Conjugate shear model for emplacement of mid-crustal plutons during dextral transpression, southern Nova Scotia, Canada: tectonic and petrological consequences
2024/05/03 by William J. Collins, J. Brendan Murphy · 1 citation
Earth and Planetary Sciences · Computer Science · #Geological and Geochemical Analysis #earthquake and tectonic studies #Geochemistry and Geologic Mapping
paper · pdf · doi:10.1139/cjes-2024-0044
Abstract
The South Mountain Batholith (SMB) is a syn-tectonic composite batholith emplaced in the upper crust within the Meguma terrane between 380 and 370 Ma during the later stages of the Neoacadian orogeny. Coeval plutons in southern Nova Scotia are surrounded by mid-crustal (∼4 kbar) andalusite–staurolite aureoles and are discordant to northeast-trending, regional Neoacadian folds. Detailed field studies, combined with published results, indicate emplacement within a dextral transpressional regime during the transition from distributed (D 1 ) to focused heterogeneous strain (D 2 ), which provided vertical conduits that facilitated magma ascent. The Port Mouton Pluton intruded along P-orientated crustal-scale fractures as a series of subvertical granitic sheets, which were progressively rotated and folded with ongoing dextral shearing. By contrast, the Barrington Passage Pluton intruded between crustal-scale, antithetic (sinistral) P-shear fractures and spread laterally between them as pulsed increments to form a layered, subhorizontal, and sill-like complex resembling the laccolithic structure of the SMB. The SMB was emplaced below the Meguma Supergroup, with magma derived from underthrust Avalon terrane and Silurian Rockville Notch Group. The lack of mantle components in the SMB suggests transpressional orogenesis facilitated conductive crustal heating without significant mantle addition, consistent with low p-wave velocities of Meguma lower crust. 400–355 Ma zircons, recorded either as inherited grains in granites or in felsic granulite xenoliths, imply the Neoacadian thermal anomaly extended for 45 Ma, but magmatism represented only ∼40% of that perturbation.
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
- Petrogenesis and regional tectonic significance of Late Devonian mafic intrusions in the Meguma Zone, Nova Scotia
- Deep seismic reflection data from the Bay of Fundy and Gulf of Maine: tectonic implications for the northern Appalachians
- 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
- The generation, segregation, ascent and emplacement of granite magma: the migmatite-to-crustally-derived granite connection in thickened orogens
- Southeastern Atlantic Canada, Northwestern Africa, and Continental Drift
- Late Paleozoic collision, delamination, short-lived magmatism, and rapid denudation in the Meguma Terrane (Nova Scotia, Canada): constraints from 40Ar/39Ar isotopic data
- Probing the composition of unexposed basement, South Portuguese Zone, southern Iberia: implications for the connections between the Appalachian and Variscan orogens
- 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
- Meguma terrane orocline: U–Pb age and paleomagnetism of the Silurian Mavillette gabbro, Nova Scotia, Canada
- The age and origin of the South Mountain Batholith (Nova Scotia, Canada) as constrained by zircon U–Pb geochronology, geochemistry, and O–Hf isotopes
Cited by
Related
- Late Paleozoic collision, delamination, short-lived magmatism, and rapid denudation in the Meguma Terrane (Nova Scotia, Canada): constraints from 40Ar/39Ar isotopic data
- New constraints on the timing and nature of metamorphism in the eastern Meguma terrane, Nova Scotia, Canada
- The interplay of regional structure and emplacement mechanisms at the contact of the South Mountain Batholith, Nova Scotia: floor-down or wall-up?
- Orogenesis and Basin Development: U‐Pb Detrital Zircon Age Constraints on Evolution of the Late Paleozoic St. Marys Basin, Central Mainland Nova Scotia
- 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