Summary The kinematic understanding of the relationship between relative plate motion and the structure of orogenic belts depends upon a knowledge of relative plate motion across the plate boundary system, the relative motion of small blocks and flakes within the system, an evaluation of orogenic body forces, and an understanding of the thermomechanical evolution of the upper part of the orogenic lithosphere in determining strength and detachment levels. We have built a preliminary model for the Cenozoic kinematic evolution of the western Mediterranean oceanic basins and their peripheral orogens that integrates (1) the motion of Africa relative to Europe based upon a new study of Atlantic fracture zones using SEASAT data and the Lamont-Doherty magnetic anomaly database, (2) a new interpretation of the rotation of Corsica/Sardinia and the opening of the Balearic and Tyrrhenian oceanic basins, (3) sedimentary facies sequences in the Apennines, Calabria, and Sicily, and (4) Apennine/Calabrian structure and structural sequence.

This paper is a structural and tectonic approach to the emplacement and deformation of granitoids. The main methods available in structural geology are briefly reviewed and this emphasises that (a) a wealth of data, particularly strain and shear sense, which pertain to these problems, can be determined in and around plutons; (b) given the nature, unlike many other crustal rock types, of granites to crystallise from isotropic through weakly anisotropic crystal suspension fluids, that deformation which has occurred in these states may not be well preserved; and (c) it is entirely possible, using this methodology, to separate deformation resulting from externally originating tectonic stresses from that which is associated with internal magma-related stresses. It is also recommended that the genetically-based Cloosian classification of granite fabrics and structures into “primary” (magmatic flow/magmatic flow current) and “secondary”, be abandoned and that a more observationally-based approach which classifies granite deformation fabrics and structures according to their time of occurrence relative to the crystallisation state of the congealing magma, be adopted (i.e. pre-full crystallisation deformation and crystal plastic strain deformation).Examples of recent, structurally based, studies of emplacement mechanisms of plutons within tectonic settings are described and these show that, in general, space for magma can be created by the combination of tectonically-created cavities and internal magma-related buoyancy. This occurs in both transcurrent and extensional tectonic settings and there is no reason to doubt that it can happen in compressive-contractional regimes. It is concluded that transient and permanent space creation, such as may be exploited by available magmas, is a typical feature of the tectonically stressed and deforming lithosphere and this, in combination with the natural buoyancy and ascending tendency of magmas, can generate the varied emplacement mechanisms of granites.

Doleritic sill complexes, which are an important component of volcanic continental margins, can be imaged using 3D seismic reflection data.

The Main Donegal Granite is shown to lie in a major, late stage, NE-SW trending transcurrent sinistral shear zone in the Caledonides of NW Ireland. The zone, which is bent both laterally and upwards around the pluton, has displacements which diminish SW along its length from a maximum of approximately 20 km at the NE end of the pluton. The granite has also been deformed by this sinistral shear but it has a strain component of its own, the nature and development of which indicate that the pluton was accommodated rather than forcefully emplaced in the shear zone. Strain variations between granite and wall rock, and an early plagioclase fabric associated with the petrographic banding of the granite, suggest that intrusion and deformation were more or less synchronous (at around 400 Ma). It is suggested that unconsolidated granite in the shear zone locally created high strain rates and instability which caused the zone to bend, split lengthwise, and progressively create an internal low pressure zone into which the Main Granite was emplaced. The wide variety of emplacement styles of the other, radiometrically synchronous, plutons of the batholith can be attributed to the progressive development of the shear zone: Thorr and Fanad in tension between the zone and a complimentary structure to the N; Ardara and Toories in local compression at the shear zone termination; Rosses in tension on the outer arc of the bending zone; and Trawenagh Bay, as displaced Main Granite magma, in a similar tensional setting during the final stages of deformation.

In recent years, most geotectonic syntheses of the North Atlantic Caledonides have adopted a two plate configuration, with a roughly E‐W closure direction between Laurentia and Baltica producing the N‐S striking Scandinavian and East Greenland Caledonides and inducing dextral strike‐slip along the NE‐SW oriented British sector of the Iapetus suture. The North German‐Polish Caledonides are a third arm to the Appalachian‐N. Atlantic Caledonide orogen. Recently, Ziegler has proposed that the mid‐Palaeozoic deformation belts of S. Britain ‐ N. Germany‐Poland and also of central Europe were produced by the northward impact of microcontinental fragments onto the southern margin of the already sutured continental mass of Laurentia‐Baltica. Some ascribe the whole Appalachian orogen to a sequence of terrane accretion events in mid‐Ordovician through mid‐Devonian time. A N‐S collision direction would induce sinistral shear across the British sector of the Iapetus suture. In this paper, we outline the evidence for sinistral displacements within the British Caledonides and for their age. We conclude that the “non‐metamorphic Caledonides” were produced by the northerly accretion of a Cadomian terrane in late Silurian‐early Devonian time, and that this event was entirely separate from the earlier Laurentia‐Baltica collision which produced the post‐Grampian thrust related “metamorphic Caledonides” of Scotland.