Ion-microprobe analysis of pyrite, chalcopyrite and pyrrhotite from the Mobrun VMS deposit in northwestern Quebec; evidence for metamorphic remobilization of gold
Ion-microprobe analysis of pyrite, chalcopyrite and pyrrhotite from the Mobrun VMS deposit in northwestern Quebec; evidence for metamorphic remobilization of gold (in Microbeam techniques in the earth sciences, Frank C. Hawthorne (editor) and R. F. Martin (editor))
The Canadian Mineralogist (April 1995) 33, Part 2: 373-388
- alloys
- Canada
- chalcopyrite
- copper
- detection limit
- Eastern Canada
- electrum
- gold
- gold ores
- ion probe data
- mass spectra
- massive deposits
- massive sulfide deposits
- metal ores
- metals
- metamorphism
- mobilization
- Noranda Quebec
- pyrite
- pyrrhotite
- Quebec
- recrystallization
- silver
- spectra
- sulfides
- veins
- volcanism
- zinc
- Mobrun Deposit
The invisible (refractory) Au contents of pyrite, chalcopyrite and pyrrhotite in the Mobrun Zn-Cu-Ag-Au deposit in the Noranda district of Quebec were determined by ion microprobe; samples were sputtered with a Cs (super +) primary beam, and negative secondary ions were measured. Mass interferences were eliminated by operating in high-mass-resolution mode, giving minimum limits of detection of 50 ppb. The primary pyrite contains up to 10 ppm Au as submicroscopic inclusions of metallic gold, as well as very fine colloid-size or structurally bound Au. It is concluded that syngenetic gold is present in the Mobrun orebodies, and that metamorphic recrystallization resulted in its release from pyrite. The remobilized Au was deposited in tectonic veins as easily recoverable electrum and as 'invisible' Au in secondary chalcopyrite.
