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TitleSouthward younging Abitibi regional faults, supracrustal assemblages and gold mineralization
AuthorAyer, J; Dubé, B; Goutier, J; Thurston, P
SourceAbitibi workshop on research improving the understanding and exploration methodologies for gold and base metals; 2014.
LinksOnline - En ligne (PDF, 8 KB)
Alt SeriesEarth Sciences Sector, Contribution Series 20160379
MeetingTimmins Northeastern Ontario Mines and Minerals Symposium; Timmins; CA; April 15-17, 2014
Documentopen file
Mediapaper; on-line; digital
File formatpdf
ProvinceQuebec; Ontario
AreaAbitibi; Timmins; Kirkland Lake
Lat/Long WENS -82.0000 -80.0000 49.0000 48.0000
Subjectsstructural geology; stratigraphy; lithostratigraphy; base metals; metals; mineralization; mineral deposits; mineral occurrences; gold; faults; molybdenite; Abitibi Subprovince; Abitibi greenstone belt; Kidd-Munro Assemblage; Larder Lake-Cadillac deformation zones; Destor-Porcupine deformation zones; Precambrian
ProgramTargeted Geoscience Initiative (TGI-4), Gold Ore Systems
AbstractRegional 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.