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TitlePetrology of the Lake George granodiorite stock, New Brunswick: implications for crystallization conditions, volatile exsolution, and W-Mo-Au-Sb mineralization
AuthorYang, X; Lentz, D R; Hall, D C; Chi, G
SourceGeological Survey of Canada, Current Research (Online) no. 2002-E14, 2002, 12 pages, (Open Access)
PublisherNatural Resources Canada
Mediapaper; on-line; digital; CD-ROM
RelatedThis publication is contained in Geological Survey of Canada; (2002). Current Research 2002, summer release, Geological Survey of Canada, Current Research no. 2002
File formatpdf
ProvinceNew Brunswick
NTS21G/14; 21G/15
AreaLake George; Fredericton
Lat/Long WENS-67.5000 -66.5000 46.0000 45.7500
Subjectsigneous and metamorphic petrology; geochemistry; granodiorites; intrusive rocks; igneous rocks; gold; molybdenum; tungsten; antimony; mineralization; vein deposits; magmatism; analytical methods; apatite; titanite; amphibole; feldspar; biotite; crystallization; exsolution; emplacement; Kingsclear Group; electron microprobe analyses; Devonian; Silurian; Paleozoic
Illustrationssketch maps; diagrams; photomicrographs; tables; ternary diagrams
ProgramTargeted Geoscience Initiative (TGI-1), 2000-2003
Released2002 09 16
AbstractThe Lake George Sb vein deposit is spatially and temporally associated with W-Mo-Au mineralization that is genetically related to an Early Devonian granodiorite stock at depth. The fine to medium-grained porphyritic granodiorite consists of quartz, plagioclase, orthoclase, biotite, and trace hornblende, with minor titanite, zircon, apatite, ilmenite, and trace magnetite. Apatite started to crystallize at 881°C to 911°C, followed by hornblende, biotite, and plagioclase at 729°C to 772°C, then quartz and orthoclase. The magmatic system was reset by late-stage subsolidus processes under 500°C. Early hornblende phenocrysts started to crystallize at 5 kbar during magma ascent, but final emplacement of the stock was epizonal (less than 2 kbar). Magmatic fluids equilibrated with biotite are characterized by Cl-rich compositions, large variations in halogen fugacity ratios, and reducing conditions; the evolving fluids emanated from the progressively crystallizing magma at depth, favouring Au partitioning from magma to the hydrothermal system.