Five generations of structures (F1–F5), excluding faults, can be recognised in granitoid and trondhjemitoid migmatites with quartzofeldspathic neosome development associated with F1–F4 structures. Areal variation in metamorphic grade is shown by the zonal development of muscovite-sillimanite, potassium feldspar-sillimanite and potassium feldspar-cordierite assemblages in the palaeosomes. The climactic metamorphism, associated with MS2–MP2 mineral growth, occurred at between 675°C, 4 kb and 825°C, 6·5 kb. These pressure-temperature conditions are consistent with at least some neosome development having resulted from partial melting. The occurrence of a relatively shallow metamorphic geotherm and the resultant products are assessed in relation to metamorphic conditions known from elsewhere in the Svecokarelides.

Four balanced cross sections, supported by longitudinal sections, structure contour maps, stratigraphic separation diagrams and hangingwall sequence diagrams are keys to this interpretation of the Moine thrust, which forms the western margin of the Caledonides in NW Scotland. New basement and cover correlations between foreland and thrust belt give new slip estimates for the Moine thrust (∼ 77 km), the Loch More klippe (≥ 43 km), Glencoul sheet (20–25 km), Ben More sheet (∼28 km), Achall and Dundonnell ‘sheet II’ (∼28 km).

Like other major thrusts the Moine thrust moved in a smooth or rough fashion at different places and times, and many structures are a footwall response to its passage. Widely developed duplexes vary in thickness so that the roof thrust is folded and occasionally faulted; many late Caledonian folds in the Moine metasediments are of this origin. The presence of igneous bodies with contact aureoles increased the propensity to rough slip and this, by causing thickening in the footwall to the Moine thrust, is partly responsible for the Assynt culmination.

The previously accepted sequence of thrusting from foreland to hinterland, which has been deduced from the concept of ‘overstep’ of the Moine thrust across lower thrusts, is considered to be a misconception of thrust geometry. Instead, a ‘piggy-back’ sequence of thrusts, from higher to lower, is proposed.

The layered syenites in the Klokken intrusion consist of horizons of fine-grained, granular-textured ferroaugite syenite showing inverted cryptic layering, interleaved with coarser, laminated, more fractionated hedenbergite syenite. Distribution of hydrous mafic phases indicates build-up of water in parallel with magmatic evolution, and druses and pegmatitic segregations in the laminated syenites are evidence for late development of a gas phase. Feldspar bulk compositions are close to the minimum on the Ab-Or binary, with An decreasing from An7 to An1 with fractionation, and normal zoning in cryptoperthite crystals. Feldspars in granular syenites are transparent coherent cryptoperthites or braid microperthites; An-content is probably the main control of fine-perthite coarseness. Laminated syenite feldspars are turbid, coarse patch microperthites with rare relics of braid textures. This non-coherent coarsening was caused by interactions between feldspars and water entrapped at magmatic temperatures which was retained within the original lithologies to low subsolidus temperatures. Fe-Ti oxides reflect this water distribution, with regular trellis ilmenite-titanomagnetite intergrowths in less fractionated rocks and ragged granule exsolution in more advanced syenites. The sharp change in exsolution textures at granular-laminated syenite boundaries implies steep water-gradients within these interleaved rock types. Water was unable to penetrate the granular layers and did not circulate freely in the cooling intrusion.

All trilobites known from the lower and upper Balclatchie and lower Ardwell groups of the Girvan district are listed and frequencies recorded. Eight new species are described, a number of generic assignments are new, and hitherto undescribed parts are illustrated. Of the 60 named species, 19 occur in the lower and upper Balclatchie and lower Ardwell groups; the upper Balclatchie Group yields the largest number of species. The assemblage is generally indicative of outer shelf conditions of deposition; a deeper water association at certain Balclatchie Group localities consists of 5 species identical with, or closely related to, species from the Liberty Hall facies of the lower Edinburg Formation of Virginia, U.S.A. This deeper water element constitutes a significantly larger proportion of the trilobite assemblages at certain localities than it does at others. A further 8 species from the Balclatchie Group are allied to lower Edinburg Formation forms, thus confirming the evidence of the brachiopods regarding the strong North American affinities of the fauna. The Balclatchie conglomerate is considered to be the result of a catastrophic event accompanied by slumping near the shelf edge causing the instantaneous entombment of the fauna.

