Hinchey, Alana M., Hinchey, John Hinchey, Sandeman, Hamish A., Lissenberg, Johan C. J.  ORCID: https://orcid.org/0000-0001-7774-2297, Rayner, Nicole and Marin, Daniela Mendoza
2025.
Silurian mafic magmatism related to post-collisional extension, Appalachian orogen, western Newfoundland.
Canadian Journal of Earth Sciences
10.1139/cjes-2025-0016
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Abstract
Gabbroic intrusions provide direct evidence of magmatic processes operating within the lithosphere and at the lithosphere-asthenosphere boundary, offering insights into magmatic differentiation, crustal growth, mantle-crust interaction, and tectonic evolution. The Taylor Brook Gabbro Suite (TBGS) is the northwesternmost expression of middle Silurian magmatism in the northern Appalachians. The petrogenesis and geochemical characteristics of the TBGS and crosscutting silicic magmatism are explored through U-Pb geochronology, mineral chemistry, lithogeochemistry, and Sr-Nd isotopic analyses, illustrating a complex history of mantle-derived mafic magmatism. The U-Pb zircon SHRIMP ages indicate that, although the intrusive history is complex, the TBGS represents a magmatic event at 431.0±2.7/4.3 Ma that was subsequently intruded by silicic magmatism at 419.7±3.0/4.5 Ma. The mineral chemistry and lithogeochemistry of the TBGS suggest fractional crystallization of a magmatic system as the primary differentiation mechanism. The TBGS is tholeiitic and transitional to calc-alkaline; consists of non-arc-like, continental magmas derived from an EMORB-like source. The silicic samples are granitic, magnesian and alkali calcic in composition. The isotopic signatures of the TBGS are mostly juvenile with εNd(430 Ma) ranging from -1.1 to +6.4 and 87Sr/86Sr(i) values ranging from 0.703373 to 0.708250; with one sample having an εNd(430 Ma) of -8.6, indicating a minor role of crustal contamination by Mesoproterozoic to Neoproterozoic basement rocks. Magma ascent may have utilized inherited deep-crustal structures, such as the precursor to the Doucers Valley Fault/Long Range-Cabot Fault systems. Lithospheric extension likely caused by slab-rollback created a window that allowed for asthenospheric upwelling, inducing partial melting and generation of the TBGS magmas.
| Item Type: | Article |
|---|---|
| Date Type: | Published Online |
| Status: | In Press |
| Schools: | Schools > Earth and Environmental Sciences |
| Publisher: | Canadian Science Publishing |
| ISSN: | 0008-4077 |
| Date of First Compliant Deposit: | 17 October 2025 |
| Date of Acceptance: | 12 October 2025 |
| Last Modified: | 30 Oct 2025 14:15 |
| URI: | https://orca.cardiff.ac.uk/id/eprint/181738 |
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