The Rogart pluton is a typical example of high Ba–Sr granitic magmatism, emplaced in northern Scotland towards the end of the Caledonian Orogeny. It consists of three granitoid facies (tonalite, granodiorite, granite) that are locally associated with large enclaves of coeval mafic appinite. The overall range of compositions is therefore extreme, with MgO from 11.6 to <0.1 wt%, SiO 2 from 47.50 to >73.0 wt%, with relatively high Na 2 O+K 2 O especially for the mafic rocks (up to 8.4 wt%), associated with K 2 O/Na 2 O≈1.5. Trace element abundances vary extensively and coherently, and the typical high Ba–Sr elemental signature of the pluton is also carried by the appinites. This is consistent with a genetic relationship throughout the suite. Sr, Nd and O isotope ratios are sufficiently similar to support this contention, but vary systematically with magma evolution. The appinites were derived from an enriched mantle source ( 143 Nd/ 144 Nd 400 ≈0.51194, 87 Sr/ 86 Sr 400 ≈0.7061) with high δ 18 O (≈+8‰), probably related to active contemporaneous subduction. Quantitative elemental and isotopic modelling suggests that the granitoid magmas evolved from the appinites by crystal fractionation accompanied by minor crustal contamination. Early fractionation from appinite to tonalite was driven by crystallization of pyroxene plus biotite with minor plagioclase, replaced by a feldspar-dominated assemblage to produce granodiorite and granite. The total amount of crust assimilated was less than 25%, highlighting the juvenile nature of the high Ba–Sr granite class.

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Two domains have previously been recognized in the Archaean Reguibat Shieldof NW Mauritania, based primarily on their gross lithological differences (Rocci et al., 1991

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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.