It is pointed out that some chemically analysed sedimentary rock series when plotted on AFM diagrams (A = Na2O + K2O; F = total iron as FeO; M = MgO) partly mimic trends generally considered characteristic of igneous variation, especially the calc-alkali trend. Although the scatter in sedimentary rock plots is generally greater than that given by igneous rocks this is not necessarily so for calc-alkali suites often show considerable scatter. These observations should be considered when deducing the origin of highly metamorphosed gneisses and quartzo-feldspathic rocks that might be meta-arkoses, meta-granites or meta-volcanic rocks.

Four vertical holes drilled into the olivine cumulates of the Jimberlana Intrusion all show a decrease in serpentinization with depth, suggesting that serpentinization can be a low temperature, present-day process.

Two new total degassing argon-40/argon-39 age determinations are quoted for crystals of adularia from hydrothermal veins within gabbro of the Lizard, Cornwall. The apparent ages of 147±3 Ma and 201±4 Ma obtained suggests the presence of at least two phases of hydrothermal mineralization long after the close of metamorphism.

An underwater study of recent submarine lava flows on São Miguel (Azores) suggests that the island has subsided by as much as 9 m relative to sea level over the last few thousand years. A spectacular system of overlapping lava arch structures occur immediately below the ancient sea level, and they are thought to have formed when tongues of molten lava flowed over a steep autochthonous submarine scree slope. The scree was subsequently removed by strong longshore currents and wave action.

A rock sample from the Lettergesh Formation, most probably from the centrifugus Zone of the early Wenlock on graptolite evidence, has yielded microfossils including spores, most of which occur in tetrads. The spores are described and illustrated and are compared with Ambitisporites avitus Hoffmeister.

The supposed cyclostome bryozoan Bolopora undosa Lewis 1926 is reinterpreted as a chemogenic and/or bacteriogenic dubiofossil.

Protoquartzites outcropping in a small anticline in the Plynlimon area of mid-Wales contain numerous flat-lying and low-angle, fibrous quartz veins, which are subparallel to the ab plane of the fold. The quartz crystals are elongated at a high angle to the vein walls, and in some cases exhibit a curvature which is thought to have been adopted as the crystals grew. The orientation and internal structure of the veins suggest that they formed on fractures initiated during compression and extended by hydraulic fracture, the crystal curvature being a result of shearing during syntectonic crystal growth. Pore water was important both in bringing about the critical effective stresses required for fracturing and as a carrier of locally remobilized free silica.