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TitleLow-temperature alteration at the world-class LaRonde Penna Archean Au-rich Volcanogenic Massive Sulfide deposit, Abitibi Subprovince, Québec, Canada: evidence from whole-rock oxygen isotopes
AuthorBeaudoin, G; Mercier-Langevin, P; Dubé, B; Taylor, B E
SourceA Special Issue on Archean magmatism, volcanism, and ore deposits:Part 2. volcanogenic massive sulfide deposits; by Mercier-Langevin, P (ed.); Gibson, H L (ed.); Hannington, M D (ed.); Goutier, J (ed.); Monecke, T (ed.); Dubé, B (ed.); Houlé, M G (ed.); Economic geology and the bulletin of the Society of Economic Geologists vol. 109, no. 1, 2014 p. 167-182,
Alt SeriesEarth Sciences Sector, Contribution Series 20110346
PublisherSociety of Economic Geologists
Mediapaper; on-line; digital
File formatpdf
NTS32D/01; 32D/08
AreaBousquet; LaRonde; Doyon
Lat/Long WENS-78.4661 -78.4150 48.2753 48.2203
Subjectsgeochemistry; alteration; Archean; volcanogenic deposits; sulphide deposits; gold; oxygen isotopes; isotopic studies; isotope geochemistry; hydrothermal alteration; lithology; structural analyses; mines; metamorphism; LaRonde Penna deposit; Abitibi Subprovince; Blake River Group; Precambrian
Illustrationsgeological sketch maps; isotopic analyses
ProgramGold Ore Systems, Targeted Geoscience Initiative (TGI-4)
Released2013 11 19
AbstractThe oxygen isotope composition of 169 whole-rock samples from the world-class LaRonde Penna Au-rich
volcanogenic massive sulfide deposit range from 6.5 to 22.0 o/oo). Fractional crystallization from basalt to rhyolite
accounts for a variation of approximately 2 o/oo) in primary whole-rock delta-18O values. The remaining variance
in whole-rock delta-18O values found at LaRonde Penna must therefore be ascribed to water-rock exchange with
hydrothermal fluids. The metamorphosed, hydrothermally altered host rocks have been subdivided according
to mineralogical assemblages, which display weak covariance with delta-18O values and whole-rock geochemical
alteration indices. Water-rock equilibrium exchange models indicate that the high delta-18O values that characterize
the LaRonde Penna deposit are compatible with low-temperature (~150ºC) hydrothermal alteration at high
water-rock oxygen atomic ratios (1-50). Zones of lower delta-18O values stratigraphically beneath the principal ore
lens (20 North) indicate local zones of higher temperature hydrothermal alteration. The oxygen isotope composition
of the hydrothermal fluid is estimated to have been ~5 o/oo, as a consequence of mixing between seawater
(delta-18O ~0 o/oo) and a component of magmatic water degassed from the volcanic and intrusive rocks associated
with the LaRonde Penna deposit.