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TitreVariations in phyllosilicate mineral chemistry from the massive sulphide deposits of the Bathurst Mining Camp, Canada: LA-ICP-MS systematics and its application in determination of volatile trace-element suite applicable in VMS exploration
AuteurSoltani Dehnavi, A; McFarlane, C R M; Lentz, D R; McClenaghan, S H
SourceNew Brunswick Exploration, Mining and Petroleum conference program and abstracts volume; 2014 p. 94
LiensOnline - En ligne
Séries alt.Secteur des sciences de la Terre, Contribution externe 20130538
RéunionNew Brunswick 2014 Exploration, Mining and Petroleum conference; Fredericton; CA; Novembre 2-4, 2014
Mediapapier; en ligne; numérique
SNRC21O/01; 21O/02SE; 21O/02NE; 21O/07SE; 21O/07NE; 21O/08; 21O/09; 21O/10SE; 21O/10NE; 21P/04; 21P/05; 21P/12
Lat/Long OENS-66.6667 -65.5000 47.7500 47.0000
Sujetsgîtes volcanogènes; sulfures; gîtes sulfureux; analyses des éléments en trace; induction électromagnétique; analyse par spectromètre de masse; méthodes analytiques; Camp minier de Bathurst; géochimie; minéralogie
ProgrammeÉtude des gîtes de sulfures massifs volcaniques, Initiative géoscientifique ciblée (IGC-4)
Résumé(disponible en anglais seulement)
An innovative approach for measuring the volatile trace-element suite (As, Cd, Hg, In, Sb, Tl, etc.) of hydrothermally altered rocks from the footwall and hanging wall of the Bathurst Mining Camp massive sulphide deposits is established in this study. The developed methodology for micro-analyses of major phyllosilicate minerals specifically white mica and chlorite, by in situ laser ablation ICP-MS includes an evaluation of optimized ablation conditions, choice of external standards, internal standardization and data reduction strategies (Iolite™ 2.5 Trace Element Data Reduction Scheme). Mineral assemblages of the BMC host rocks are predominantly composed of chlorite, white mica, and subordinate quartz, barium feldspar, plagioclase, septechlorite (greenalite), stilpnomelane, etc. Chlorite is a major silicate constituent, associating with the massive sulphides (disseminated to submassive sulphides) and exhalative sedimentary rocks along mineralized horizons. Optically, chlorite is typically pale-green or grass-green to yellowgreen in colour with typical Berlin-blue interference colour for Fe-rich varieties. Results of LA-ICP-MS of chlorite indicate average values of As=131 and Sb=589 ppm. Average contents of Tl (11.9 ppm), In (5.35 ppm), Hg (1.31 ppm), and Cd (0.43) were also established. White mica is ubiquitous in potassic (sericitic) alteration zones in quartzofeldspathic volcaniclastic, clastic and exhalative sedimentary rocks. In host rocks and semi-massive sulphide lenses, muscovite is typically associated with chlorite, forming fine-grained fibrous intergrowths in the groundmass. Based on previous studies, the composition of white mica is defined as solid solution between muscovite and celadonite (phengitic). White mica shows extensive systematic substitutions (e.g., Tschermaks substitution) allowing it to host a wide range of trace elements. Results from this study yielded an average As content of 90 ppm (ranging from 1.62 to 700 ppm) with the highest value recorded in the Halfmile lake deposit. Similarly, thallium is more enriched in this deposit ranging from 0.02-43.5 ppm. Other volatile trace elements occur in lower concentration in muscovite, including In (6 ppm), Sb (3.2 ppm), Hg (1.9 ppm), and Cd (0.17 ppm). Phyllosilicate chemistry can be used to distinguish the hydrothermal alteration zoning associated with massive sulphide deposition (e.g., proximal and distal halos). The knowledge obtained from the trace-element content of phyllosilicate minerals can, therefore, help to elucidate the processes controlling mineralization and the effects that metamorphism and deformation have on the dispersion of the volatile trace elements. Furthermore, the enrichment of volatile trace elements toward the upper stratigraphic sections of the drill cores examined to date can be used to map hydrothermal systems and to aide in VMS exploration.