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TitreFluid inclusion and stable isotope evidence for mixing of magmatic - hydrothermal fluids with meteoric water in vein-type Cu-Au-Bi deposits, southern New Brunswick, Canada
TéléchargerTéléchargement (publication entière)
AuteurHanley, J J; Tweedale, F; Neyedley, K; Sharpe, R; Fayek, M
SourceTGI 4 - Intrusion Related Mineralisation Project: new vectors to buried porphyry-style mineralisation; par Rogers, N (éd.); Commission géologique du Canada, Dossier public 7843, 2015 p. 361-368, https://doi.org/10.4095/296476
Année2015
ÉditeurRessources naturelles Canada
Documentdossier public
Lang.anglais
DOIhttps://doi.org/10.4095/296476
Mediaen ligne; numérique
Référence reliéeCette publication est contenue dans Rogers, N; (2015). TGI 4 - Intrusion Related Mineralisation Project: new vectors to buried porphyry-style mineralisation, Commission géologique du Canada, Dossier public 7843
Référence reliéeCette publication est reliée à Hanley, J J; Tweedale, F; Neyedley, K; Sharpe, R; Fayek, M; (2014). Fluid inclusion and stable isotope evidence for mixing of magmatic- hydrothermal fluids with meteoric water in vein-type Cu-Au-Bi deposits, southern New Brunswick, Canada, L'Association géologique du Canada-L'Association minéralogique du Canada, Réunion annuelle conjointe, Recueil des résumés vol. 37
Formatspdf
ProvinceNouveau-Brunswick
SNRC21A; 21G; 21H
Lat/Long OENS -68.0000 -66.5000 46.0000 45.0000
Sujetsgisements porphyriques; cuivre porphyrique; prospection minière; minéralisation; tungstène; molybdène; étain; bismuth; cuivre; or; inclusions fluides; gîtes magmatiques; altération hydrothermale; études des isotopes stables; filons de quartz; salinité; gisements filoniens; eaux atmosphériques; Dépôt de Mount Pleasant ; Groupe de Broad River ; géologie économique; géochimie; minéraux métalliques; Paléozoïque; Dévonien
Illustrationslocation maps; plots; photographs; photomicrographs
Consultation
Endroit
 
Bibliothèque de Ressources naturelles Canada - Ottawa (Sciences de la Terre)
 
ProgrammeÉtude des gîtes porphyriques, Initiative géoscientifique ciblée (IGC-4)
LiensCanadian Database of Geochemical Surveys, downloadable files
LiensBanque de données de levés géochimiques du Canada, fichiers téléchargeables
Diffusé2015 06 11
Résumé(disponible en anglais seulement)
Vein-type Cu-Au-Ag-Bi mineralization in the Caledonian Highlands, southern NB, Canada, is hosted within quartz-carbonate-rich shear zones cutting felsic lithic tuffs, intermediate intrusives and interbedded felsic and mafic flows of the Neoproterozoic Broad River Group. Mineralization in the veins consists of bornitechalcocite- hematite, coprecipitated with electrum and bismuthinite; ore minerals post-date quartz and REE-rich carbonates in the veins, with later supergene oxidation and hydration of the ores to cuprite-malachite. Wall-rock alteration is characterized by albitization and paragonitization. Replacement of bornite by chalcocite- hematite indicates changes in fluid redox with mineralization progression.
Trails of secondary fluid inclusions in the quartz veins are two-phase liquid-vapour at room temperature. Homogenization occurs by vapour bubble disappearance between 150-270°C for all assemblages; individual assemblages show relatively narrow ranges (e.g., 173-191°C, n=22). Bulk salinities from final ice melting range from 4 to 13 wt% NaCl eq. with individual assemblages showing similarly narrow ranges.
Stable isotope data (bulk separates, and in-situ by secondary ion mass spectrometry [SIMS]) for vein-stage quartz (d18Obulk = 13.7-15.1perthousand; d18OSIMS-qtz = 10.8±1.5 perthousand, 1c, n=32) and carbonate (d13Cbulk = -4.4 to -4.6 perthousand) combined with microthermometric data rule out unmodified, heated seawater and meteoric water as the dominant fluid components, and suggest that the metal-bearing fluids were magmatic in origin or represented saline formation waters modified through fluid-rock interaction with the host volcanic rocks (calculated d18Ofluid ~ 6-7 perthousand). However, significant variations in d18OSIMS-qtz are observed within single quartz crystals across growth zones and in massive quartz texturally predating sulfides and gold (from as low as 8.2 perthousand to 14.8 perthousand in quartz enclosed entirely within bornite-chalcocite). This indicates either (i) localized mixing of the metal-bearing fluid with low latitude meteoric water (calculated d18O = -1.0 to 0 perthousand), or (ii) fluctuations in fluid temperature during vein formation, with the lowest T portions of the vein associated with base metal-gold precipitation, or (iii) both. The isotopic composition of coeval quartz-carbonate predict a crystallization/final equilibration T of vein-stage at ~250- 270°C; if inclusions are primary, then a maximum Ptrapping = ~1.5 kbar, based on the lowest T assemblages, is estimated.
Significant fluctuations in fO2, fluid temperature or fluid composition during vein precipitation highlight the importance of fluid mixing for mineralization. These characteristics, combined with the style of mineralization, link these deposits in NB genetically to much larger vein Cu deposits worldwide (e.g., Churchill, Davis-Keays, and Mamainse Point, Canada; Inyati, Zimbabwe; Copper Hills, Australia; Messina, South Africa; Cornwall, UK).
GEOSCAN ID296476