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TitleSn-W-Mo polymetallic behaviour during magmatic evolution of Late Devonian Mount Douglas leucogranites, southwestern New Brunswick, Canada
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LicencePlease note the adoption of the Open Government Licence - Canada supersedes any previous licences.
AuthorMohammadi, N; Lentz, D R; Thorne, K G
SourceTGI 4 - Intrusion Related Mineralisation Project: new vectors to buried porphyry-style mineralisation; by Rogers, N (ed.); Geological Survey of Canada, Open File 7843, 2015 p. 567-568, Open Access logo Open Access
LinksCanadian Database of Geochemical Surveys, downloadable files
LinksBanque de données de levés géochimiques du Canada, fichiers téléchargeables
PublisherNatural Resources Canada
Documentopen file
Mediaon-line; digital
RelatedThis publication is contained in TGI 4 - Intrusion Related Mineralisation Project: new vectors to buried porphyry-style mineralisation
File formatpdf
ProvinceNew Brunswick
AreaMount Douglas
Lat/Long WENS -68.0000 -66.5000 46.0000 45.0000
Subjectseconomic geology; tectonics; mineralogy; porphyry deposits; porphyry copper; mineral exploration; mineralization; leucogranites; hydrothermal deposits; hydrothermal alteration; tungsten; molybdenum; gold; antimony; magmatic rocks; magmatic deposits; magmatism; evolution; Paleozoic; Devonian
Illustrationslocation maps; plots; ternary diagrams
ProgramTargeted Geoscience Initiative (TGI-4) Intrusion/Porphyry Ore Systems
Released2015 06 11
AbstractThe Mount Douglas intrusive suite consists of an assemblage of peraluminous leucogranites located along the eastern part of the Saint George Batholith in southwestern New Brunswick, Canada. This late Devonian suite extends from Red Rock Lake to Mount Douglas, and is interpreted to represent the subvolcanic portion of the Mount Pleasant Sn-W-Mo-Bi-In-Zn deposits. The magmatic systems in the Mount Douglas suite have undergone extreme differentiation producing three distinct phases, including Dmd1, Dmd2, and Dmd3, and are associated with various granophile-element occurrences, such as Sn, W, and Mo. It seems the three phases might originate from a single source that evolves with increasing fractionation from the earliest unit (Dmd1) to the youngest unit (Dmd3).
Metal behavior during fractional crystallization is one of the most important factors affecting the types of mineral occurrences associated with the Mount Douglas granites. To establish the metal behavior in the Mount Douglas suite, analytical data from Malcolm McLeod's 1990 report was used in this study. The most incompatible element, Ta, has been selected for defining partition coefficients (D) using the Allegre method. Based on their D values, as expected, Sn with Rb, Y, Nb, LREE [La, Ce, Nd, and Sm], HREE [Tb, Dy, Tm, Yb, and Lu], Pb, Th, and U behave as incompatible elements; showing the Mount Douglas Granite could be considered for exploration of Sn deposits as previous studies have mentioned. However, W and Mo accompanied with the other elements, such as Li, P, Sc, Ti, Cu, Zn, Sr, Zr, Cs, Ba, Eu, and Hf seem to act as compatible elements during magmatic evolution, although melt - supercritical fluid evolution can easily affect W, Mo, Cs, and Li abundances. The apparent compatibility of W and Mo is in contrast with the expected results in which they might act as incompatible elements for developing considerable potential for W-Mo deposits. However, W and Mo concentrations increased with the degree of fractionation and show a significant enrichment in the Mount Douglas granites relative to other granitoid suites in the region; thus their compatibility may be the result of leaching or partitioning out during volatile exsolution, or low pressure fractionation. Furthermore, very low K/Rb (average 102.7), Nb/Ta (? 6.83), and Zr/Hf (? 35.58) ratios, and high Ti/ Sc (125.3 ?) ratio in Dmd3 compared to Dmd1 possibly reflect significant involvement of extreme low T crystal fractionation or even fluid fractionation in the last-stage magmatic differentiation. Consequently, although much more analytical data are needed for exact evaluation of the mineral occurrences in the Mount Douglas Granites, Dmd3 as the most highly differentiated phases might be considered a superior candidate for hosting of Sn-W-Mo deposits.
Summary(Plain Language Summary, not published)
The Targeted Geoscience Initiative (TGI-4) is a collaborative federal geoscience program that provides industry with the next generation of geoscience knowledge and innovative techniques to better detect buried mineral deposits, thereby reducing some of the risks of exploration. This volume summarises research activities completed under the TGI 4 Intrusion Related Mineralisation Project that focused on porphyry-style ore systems related to the Cu- and Cu-Mo deposits of South-Central British Columbia and the Sn-W-Mo-In deposits in New Brunswick, Nova Scotia and Newfoundland.

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