Andean style 1.50–1.35 Ga arc dynamics in the Southeastern Laurentian margin: The rifting and reassembly of Quebecia

Abstract

AbstractQuebecia is a unique Geon 15 to 13 composite arc belt in the central Grenville Province that preserves record of rifting and subsequent re‐amalgamation of part of the Laurentian margin. Key lithological components include: (a) c. 1.5 Ga metasedimentary sequences indicative of earlier rifting of the Laurentian margin; (b) remnants of 1.50–1.45 Ga peri‐Laurentian island arcs to the south built on rifted crustal slivers; (c) 1.45–1.42 Ga mafic dyke swarms to the northwest, linked to an asthenospheric window or back‐arc opening; (d) a major 1.43–1.37 Ga felsic plutonic belt marking the time of accretion to Laurentia; and (e) 1.38–1.35 Ga AMCG complexes suggesting slab‐breakoff and mafic underplating of the lower crust during arc accretion. Differences between Quebecia and continental arcs of the same age on both sides attest to lateral variations in subduction dynamics under Laurentia comparable to the modern‐day Andean system.