The extent of 64 glaciers that existed in the Lake District during the Loch Lomond Stadial is inferred from end, hummocky and fluted moraines and illustrated by detailed maps. Glacier surfaces are contoured and the equilibrium firn lines of the glaciers are calculated. Firn line altitudes were strongly influenced by snowfall, glacier aspect and the transfer of snow by wind from adjacent high ground. Snowfall was associated mainly with south to southeast winds and the mean direction of winds responsible for snow transfer was probably slightly west of south. It is inferred that mean July temperature at sea-level was slightly below 8°C. Protalus ramparts and other snowbed deposits indicate the former presence of numerous perennial snow beds down to altitudes of 200-300 m although the widespread occurrence of fossil gelifluction sheets and lobes points to large snow-free areas above these altitudes in summer. Fossil valley-wall rock glaciers indicate a mean annual temperature at sea-level no higher than 1°C. During deglaciation the great majority of the small glaciers retreated actively for 100-150 m and then probably decayed in situ, but some, at least, of the larger glaciers were active during much of the time their margins retreated.

In this feasibility study, Sm/Nd and 143Nd/144Nd ratios have been determined on garnets and coexisting mineral and whole-rock phases from a selection of amphibolite facies rocks, granulite facies rocks and an eclogite. In two micaceous schists and an eclogite the distribution coefficient of the Sm/Nd ratio in garnet relative to other phases is in the range 2-3, i.e. comparable to values for phenocrysts in igneous rocks. In two granulite facies rocks the garnets have Sm/Nd distribution coefficients relative to other phases in the range 13-20 and have yielded precise ages.

Garnet from a granulite facies shear zone from the Limpopo belt in southern Africa, of Archaean age, has yielded concordant duplicate ages of 1974±14 Ma and 1988±14 Ma. These results have been interpreted as relating to the last tectonic event in the region, long after the main gneiss-forming event. Garnet from a granulite facies xenolith from a Carboniferous vent in the Midland Valley of Scotland has yielded an age of 356±10 Ma; this is related to the onset of basic magmatism in the region.

Minimum T and P conditions for the crystallisation of banded amphibole (tschermakitic pargasite)-bearing garnet metapyroxenites that occur beneath and within a tectonically emplaced unit of serpentinite are 900±70°C and 10–11 (possibly 14–15) kb. This indicates both a depth provenance of at least 35–45 km for the obducted oceanic lithosphre which forms part of the ophiolite assemblage of the Ballantrae complex and also a palaeoheat-flow of at least 20°C/km. The metapyroxenites are interpreted as representing the products of subsolidus recrystallisation of a mantle accumulate pyroxenite. Together with associated amphibolites and epidote-rich mylonites formed at higher levels, they constitute a thin, transported and telescoped aureole made up of tectonic pieces of successively-formed metamorphic rocks that welded on to the base of an upward-moving and progressively-cooling peridotite slab.

Estimates of temperature of recrystallisation of the metapyroxenites were obtained using the garnet-pyroxene and garnet-amphibole exchange reactions as geothermometers. Estimates of pressure were obtained from assessments of the stability fields of the amphiboles, clinopyroxenes and garnets present and of the mineral assemblages in relation to published studies on the eclogite-granulite-amphibolite facies system.

All trilobites known from the Ardwell Group, Craighead Inlier, Girvan district are listed and frequencies recorded. Encrinuroides lapworthi n. sp. from the Sericoidea Mudstones, and Bumastoides fornax n. sp. from the Kiln Mudstones, are described. The Sericoidea Mudstones constitute a deeper water interlude in the complex succession which comprises the Craighead Limestone Formation; graptolites from this horizon indicate low Dicranograptus clingani zone. The closest resemblance of the trilobite assemblage as a whole is to faunas of Trenton age in North America. The occurrence of forms allied to Boda Limestone (Ashgill) species suggests that these are long-ranging, carbonate associated, trilobite stocks.

British and Irish species of the trilobite family Trinucleidae are investigated by numerical taxonomie methods. Forty-five attributes are defined, relating mainlyto the dorsal surface of the cephalon, and several of them representing new concepts. Of the 106 described species from the British Isles, 31 are fully codable on the basis of topo types. An analysis is based on these species, together with 28 partly topotypically codable species and samples of 9 other species (undescribed, non-topotypic or non-British). The relations of the species are depicted in an ordination derived by principal components analysis of the interattribute correlation matrix and with superimposed minimal spanning tree. On the basis of the ordination most of the analysed species can be grouped into two subfamilies, Trinucleinae and Cryptolithinae (including Marrolithinae); thersites is excluded from Reedolithinae. Trinucleinae and Cryptolithinae are strongly differentiated on the y1 axis of the ordination. The two subfamilies show parallel evolution during the Ordovician in general cranidial attributes (e.g. increasing length, declination of fringe). In Trinucleinae the fringe also shows evolutionary changes (e.g. increases in numbers and regularity of arcs); in Cryptolithinae the fringe evolves very little. Ordination of the attributes is by non-linear mapping based on a distance matrix derived from the interattribute correlation matrix by the transformation (tanh-1|r|)-1. Lectotypes of 12 species are here selected: albidus Reed, ceryx Lamont, gibbsii Salter, girvanensis Lamont, hibernicus Reed, inconstans Whittard, persulcatus Reed, praeterita Reed, rhodesi Whittard, sortita Reed, subradiatus Reed and thersites Salter.

