|Titre||Southward younging Abitibi regional faults, supracrustal assemblages and gold mineralization|
|Auteur||Ayer, J; Dubé, B; Goutier, J; Thurston, P|
|Source||Abitibi workshop on research improving the understanding and exploration methodologies for gold and base metals; 2014.|
|Séries alt.||Secteur des sciences de la Terre, Contribution externe 20160379|
|Réunion||Timmins Northeastern Ontario Mines and Minerals Symposium; Timmins; CA; avril 15-17, 2014|
|Media||papier; en ligne; numérique|
|Lat/Long OENS|| -82.0000 -80.0000 49.0000 48.0000|
|Sujets||lithostratigraphie; métaux de base; métaux; minéralisation; gisements minéraux; gîtes minéralogiques; or; failles; molybdenite; Subprovince d'Abitibi ; Ceinture d'Abitibi Greenstone ; Assemblage de
Kidd-munro ; géologie structurale; stratigraphie; Précambrien|
|Programme||Étude des gîtes d'or, Initiative géoscientifique ciblée (IGC-4)|
|Liens||Online - En ligne (PDF, 8 KB) |
|Résumé||(disponible en anglais seulement)|
Regional faults and associated gold deposits young southward across the Abitibi. In the north, late tectonic assemblages, e.g. the Caopatina assemblage
turbiditic sediments, deposited ca. 2,700 Ma, are unconformably overlain by sediments and alkalic volcanics of the ca. 2,692 Ma Opemisca assemblage. In the NE Abitibi, gold mineralization associated with D1 is tightly constrained at 2,697±1 Ma by
mineralized and post-ore porphyry dikes. In the NW Abitibi at the Detour Mine, D1 resulted in ca. 2,725 Ma Deloro assemblage volcanics thrust over the Caopatina assemblage to the south along the Sunday Lake deformation zone (SLDZ). Subsequent
oblique-slip deformation overprinted D1 with both dextral and sinistral components of displacement. Gold occurs in the hanging wall of the SLDZ in narrow high grade zones next to flexures along the faulted contact between sediments and volcanics, and
also as broad, stockworkdisseminated lower grade zones in structurally overlying mafic flows. The age of a barren albitite dike cutting mineralization indicates that gold also occurred around 2,697 Ma.
South-verging auriferous thrusts extend south
to the Pipestone deformation zone (PDZ). Here, 2,720-10 Ma Kidd Munro assemblage volcanics were thrust over 2,690-80 Ma Porcupine assemblage turbidites. Gold occurs in the hanging wall of the PDZ and in intrusions within the fault zone. The timing of
D1 and gold mineralization is younger (i.e. <2,680 Ma) than in the northern Abitibi.
The Porcupine-Destor and Larder Lake-Cadillac deformation zones (PDDZ & LLCDZ) differ from more northerly structures in the spatial association with younger
unconformably overlying sediments and alkalic volcanics of the Timiskaming assemblage (2,676-70 Ma), and north-verging thrusting. Oblique-slip deformation overprinted the thrusting with sinistral followed by dextral displacements. Truncation of the
PDZ by the PPDZ also indicates the former is an older structure. Significant gold mineralization occurred at around 2,665-60 Ma along the PDDZ and LLCDZ. Further to the south, in the Shining Tree area, molybenite associated with gold mineralization
in a breccia pipe has been dated as young as ca. 2,630 Ma, further supporting the progressive southward younging and/or telescoping of gold events.
Controls on southward younging of tectonic events and gold mineralization are best explained by
successive episodes of accretion of terranes proceeding from collision of the Abitibi with the Opatica in the north and culminating in collision with the Minnesota River Valley terrane to the south. Southward younging accretionary-related fault
structures are thus considered the pathways for fluids bringing gold to the presently exposed crustal level.