Economic Geology最新文献

{"title":"Geology and Structural Evolution of the La Huifa Ore Deposit, Central Chile: A Newly Discovered Porphyry Cu-Mo System in the El Teniente District","authors":"J. Piquer, J. Hermosilla, Nicolás Oyarzún, Patricio Cuadra, Ricardo Floody, L. Troncoso, Rubén Pardo","doi":"10.5382/econgeo.4980","DOIUrl":"https://doi.org/10.5382/econgeo.4980","url":null,"abstract":"\u0000 La Huifa is a breccia-related Cu-Mo porphyry deposit located in the Andes of central Chile, 3 km northeast of the giant El Teniente porphyry Cu-Mo orebody. It was discovered as part of Codelco’s brownfield exploration activities in the El Teniente district. It is the first major discovery in the area, and this work presents its first detailed geologic description.\u0000 The La Huifa orebody is related to a complex of late Miocene diorite and granodiorite intrusions and hydrothermal breccias, the latter characterized by abundant tourmaline-anhydrite cement, emplaced in middle to late Miocene volcanic and subvolcanic rocks. The structural architecture of La Huifa is dominated by WNW-and NE-striking high angle faults. Usually, slip on the WNW-striking faults involves a sinistral component, whereas slip on the NE-striking faults is predominantly dextral. The main hydrothermal breccia body at La Huifa is located at the intersection of WNW- and NE-striking faults.\u0000 Four stages are proposed for the tectono-magmatic-hydrothermal evolution of La Huifa:Premineralization, involving tourmaline-albite veins and sodic calcic alteration emplaced under a transpressive tectonic regime with a subhorizontal, ~E-W–trending σ1 (~N-S–trending σ3);Early mineralization, involving a polydirectional vein system associated with poorly developed potassic and transitional alteration zones with a scarce presence of Cu and Mo sulfides;Main mineralization, involving Cu- and Mo-rich anhydrite-tourmaline hydrothermal breccias and polydirectional veins associated with strong chlorite-sericite alteration with a 270° to 290°C emplacement temperature, obtained from chlorite geothermometry. The regional stress field during this period was exceeded by the local fluid pressure. These breccias and veins are followed by the emplacement of NE-striking C and D type veins associated with gray and white sericite alteration, respectively, which show a similar temperature range.Late mineralization, involving a NE-striking, carbonate-rich vein system containing polymetallic sulfides. It is associated with argillic alteration, whose temperature was 200° to 260°C. This stage occurred under a compressive tectonic regime with NE-trending σ1.\u0000 The relatively low temperature at which mineralization was introduced in this deposit (~270°–290°C) and the predominantly vertical fluid flow pattern typical of hydrothermal breccia systems allow us to infer the presence of more mineralized rock at depth, below the recognized portion of the system. The association of Cu and Mo enrichment with chlorite-sericite alteration, instead of higher-temperature potassic or gray sericite alteration events, makes La Huifa a unique case among the porphyry deposits of central Chile and broadens the scope of mineralization styles that could be targeted in this belt. Finally, the intersection of arc-oblique, high-angle faults and, in particular, the presence of fault systems orthogonal to the main compression direction, favorable","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"26 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80185288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Timing of Magmatism and Skarn Formation at the Limon, Guajes, and Media Luna Gold ± Copper Skarn Deposits at Morelos, Guerrero State, Mexico","authors":"M. Burisch, Steven D. Bussey, Nicolas Landon, Carlo Nasi, Alejandro Kakarieka, A. Gerdes, R. Albert, H. Stein, Janet A. Gabites, R. Friedman, L. Meinert","doi":"10.5382/econgeo.4985","DOIUrl":"https://doi.org/10.5382/econgeo.4985","url":null,"abstract":"\u0000 The Morelos district, located in the center of the Guerrero gold belt, Guerrero State, southern Mexico, has been the site of several recent gold ± copper skarn discoveries (total of ~8.5 Moz Au) associated with Upper