Marion Island is a youthful intraplate shield volcano in the Southern Ocean, generally considered to represent the location of a mantle plume. New K–Ar age determinations on 37 whole rock samples of so-called older grey basalt from the island range from 450±10 to ∼30 ka. The lavas are remarkably fresh and holocrystalline, appearing to be ideal for dating. The age results from two almost vertical sections, where relative age relationships are not in doubt, are in accord with the stratigraphy. A third section gave aberrant ages that indicate the presence of inherited or excess radiogenic argon. This is highly unusual for subaerial flows on an oceanic island. We therefore urge caution in accepting K–Ar ages on samples without stratigraphic control. Volcanic activity on Marion could have been essentially continuous during the last half million years but on the basis of local unconformities and gaps between the measured ages it is considered more likely to have been episodic. Eight periods of effusive activity at approximately 450, 350, 240, 170, 110, 85, 50 and <10 ka ago can be distinguished with varying degrees of confidence. Glacigene deposits that are intercalated with the lavas can be correlated with glacial stages 2, 4, 6, 8 and 12 of the Pleistocene time scale based on the marine oxygen isotopic record. Indications are that at least some of the earlier volcanic activity coincided with glacial stages but the two most recent episodes, including the Holocene one extending up to the present, are clearly interglacial.

New deep seismic profiles in the southern Baltic region have failed to image the Trans-European Fault. Evidence for this structure, of suggested pre-Cadomian age, is critically re-examined. Localized geophysical anomalies are present, but these cannot be correlated with known structural features of the region. Based on the inconclusive evidence for this structure, we would therefore propose that the term ‘Trans-European Fault’ should not be used in the future, and that, to avoid confusion, authors use local names for local structures.

The conflict between independently published ages for the Mushandike Granite, Zimbabwe (2.92 ± 0.17 Ga and 3.45 ± 0.13 Ga) has been resolved in favour of the older age by SHRIMP U–Pb analyses of zircon. Two samples yield indistinguishable estimates of 3374 ± 7 and 3368 ± 11 Ma for the crystallization age of the magma. Together with published data from elsewhere in southern Zimbabwe, the results imply a widespread magmatic event at about 3.35 Ga. A single zircon core giving 3.46 Ga, together with the granite's previously measured Nd model age, suggests that the Mushandike magma could have incorporated remobilized basement similar to the c. 3.5 Ga Tokwe gneisses which crop out 30 km to the west. The published Rb–Sr and Pb–Pb datasets show evidence of late Archaean disturbance of Sr and Pb isotope systematics. In the absence of exposed contacts between the Mushandike granite and the neighbouring Mushandike stromatolitic limestone, the new U–Pb emplacement age suggests that the limestone is unconformable on the granite.

The leaf longevity and seasonal timing of leaf abscission within a plant community is closely related to climate, a phenomenon referred to as leaf phenology. In this paper the leaf phenology of some mid-Cretaceous (late Albian) forests which grew at latitude of 75° S on Alexander Island, Antarctica, is analysed. Five independent techniques for determining leaf longevity are applied to the fossil remains of each of the canopy-forming trees. These techniques utilize: (1) the anatomical character of growth rings in trunk woods, (2) leaf trace persistence in juvenile branch and stem woods, (3) leaf physiognomy, (4) comparison with nearest living relatives, and (5) leaf taphonomy. The application of techniques 1–5 suggests that the araucarian and podocarp conifers, which comprised more than 90% of the canopy-forming vegetation, were evergreen with leaf retention times in excess of 5–13 years. The application of techniques 3–5 to rare taxodioid conifers indicates the existence of both evergreen and deciduous habits in this group, whilst both ginkgos and taeniopterids, which are locally abundant, are interpreted as possessing a deciduous habit. The polar forests of Alexander Island were therefore dominantly evergreen. Preliminary analysis of five other mid-Cretaceous polar forests suggests the presence of dominantly evergreen vegetation in Australia and Antarctica, and mixed evergreen–deciduous vegetation in Alaska, northern Russia and New Zealand. Cold month mean temperature probably exerted the largest influence on the leaf phenology at each of these forest sites.