A sequence of upward fining cycles contain braid bar structures in the coarse member. Bars, medially placed in the stream are recognised either by radiating large foresets or by identifying bar tail sediments with converging dips to their foresets. Lateral bars are recognised by the growth of major sandstone sheets oblique to the direction of channel trend and over slough mudstone. The fine member contains structures which indicate a direction of flow in the same direction as the channel, suggesting that only the unlevéed part of the floodplain is preserved.

The direction of transport for the Old Red Sandstone sediments is perpendicular to the direction of bar accretion. This is accounted for by assuming the section dealt with to be on the NNW margin of a cone which builds outward to the NE, and where the river building the cone swings from one side to the other. An upward increase in cycle thickness within the section is possibly the result of an increase in the size of the cone and the consequent amalgamation of the coarse members.

Metamorphosed abyssal ocean-floor tholeiitiic rocks, little affected by crustal contamination and probably formed at a spreading ridge, occur as a dyke complex in banded gabbros with oceanic affinities and as small tectonic lenses in serpentinised peridotite. Igneous textures and mineral assemblages have been partly or completely replaced in both dykes and gabbros. Metamorphic development of clinopyroxene and very Ti-rich hornblende at 900-1000°C was followed by a low temperature actinolite-chlorite assemblage and then by pectolite-bearing veins. Geochemical variations resulting from magmatic and metasomatic processes have been distinguished and plots of major and trace elements used to establish tectonic environment. The very high temperature metamorphic mineral growth associated with beerbachite formation indicates that the dyke rocks were in a high heat-flow environment for a considerable time, presumably in the vicinity of a spreading ridge. Obduction of a very hot slab of oceanic lithosphere accounts for the superimposed mineral assemblages.

Spatially associated pillow lavas have been affected by crustal contamination and are not comagmatic with the dykes. There are petrochemical characters indicating that some of the lavas are ocean-floor basalts. For other lavas, features suggesting emplacement in a continental or an island-arc environment could also be consistent with development in a marginal basin. However, there is so much variation in composition of pillows from margin to centre, from small to large and from metasomatic activity, that their compositional fields cannot be used for discrimination of basaltic type with the same confidence as for the dykes. Accordingly, it is suggested that the petrochemistry of sheeted dyke complexes, rather than of pillow lavas, be used for this purpose in the study of ophiolites.

Total contents of 29 trace and major elements and extractable contents of 20 elements were determined in the horizons of 4 profiles, 2 freely drained and 2 very poorly drained, of Scottish soils on drifts of basic igneous or granitic origin. The probable behaviour of other elements is suggested in the light of the results obtained. It is shown that in the course of pedological weathering, many elements are mobilised and become extractable by relatively weak reagents such as ammonium acetate (when readily exchangeable), dilute acetic acid (when less readily exchangeable or acid-soluble) or EDTA (when chelated or exchangeable). The forms in which different elements occur in the different horizons are assessed. In the surface horizons rich in organic matter many elements, such as Co, Ni, Fe, V, Cu, Cd, Sn and Pb, appear to occur mainly in chelated form; fewer, particularly Mn, are only in exchangeable form with plant uptake being largely responsible. Lower in the profiles the most common forms are acetic acid-soluble or, in gleyed horizons, exchangeable. In these horizons the degree of mobilisation is greater than in the corresponding freely drained horizons, the effect being most apparent for elements in readily weathered minerals.

Cell culture systems have been developed to assess the potential pathogenicity of mineral dusts. The in vitro cytotoxicities of a variety of dusts towards mouse peritoneal macrophages, Chinese hamster lung cells (V79 cell line) and human alveolar type II cells (A549 cell line) were investigated.

Non-pathogenic dusts were found to be inert in vitro. Fibrogenic non-fibrous dusts such as silica were only cytotoxic towards macrophages. Fibrous dusts which are both fibrogenic and carcinogenic in vivo are cytotoxic towards all three cell types, their cytotoxicity being dependent on fibre size. The size range important for the observed biological effect is longer than about 8 μm and thinner than about 1·5 μm.

