A series of dioritic, granodioritic and granitic igneous rocks, of Pre-Cambrian age, is exposed near Johnston in south Pembrokeshire. Chemical analyses of representative rocks show the suite to be of calcalkaline type. An origin is suggested involving magmatic differentiation of a diorite parent magma, and the granitic rocks are compared with a granophyre of similar composition in north Pembrokeshire.

An index of weathering for silicate rocks is proposed, based on the proportions of the alkali and alkaline earth metals present. These are considered to be the most mobile of the major elements. The bond strengths of the elements with oxygen are used as weighting factors in the index, which measures both the degree to which a rock has already been weathered with respect to the parent material, and also its susceptibility to further weathering.

Recent detailed mapping to the north-east of the Harlech Dome in North Wales has produced clear evidence of an early deformation. Thus four distinct deformations can be recognised in the Welsh Caledonides, and their resultant structures are described.

Preliminary Rb-Sr whole-rock isotopic analyses of some East African granulites give the following ages and initial ratios:

The initial ratios, at the 0.705–0.706 level, conform with a world-wide pattern found for granulites and other deep crustal rocks. The whole-rock ages are the first such study on East African granulites. They confirm in West Nile the suspected early Pre-Cambrian age of the Uganda basement, and in Tanzania raise source rock problems which involve the Mozambique Front.

The Ethiopian Cainozoic volcanics associated with the African rift system comprise one of the world's most voluminous alkaline igneous provinces. The Simien Mountains are the remnants of a Miocene alkali olivine-basalt volcanic centre in the north-western part of this province. The end-phase activity at Simien featured intrusion of dyke-swarms of two trends, one parallel to the rift system, the other almost perpendicular to it. Dykes of the rift trend are typically alkaline, but a dyke sampled from the other trend proves to be an olivine-tholeiite. Its presence is interpreted, along with similar rocks from the Harar region in eastern Ethiopia, in terms of upper mantle rifting extending from the Gulf of Aden and Red Sea under the continental blocks of the Ethiopian swell.

The Highland Border Ridge is a present day positive physiographic element whose activity can be traced back to Devonian time. A change from a distant Lower Dalradian to a nearby Middle and Upper Dalradian source area during Lower Old Red Sandstone times reflects the initial development of the ridge. A model for ridge uplift is outlined and some of its implications discussed.

Caledonian dolerite dykes in northwest County Mayo, Ireland, are differentially metamorphosed with volumes of largely unmetamorphosed dolerite grading into marginal amphibole schists with no preserved igneous textures. Deformation controlled the extent of the metamorphism. The lack of a significant differential strain in the volumes of preserved igneous rock is considered to be the cause of the preservation.

The Comores Archipelago comprises four principal islands, lying in a WNW–ESE line at the northern end of the Mozambique Channel. The Islands are almost entirely volcanic and show a simple age progression from Grande Comore, with its active shield volcano Kharthala (2650m), east-south-eastwards through Mohéli and Anjouan, which are quite deeply dissected, to Mayotte, which is in an advanced stage of erosion and subsidence, and is encircled by a barrier reef. There is also evidence of minor volcanic rejuvenation in relatively recent times in Mayotte, and perhaps Anjouan and Mohéli. The lavas of Kharthala, and the neighbouring extinct shield volcano (Massif de la Grille) on Grande Comore are all basaltic, ranging from oceanitic and ankaramitic to aphyric types. Numerous tuff cones occur, especially on the flanks of Massif de la Grille. Basaltic lavas, similar to those of Grande Comore, form the bulk of the dissected volcanic shields of Mohéli and Anjouan, but there is also evidence of differentiation towards alkalic under-saturated end products, both as lavas and as intrusive bodies. Lherzolitic and gabbroic nodules are locally abundant on each of the islands, while xenoliths of sandstone and quartzite have been found on the three westernmost islands. Petrochemical data are presented for a considerable variety of Comores rocks, and the volcanic activity is discussed in terms of the major structural features of the Madagascar-Mozambique region.

Phonolite lava from the Viejo and Teide volcanoes show a wide variation in flow morphology, from viscous, spoon-shaped lavas to thin flows more than 8km long that often show well developed lava channels. The apparent fluidity of these lavas is considered to be largely due to their strongly alkaline character.