In the Musa Valley area rocks of the Papuan Ultramafic Belt outcrop discontinuously over an area of 25 miles by 45 miles. The rocks are part of a folded layered sequence ranging from magnesian dunite and peridotite, chemically and petrographically typical of the alpine ultramafic suite, to olivine gabbro and bytownite gabbro. Agglomerate like breccias consisting of fragments of ultramafic rock in a variable matrix occur as irregular vent-like bodies in the peridotite and dunite and as horizontal sheets in a Pleistocene-Recent sedimentary sequence. The breccias are interpreted as vent and extrusive breccias resulting from the penetration, brecciation and local entrainment (fluidization) of peridotitic country rock by volcanic gases. Olivine alkali basalt was probably the parental magma responsible for the gaseous activity. The breccias show a sequence of stability fields for the assemblages mesh-texture serpentine and bastite (i.e. chrysotile and lizardite mixtures); antigorite; olivine and enstatite; and these are correlated qualitatively with variation in intensity of the brecciation process. Chemically the brecciation process was responsible for the addition of H2O, SiO2, CO2, Al2O3 and O2 and the removal of Fe and Mg from the fragmented rock. Minerals which are of direct crystallization in the matrix fluid environment include chalcedony, fibrous serpentine (chrysotile), magnesite, quartz, andradite, and garnierite. There is no evidence of the presence of an ultramafic, serpentine magma in the genesis of the breccias.

Cross-bedding within the sandstones of eastern Fife indicates a predominant north to north-easterly source for the clastic debris. This inference is in accordance with cross-bedding data from sandstones of similar age in southern Fife and West Lothian.

The uncertainty of the most frequent orientations of β and fold axes relative to tectonic co-ordinates has possibly been overemphasized in tectonic literature. The β concentrations of obliquely deformed folds will be spread along characteristic paths. The superposed deformation would in most cases of flexural slip appear as folds in certain predominant directions and on suitably oriented surfaces. In tectonites with a single, nearly horizontal mode for the orientations of the lamination, β maxima formed by flexural slip should mostly be parallel to the axes of rotation.

The eastern limit of a narrow belt of rocks, running from Co. Antrim through Cowal and into Perthshire, containing abundant albite porphyroblasts, has been mapped in detail. Albite is shown to have recrystallized as large porphyroblasts (up to 23 mm. in diameter in some cases) after the last main phase of deformation affecting these rocks. It is concluded that a large scale, late stage, regional metasomatism in the metamorphic history of the rocks of this area was the causal mechanism of the growth of albite porphyroblasts.

PT curves for the beginning of melting of five analysed shales in the presence of water vapour under pressure are 20° C. to 40° C. higher than the corresponding curve for granite. About 150° C. above the beginning of melting, the shales are half-melted; this is higher than the liquidus curve of most granites. Refractive indices of the quenched liquids (1·495–1·505) indicate a granitic or granodioritic composition. Quartz, cordierite, mullite, hypersthene, anorthite, etc., are developed in the partially fused shales. Partial fusion of shales by a granitic magma, even if superheated, would produce a liquid no more basic than granodiorite. The chemical characteristics of the shales are compared with average igneous rocks, and there appears to be no possibility that fusion of shales could produce a basaltic magma. Complete fusion would produce a melt with composition distinct from normal igneous magmas.

The sill shows the normal type of spatial relationship found in composite intrusions of the British Tertiary, i.e. basic-acid-basic. The basic rocks are Talaidh type tholeiites while the acid rock is a rhyolite. Xenoliths appear to be concentrated in the upper and lower tholeiites. This fact has suggested to the authors of the Mull Memoir that a process of gravitational differentiation resulted in the formation of the basic and acid magmas. The evidence is inconclusive as to what process operated in magma genesis. The mineralogy of the xenoliths found in the sill is described in detail.

A thin section of garnetiferous pelitic schist is described in which the rotation of the garnets is in either of two directions. Microfolds are seen in the slide and the garnets were rotated in opposite directions on opposite limbs of the folds. Their relation to minor structures is suggested.

A petrographical description is given of some erratics from the Teifi Estuary, Cardiganshire. Rock types present include granite from Ireland; greisen and Eskdale granite from the Lake District; granophyre, picrite, diabase and gneiss from the Lleyn Peninsula; granophyre and diabase from Merionethshire.