Thirty-nine K–Ar and one Ar–Ar radiometric dates from the eastern central Meso-Cenozoic Patagonian Batholith and eastern satellite plutons of the Aysén Region, of southern Chile between latitudes 45° and 48° S, combined with previous dating of seven plutons, have yielded six age groups: (1) Middle to Late Jurassic, (2) Early Cretaceous, (3) mid-Cretaceous, (4) Late Cretaceous, (5) Oligocene and (6) Miocene. In general, the Cretaceous and younger ages correspond to previous reported ages for other parts of the main batholith, but for the satellite plutons to the east show a wider age spectrum than the previously accepted Late Miocene dates. These results indicate a relatively continuous Late Jurassic to mid-Cretaceous plutonism, known to have been coeval with volcanic activity, followed by intermittent magmatism. Biotite K–Ar dates of c. 143–151 and 106–109 Ma, from cataclastic granitoids, may be marking the time of deformation. A review of all radiometric data on magmatic rocks from the region between 45° and 48° S in Chile shows a gap in Palaeocene ages that may correlate with a period of low-angle (flat slab) subduction between 65–50 Ma.

The Mount El-Sibai alkaline granitic complex (eastern Egypt) forms an elongate body, which was emplaced at the extension of a NW-trending shear zone, within voluminous calc-alkaline Pan-African host rocks. The complex is hypersolvus in nature and is composed of perthite, quartz, alkali amphibole, Fe-rich biotite, and accessory zircon, apatite, fluorite, aenigmatite and ilmenite. Data on mineral chemistry show that the amphibole ranges in composition from hastingsite to pure end-member arfvedsonite, and the biotite is largely titaniferous annite. Geochemically, the complex is highly evolved in composition (with 72–78 wt% SiO2, and DI values of 85–98), is enriched in Rb (48–291 ppm), Nb (28–237 ppm), Y (47–269 ppm), Zr (58–618 ppm), Ga (17–41 ppm) and the REE (176–437 ppm), and depleted in Al, Mg, Ca, Sr and Eu. The complex exhibits a wide trace-element compositional range. The REE patterns are uniform, parallel to sub-parallel, fractionated ((La/Yb)n = 4.7), LREE enriched over HREE, and show prominent negative Eu-anomalies. The albitized facies of this complex shows the highest concentrations of large ion lithophile (LIL) and high field strength (HFS) elements. The complex exhibits mineralogical and chemical traits typical of within-plate A-type granites. Mount El-Sibai is interpreted to have been developed during a phase of cooling, relaxation, crustal attenuation, and fracturing of the newly formed Pan-African crust. Results of geochemical modelling indicate that the magma may have formed by a large degree of batch partial melting (F=0.65) of Pan-African calc-alkaline rocks, which had been metasomatized. Metasomatism of source rocks may have been caused by a Na–F-rich fluid phase compositionally similar to that which produced the albitized facies. The volatile flux may have caused fenitization-type reactions along fissures and re-activated Pan-African fractures prior to anatexis, and is considered to have played a role as an important agent of heat transfer. Temperature necessary for crustal anatexis is likely to have been produced as a result of shear heating, caused by a rapid change in the direction of plate motions beneath eastern Egypt during Early Palaeozoic times. The confining pressure must have been released by fissuring of the crust. Magma ascent may have been facilitated by reactivation of pre-existing faults and shear zones. This model may have wider implications for the generation of within-plate felsic magmas in other regions.

The basement of the North China Craton consists of the Eastern and Western blocks, separated by the Central Zone. Both the Eastern and Western blocks are dominated by late Archaean tonalitic–trondhjemitic–granodioritic gneiss complexes interdigitated with minor supracrustal rocks metamorphosed at ∼2.5 Ga, with anticlockwise P–T paths. The Central Zone is composed of reworked late Archaean components and Palaeoproterozoic juvenile crustal materials that underwent regional metamorphism at ∼1.85 Ga, with clockwise P–T paths involving isothermal decompression as a result of collision between the Eastern and Western blocks, which resulted in the final assembly of the North China Craton.