Mineral and whole-rock isotope data for a massive charnockite from Kottaram in the Nagercoil Block at the southern tip of Peninsular India yield Sm—Nd and Rb—Sr ages of 517 ± 26 Ma and 484 ± 15 Ma respectively. The Nd model age calculated for the charnockite is c. 2100 Ma. Our study reports the first Pan-African mineral isochron ages from regional charnockites of Peninsular India, which are in good agreement with the recently obtained ages of incipient charnockites in the adjacent blocks, as well as alkaline plutons within the same block. Our results indicate that the Pan-African tectonothermal event in the granulite blocks south of the Palghat—Cauvery shear zone was regional, with terrain-wide rejuvenation. These results correlate with similar Pan-African tectono-thermal events reported from Sri Lanka and East Antarctica, and have an important bearing on Gondwana reconstructions.

The ˜ 7 km thick Freetown layered complex of Sierra Leone consists of four zones each composed of a cyclically layered sequence of troctolite, gabbro, olivine gabbro, gabbronorite, and anorthosite. The complex is thought by previous workers to have solidified in situ from a single parental magma without stratigraphic changes in mineral compositions. Evidence for cryptic variation is presented based on electron microprobe analyses of mega-unit Zone 3. Two reversals in olivine forsterite content, plagioclase anorthite content, and 100 Mg/(Mg Fe2) in clinopyroxene match the variations of Ni in olivine and Cr in clinopyroxene. These changes are consistent with a magma chamber that was open to periodic influxes of new magmas, and the mixing of new and fractionated resident magmas. Expansion of the magma chamber is thought to have occurred at 2000 m, corresponding to the level of a major influx.

In the Welsh Basin, turbidites of Llandovery age at Cwmerfyn, near Goginan (Devil’s Bridge Formation) and Neuadd Fawr, near Lampeter, contain similar, diverse, ichnofaunal assemblages, despite strong sedimentological differences between the two localities. The sediments at Cwmerfyn are a series of very thin- to thin-bedded silt/mud couplets. The silt-grade lower half of each couplet is ripple-cross- and/or planar-laminated; the mud-grade upper part is massive. At Neuadd Fawr, the strata are thin- to medium-bedded, and composed of fine- to medium-grained sand; individual beds are parallel-laminated or display pronounced convolute lamination. At both localities, the ichnofaunal assemblage is dominated by endostratal pascichnia observed on intrastratal, bedding-parallel, planes of splitting. All the ichnofauna is post-depositional. Both assemblages are dominated by examples of Nereites cambrensis and macleayii; examples of Neonereites uniserialis and biserialis, Protovirgularia dichotoma, Chondrites, Dictyodora scotica, Helminthoida crassa, two other ichnospecies of Nereites and examples of Nereites isp., Palaeophycus tubularis, Macaronichnus segregatus, Planolites beverleyensis and montanus and a ‘braided trace’ are also present. In contrast, the diverse ichnofaunal assemblage recorded from the Aberystwyth Grits Group by others is both pre-depositional and post-depositional in origin. The former include agrichnia (Paleodictyon and Squamodictyon) and cubichnia (Asteracites and Bergaueria), observed as secondary casts on the soles of turbidites. The differences in composition between this ichnofaunal assemblage and those at Cwmerfyn and Neuadd Fawr are interpreted to be a result of the degree of oxygenation of the sediment profile. In the Aberystwyth Grits, the producers of the agrichnia and cubichnia would have been able to tolerate reduced oxygen levels in the sediment profile, because they maintained a connection with an oxygenated water column. The post-depositional component of the Aberystwyth Grits assemblage is interpreted to represent opportunistic colonization of the sediment profile during short intervals of elevated oxygen conditions produced by episodic turbidite deposition. The producers of the endostratal pascichnia at Cwmerfyn and Neuadd Fawr did not maintain connections with the water column, implying the presence of oxygenated interstitial porewaters during their emplacement.

The protoliths of mylonitized augen gneisses exposed in the southern sector of the Menderes Massif (West Turkey) are calc-alkaline, peraluminous, S-type, late- to post-tectonic tourmaline- and garnet-bearing, two-mica leucogranites. They cut and post-date the fabrics of the ‘main Menderes metamorphism’ which took place between the early Eocene and early Oligocene and intrude metamorphic basement rocks comprising the so-called ‘Palaeozoic schist envelope’ of the massif. They are themselves cut by an extensive network of tourmaline-rich dykes. Chemical, mineralogical, isotopic and field relations suggest that the granitic protolith crystallized from a boron-rich, water-saturated melt, derived from partial melting of metagreywacke in the lower crust during peak Barrovian-type metamorphism. The protolith was probably emplaced during lateorogenic extensional collapse of the thickened crust in west Turkey during late Oligocene time.