Cretaceous-Paleocene granodiorite intrusions. The Limon, Guajes, and Media Luna skarn deposits developed along the contact of the El Limon granodiorite and the sedimentary host rocks. Native gold is associated with retrograde alteration of garnet-pyroxene skarn and is accompanied by native bismuth as well as telluride and sulfide minerals. The Media Luna deposit is characterized by a distinct magnesium-rich skarn mineralogy and contains an average of ~1 wt % Cu, in addition to gold and silver. This distinguishes it from the other gold-only skarn deposits in the Guerrero gold belt. This observation suggests that skarns in the Guerrero gold belt, which replaced magnesium-rich sedimentary protoliths, may host significant copper resources in addition to gold.\u0000 Uranium-lead laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) zircon ages of the El Limon granodiorite range from 66.86 ± 0.40 to 65.88 ± 0.79 Ma. Preskarn molybdenite-quartz veins cut through the El Limon granodiorite and yield Re-Os molybdenite ages between 66.63 ± 0.22 and 65.55 ± 0.25 Ma. A series of pre-, syn-, and postskarn porphyritic dikes intruded the El Limon granodiorite, having zircon ages ranging from 65.9 ± 1.1 to 64.68 ± 0.38 Ma. The timing of skarn formation at Limon and Media Luna was constrained to 64.6 ± 1.2 to 63.2 ± 1.0 Ma, applying U-Pb LA-ICP-MS to garnet. The ubiquitous presence of garnet in skarn deposits and the time- and cost-efficiency of in situ geochronology are striking advantages of this method to constrain the timing of mineralization.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"18 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"73010770","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genesis of the Loma Galena Pb-Ag Deposit, Navidad District, Patagonia, Argentina: A Unique Epithermal System Capped by an Anoxic Lake","authors":"V. Bouhier, M. Franchini, F. Tornos, A. Rainoldi, P. Patrier, D. Beaufort, A. Boyce, Warren T. Pratt, A. Impiccini","doi":"10.5382/econgeo.4968","DOIUrl":"https://doi.org/10.5382/econgeo.4968","url":null,"abstract":"\u0000 Loma Galena (978,852 t Pb, 206 Moz Ag) is one of eight epithermal deposits in the world-class Navidad Pb + Ag ± (Zn, Cu) district located in the Cañadón Asfalto continental foreland basin, northern Patagonia, Argentina. This basin formed during the Jurassic in an extensional tectonic regime during the breakup of Gondwana. Host rocks comprise major listric faulted and tilted blocks of K-rich andesite to dacite lava flows (173.9–170.8 Ma; U-Pb ages for zircon) unconformably overlain by mudstone interbedded with stromatolitic and pisolitic limestones, sandstone, coal, and an Sr-rich evaporite layer deposited in a lacustrine environment. The mineralization occurs as disseminations in the organic-rich sedimentary rocks, in veins and hydrothermal breccia dikes in the hanging walls and footwalls of NW- and NE-striking normal faults, in volcanic autobreccias, and in a phreatic breccia at the contact of volcanic and sedimentary rocks.\u0000 The earliest hydrothermal minerals consist of veins of colloform, crustiform, and cockade calcite 1 (δ13Cfluid –4.7 to 0.8‰; δ18Ofluid 4.8–11.6‰) and siderite. The precipitating fluids were likely basement-exchanged basinal brines having salinities of 9.5–16.4 wt % NaCl equiv and temperatures of 154.7°–212°C. The interaction of these fluids with the host volcanic rocks formed calcite, albite, adularia, and celadonite-glauconite-group minerals followed by chlorite and siderite as fO2 decreased. Fluids intermittently boiled, as evidenced by bladed (platy) texture in calcite 1.\u0000 Subsequent mineralizing stages contributed to the metal endowment of Loma Galena. The abundance of organic-rich mudstone and δ34S from –15.4 to 12.9‰ for sulfides suggests that the bottom waters of the lake were anoxic and the loci of microbial sulfate reduction (evaporites have δ34S 35‰). Mixing of upflowing metal-rich basinal fluids carrying some S from depth with this H2S-rich connate water efficiently precipitated Ag-bearing framboidal pyrite, colloform pyrite-marcasite, chalcopyrite, bornite, tennantite-tetrahedrite, sphalerite, and galena as veins, breccias, and disseminations in host rocks. The highest grade and tonnage of the ores are found in autobreccias at the junction of the uppermost lava flow and in the overlying mudstone, where the addition of a strong microbial signature is recorded in sulfides. This event also led to partial dissolution of magmatic and hydrothermal feldspar and calcite 1 in the altered volcanic rocks.