A metamorphic map of the British and Irish Caledonides

Abstract

Summary The metamorphic rocks of the British and Irish Caledonides fall into two groups. The first group constitutes the northern belt. These rocks have been subjected to a lower Ordovician metamorphism (Grampian event of Lambert & McKerrow 1976) which was probably, in part at least, diachronous. The metamorphic pattern ranges from the low- to the intermediate-pressure facies series and from the low greenschist- to the upper amphibolite-facies groups. The distribution of facies within the belt is complex and may relate to a depth-controlled metamorphism with locally induced thermal highs. The second group constitutes the southern belt. Here the rocks have been subjected to a late-Silurian event which, in general, causes slight crystallisation but very locally rises to upper greenschist facies.

Late Precambrian U–Pb titanite age for peak regional metamorphism and deformation (Knoydartian orogeny) in the western Moine, Scotland

“…This conclusion followed from the observation that metamorphic isograds based on the calc-silicate assemblages appear to cross the line of the Slide (Fig. 3) (Tanner 1976;Fettes 1979, fig. 3), as do swarms of axial planar pegmatites related to the D 2 (not D 3 , Powell 1974) Sgurr nan Eugallt fold (Tanner 1971).…”

“…The regional metamorphic peak was reached during the D 2 event (MacQueen & Powell 1977). Barrovian index minerals in pelites, such as kyanite and staurolite, are rare, and the mapping of isograds is largely dependent upon the mineral assemblages found in thin layers of calcareous psammite (calc-silicate pods) (Kennedy 1949;Winchester 1974;Tanner 1976;Fettes 1979).…”

“…4, where bytowniteanorthite is replaced by andesine (Tanner 1976;Fettes 1979). In addition, gently inclined and warped microdiorite dykes that cut across the upright D 3 folds are metamorphosed to amphibolitefacies assemblages in the same part of the area (Fig.…”

A black shale protolith for gold-tellurium mineralisation in the Dalradian Supergroup (Neoproterozoic) of Britain and Ireland

“…The Dalradian rocks were deformed and regionally metamorphosed, during and following Ordovician closure of the Iapetus Ocean. Metamorphism varies from greenschist facies to amphibolite facies (Harte 1988 Fettes 1979), but some including the two pyrrhotitebearing localities are in amphibolite facies (Table 1).…”

Scandian-Acadian-Caledonian sensu strictu metamorphism in the age range 430–360 Ma

“…4) affects lower Palaeozoic rocks in the Southern Uplands of Scotland, the Lake District, the Isle of Man, N Wales and Ireland (Fettes 1979). The regional metamorphism is almost uniformly of low grade, ranging from slight recrystallization to greenschist facies locally; one exception is a very small area of intermediate-pressure low amphibolite facies on the Isle of Man.…”