Setting, age, and hydrothermal footprint of the emerging Meliadine gold district, Nunavut.

The Meliadine gold district comprises a combination of orogenic greenstone- and BIF-hosted gold mineralisation. The largest gold deposits (Tiriganiaq, Wesmeg, Normeg, F Zone, Pump, Discovery, and Wolf) are cospatial with the northwest-trending Pyke Fault. Gold in the district is associated with hydrothermally altered and sulphidised BIF and fault-fill quartz (± ankerite) veins. Hydrothermal alteration and pathfinder element enrichment (As-Te-Bi-Sb) can be mapped following a multivariate and probabilistic approach for 10s to 100s of meters beyond BIF-hosted replacement-style mineralisation. Coarse-grained and idioblastic arsenopyrite crystals occur within and at the margins of folded quartz (± ankerite) veins and are also a good visual gold indicator. Gold is paragenetically late and occurs at arsenopyrite grain boundaries and/or as fracture fills. Clusters of gold inclusions coincide with recrystallised and sieve-textured arsenopyrite domains, suggesting that sulphide recrystallisation liberated gold was redistributed, concurrent with the growth of xenotime at ca. 1.86 Ga (new U-Pb ages). New Re-Os arsenopyrite model ages range from 2.3 to 1.8 Ga and document a hitherto unrecognised pre-1.86 Ga hydrothermal and sulphide history. It is speculated that gold at the Meliadine gold district was initially introduced at 2.27 Ga and/or 1.90 Ga along with arsenopyrite and was subsequently remobilised, coupled with arsenopyrite recrystallisation, during the Trans-Hudson Orogeny at 1.86-1.85 Ga.
The Meliadine gold district comprises a combination of orogenic greenstone- and BIF-hosted gold mineralisation. The largest gold deposits (Tiriganiaq, Wesmeg, Normeg, F Zone, Pump, Discovery, and Wolf) are cospatial with the northwest-trending Pyke Fault. Gold in the district is associated with hydrothermally altered and sulphidised BIF and fault-fill quartz (± ankerite) veins. Hydrothermal alteration and pathfinder element enrichment (As-Te-Bi-Sb) can be mapped following a multivariate and probabilistic approach for 10s to 100s of meters beyond BIF-hosted replacement-style mineralisation. Coarse-grained and idioblastic arsenopyrite crystals occur within and at the margins of folded quartz (± ankerite) veins and are also a good visual gold indicator. Gold is paragenetically late and occurs at arsenopyrite grain boundaries and/or as fracture fills. Clusters of gold inclusions coincide with recrystallised and sieve-textured arsenopyrite domains, suggesting that sulphide recrystallisation liberated gold was redistributed, concurrent with the growth of xenotime at ca. 1.86 Ga (new U-Pb ages). New Re-Os arsenopyrite model ages range from 2.3 to 1.8 Ga and document a hitherto unrecognised pre-1.86 Ga hydrothermal and sulphide history. It is speculated that gold at the Meliadine gold district was initially introduced at 2.27 Ga and/or 1.90 Ga along with arsenopyrite and was subsequently remobilised, coupled with arsenopyrite recrystallisation, during the Trans-Hudson Orogeny at 1.86-1.85 Ga.