Detrital and metamorphic 40Ar/39Ar ages from muscovite and whole-rock samples, Meguma Supergroup, southern Nova Scotia

1999/01/20 by Roberta J Hicks, Rebecca A Jamieson, Rebecca A. Jamieson +2 · 91 citations
Computer Science · Earth and Planetary Sciences · #Dalradian #Devonian #Facies #Geochemistry #Geochemistry and Geologic Mapping #Geochronology #Geological and Geochemical Analysis #Geology #Metamorphic rock #Metamorphism #Mineralogy #Muscovite #Overprinting #Paleontology #Petrography #Phyllite #Quartz #Schist #Siltstone #Zircon #earthquake and tectonic studies

paper · doi:10.1139/e98-081

published in Canadian Journal of Earth Sciences 36(1), 23-32 (NRC Research Press)

openalex publication_date 1999/01/20 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/25

Abstract

40 Ar/ 39 Ar dates from eight muscovite separates and two whole-rock samples of slate, siltstone, and sandstone provide detrital, metamorphic, and post-metamorphic overprinting ages for the low-grade metamorphic rocks of the Meguma Supergroup in the Mahone Bay region of southern Nova Scotia. Variably reset detrital muscovite ages of 600-550 Ma agree with previously obtained U-Pb dates from detrital zircon. Separates of foliation-parallel muscovite yield precise 40 Ar/ 39 Ar ages of 395-388 Ma. Petrographic and metamorphic data indicate that these are metamorphic mica growth ages. The range overlaps with the younger limit of previously reported whole-rock ages (410-380 Ma), but is more tightly constrained. An apparent inconsistency between previous 40 Ar/ 39 Ar whole-rock ages as old as 410 Ma and regional deformation that affected sedimentary rocks as young as 385 Ma has been resolved by the younger ages reported here and by recent adjustments to the early Paleozoic time scale which suggest that the Lochkovian to Emsian Torbrook Group was deposited between 419 and 394 Ma. A muscovite plateau age of 376 Ma from one sample may be related to late-stage flexural slip deformation in the Ovens gold district.

Citations

• The Goldenville–Halifax transition, Mahone Bay, Nova Scotia: relative sea-level rise in the Meguma source terrane
• Late Paleozoic collision, delamination, short-lived magmatism, and rapid denudation in the Meguma Terrane (Nova Scotia, Canada): constraints from 40Ar/39Ar isotopic data

Cited by

• Devonian plutons in the eastern Meguma terrane, Nova Scotia, Canada: zircon U–Pb, Lu–Hf, and O isotopic compositions, age, and petrogenetic implications
• Interaction among upper crustal, lower crustal, and mantle materials in the Port Mouton pluton, Meguma Lithotectonic Zone, southwest Nova Scotia
• Saddle reef auriferous veins in a conical fold termination (Oldham anticline, Meguma terrane, Nova Scotia, Canada): reconciliation of structural and age data
• The interplay of regional structure and emplacement mechanisms at the contact of the South Mountain Batholith, Nova Scotia: floor-down or wall-up?
• The age and origin of the South Mountain Batholith (Nova Scotia, Canada) as constrained by zircon U–Pb geochronology, geochemistry, and O–Hf isotopes
• Chronology of Devonian to early Carboniferous rifting and igneous activity in southern Magdalen Basin based on U-Pb (zircon) dating
• 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
• New constraints on the timing and nature of metamorphism in the eastern Meguma terrane, Nova Scotia, Canada
• Meguma terrane orocline: U–Pb age and paleomagnetism of the Silurian Mavillette gabbro, Nova Scotia, Canada
• Conjugate shear model for emplacement of mid-crustal plutons during dextral transpression, southern Nova Scotia, Canada: tectonic and petrological consequences
• 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
• Evaluating the Origin of Garnet, Cordierite, and Biotite in Granitic Rocks: a Case Study from the South Mountain Batholith, Nova Scotia
• Orogenesis and Basin Development: U‐Pb Detrital Zircon Age Constraints on Evolution of the Late Paleozoic St. Marys Basin, Central Mainland Nova Scotia
• Derivation of the Early Carboniferous Wedgeport pluton by crystal fractionation of a mafic parental magma: a rare case of an A-type granite within the Meguma terrane (Nova Scotia, Canada)
• A paleogeographical review of the peri-Gondwanan realm of the Appalachian orogen1This article is one of a series of papers published in this CJES Special Issue: In honour of Ward Neale on the theme of Appalachian and Grenvillian geology.

Related

• 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
• 40Ar/39Ar age of shear zones in the southwest Meguma Zone between Yarmouth and Meteghan, Nova Scotia
• New constraints on the timing and nature of metamorphism in the eastern Meguma terrane, Nova Scotia, Canada
• 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
• Late Paleozoic collision, delamination, short-lived magmatism, and rapid denudation in the Meguma Terrane (Nova Scotia, Canada): constraints from 40Ar/39Ar isotopic data