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TitleLate Devonian shear zone reactivation in the Canadian Appalachian orogen
AuthorPiette-Lauziere, NORCID logo; Larson, K P; Kellet, D AORCID logo; Rogers, N; Powell, JORCID logo; Apen, F
SourceGeological Society, Special Publication vol. 542, 2023 p. 1-28, Open Access logo Open Access
Alt SeriesNatural Resources Canada, Contribution Series 20220413
PublisherThe Geological Society
Mediapaper; digital; on-line
File formatpdf
ProvinceNova Scotia
Lat/Long WENS -60.8333 -60.4000 46.8000 46.4667
Subjectsgeneral geology; Science and Technology; geochronology; shear zones; Canadian Appalachian orogen; Neoacadian; Devonian
Illustrationslocation maps; photographs; cross-plots; graphs; diagrams
ProgramTargeted Geoscience Initiative (TGI-6) Ore systems
Released2023 05 12
AbstractOblique accretion zones often display transpressive, strike-slip, and transtensive structures of different orientations with respect to the convergence axis. The Late Devonian oblique collision of Meguma within the Canadian Appalachian orogen is often characterized as transpressive. However, the simultaneous opening of the Maritimes basin indicates that the orogenesis also partitioned into an extensional component. In this context, few of the shear zones reactivated during this time period have been characterized while accounting for the possibility of strain partitioning. To do so, we characterize the kinematics and timing of deformation of the Eastern Highlands shear zone (EHSZ) and the Coinneach Brook shear zone on Cape Breton Island, Nova Scotia, using a combination of U/Pb geochronology (zircon, monazite, xenotime, and apatite) and 40Ar/39Ar geochronology in situ and step heating experiments (amphibole, muscovite, and biotite). Results show that the Silurian EHSZ was reactivated ca. 385 to 367 Ma and the Coinneach Brook shear zone was formed ca. 395 to 369 Ma both yielding oblique kinematics. Together, these structures accommodated the rapid exhumation of the Cape Breton highlands during the docking of the Meguma terrane. This study thus highlights the heterogenous distribution of transtensive and transpressive deformation during the Neoacadian Orogeny.
Summary(Plain Language Summary, not published)
The mountain belt that formed across Atlantic Canada during the Paleozoic was formed by accretion of several blocks of crust over hundreds of millions of years. In this contribution, we use structural geology and geochronology approaches to study how major fault zones in the mountain belt reactivated over time due to these accretion events. This study helps to explain why Cape Breton highlands rocks were rapidly exhumed during the docking of Meguma, the block of crust that includes south and central Nova Scotia, during the late Devonian period.

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