\u0000 Mineralization was followed by hydrothermal brecciation and successive precipitation of chalcedony (δ18Ofluid 2.6–4.8‰), barite (δ34S 15.7–22‰; 160.9°–183.8°C; 7.7–9.7 wt % NaCl equiv), calcite 2 (δ18Ofluid –10.2 to –3.7‰, 58°–95°C; 1.9–7.0 wt % NaCl equiv), strontianite, and quartz in brecciated veins and breccias; kaolinite (δ18Ofluid 2–6.2‰), illite-smectite, smectite, and carbonates with minor chalcedony and barite in the volcanic rocks; and calcite, chalcedony, and barite in the sedimentary rocks. A trend of decre","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"1 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81292262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"IN SITU U-Pb MONAZITE GEOCHRONOLOGY RECORDS MULTIPLE EVENTS AT THE MOUNT ISA Cu (± Zn-Pb-Ag) DEPOSIT, NORTHERN AUSTRALIA","authors":"B. Cave, R. Lilly, P. Rea","doi":"10.5382/econgeo.4964","DOIUrl":"https://doi.org/10.5382/econgeo.4964","url":null,"abstract":"\u0000 The Mount Isa Cu (± Zn-Pb-Ag) deposit is the largest Cu deposit in the Western fold belt of the Mount Isa inlier. Previous geochronological studies on the deposit have produced a large range (>150 m.y.) in ages for Cu mineralization and associated hydrothermal alteration. This study combines detailed petrology with in situ monazite U-Pb geochronology on four monazite-bearing samples in order to constrain the age of hydrothermal and tectonic events experienced by the Mount Isa Cu (± Zn-Pb-Ag) deposit and enclosing host shale. Samples EY108402 and EX102476 contain singular subangular monazite grains included in dolomite and siderite, which are associated with premineralization silica-dolomite alteration. Monazite from these samples yields mean weighted 207Pb/206Pb ages of 1587 ± 43 (mean square of weighted deviates [MSWD] = 0.57) and 1623 ± 25 Ma (MSWD = 0.61), respectively. These ages constrain the maximum age of silica-dolomite alteration and Cu mineralization, reflecting monazite growth during periods of peak metamorphism and early basin inversion, respectively. A sample from the 1100 Cu orebody (DDR012-2) contains two clusters of fine-grained monazite that replace siderite associated with silica-dolomite alteration, envelop chalcopyrite, and are crosscut by chlorite-quartz-orthoclase microveins. Monazite from these clusters produces 207Pb/206Pb ages ranging from ca. 1620 to ca. 1360 Ma. The large variation in ages is attributed to variable radiogenic Pb loss from a precursor monazite due to (1) continuous coupled dissolution-reprecipitation reactions over ca. 260 m.y. or (2) partial recrystallization by a ca. 1360 Ma fluid event. As monazite from this sample envelops chalcopyrite, the ca. 1360 Ma age can be used to infer the minimum age of Cu mineralization. Sample 1758-1 is from a highly silicified and fractured section of the Eastern Creek Volcanics located adjacent the deposit. The sampled fracture plane bears a chlorite-illite-rutile infill assemblage with fine-grained irregular-shaped monazite. Monazite from this sample produces a lower intercept age of 1376 ± 32 Ma (MSWD = 1.3) and is interpreted to represent the age of a major fluid flow event coeval with uplift along the Mount Isa fault. The monazite U-Pb geochronology presented in this study brackets the age of Cu mineralization and records the presence of multiple tectonic/hydrothermal events over the history of the deposit and enclosing host rocks.