Meeting to take place live and on zoom on July 3rd at 7pm.
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Abstract:
The Porcupine Mining District with ~90 Moz Au in production and resources lies in the Archean age western Abitibi Greenstone Belt adjacent to the Destor-Porcupine Fault system. Principal host rocks are mafic volcanic units of the Tisdale Assemblage which are affected by pre-metamorphic folds, and locally, are structurally interleaved with turbidites of the Porcupine Assemblage. These units are unconformably overlain by a belt of clastic, syn-tectonic Timiskaming Assemblage metasedimentary rocks that occur along the north side of the Destor-Porcupine Fault.
Gold deposits comprise quartz-carbonate vein arrays in areas of carbonate alteration that have been superimposed on already deformed host rocks. The vein arrays have been interpreted to have formed during D3 post-Timiskaming greenschist facies, syn-metamorphic, NE-SW directed, sinistral transpression. Vein style and orientation evolved in each deposit as deformation proceeded and are kinematically and temporally linked to the metamorphic fabrics. These include the moderate to steep D3 east-plunging stretching lineation, which coincides with the principal oreshoot plunge in most deposits.
Mineralization in the giant Hollinger-McIntyre (>34 Moz Au) and Dome-Preston-Paymaster (>30 Moz) deposits occur over plunge lengths of >2.5 km in arrays of oblique, reverse-sigmoidal, extension and shear veins. Both deposits occur within areas of early structural complexity where pre-metamorphic faults and folds focus shear strain and vein sets in areas of high, rheological contrast and complexity. The Pamour deposit (~12 Moz) comprises conjugate shear and extension veins that straddle the Timiskaming unconformity. The Hoyle Pond, Bell Creek and Aunor-Delnite deposits comprise early stage, grey-quartz shear veins hosted by thin, mafic belts between reactivated, early, pre-metamorphic thrust faults.
The deposits of the Porcupine District show comparable setting and style to other orogenic gold deposits globally and provide predictive understanding for this classic style of mineralization. New discoveries in the Matheson area and along the Pipestone Fault corridor illustrate the potential for further deposit styles east and north of the core of the main district.