Origin of ultramafic–mafic bodies on the Isles of Lewis and Harris (Scotland, UK): Constraints on the Archean–Paleoproterozoic evolution of the Lewisian Gneiss Complex, North Atlantic Craton

The Lewisian Gneiss Complex (LGC) is a tonalite-trondhjemite-granodiorite (TTG)-dominated fragment of the North Atlantic Craton (NAC) in northwest Scotland. End-member models describe LGC as representing either continuous piece Archean crust or up to 12 geologically distinct terranes, with interpretations sitting on spectrum between these end-members. There particular uncertainty over correlations Archean–Paleoproterozoic magmatic and metamorphic events recorded by mainland part exposed Outer Hebridean islands Lewis Harris. In this paper, we present results field mapping, petrography, major, trace platinum-group element (PGE) bulk-rock geochemistry for four ultramafic–mafic bodies Harris, namely: Maaruig, Loch Mhorsgail, Coltraiseal Mor Beinn a’ Chuailean. We consider effects metamorphism mobility, their petrogenesis, potential rocks elsewhere LGC. Our data indicate that studied can be subdivided into two petrologically groups. Metaperidotites metapyroxenites from Maaruig Mhorsgail are interpreted (>2.8 Ga) cumulates anything currently identified LGC, interpretation based distinctive modal layering, discordance surrounding TTG gneiss, fractionated PGE patterns ([Pd/Ir]N = 1.3–6.6) negative HFSE anomalies ([Nb/La]N 0.2–0.8). Metagabbronorites Chuailean, which also exhibit high strength-element (HFSE) 0.2–0.7) show mildly 1.2–2.8) patterns, most likely represent deformed Paleoproterozoic dykes. These occurrences could correlatives suite ca. 2.4 Ga mafic dykes throughout (the Scourie Dykes), having experienced more intense (Laxfordian) deformation/reworking. suggest lithologies Harris were proximal LGC’s Central Region early but raises possibility they crustal blocks Mesoarchean.