Meguma terrane orocline: U–Pb age and paleomagnetism of the Silurian Mavillette gabbro, Nova Scotia, Canada
2020/09/15 by Halima S. Warsame, P. J. A. McCausland, Phil J.A. McCausland +5 · 2 citations
Earth and Planetary Sciences · Biochemistry, Genetics and Molecular Biology · #Geological and Geochemical Analysis #earthquake and tectonic studies #Geomagnetism and Paleomagnetism Studies
paper · doi:10.1139/cjes-2020-0089
Abstract
Paleomagnetic results and a U–Pb baddeleyite age from the Silurian Mavillette gabbroic sill in southwest Nova Scotia, Canada, provide new evidence about the Paleozoic tectonic evolution of the Meguma terrane. The Mavillette gabbro sill intruded ca. 440–430 Myr old bimodal rift-related metavolcanic and metasedimentary rocks of the White Rock Formation in the Silurian–Devonian Rockville Notch Group. The 426.4 ± 2.0 Ma Mavillette gabbro age is notably younger than the ca. 440 Ma magmatism, but is part of a geochemically defined suite of within-plate sills and volcanic rocks of the Rockville Notch Group with ages as young as Early Devonian. Paleomagnetic investigation of 13 sites distributed along the Neoacadian (ca. 390 Ma) synclinal limbs of the Mavillette sill reveal magnetization directions that fail a fold test and therefore postdate Silurian emplacement of the gabbro. The post-folding remanence has a mean direction of D = 153.4, I = 17.1°; α 95 = 6.5° (n = 12 sites), with corresponding paleopole 31.9 °S, 325.2 E; dp = 3.5°, dm = 6.7° that resembles a pervasive late Carboniferous Kiaman overprint magnetization in North America, but is rotated significantly 22.2° ± 8.1° counter-clockwise (CCW). Mavillette remanence acquisition likely occurred in concert with fluid mobilization related to Alleghanian deformation, recorded locally by ca. 320 Ma muscovite 40 Ar– 39 Ar ages. Previously published paleomagnetic results from the Meguma terrane also have Carboniferous remanence directions with similar ∼24° CCW discordance. The regional CCW rotation of the southwest Meguma terrane post-dates this ca. 320 Ma tectonothermal remanence acquisition event, likely recording the development of an oroclinal bend of the Meguma terrane during the Alleghanian orogeny.
Citations
- Anatomy of a terrane boundary: an integrated structural, geographic information system, and remote sensing study of the late Paleozoic Avalon-Meguma terrane boundary, mainland Nova Scotia, Canada
- Detrital and metamorphic 40Ar/39Ar ages from muscovite and whole-rock samples, Meguma Supergroup, southern Nova Scotia
- A Middle Cambrian trilobite faunule from the Meguma Group of Nova Scotia
- Deep seismic reflection data from the Bay of Fundy and Gulf of Maine: tectonic implications for the northern Appalachians
- Chronology of Devonian to early Carboniferous rifting and igneous activity in southern Magdalen Basin based on U-Pb (zircon) dating
- 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
- Late Paleozoic collision, delamination, short-lived magmatism, and rapid denudation in the Meguma Terrane (Nova Scotia, Canada): constraints from 40Ar/39Ar isotopic data
- The evolutionary significance of a Lower Cambrian trace-fossil assemblage from the Meguma terrane, Nova Scotia
- 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
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