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"95 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"81298783","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Formation of High Field Strength Element-Rich Glimmerites by Silicate Liquid-Liquid Immiscibility, Suzhou Pluton, Eastern China","authors":"Lei Xie, Rucheng Wang, Huan Hu, S. Erdmann","doi":"10.5382/econgeo.4965","DOIUrl":"https://doi.org/10.5382/econgeo.4965","url":null,"abstract":"\u0000 Understanding the formation of high field strength element (HFSE) mineralization remains a challenge. Processes ranging from melt generation to final crystallization have been invoked to play a key role in the enrichment of HFSEs in magmatic-hydrothermal systems, yet the importance of crystal-liquid fractionation, liquid immiscibility, and/or fluid unmixing remains debated. Here, we present results of a study of granites and HFSE-mineralized glimmerites from the granitic Suzhou pluton, eastern China. We provide whole-rock major and trace element compositions, a description of mineral assemblages, and a detailed description of zircon textures, zircon Raman spectra, zircon major and trace element and δ18O compositions, and U-Pb ages. The granites and glimmerites have been dated at ~126–124 Ma and are thus coeval. The granites range from biotite and zircon poor to biotite and zircon rich and are in contact with glimmerites. The glimmerites form lenses and layers close to and along the margin of the Suzhou granite, comprising up to ~37 vol % biotite and up to ~2 vol % zircon and other HFSE-rich accessory minerals. The biotite-poor granites contain a single type of zircon (type-A: single crystals, oscillatory zoned, fully crystallized structure, relatively poor in trace elements, and relatively high δ18O), whereas the biotite-rich granites and the glimmerites contain two zircon types (type-A crystals: same features as in the biotite-poor granites; type-B crystals: clustered, unzoned, partially metamict structure, rich in trace elements, and relatively low δ18O). Both granite types are Si, Al, and Na rich, whereas the glimmerites are Fe, Ti, Mn, Mg, Ca, P, F, and HFSE rich and, compositionally, fall off simple fractionation trends. We interpret the textural, mineralogical, and compositional relationships to indicate that the glimmerites are the products of Fe-, F-, and HFSE-rich immiscible melts that unmixed from an alkali-rich, moderately reducing (~QFM + 0.5 and ~QFM + 1.0; QFM = quartz-fayalite-magnetite buffer) Suzhou magma system at low crustal pressure. In addition, we note that the zircon textures and compositions are important recorders of the processes and conditions that led to the HFSE mineralization.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"21 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-10-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"78150001","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Rare Earth Element Mobility and Sr Isotope Systematics of Altered Volcanic Rocks from Seawater-Based and Magmatically-Influenced Hydrothermal Systems: Brothers Volcano, Kermadec Arc (IODP Expedition 376)","authors":"S. Humphris, J. Blusztajn, Yuanfeng Cai","doi":"10.5382/econgeo.4961","DOIUrl":"https://doi.org/10.5382/econgeo.4961","url":null,"abstract":"\u0000 In 2018, International Ocean Discovery Program (IODP) Expedition 376 successfully drilled into seawater-based and magmatically-influenced hydrothermal systems within and on the wall of the caldera of Brothers volcano, an active submarine volcano in the Kermadec arc. We report rare earth element (REE) abundances and ratios for altered volcanic material recovered from three holes to assess mobility and partitioning under the different conditions of fluid-rock reactions. We combine these with loss on ignition (LOI) and X-ray diffraction (XRD) data to document the extent of alteration, and with Sr concentration and isotope data to evaluate water/rock (W/RSr) ratios and provide constraints on hydrothermal exchange and conditions of alteration. Rocks recovered from the seawater-based NW Caldera hydrothermal system show variable extents of alteration (LOI values of 1–11 wt %) at low W/RSr ratios (1–14) to chlorite- and quartz-rich alteration mineral assemblages. We attribute the limited changes observed in total REE content (ΣREE) and chondrite-normalized REE patterns to a combination of their incorporation into secondary minerals such as chlorite and smectite and complexation with chloride ligands in the reacting fluids. Rocks recovered from the magmatically-influenced Upper Cone hydrothermal field (and from an older