The geochemistry of late Caledonian minettes from across the orogenic belt is compared in order to constrain the composition of the Caledonian sub-continental lithospheric mantle (SCLM). All the minettes are similar petrographically and chemically and several samples have characteristics typical of near primary mantle melts. Samples from the Northern Highlands and the Caledonian foreland show enrichment in many trace elements (notably LILE and LREE) relative to those from the Grampians, the Southern Uplands and northern England, coupled with distinct Nd and Sr isotope characteristics. Processes such as fractional crystallization, crustal assimilation, and partial melting played a negligible role in creating the differences between the two groups which reflect long-term, time-integrated differences in the compositions of their SCLM sources. The Great Glen Fault appears to represent the boundary between these two lithospheric mantle domains. Other currently exposed Caledonian tectonic dislocations cannot be correlated directly with compositional changes within the SCLM. The chemical provinciality displayed by the minettes shows some resemblance to that within other late Caledonian igneous suites, including the newer granites, suggesting that the minettes may represent the lithospheric mantle contributions to these rocks.

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Net-depositional submarine canyons are common in continental slope strata, but how they survive and prograde on constructional margins is poorly understood. In this study we present fi eld evidence for the coevolution of a submarine canyon and the adjacent continental slope. Using a three-dimensional seismic data cube that images the Ebro margin (northwest Mediterranean), we identify a preserved canyon on a middle Pleistocene paleosurface and relate it directly to its expression on the present-day seafl oor. A subparallel stacking pattern of seismic refl ectors, similar to that seen between prograding clinoforms in intercanyon areas, is observed between the modern and paleocanyon thalwegs. The concavity of the modern long profi le differs from the convexconcave long profi le on the middle Pleistocene surface, suggesting a long-term change in canyon sedimentation. We interpret this change as a shift to a canyon dominated by turbidity currents from one strongly infl uenced by the pattern of sedimentation that built the open-slope canyon interfl uves. We fi nd support for our interpretation in previous studies of the Ebro margin.

Two lamprophyre suites are used to constrain sub-continental lithospheric mantle domains in Late Caledonian Northern Britain (at 400 Ma). A Northern Highlands and a Southern domain are resolved. The first has low (ɛNd (−6.4 to − 12.8); the latter has higher (+3.9 to −3.4). The boundary between them is coincident with the surface expression of the Great Glen Fault. The two mantle domains tightly bracket the fault. The lamprophyre magmas were generated at depths of at least 100 km. At the end of the Caledonian Orogeny the Great Glen Fault was a major vertical discontinuity that transected the sub-continental lithospheric mantle.