Cumulate apatite crystals with infilled tube-like cavities parallel to the c-axis are described from a layered gabbro intrusion in Northern Norway. These are considered to be skeletal crystals produced by rapid growth in the supercooled roof zone of the magma chamber. At least two stages of growth are suggested on the basis of the morphology of the apatites. The interiors of the crystals contain phases representing the trapped magma or the cumulus mineral phase within which they are enclosed. Recirculation of the apatite primocrysts by convection currents is indicated by the interrupted form of some of the tubes.

The Vesturhorn Intrusion of SE Iceland contains a tilted block consisting largely of size-graded, igneous-layered, eucritic gabbro, which is described in some detail. Size-graded, igneous layering is remarkably uncommon and at present there appear to be only two known occurrences. The physical properties of basalt magma suggest that most igneous layering is likely to form from currents moving by laminar flow. Considerations of flow in such a simple system do not satisfactorily account for the scarcity of this structure. It is suggested that size-graded, igneous layering may reflect the availability of convecting magmas containing crystals with appreciable proportions of different grain sizes of each mineral species. Such a grain size distribution, together with other features considered here, may indicate primocryst growth outside the chamber of deposition.

The toolmark pattern on an erosional furrow from the Llandovery shelf sequence in the Welsh Borderland indicates that there was:— (i) local helical flow within the furrow similar to that found in sinuous alluvial streams and (ii) a moderately powerful current which moved towards the shore. Erosion by a shallow water turbidity current or storm surge tidal ebb flow therefore seems unlikely. A flood tidal current super-imposed on storm wave oscillatory disturbance of the sea-floor provides a possible mechanism.

A reconstruction of the tectonic history of part of the Benue Trough is made from a study of the marine transgressions and regressions in SE Nigeria. Two periods of deformation involving essentially the interaction of continental plates are suggested. The oceanic crust produced by crustal attenuation in the Benue rift is very minimal. Unstable tectonic conditions in the Benue Trough may have created conditions for the development of an evaporite sequence.

Potassium–argon ages of a variety of rocks and minerals from the Cheviot Hills, northern England, lie in the range 390 m.y. to 370 m.y. The Cheviot granite, dated at 380 m.y., has an age similar to that of many of the younger members of the British late Caledonian granites.

A rhyolitic breccia-body is emplaced within an indurated mafic tuff which outcrops along the south-western margin of the Beinn na Caillich granophyre mass in the Isle of Skye. The breccia provides evidence of two distinct processes in operation during and prior to emplacement. The tuff which includes felsic rock debris has an intrusive near-vertical junction with the Liassic sediments. It is believed that the tuff was emplaced within a pre-existing volcanic channel. The sequence of post-Liassic eruptive activity in this area ended with the emplacement of the granophyre.

Three subfacies of the granulite facies are recognized: garnet–diopside–quartz subfacies; pyroxene–granulite subfacies; and hornblende–granulite subfacies The erection of a garnet–diopside–quartz subfacies follows De Waard's suggestion (1965) of a garnet–clinopyroxene subfacies. Two major divisions of the hornblende–granulite subfacies are now recognized, (i) garnet–biotite division, (ii) cordierite division. Three sub-divisions of the former are suggested on the basis of critical basic assemblages. Since wollastonite has been found to have a limited areal occurrence within the latter, a two-fold sub-division of the cordierite division is suggested on the basis of the assemblages, (a) calcite–quartz, (b) wollastonite. A seven-fold sub-division of the granulite facies is thus proposed for Ceylon rocks. An attempt is made to trace briefly the major events in the metamorphic history of the rocks supported by available geochronological evidence.

The stretched crystals of tourmaline occur in the Orange Group gneisses of the Lucomagno massif and in the quartzite of Piano Croce Group in the Molare region, Ticino, Switzerland. They were stretched as a result of an extension acting in the plane containing the tourmaline crystals by the tectonic strain of F3 phase of deformation. The crystals show extension parallel to the F3 fold axes. The computation of the values of the finite strain from stretched tourmaline crystals indicates a constriction-type ellipsoid for the tectonic strain of F3 phase of deformation.