interval deep beneath the NW Caldera wall) are more extensively altered (LOI values of 4 to >22 wt %), although at similar low W/RSr ratios (~1–16) to heterogeneous natroalunite- and pyrophyllite-bearing assemblages. The REEs exhibit considerably greater mobility with lower ΣREE contents, particularly in the middle and heavy REEs (LaN/YbN ratios up to 4). We suggest that accommodation in secondary minerals is unlikely to play a role in REE behavior due to their lack of substitution sites for the REEs. We attribute enhanced mobility of all the REEs to increased solubility due to the very low pH, and fractionation of the middle and heavy REEs as likely due to complexation with fluoride which enhances their solubility relative to the light REEs.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"314 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80057748","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"AN UNUSUAL EARLY EOCENE, SYNCOLLISIONAL CARBONATITE COMPLEX AND RELATED RARE EARTH ELEMENT DEPOSIT IN THE INDIA-ASIA COLLISION ZONE, NORTHWESTERN VIETNAM","authors":"Xiaochun Li, Mei‐Fu Zhou, Shi-Hu Li, Xiao-Ran Zhang, H. Fan, D. Groves, Ngo Xuan Dac","doi":"10.5382/econgeo.4969","DOIUrl":"https://doi.org/10.5382/econgeo.4969","url":null,"abstract":"\u0000 Carbonatite-related rare earth element (REE) deposits, the most significant source of REEs globally, are normally generated in extensional settings, such as intracontinental rifts, mantle plume-related environments, or postcollisional orogens. Syncollisional orogens represent overall compressional regimes, so carbonatites and related REE deposits are rarely identified in such a setting. However, this study reports an anomalous syncollisional carbonatite-related REE deposit, Dong Pao, in the India-Asia collision zone in northwestern Vietnam. The Dong Pao deposit is dated at ca. 52–51 Ma through zircon and bastnäsite Th-U-Pb chronometers. The ore-hosting carbonatites were emplaced as stocks with associated syenite. The carbonatite-syenite complex is significantly enriched in light REEs, Ba, and Sr and depleted in high-field strength elements, and has high (87Sr/86Sr)i ratios (>0.707) and low εNd(t) values (–6.5 to –5.6). These geochemical signatures imply that the carbonatite-syenite complex was derived from partial melting of subcontinental lithospheric mantle previously metasomatized and fertilized by REE- and CO2-bearing fluids. Timing of the REE-rich carbonatite-syenite complex indicates that it was related to a far-field stress within the early Eocene main-collision stage at 52–51 Ma rather than the late-collision stage at 42–35 Ma as previously thought. Collisional tectonism involving block rotation and fault activation are interpreted to have induced disturbance of the lithosphere mantle and created localized, transtensional/extensional environments oblique to the trend of the orogen that facilitated emplacement of the REE-rich carbonatitic magmas. Dong Pao appears to be the first identified, high-tonnage REE deposit that formed in the syncollisional geodynamic setting. Such a finding highlights that tectonic disturbance of an REE-rich lithosphere mantle distal to collision sutures has the potential to generate REE deposits, even during prominent convergence and collision of continents. As such, it defines additional search spaces for exploration of other REE orebodies of this style in complex collisional orogens.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"28 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-09-14","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72849214","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Combined X-Ray Computed Tomography and X-Ray Fluorescence Drill Core Scanning for 3-D Rock and Ore Characterization: Implications for the Lovisa Stratiform Zn-Pb Deposit and Its Structural Setting, Bergslagen, Sweden","authors":"S. Luth, Fredrik Sahlström, M. Bergqvist, Alexander Hansson, E. Lynch, Stefan Sädbom, E. Jonsson, S. Andersson, N. Arvanitidis","doi":"10.5382/econgeo.4929","DOIUrl":"https://doi.org/10.5382/econgeo.4929","url":null,"abstract":"\u0000 We present the results of a pilot study that integrates automated drill core scanning technology based on simultaneous X-ray computed tomography (XCT) and X-ray fluorescence (XRF) analyses to provide high-spatial-resolution (<0.2 mm) information on 3-D rock textures and structures, chemical composition, and density. Testing of its applicability for mineral exploration and research was performed by scanning and analyzing 1,500 m of drill core from the Paleoproterozoic Lovisa stratiform Zn-Pb sulfide deposit, which is part of a larger mineral system also including Cu-Co and Fe-(rare earth element) mineralization, hosted by the highly strained West Bergslagen boundary zone in south-central Sweden.