Petrofabric analyses of marble specimens from three widely separated localities in Mid-Strathspey and Strathavon are recorded. Preferred orientation of [0001] in the constituent grains of calcite conforms to a B-tectonite pattern, the symmetry axis (B) of which coincides with the b axis of the megascopic fabric (lineation and fold axis) at each locality. Development of {011¯2} lamellae in calcite grains is attributed to late minor compression, the direction of which is more or less horizontal and trends between N.E.–S.W. and E.N.E.–W.S.W.

An occurrence of chrysotile asbestos in the Usushwana river valley some 10 miles west of Mbabane, has been sporadically prospected since its discovery in 1946. No fibre of economic grade has, however, been discovered but certain features concerning the genesis of this deposit are described and may prove of value in the further search for this valuable mineral.

Cross-fibre asbestos is confined to narrow mylonitized apple green serpentinite (totally serpentinized) occurring as sharply demarcated bands in dark blue-green serpentinite (partially serpentinized). As these mylonitized bands decrease in width they pass out into fractures less than an inch thick filled by verde antique, sometimes with traces of slip fibre. The widest mylonitized band located was 18 inches wide in which were up to a dozen seams of fibre of maximum width ½ in.

The features of the occurrence suggest that fault or shear action has been primarily responsible for the localization of this deposit.

West of Armidale occur a number of dykes which intrude Woolomin Group greywackes and which are genetically associated with Permian granite. The rocks are similar to bostonites and quartz-bostonites and show remarkably developed flow structures which indicate the condition of the magma at the time of intrusion. It is shown that intrusion probably took place by laminar flow despite the occurrence of a pseudo-turbulent structure in one dyke and it is suggested that evidence of turbulent flow is unlikely to be preserved in intrusions even if such flow did occur.

The results of gravity surveys over various exposed and buried acid intrusions are summarized. Some sample density determinations are discussed. It is found that the acid intrusions considered are almost invariably associated with negative Bouguer anomalies, which are certainly often caused by direct density contrast between the less dense acid intrusive, and the denser country rock. This has two immediate implications. (1) Large negative Bouguer anomalies over “granites” may suggest magmatic origin. (2) These gravity anomalies, supported by seismological and seismic evidence, and the petrological distribution of igneous rocks, lead to the postulation of a denser “metasedimentary” layer overlying the “granitic” layer. The bearing of this on the mechanism of intrusion is briefly discussed.

Tholeiitic rocks, which are well represented in the igneous history of the African Continent, occur as a dyke and related flow found by the writer in the north-east corner of Uganda. They outcrop in an area which is notable mainly for alkaline intrusions and lavas, so a brief attempt is made to explain the relationships and origins of the rocks in this limited area of the continent.

A structural study of rocks of the Hecla Hook formation in the area of Forlandsundet of Vestspitsbergen reveals the presence of two B–axes. The earlier (B1) trends roughly east–west and affects only the Hecla Hook formation; the later axis (B2) trends roughly north–south, and affects also rocks of Carboniferous age. It is suggested that B1 is the main “Caledonian” axis in this area, and that B2 and the roughly north–south “grain” of the rocks concerned are Lower Tertiary phenomena.

From an analysis of data concerning five breccias in the Billefjorden area, Central Vestspitsbergen, and from a consideration of explanations previously advanced of other breccias, it is concluded that the main breccias are due to collapse following solution within the underlying beds.