Publication Type:Book Chapter
Source:An in-depth look into the dynamics of Precambrian volcanic and sedimentary terranes; in memory of Wulf U. Mueller, Elsevier, Amsterdam, International, Volume 214-215, p.1-27 (2012)
Keywords:Abitibi Belt, absolute age, Archean, Blake River Group, calderas, Canada, Canadian Shield, collapse structures, dates, dikes, domes, eastern canada, faults, grabens, igneous rocks, intrusions, lithostratigraphy, mafic composition, metamorphic belts, Metamorphic rocks, metavolcanic rocks, models, North America, Pontiac County Quebec, Pontiac Subprovince, Precambrian, quebec, rhyolites, sills, superior province, systems, U/Pb, volcanic features, volcanic rocks
The Archean Blake River Group of the Abitibi greenstone belt represents a megacaldera complex which evolved over 8-11 M.y. from approximately 2704 to 2696 Ma. The early Misema Caldera developed from a series of amalgamated shield volcano complexes identified by the remnants of mafic dyke and sill systems. These remnants are found in the Jevis-Clericy, Montsabrais-Renault, Clifford-Tannahill and Colnet regions, where summit calderas are delineated by circular ring dyke structures. The secondary 330 degrees -trending New Senator Caldera formed within the envelope of the Misema Caldera and exhibits a box-work graben-type structure. Finally, the felsic-dominated, 070 degrees -striking Noranda Caldera, well known for its VMS endowment, represents the final collapse of the megacaldera complex. Deformation has overprinted the calderas, but structural patterns can be used in order to reconstruct the pre-existing volcanic architecture. Structures such as mafic ring dyke complexes and rhyolitic dome-flow complexes have nucleated fold geometries and synvolcanic fractures were reactivated within zones of ductile deformation. Precise U-Pb geochronological analyses were conducted in selected areas with specific emphasis on the Misema and New Senator calderas. Felsic volcanism progressed throughout the evolution of the megacaldera complex and intermediate to felsic units have been dated to limit this evolution. The Misema Caldera formed between 2704 and 2702 Ma via the amalgamation of shield volcanoes that were probably active prior to 2704 Ma. The New Senator Caldera was generated between 2702 and 2700 Ma during paroxysmal felsic volcanism, followed by the collapse of the Noranda Caldera culminating between 2700-2696 Ma. The Misema Caldera was generated by a gravitational stress field consistent with the formation of ring and radial dyke architecture, whereas the SE-trending New Senator Caldera is more compatible with a SW-trending principal compression direction related to oblique convergence in the Abitibi belt. The Noranda Caldera is interpreted as a NE rift structure that formed in the final stages of megacaldera evolution. Abstract Copyright (2012) Elsevier, B.V.
GeoRef, Copyright 2018, American Geological Institute.<br/>2013-064990<br/>Clifford-Tannahill Quebec<br/>Colnet Quebec<br/>Jevis-Clericy Quebec<br/>Misema Caldera<br/>Montsabrais-Renault Quebec<br/>New Senator Caldera<br/>Noranda Caldera