Structural characterization and tectonic evolution of 1.3 Ga REE-bearing Fox Harbour Volcanic Belt, southeast Labrador - Canada

Abstract

The Southeastern Labrador region, Canada, preserves a complex geological history shaped by multiple deformation and metamorphic events. This study investigates the structural evolution, metamorphism, and deformation of the 1.3 Ga Fox Harbour Volcanic Belt (FHVB), a bimodal volcano-sedimentary sequence of peralkaline rhyolites enriched in rare earth elements (REE), mafic rocks, and sedimentary rocks deposited on 1.7-1.5 Ga basement rocks in an extensional setting along the Laurentian margin. Hosted in a highly strained amphibolite-facies corridor within the Lake Melville terrane (LMT), the FHVB domain is bordered by the Long Harbour (LHsz) and Fox Harbour (FHsz) shear zones to the south and north, respectively. Field observations, structural and petrographic analyses, along with U-Pb petrochronology on zircon, monazite, and titanite, reveal a multi-stage tectonic evolution. Deformation that accompanied the main phase of Grenvillian metamorphism (D1; ~1.06–1.04 Ga) locally involved amphibolite-facies metamorphism and anatexis, tight buckle folding, and tectonic burial of the LMT during Grenvillian convergence. The Pinware and Mealy Mountains terranes remained structurally higher in the tectonic pile and were shielded from significant metamorphism. Continued deformation (D2; ~1.04–1.02 Ga) was characterized by cooling, folding, and localized strain during a period of orogenic collapse, characterized by extensional adjustments of the orogenic crust. Late-stage transpressive deformation (D3; ~1.0 Ga) involved greenschist-facies oblique-slip and strike-slip shearing, overprinting earlier amphibolite-facies fabrics and facilitating the FHVB exhumation. These findings refine the tectonometamorphic history of the FHVB, providing new insights into the kinematic evolution of the Southeastern Grenville Province