Publication Type:
Book ChapterSource:
Targeted Geoscience Initiative 4; Canadian nickel-copper-platinum group elements-chromium ore systems; fertility, pathfinders, new and revised models, Geological Survey of Canada, Calgary, AB, Canada, p.287-301 (2015)Keywords:
absolute age, alkaline earth metals, Ar/Ar, Archean, Canada, Canadian Shield, chalcopyrite, copper ores, dates, eastern canada, gabbros, Hydrothermal alteration, igneous rocks, isotope ratios, Isotopes, metal ores, metals, metasomatism, mineral deposits, genesis, nickel ores, North America, O-18/O-16, Ontario, oxygen, Petrology, platinum group, plutonic rocks, Precambrian, S-34/S-32, Sr-87/Sr-86, Stable isotopes, strontium, Sudbury Igneous Complex, sulfides, sulfur, superior province, U/Pb, veinsAbstract:
An integrated geological, petrological, and geochronological study of the Grey Gabbro (GG) unit of the Podolsky Cu-(Ni)-PGE deposit, which is located in a radial dyke of the 1850 Ma Sudbury Igneous Complex (SIC), indicates it is a dislodged fragment of alkalic gabbroic basement rock with a minimum age of ca. 2714 Ma (U-Pb zircon). Petrographic textures in the GG record both the impact event (e.g. planar deformation features in zircon) and subsequent thermal overprinting from the cooling SIC melt sheet; U-Pb dating of epitaxial zircon overgrowths yielded concordant dates at ca. 1850 Ma. Petrological study of the GG adjacent to sharp-wall chalcopyrite veins provides a number of insights into the origin of mineralization in the high-sulphide Cu-PGE Podolsky deposit. 1) Actinolite fibres (1 m from the sulphide veins, geochemical modification from fluid:rock interaction is minimal in the GG, with Cu the only distal indicator of mineralization (i.e. 100s ppm Cu). 4) Isotopic data (Sr, O, S) indicate that S in the Podolsky deposit is similar to that of the Whistle contact Ni-Cu deposit and is sourced from the melt sheet (delta 34S (sub cpy) = 4.3ppm). These observations indicate that alteration within the GG is the result of the equilibration of hightemperature magmatic-derived fluids with the GG and that the GG is part of the pre-impact history of the area. Intense hydrothermal alteration in the GG occurs only adjacent (<10s cm) to the sharp-walled sulphide veins and thus does not provide a significant vector for exploration.
Notes:
GeoRef, Copyright 2018, American Geological Institute.<br/>2016-108644<br/>Grey Gabbro<br/>Norman Ontario<br/>Podolsky Deposit
