect is found within the Macquarie Arc of the Lachlan Fold Belt, in the Lachlan Transverse Zone, a cross-arc structure hosting significant world-class mineralization, including the Cadia and Northparks districts. Several geochemical and geophysical surveys of the prospect have been complimented by a total of 19,819 m of drilling, with only four holes reaching a depth greater than 300 m. Positive lithogeochemistry (fertility indices, comparisons with the Cadia and Northparks systems) subtle alteration, and mineralized intercepts indicate heightened mineral potential, yet the prospect has lacked a comprehensive geochemical survey outlining the extent of the mineralized target at surface. Soil samples and Monterey pine (Pinus radiata) tree cores were collected above and distal to mineralization intercepted by prior drilling in order to outline the ore deposit footprint and test the viability of dendrogeochemistry as an exploration tool for porphyry Cu mineralization. Ultimately, this study documented the spatial extent of the Racecourse target and identified potential areas for additional Cu mineralization. Soil samples were separated with the <250 μm size fraction analyzed and show distinct anomalous populations of Au, Cu, Mo, Pb, and Zn above prior drilling. Tree cores were collected by increment borer and tree rings of the Pinus radiata were counted and measured, with an age interval of 2003–2008 exhibiting the least ring-width variability chosen to chemically analyze. Selected intervals were digested and analyzed and have elevated Cu, Mo, and Zn in an area that overlaps a previously drilled soil anomaly, whereas an anomaly in the southwest of the survey area documents a Cu, Pb anomaly corresponding to localized faulting and tertiary basalt subcrop. Tree roots are directly tapping chemical variability at depth, aided via metal mobilization through faulted fluid conduits. Lead isotope ratios from the Pinus radiata identify distinct groups of lead spatially associated with discrete metal anomalies of varied lithological ages. At the Racecourse target, anomalous Pinus radiata samples yield a similar isotopic signature to the faulted southwestern anomaly, potentially linking the source of these two metal anomalies. When these results are integrated with the current understanding of the mineralized body, geochemical media suggest that mineralization may continue down-plunge at depth.","PeriodicalId":134244,"journal":{"name":"The Canadian Mineralogist","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121222102","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}