Tectonic evolution of the Northern Volcanic Zone, Abitibi belt, Quebec

Abstract

The Archean Abitibi Subprovince has been divided formally into a Northern Volcanic Zone (NVZ), including the entire northern part of the subprovince, and a Southern Volcanic Zone (SVZ) on the basis of distinct volcano-sedimentary successions, related plutonic suites, and precise U–Pb age determinations. The NVZ has been further formally subdivided into (i) a Monocyclic Volcanic Segment (MVS) composed of an extensive subaqueous basalt plain with scattered felsic volcanic complexes (2730–2725 Ma), interstratified with or overlain by linear volcaniclastic sedimentary basins; and (ii) a Polycyclic Volcanic Segment (PVS) comprising a second mafic–felsic volcanic cycle (2722–2711 Ma) and a sedimentary assemblage with local shoshonitic volcanic rocks.A sequence of deformational events (D1–D6) over a period of 25 Ma in the NVZ is consistent with a major compressional event. North–south shortening was first accommodated by near-vertical east-trending folds and, with continued deformation, was concentrated along major east-trending fault zones and contact-strain aureoles around synvolcanic intrusions, both with a downdip movement. Subsequent dextral strike-slip movement occurred on southeast-trending faults and major east-trending faults which controlled the emplacement of syntectonic plutons (2703–2690 Ma).This study suggests that the NVZ, which is a coherent geotectonic unit, initially formed as a diffuse volcanic arc, represented by the MVZ, in which the northern part, represented by the PVS, evolved into a mature arc as documented by a second volcanic and sedimentary cycle associated with major plutonic accretion. Volcano-sedimentary evolution and associated plutonism, as well as structural evolution, are best explained by a plate-tectonic model involving oblique convergence.

Physical volcanology, stratigraphy, and lithogeochemistry of an archean volcanic arc :

“…2730-2710 Ma NVZ and ca. 2705-2695 Ma SVZ (Corfu et al, 1989;Mortensen, 1993a;Mortensen, 1993b) is by a series of east-west faults such as the Destor-Porcupine and Manneville Faults (Chown et al, 1992;Daigneault et al, 1994) as well as by collisional flysch-type sedimentary basins (Mueller et al, 1996). An overall younging direction towards the south from the NVZ to the SVZ suggests a progressive evolution, which is supported by southward evolution of the sedimentary basins (Mueller and Donaldson, 1992).…”

“…Study area is outlined. Modified from Chown et al (1992), Mueller and Donaldson (1992), and Mueller at al. (1996).…”

“…Further work by Dimroth et al (1982) defined a northern Internal and a southern External zone based on the large volume of komatiitic volcanism in the south and the greater amount of intrusions, and mafic and ultramafic sills in the north and an overall difference in thickness. Recent work identified two distinct zones based on similar plutonic, volcanic, and deformation histories, as well as age constraints and are referred to as the Northern (NVZ) and Southern Volcanic Zones (SVZ) (Figure 3; Chown et al, 1992). The division between the ca.…”

“…Through sedimentary and structural work, the Abitibi Greenstone Belt is considered to represent a well-defined arc collage (Chown et al, 1992). Subsequent work recognized four evolutionary phases spanning the 90 My formation of the Abitibi belt from: (1) arc formation and construction (2730-2698 Ma); (2) arc-arc collision (2696-2690 Ma); (3) arc fragmentation (2689-2680 Ma); and (4) arc exhumation (2660-2640 Ma) (Mueller et al, 1996).…”

Caractérisation d'une minéralisation aurifère centrée sur une brèche intrusive, propriété Dubuisson, Val d'Or, Québec, Canada /

“…Toutes les phases répertoriées sur le terrain sont antérieures à l'hydrothermalisme de la veine #5. Plusieurs études structurales ont été effectuées en Abitibi afin d'établir l'évolution tectonique de cette partie du Supérieur (Dimroth et al, 1983;Robert, 1989;Chown et al, 1992;Desrochers et al, 1993;Kimura et al, 1993;1994;Daigneault, 1996;Desrochers et Hubert, 1996;Mueller et al, 1996;Daigneault et al, 2002;2004).…”