The Geon 14 arc-related mafic rocks from the central Grenville Province

Abstract

The late Paleoproterozoic to Mesoproterozoic (ca. 1.7–1.2 Ga) evolution of the active southeastern margin of Laurentia terminated with the Grenvillian continental collision and the development of a large, hot, long-duration orogen at ca. 1.09–0.98 Ga. As a result, much of the hinterland of the Grenville Province consists of Paleoproterozoic and Mesoproterozoic rocks, mostly preserved as an imbricate stack of high-grade gneisses, that represent a potential repository of active-margin processes. This study presents geochronologic, geochemical, and isotopic analyses of two granulite-facies suites of ca. 1.45–1.40 Ga mafic tholeiites from the Canyon domain (Manicouagan area, central Grenville Province). One suite consists of 1439 +76/–68 Ma high-FeTi mafic sills with εNd values of –0.4 (TDM 2.57–2.72 Ga), indicate derivation from variably depleted to enriched MORB-type mantle sources, probably in an extensional back-arc setting, before intrusion in a ca. 1.5 Ga supracrustal metasedimentary sequence. The other, previously dated, 1410 ± 16 Ma Mafic to intermediate unit exhibits εNd values of 0.0 to +0.9 (TDM 2.02–2.25 Ga), and variably enriched MORB to arc geochemical signatures, for which formation in a transitional back-arc to arc setting is suggested. Integrated with published information, the new data support a model of a long-lived continental-margin arc and intermittent back-arc development on southeast Laurentia during the mid-Mesoproterozoic (ca. 1.5–1.4 Ga), in which repeated short periods of extension and crustal thinning in the back-arc or intra-arc regions were followed by compression and crustal thickening.

Petrogenesis of LREE-rich pegmatitic granite dykes in the central Grenville Province by partial melting of Paleoproterozoic-Archean metasedimentary rocks: Evidence from zircon U-Pb-Hf-O isotope and trace element analyses

“…2 and 3), showing deposition ages around ca. 1.5 Ga that correspond to the youngest U-Pb ages on detrital zircon from a quartzite (Lasalle et al, 2013) and to the crystallization age (1497 Ma, U-Pb on zircon, Augland et al, 2015) of the intrusive Bardoux Plutonic Suite (Moukhsil et al, 2013b(Moukhsil et al, , 2014Maity and Indares, 2018). Detrital zircon grains in these paragneisses yield U-Pb ages between 2.7 and 1.5 Ga, but most grains gave ages between 1.9 and 1.5 Ga (Lasalle et al, 2013).…”

“…Detrital zircon grains in these paragneisses yield U-Pb ages between 2.7 and 1.5 Ga, but most grains gave ages between 1.9 and 1.5 Ga (Lasalle et al, 2013). These sediments deposited in an active margin context along the southeastern boundary of Laurentia marked by the formation of continental arcs and/or back-arc basins (Augland et al, 2015;Maity and Indares, 2018) and the accretion of island arcs preserved in the Grenville Orogen, such as the Coal Creek Domain (Roback, 1996), the Escoumins supracrustal belt (Groulier et al, 2018b) or the Montauban terrane (Corrigan and van Breemen, 1997;Dunning and Indares, 2010;Sappin et al, 2009). Volcaniclastic sequences and granodiorite to granitic plutonic rocks exposed in the study area and dated at ca.…”