The Vesturhorn Intrusion, exposed over 19 km2 of the south-eastern coast of Iceland, comprises two mafic complexes and a central core of epigranites. The latter can be subdivided into a central area with a flat-lying sheet structure, surrounded and separated from the mafic complexes by a more massive belt called the Transitional Epigranites with variable colour index and containing many rounded-to-angular inclusions and net-veined complexes. The consideration of several lines of evidence suggests that the components were emplaced as magmas in the sequence, first the epigranites with a sheet structure and second the basic complexes. The Transitional Epigranites appear to have originated by the remobilization and local hybridization of the early, sheet-structured epigranites. The relatively large volume of remobilized material and an absence of partially melted zones are considered to result from the early epigranites being still partially molten at the time of emplacement of the mafic complexes, together with a ponding of remobilized material beneath the chamber roof. A final intrusive episode occurred with the emplacement of a body of fayalite—hedenbergite epigranite largely into the Transitional Epigranites, probably after the consolidation of the latter.

The mechanical process for producing foliation (banding) in metamorphic rocks, as proposed by Schmidt (1932), is shown to be inadequate. Examples in the literature ascribed to the mechanism are insufficiently supported and the metallurgical analogy for the process is found to be false. A possible restatement of a mechanical process by analogy with particle interaction effects during the laminar flow of suspensions is discussed. Evidence from metamorphic rocks indicates, however, that the modified mechanical process cannot be responsible for common metamorphic layering.

A method for measuring volume change, which involves combining measurements of the strain ratio with the angle between the surface of no finite longitudinal strain and the principal extension direction in a principal plane, has been used to obtain values for the volume change in two groups of deformed rocks in southern Africa.

Ooids and grapestones from some parts of the Corallian Beds (Oxfordian) contain encrustations of the foraminiferid Nubeculinella. Encrusted layers within ooids clearly reveal lengthy periods when the grains were stationary and not accreting carbonate laminae. It seems likely that during colonisation by the foraminiferids the ooids were immobilised beneath a subtidal algal mat and there are indications that the mats were sufficiently coherent to bind lumps of sediment together during disruption by burrowing organisms.

Calcareous nannoplankton from the Globigerina silts of the western approaches of the English Channel indicate the presence of standard nannoplankton zones NN2, NN 4 and NN 5, part of which can be correlated with Neogene beds in Belgium and Northern Germany. The calcareous nannoplankton support the possibility of a connexion between the North Sea Basin and the Atlantic Ocean through the English Channel during part of the Lower Miocene.

The localization of graphite veins in well-defined regions within anticlinal structures of the SW sector of the island, where the rocks have been migmatitized partially by a reactivation, is very significant. The graphite mineralization seems to have taken place during the above mentioned reactivation and has followed regions of structural weakness developed during the folding of the metasedimentary rocks.

In high-grade regionally metamorphosed tectonites three varieties of micro- structures are recognized, namely (1) granoblastic, (2) granoblastic elongate, (3) anastomosing. Relative and absolute grain size, combined with grain boundary shape, provide the basis for their description. This microstructural classification is directly applicable to granulite facies and transitional granulite to amphibolite facies rocks and avoids some of the shortcomings inherent in previous terminologies.

Observations on the structure, fabrics, mineral assemblages and distributions of plagioclase compositions from migmatites of the Barousse Massif, Central Pyrenees, are related to the mode of differentiation of leucosome from melanosome. It is concluded that the majority of these migmatites have formed from recrystallization of sedimentary horizons, often accompanied by metamorphic differentiation, although some migmatites appear to have formed from anatexis or magmatic injection.

Along the length of the Swansea Valley Disturbance, from Clydach (near Swansea) to Hay-on-Wye (Herefordshire), 4 main joint sets are developed. They are NE—SW, NW—SE, N—S and E—W in trend. On the NW and SE sides of the main fault zone only the N—S and E—W sets tend to be developed, whereas within this fault zone only the NE—SW and NW—SE sets are found. It is suggested that the NE—SW and NW—SE sets are shear joints developed at the same time as the main fault zone and the N—S and E—W sets have been developed in response to the release of residual strain energy after the end of the Variscan orogeny.

Near one of the Younger Granite intrusives of the Jos Plateau is a series of steeply dipping dark and predominantly fine grained rocks. Originally interpreted as argillaceous sediments thermally metamorphosed by the adjacent granite, with development of andalusite, later work established their volcanic origin but did not account for the andalusite. Field relationships and petrography of the rocks suggest they are tuffisites, emplaced by volcanic fluidization processes into part of the fracture system associated with the Younger Granite magmatism. The ‘andalusite’ is topaz, widespread in this province, mainly in the Younger Granite tin veins and greisens, sometimes as an accessory in the granites themselves, but not known from the volcanics — yet abundant in some of these tuffisites. It occurs in well formed crystals, displaying a ‘chiastolite-cross’ arrangement of inclusions, characteristic of andalusite but appearing not to have been previously recorded in topaz. The origin of the topaz must lie either in late-volcanic emanations or in hydrothermal fluids from the mineralizing stage of Younger Granite emplacement.

The Mbalevuto sill intrudes sedimentary rocks on the SW flank of Tavua volcano, Viti Levu, Fiji. It appears to have been intruded at shallow depth in a semi-molten state. The sill is of essexitic composition and petrochemical evidence suggests that magmas forming the sill and lavas of the Tavua volcano are consanguineous.

Regulaecystis devonica, which is probably from the Meadfoot Beds (Siegeman— Emsian) near Torquay, Devon, is characterized by smooth thick thecal plates and a deeply sunken pectinirhomb. Coopericystis Parsley from the Middle Ordovician of Tennessee is considered a junior synonym of Regulaecystis from the Lower Devonian of Europe.