Abstract
AbstractThe detrital zircon perspective on the pre-collisional crustal evolution of the Grenville Province remains poorly explored. In this study, we conducted in situ laser ablation U–Pb–Hf isotopic microanalysis on detrital zircon grains from three pre-orogenic (>1 Ga) supracrustal sequences that crop out in the Central Grenville Province (Lac Saint-Jean region, QC, CA). Detrital zircon grains from vestiges of these sequences record three dominant age peaks at c. 1.46 Ga, 1.62 Ga, 1.85 Ga, and a subordinate peak at 2.7 Ga. The 1.46 Ga and 1.62 Ga age peaks are recorded in detrital zircon grains from a quartzite associated with a metavolcanic sequence (i.e. Montauban Group) with a maximum depositional age of c. 1.44 Ga. In contrast, the c.1.85 Ga age peak is observed from recycled zircon grains in metasediments with maximum depositional ages between 1.2 and 1.3 Ga. The suprachondritic Hf isotope composition in detrital zircon grains of the 1.46 Ga and 1.62 Ga age populations records juvenile crustal growth during peri-Laurentian accretionary orogenesis related to the Pinwarian (1.4–1.5 Ga) and Mazatzalian–Labradorian (1.6–1.7 Ga) events. The detrital zircon grains associated with Penokean–Makkovikian (1.8–1.9 Ga) source rocks record reworking of c. 2.7 Ga continental crust derived from a near-chondritic mantle reservoir. Overall, crust-forming and basement reworking events associated with accretionary orogenesis in southeastern Laurentia are retained in the detrital zircon load of Precambrian basins even after the terminal Grenvillian collision and assembly of Rodinia.
Highlights
The Grenville orogen (c. 1090–980 Ma; Rivers, 2008, 2021) is a global-scale collisional orogenic system that terminated the long-lived accretionary growth of Laurentia, leading to the formation of the supercontinent Rodinia (Hoffman, 1988; Whitmeyer and Karlstrom, 2007)
In the Adirondack region, three quartzites from metasedimentary sequences with Maximum depositional ages (MDAs) at c. 1.25–1.3 Ga contain a higher proportion of Elzevirian and a lower proportion of Penokean detrital zircon grains than those found in Quebec (Fig. 6f; Chiarenzelli et al 2017)
From the examination of three poorly exposed Mesoproterozoic supracrustal complexes from Precambrian basins of the Central Grenville Province we show that:
Summary
The Grenville orogen (c. 1090–980 Ma; Rivers, 2008, 2021) is a global-scale collisional orogenic system that terminated the long-lived accretionary growth of Laurentia, leading to the formation of the supercontinent Rodinia (Hoffman, 1988; Whitmeyer and Karlstrom, 2007). The perspective of detrital zircon on the pre-collisional crustal growth of the Grenville Province remains underexplored despite zircon grains of Laurentian affinity being documented in pre-, syn- and post-collisional metasedimentary sequences (SagerKinsman and Parrish, 1993; Van Breemen and Corriveau, 2005; David et al 2010; Kamo et al 2011; Lasalle et al 2013; Spencer et al 2015; Groulier et al 2018; Peck et al 2019) Together, these studies have documented, through detrital zircon U–Pb geochronology, the presence of 1.4–1.9 Ga sources but, further insights about their crustal production and evolution are missing. The main aims of our study are to: (a) provide new constraints on the pre-collisional geodynamic evolution and crustal growth of the Grenville Province through examination of the U–Pb–Hf detrital zircon record, (b) compare the zircon U–Pb–Hf isotope signatures with the existing wholerock Nd isotopic record of crustal growth in the central Grenville Province and (c) better constrain the depositional ages and sources of these poorly documented supracrustal sequences
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