The Caledonian Hecla Hoek succession in Ny Friesland, eastern Svalbard has been interpreted, for many decades, to be a continuous stratigraphic sequence. Early Palaeozoic and Neoproterozoic strata in its upper parts pass more or less conformably down into amphibolite facies rocks (Stubendorffbreen Supergroup) at depth. Recent isotopic age-determination and structural studies have indicated that the Stubendorffbreen succession is tectonostratigraphic and made up of at least three major thrust sheets. This paper provides new data from two meta-igneous units within the succession, the Bangenhuk and Instrumentberget gneisses. Both are granitoid sheets, consisting mainly of red, strongly lineated gneisses of monzogranitic composition; the Bangenhuk unit also contains some lenses of little deformed granitoids, as well as cross-cutting aplite dykes, amphibolitized dolerites and subordinate metasedimentary rocks. The latter are locally cut by granitoids. U—Pb zircon dating of six samples of variably deformed Bangenhuk granitoids, including one cross-cutting aplitic dyke, has yielded ages between 1720 and 1770 Ma, the higher values generally from the less deformed samples. The Instrumentberget gneissic granite yielded an age of 1737+46−41 Ma. These ages are interpreted to date the time of intrusion of the granitoids at around 1750 Ma; the younger ages may have been slightly lowered by Caledonian deformation, particularly those from specimens located close to a major fracture (the Billefjorden Fault Zone) in Wijdefjorden—Austfjorden. U—Pb dating of titanite from the least deformed granitoid also yields comparable Palaeoproterozoic ages; in the more deformed rocks, however, titanites give evidence of Caledonian ductile deformation at c. 410 Ma. The Rb—Sr system of the corresponding whole rock samples has been disturbed and yields an errorchron age of about 1650 Ma and, for some samples, an impossibly low initial Sr ratio. The Sm—Nd system may be more intact and yields initial εNd values of −2 to −3, suggesting some contribution from older crustal material to the granitoid magmas. The results indicate the presence of extensive units of Palaeoproterozoic granitic basement within the Lower Hecla Hoek succession of Ny Friesland, supporting the hypothesis that the latter is composed of tectonically intercalated basement and cover units.

High-grade basic and acidic meta-igneous rocks are widespread in the bimodal amphibolitic—felsic gneiss complexes, which are characteristic formations of the ‘Middle Allochthonous Unit’ from eastern and southern French Massif Central. The metabasites from the Lyonnais and Doux complexes are chemically diverse and range from N-MORB type tholeiitic to transitional types. The two populations are not related by fractional crystallization or crustal contamination processes and their chemical characteristics reflect differences in their mantle sources. An ensialic setting is supported by the crustally-derived character of some of the associated felsic rocks, but the presence of N-MORB-type metabasites argues for an extensional environment. This bimodal association compares well with the magmatism of rifted continental margins and may reflect a transitional stage between continental rifting and oceanic crust formation during the Cambro-Ordovician spreading event.

Volcanic rocks of Neoproterozoic age form several fault-related inliers in Wales and the Welsh Borderland. Those in North Wales and the Borderland have been investigated recently, while those in southwest Wales remain little studied. In southwest Wales, basic to intermediate lavas and related volcaniclastic rocks and silicic tuffs in the St David’s area comprise the Pebidian Supergroup, which is intruded by minor basic intrusions, while the Coomb Volcanic Formation, exposed farther east around Llangynog, is composed of basic and silicic lavas and silicic tuffs, intruded by a single dacite sill and numerous dolerite sills. New geochemical data show that both the Pebidian and Coomb basalts have subduction-related characteristics. The Coomb basalts are geochemically similar to those of the Uriconian Group of the Welsh Borderland, while the Pebidian basalts bear a similarity to volcanic rocks recovered from the Bryn-teg Borehole, in the Harlech Dome. Uriconian-type volcanic rocks may underlie much of the Midlands Microcraton, with the Welsh area underlain by volcanic rocks of Pebidian type.