Publication Type:

Journal Article

Authors:

Kontak, Daniel J.; Horne, Richard J.; Kyser, Kurt

Source:

Mineralium Deposita, Springer-Verlag, Berlin, Germany, Volume 46, Number 3, p.289-304 (2011)

ISBN:

0026-4598

Keywords:

Canada, eastern canada, folds, geochemistry, gold ores, intrusions, isotope ratios, Isotopes, Maritime Provinces, Meguma terrane, metal ores, Metallogeny, Metamorphic rocks, metasedimentary rocks, mineral deposits, genesis, Mineral exploration, modal analysis, Nova Scotia, O-18/O-16, orogenic belts, oxygen, Petrology, South Mountain Batholith, Stable isotopes, structural controls, tectonics, terranes, veins

Abstract:

Sampling of quartz vein material from two gold deposits of similar geological setting but different ages (The Ovens, 408 Ma; Dufferin, 380 Ma) in the Meguma Terrane of Nova Scotia has been done to compare and contrast their delta (super 18) O (sub quartz) signatures. Despite different ages of formation, quartz from all vein types in each of the deposits (i.e. saddle-reef, bedding-concordant leg reefs, en echelon, discordant) shows limited intra-deposit variation with similar average delta (super 18) O values of +15.2+ or -0.9 ppm (n=16) for The Ovens and +15.7+ or -0.6 ppm (n=12) for Dufferin. Using an average delta (super 18) O value of +15.4 ppm for the two deposits, the corresponding delta (super 18) O (sub H2O) values, calculated for 400 degrees C and 350 degrees C based on constraints from mineral assemblages and fluid inclusion studies, indicate averages of 11.4+ or -0.2 ppm and +10.2+ or -0.2 ppm, respectively. The isotopic data indicate that: (1) the vein-forming fluids have a metamorphic signature, (2) all vein types in the two deposits represent formation from a single, isotopically homogeneous fluid, and (3) a fluid of similar isotopic signature was generated by two contrasting tectono-thermal events in the Meguma Terrane that were separated by 30 Ma. Integration of these results with previously published data for 14 Meguma gold deposits indicate a general stratigraphic dependence in delta (super 18) O (sub H2O) values for deposits when arranged in their relative stratigraphic position such that delta (super 18) O (sub H2O) values increase upwards in the stratigraphy. This apparent trend cannot be explained by models involving either fluid mixing or cooling of the vein-forming fluids, but instead is modelled using fluid/rock interaction taking into account a change in the modal mineralogy of the metasedimentary rocks upwards in the stratigraphy. Copyright 2011 Springer-Verlag

Notes:

GeoRef, Copyright 2018, American Geological Institute.<br/>2011-076687<br/>Dufferin Deposit<br/>The Ovens Deposit