New constraints on the timing and nature of metamorphism in the eastern Meguma terrane, Nova Scotia, Canada
2024/11/05 by Deanne van Rooyen, Donnelly B. Archibald, Chris E. White +3
Earth and Planetary Sciences · #Geology and Paleoclimatology Research #Geological formations and processes #Geological Studies and Exploration
paper · doi:10.1139/cjes-2024-0024
Abstract
The Meguma terrane in Nova Scotia consists mainly of Cambrian to Ordovician metasedimentary rocks intruded by abundant peraluminous granite, granodiorite, and minor diorite–tonalite–plutons between ca. 380 and 360 Ma. The metasedimentary rocks were variably metamorphosed to greenschist- to amphibolite-facies during the Early Devonian. In the eastern Meguma terrane, the regional M1 chlorite- and biotite-zone assemblages are overprinted by two types of high-temperature low-pressure M2 metamorphism. In contact aureoles around plutons the regional M1 assemblages are overprinted by cordierite- and andalusite-bearing M2 contact metamorphic assemblages, and away from plutons chlorite-bearing, (or biotite-bearing) regional M1 assemblages are overprinted by staurolite-, garnet-, and (or) cordierite-bearing M2 regional assemblages that represent metamorphism driven by a regional elevated thermal gradient. The interpreted metamorphic conditions in the eastern Meguma terrane range from ca. 480–550 °C and pressures below 2.5 kbar up to 550–650 °C with pressures between 4 and 5 kbar. Based on a new garnet Lu–Hf age, regional metamorphism was ongoing at ca. 372 Ma, hence broadly coeval with pluton emplacement. Metamorphism and pluton emplacement took place in a largely transpressional tectonic setting during the collision of the Meguma terrane with Avalonia. After pluton emplacement, peak metamorphic assemblages were variably overprinted with retrograde chlorite and sericite M3 assemblages while deformation continued. Regional structures were transposed into a composite transposition foliation as a result of continued motion along the terrane-bounding Minas Fault Zone and associated ductile shear zones.
Citations
- Detrital and metamorphic 40Ar/39Ar ages from muscovite and whole-rock samples, Meguma Supergroup, southern Nova Scotia
- Provenance of the Meguma terrane, Nova Scotia: rifted margin of early Paleozoic Gondwana
- 40Ar/39Ar age of shear zones in the southwest Meguma Zone between Yarmouth and Meteghan, Nova Scotia
- Abbreviations for names of rock-forming minerals
- Southeastern Atlantic Canada, Northwestern Africa, and Continental Drift
- 40Ar/39Ar dating in the LochaberMulgrave area, northern mainland Nova Scotia: implications for timing of regional metamorphism and sediment provenance in the Late Devonian Early Carboniferous Horton Group
- Late Paleozoic collision, delamination, short-lived magmatism, and rapid denudation in the Meguma Terrane (Nova Scotia, Canada): constraints from 40Ar/39Ar isotopic data
- Cape St. Marys shear zone and the Halifax Group – Rockville Notch Group disconformity, southwestern Nova Scotia: structural development and tectonic significance
- U–Pb (zircon) ages and provenance of the White Rock Formation of the Rockville Notch Group, Meguma terrane, Nova Scotia, Canada: evidence for the “Sardian gap” and West African origin
- The age and origin of the South Mountain Batholith (Nova Scotia, Canada) as constrained by zircon U–Pb geochronology, geochemistry, and O–Hf isotopes
- Conjugate shear model for emplacement of mid-crustal plutons during dextral transpression, southern Nova Scotia, Canada: tectonic and petrological consequences
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- Late Paleozoic collision, delamination, short-lived magmatism, and rapid denudation in the Meguma Terrane (Nova Scotia, Canada): constraints from 40Ar/39Ar isotopic data
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- U‐Pb Geochronology of Devonian Granites in the Meguma Terrane of Nova Scotia, Canada: Evidence for Hotspot Melting of a Neoproterozoic Source
- Provenance of the Meguma terrane, Nova Scotia: rifted margin of early Paleozoic Gondwana
- Interaction among upper crustal, lower crustal, and mantle materials in the Port Mouton pluton, Meguma Lithotectonic Zone, southwest Nova Scotia