\u0000 The obtained scanning data complements data derived from structural field mapping, drill core logs, and chemical analysis as well as from multiscale 3-D geologic modeling at Lovisa. Data integration reveals macro- and mesoscopic folding of S0/S1 by asymmetric steeply SE-plunging F2 folds and N-striking vertical F3 folds. Stretching lineations, measured directly from the scanning imagery, trend parallel to F2 fold hinges and modeled ore shoots at the nearby Håkansboda Cu-Co and Stråssa and Blanka Fe deposits. The textural character of the Lovisa ore zones is revealed in 3-D by XCT-XRF scanning and highlight remobilization of Zn and Pb from primary layering into ductile and brittle structures. The downhole bulk geochemical trends seen in scanning and traditional assay data are generally comparable but with systematic variations for some elements due to currently unresolved XRF spectral overlaps (e.g., Co and Fe).\u0000 The 3-D deformation pattern at Lovisa is explained by D2 sinistral transpression along the West Bergslagen boundary zone in response to regional north-south crustal shortening at ca. 1.84–1.81 Ga. Local refolding was caused by D3 regional east-west crustal shortening resulting in dextral transpression along the West Bergslagen boundary zone, presumably at ca. 1.80–1.76 Ga. Based on polyphase ore textures and modeled ore shoots aligned to F2 fold hinges, we postulate that D2 and D3 transpressive deformation exerted both a strong control on ore remobilization and the resulting orebody geometries at Lovisa and neighboring deposits within the West Bergslagen boundary zone.\u0000 We conclude that the combined XCT-XRF drill core scanning technique provides a valuable tool for 3-D ore and rock characterization, generating continuous downhole data sets, with the potential for increasing precision and efficiency in mineral exploration and mining.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"55 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"77345479","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Genesis of the Florida Canyon Nonsulfide Zn Ores (Northern Peru): New Insights Into the Supergene Mineralizing Events of the Bongará District","authors":"Rita Chirico, N. Mondillo, M. Boni, M. Joachimski, M. Ambrosino, Y. Buret, A. Mormone, Luis Enrique Nazareno Beteta Leigh, Willy Huaman Flores, G. Balassone","doi":"10.5382/econgeo.4941","DOIUrl":"https://doi.org/10.5382/econgeo.4941","url":null,"abstract":"\u0000 The Florida Canyon Zn deposit in the Bongará Province of northern Peru consists of sulfide and nonsulfide mineralizations within dolomitized strata of the Triassic Chambará Formation, a member of the Triassic-Jurassic Pucará Group. The nonsulfide mineralization, which represents one third of the total resource, formed by supergene alteration of Mississippi Valley-type sulfide bodies. The nonsulfide assemblages occur in stratabound or fault-related, discordant zones that mimic the shapes of the former sulfide zones. Two nonsulfide facies can be distinguished: facies 1 – red zinc ores, which are characterized by smithsonite, or hemimorphite-dominant bodies that formed by direct replacement of primary sulfide assemblages, and facies 2 – white zinc ores, which are characterized by masses of colloform smithsonite formed by replacement of wall rock. The facies are distinct in bulk chemical composition and stable isotope geochemistry. Facies 1 shows high concentrations of Zn, Pb, Fe, Ge, Mn, and As, whereas facies 2 shows only high Zn and Cd concentrations. Enrichments in Ge, which have been reported