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TitleUsing magmatic biotite chemistry to differentiate barren and mineralized Silurian-Devonian granitoids of New Brunswick, Canada
AuthorAzadbakht, ZORCID logo; Lentz, D R; McFarlane, C R M; Whalen, J B
SourceContributions To Mineralogy and Petrology vol. 175, 69, 2020 p. 1-24,
Alt SeriesNatural Resources Canada, Contribution Series 20200115
Mediapaper; on-line; digital
File formatpdf; html (Adobe® Reader®); xlsx (Microsoft® Excel®)
ProvinceNew Brunswick
NTS21G; 21I/12; 21I/13; 21J; 21O; 21P/04; 21P/05; 21P/12; 21P/13
AreaBathurst; Fredericton; Saint John
Lat/Long WENS -68.0000 -65.5000 48.0000 45.0000
Subjectseconomic geology; geochemistry; mineralogy; tectonics; Science and Technology; Nature and Environment; mineral potential; mineralization; bedrock geology; lithology; igneous rocks; intrusive rocks; felsic intrusive rocks; granodiorites; granites; leucogranites; tectonic setting; magmatism; intrusions; magmas; biotite; apatite; geochemical analyses; trace element analyses; major element analyses; electron probe analyses; mass spectrometer analysis; mineralogical analyses; crystal fractionation; fractional crystallization; crystallization; metallogeny; petrographic analyses; pressure-temperature conditions; geothermometry; petrogenesis; fluid dynamics; Appalachian Orogen; Central Plutonic Belt; Mount Elizabeth Granite; Mount Douglas Granite; Phanerozoic; Paleozoic; Devonian; Silurian
Illustrationslocation maps; geoscientific sketch maps; tables; photomicrographs; ternary diagrams; plots; phase diagrams
ProgramTargeted Geoscience Initiative (TGI-5) Intrusion/Porphyry ore systems - arc-related porphyry systems - time and space
Released2020 06 23
AbstractThe geochemistry of biotite crystals from thirty fertile and barren Silurian-Devonian granitoids of New Brunswick, Canada, was studied in situ using electron microprobe and laser ablation inductively coupled plasma-mass spectrometry to investigate the suitability of biotite geochemistry as a diagnostic fertility index among these intrusions. The Fe2+/(Fe2+ + Mg2+) ratio of biotite varies as a function of intrusion metal affinity, increasing from Cu-Mo-related (mean of 0.56 ± 0.12), to Mo-related (mean of 0.69 ± 0.06) to Sn-W-related (mean of 0.77 ± 0.16), with barren granitoids lying between Cu-Mo and Mo types (mean of 0.66 ± 0.06). The results show a distinctive geochemical contrast between mineralized and barren samples. Compatible elements (Ti, Mg, Co, Ni, V, Cr, Ba, and Sr) decrease from barren to Cu-Mo, Mo, and Sn-W granitoids, whereas incompatible elements (Mn, Zn, Sn, W, Rb, Cs, and Li) show the opposite trend. These two trends might indicate higher degree of fractionation indicated by biotite chemistry in Sn-W-related granites. Furthermore, barren intrusions have the lowest water content (1-3 wt.% H2O), whereas Sn-W and Cu-Mo-related intrusions have between 3 and 6 wt.% H2O. Mo-bearing intrusions have a limited range of H2O contents (4-4.5 wt.%). A high degree of halogen enrichment related to degree of fractional crystallization results in enrichment of incompatible elements in the magmas associated with Sn-W mineralization and is reflected by the geochemical characteristics of biotite from these systems. New metallogenic classifications are introduced using ternary V-Na-Li (ppm) and Sn + W (ppm) versus Ga (ppm) to differentiate barren and mineralized granitic systems in New Brunswick.

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