Origin and emplacement of the Variscan Lizard Ophiolite, and underlying thrust sheets, Cornwall, SW England

Journal article

The earliest stage of the Variscan orogeny in SW England is marked by the formation and obduction of the Mid-Devonian Lizard ophiolite from the Rheic ocean northwestward onto the previously passive continental margin of Avalonia (Laurussia). The Lizard ophiolite comprises an almost complete thrust slice of oceanic crust (U-Pb zircon: ∼386.8 ± 0.3 Ma; Givetian) and upper mantle formed above a south-dipping subduction zone, with an amphibolite to greenschist facies metamorphic sole (U-Pb zircon: ∼395 Ma; late Emsian). The Kennack Igneous Complex includes a suite of granitoids that intrude the base of the ophiolite and its metamorphic sole and records melting of diverse protoliths beneath the ophiolite during subduction and later obduction. Structurally beneath the ophiolite is a complex unit of mélange and a series of strongly folded and thrust units of Middle Devonian – Carboniferous sedimentary rocks that form the Dodman, Veryan and Carrick thrust sheets. Thrusting propagated from SSE to NNW as distal Gramscatho Group rocks were progressively emplaced onto the passive continental margin below the Lizard ophiolite. Early crustal shortening was subsequently followed by late Carboniferous-Early Permian extensional reactivation and crustal melting that resulted in intrusion of the Cornubian granites (295–275 Ma). The tectono-stratigraphy of the Lizard ophiolite and the metamorphic sole, together with structures in thrust sheets beneath the ophiolite, are directly comparable to similar allochthonous rocks beneath the Semail ophiolite, Oman.

Authors: Searle, MP; Willment, GH; Mackay-Champion, TC; Evans, JT; Shail, RK

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Cambridge University Press
• Journal: Geological Magazine
• Volume: 163
• Article number: e30
• Publication date: 2026-05-28
• Acceptance date: 2026-04-17
• DOI: 10.1017/s0016756826100715
• EISSN: 1469-5081
• ISSN: 0016-7568
• Language: English
• Keywords: subduction; obduction; tectonic evolution; Lizard ophiolite; SW England