Garnet-bearing xenoliths from Letseng-la-Terae display a range of textures from coarse to granuloblastic. Equilibration temperatures and pressures of primary phases are in the ranges 950-1400°C and 27-50 kb, respectively. Deformed lherzolites equilibrated throughout this temperature range but coarse xenoliths are restricted to low temperature equilibration.

All garnets display coronas developed during the reaction:

In some rocks, reaction has completely eliminated garnet.

In rocks where garnet is disrupted, the corona minerals are strung out in the fluidal texture indicating that reaction occurred before deformation. Rocks transitional to, and of granuloblastic texture, contain garnet and aluminous spinel; in addition ‘pools’ of minerals originating by dynamic separation of corona fragments are observed.

Chemical comparison between the corona minerals and minerals in a garnet-spinel rock and two spinel granuloblastites, suggests that these spinel-bearing rocks may be derived from normal garnet peridotite by a complex sequence of reaction, followed by deformation, annealing and chemical homogenisation. The conclusion that reaction and deformation took place at high levels in the upper mantle is contrary to some earlier hypotheses of shearing within the low velocity zone in response to continental plate movement, but is consistent with mantle diapir models.

The lower Palaeozoic rocks of the Southern Uplands of Scotland have been interpreted as an accretionary prism of slivers of oceanic basalt and associated deep sea sediments situated on the northern margin of the lape tus Ocean. Electron microprobe analyses confirm the presence of albite, prehnite, pumpellyite, chlorite, phengite, calcite, hematite and quartz-bearing metamorphic assemblages in basalts and basic-clast greywackes in the prism. The metamorphism is prehnite-pumpellyite facies and inferred to be related to tectonic burial of the various slices of the prism as they were accreted during the closure of the lape tus Ocean.

In spite of the structural complexity of polyphase deformed gneisses and migmatites and the absence of distinctive marker horizons, these rocks are amenable to structural investigation and interpretation with resolution of their tectonic history possible, particularly in regions of reasonable exposure. Although methods such as those employing interpretation of stereo-plots can seldom be used, direct observation of refold relationships on the outcrop using all available structural, igneous and metamorphic features will ultimately lead to the resolution of the deformational history. This is achieved by determining the relationships of fold sets observed at the various localities examined throughout the field of investigation and then combining these by correlation according to basic stratigraphical principles. The effects of weak deformation normally not discernible in complicated successions may be detected by the simple form of folded planar and linear structures in igneous masses emplaced in complex structures at intermediate stages in the deformational history.

Synthesis of the total succession and determination of the overall sequence of deformation in particularly complex terranes is made easier if at least one distinctive set of structures can be recognised throughout the area. These key structures have the effect of subdividing the long succession into two in which refold relationships are generally more easily determined. An example of the method is given using photographs from the migmatite terrane in southern Finland.

Metamorphic rocks showing an inverted metamorphic zonation from upper amphibolite fades immediately beneath the peridotite to greenschist fades at lower levels, crop out discontinuously along the base of the Semail ophiolite thrust sheet in the Oman Mountains of eastern Arabia. These metamorphic rocks show polyphase deformation, mylonitic fabrics, and have been disrupted, folded and imbricated, and in places form tectonic inclusions in a serpentinite melange. In the more intact sequences, garnet-clinopyroxene amphibolites, with rare hornblende-bearing marbles and banded quartzites, occur at the higher levels, whilst a wide range of metasedimentary and metabasaltic rocks occur in the greenschist fades. Low glaucophane content of amphiboles and low jadeite content of clinopyroxenes suggest relatively low pressures of crystallisation. The distribution coefficient KD for co-existing garnet and clinopyroxene suggests a temperature range of 670 to 750°C. Residual heat from the recently formed ophiolite probably provided the dominant heat source for metamorphism, although frictional heating could have supplemented this. The metamorphic rocks were produced during Cenomanian-Turonian (late Cretaceous) times.

The sub-ophiolite metamorphic rocks, together with basal serpentinite, Triassic alkaline and tholeiitic basalts (Haybi volcanic group), mountain-sized ‘exotic’ limestones and an upper Cretaceous sedimentary melange, comprise a distinct thrust slice termed the Haybi complex, which always overlies marine sediments of the allochthonous Hawasina complex and underlies the Semail ophiolite. The rocks of the Haybi complex are bounded by major thrust planes, the Semail thrust above and the Haybi thrust beneath, which truncate all schistosities, fold axes, imbricate thrusts and associated features. A model for ophiolite obducton is presented based on a palinspastic reconstruction of the allochthonous rocks on the Oman continental margin.