in other Zn deposits of the Bongará Province, are associated with hemimorphite, Fe hydroxides, and remnant sphalerite in facies 1. The δ13C and δ18O signatures of smithsonite in both facies suggest that meteoric waters infiltrating the precursor sulfide bodies were affected by kinetic fractionation and originated from multiple sources at different altitude.","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"340 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"76865215","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"THE IMPORTANCE OF GEOLOGY IN ASSESSING BY- AND COPRODUCT METAL SUPPLY POTENTIAL; A CASE STUDY OF ANTIMONY, BISMUTH, SELENIUM, AND TELLURIUM WITHIN THE COPPER PRODUCTION STREAM","authors":"Brian A. McNulty, S. Jowitt, I. Belousov","doi":"10.5382/econgeo.4919","DOIUrl":"https://doi.org/10.5382/econgeo.4919","url":null,"abstract":"\u0000 The ongoing global transition to low- and zero-CO2 energy generation and transport will require more raw materials and metals than ever produced before in human history to develop the necessary infrastructure for solar and wind power generation, electric power grid distribution, and electric vehicle componentry, including batteries. In addition to numerous critical elements, this transition will also require increased production of a range of other metals. This includes copper, with increased production of this metal providing the minerals industry with enhanced opportunities to secure the additional supply of associated or potential by-product elements. These include tellurium, selenium, bismuth, and antimony (among others), some of which are already predominantly produced as by-products from copper anode slimes. This study examines the geologic origins of over 240 active copper mines and over 200 electrolytic and electrowinning copper refineries worldwide. Although porphyry copper deposits dominate the copper supply trend, significant amounts of copper are supplied from the mining of sediment-hosted, massive sulfide, volcanogenic massive sulfide (VMS), and iron oxide-copper-gold (IOCG) mineral deposits. We integrate sources of copper concentrate with publicly available operational data for 32 copper electrorefineries to evaluate the geologic controls on the by-product supply potential of tellurium, selenium, bismuth, and antimony from copper anode slimes. These data represent some 32% of worldwide copper refineries and indicate that electrolytic refining of copper has the potential to supply ~777 t/yr tellurium, ~4,180 t/yr selenium, ~1,497 t/yr antimony, and 1,632 t/yr bismuth if 100% recovery of the by-product critical element proxies outlined in this study could be achieved. This is compared to current global production of ~490, ~2,900, ~153,000, and ~17,000 t/yr from all sources (rather than just copper by-products), respectively. Our analysis shows that there is no correlation between by-product potential and the amount of refined copper cathode production per year, but instead, the geologic origin of the copper concentrates is the key control on refinery by-product potential. This is exemplified by the fact that copper anode slimes derived from concentrates sourced from magmatic sulfide and VMS orebodies have an order of magnitude higher tellurium concentrations than those derived from porphyry deposits, reflecting the different abundances of tellurium within these mineral systems. These results are not surprising but demonstrate the possibilities for the development of robust proxies for by-product critical element supply potential using downstream data from copper (and potentially other base and precious metal) refineries. Equally significant, this study demonstrates the importance of downstream-up assessments of critical element potential as a complement to the more typical upstream-down deportment analyses undertaken to date. Finall","PeriodicalId":11469,"journal":{"name":"Economic Geology","volume":"4 1","pages":""},"PeriodicalIF":5.8,"publicationDate":"2022-09-01","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"82024798","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":1,"RegionCategory":"地球科学","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}