bluuebunny/crossref_metadata_2025_split huggingface dataset:
The distribution of pre-Caledonian basement in the Ox Mountains inlier, Ireland
Authors: Long Charles Barry , Yardley Bruce William 
Published: May 2008

Summary
Studies in the Ox Mountains inlier of NW Ireland in recent years have led to conflicting views by two groups of workers as to whether the inlier comprises (1) mainly pre-Caledonian basement with small areas of Dalradian (Caledonian) rocks, or (2) mainly Dalradian rocks excepting a pre-Caledonian area in the northeast. Both views are outlined here with the main arguments of the protagonists.
Pre-Caledonian basement to the paratectonic Caledonides in Ireland
Authors: Kennan P. S. , Phillips W. E. A. , Strogen P. 
Published: May 2008

Summary
In NW Ireland the exposed pre-Caledonian basement adjacent to the paratectonic Caledonides contains Grenville gneisses in N Mayo. A pre-Caledonian age is preferred for the amphibolite- and granulite-facies metasediments of the Ox Mountains, Lough Derg and Central Tyrone inliers. Gneissic xenoliths in lower Carboniferous agglomerates indicate that a comparable basement extends southwards beneath a considerable part of the Longford-Down zone in central Ireland. Pre-Caledonian basement is also exposed in SE Ireland. An important change of basement composition is inferred across central Ireland from regional magnetic data and from lead isotope data. This change occurs in the vicinity of the Iapetus suture both in Ireland and Britain.
Deformation in the Caledonides of England, Ireland and Scotland
Authors: Johnson M. R. W. , Sanderson D. J. , Soper N. J. 
Published: May 2008

Summary
The past few years have witnessed a remarkable change in our view of the British Caledonides resulting from radiometric work, application of plate tectonic models as well as basic field work. Overshadowing all else has been the acceptance of a later Proterozoic (probably Grenville) orogeny in the Moine rocks occurring between the Moine thrust and the Great Glen fault. The northern Moines are clearly polymetamorphic in character, but several matters are still controversial, for example the separation of Proterozoic and Caledonian fabrics and the areal extent of the older orogeny. This northern block was subjected to intense and repeated tectonism and, above all, large thrust translation during the Caledonian orogeny and the rocks are now juxtaposed with the older Proterozoic and Archaean gneisses of the Caledonian foreland. In Ireland small areas of Grenville basement are in slide contact with the younger Moine and Dalradian rocks.
South of the Great Glen fault above a postulated Grenville basement, are late Proterozoic sediments (Central Highland Granulites and Dalradian) which were orogenically deformed in lower Ordovician times. In this area the essence of the structural pattern established some years ago stands unquestioned for the most part, but significant modifications have been made, notably the recognition of a slice of ‘Cadomian’ basement in the Dalradian pile of NE Scotland, and possible pre-Caledonian basement in W Ireland. In Ireland the structural pattern in the Scottish Highlands may be recognised in the north, but becomes considerably modified in the west where the strike becomes E-W.
The picture of the Scottish Highlands as a metamorphic Alpine-type orogen, dating from the early Ordovician, and undergoing uplift during Ordovician and later times, is complemented by the recent recognition of the Southern Uplands zone (later, non-metamorphic Caledonides) as being an accretionary prism, on the Aleutian model, in which imbricate thrusts developed in series towards the south above the subducting oceanic crust of Iapetus. The Iapetus suture lies between the Southern Uplands and northern England and passes through central Ireland. The pattern of Ordovician vulcanicity in northern England, Wales and SE Ireland has been attributed to southerly directed subduction of the Iapetus crust beneath the opposing continental margin.
Final closure of Iapetus in Silurian and Devonian times, seems to have been marked by relatively mild tectonic activity in the ‘metamorphic Caledonides’, but by considerable compression across the slate belts of the Lake District, Wales and SE Ireland with polyphase structural evolution.
The tectonic evolution of the Welsh Caledonides
Authors: Coward M. P. , Siddans A. W. B. 
Published: May 2008

Summary
The succession, metamorphism, geochronology and major structure of the Mona Complex, Arvonian and Lower Palaeozoic rocks of N Wales are outlined. This results in a model which relates early (pre-Ordovician) NW-verging structures to the closing of an early Caledonian ocean and obduction of deep water sediments, slide breccia and basic volcanic rocks on to the sediments previously metamorphosed, locally at high temperatures, and intruded by granites in central and N Anglesey.
The pattern of folds, cleavages, thrusts and finite strain states in N Wales are described. A maximum of 43 km shortening between the Menai Straits and the Welsh Borderlands is estimated across the more highly deformed part of central Snowdonia, during end-Silurian deformation. The amount of shortening decreases to the northeast (Denbighshire Basin) and south (Harlech Dome) ends of the arc. This is attributed to compression of Snowdonia against a rigid block situated in the Berwyn Hills. The SE-verging structures are thought to pass downwards, with listric geometry, into a decollement zone at some unknown depth in the basement, which accommodated Caledonian crustal shortening across Wales, and must itself either descend into the mantle or root in any Caledonian suture beneath the Irish Sea.
Stratigraphical and structural correlation between the Dalradian rocks of the SW and Central Highlands of Scotland
Authors: Roberts J. L. , Treagus J. E. 
Published: May 2008

Summary

The stratigraphical continuity between the SW and Central Highlands of Scotland is clarified with particular reference to the lower Dalradian rocks. The structural disposition of the rocks reveals the presence of the same two structural elements as found in the SW Highlands, namely, the Ardrishaig anticline and the Ben Lui fold. The mushroom structure of the Central Highlands is rejected, while the Boundary Slide is shown to be a diffuse D
2
structure, which is probably of no great mechanical importance.
Geometry and emplacement of nappes in the Central Scottish Highlands
Authors: Bradbury H. J. , Harris A. L. , Smith R. A. 
Published: May 2008

Summary
A deformation history related to polyphase nappe formation is presented for the Central Scottish Highlands as a model for the Dalradian tract. The genesis of a four-fold pattern of tectonic belts recognisable throughout this tract is discussed. The fan structure of the Tummel steep belt is argued to be a deep-seated rotation zone. Movements within this zone spanned the climax of Barrovian metamorphism and were responsible for creating the major belt of inverted rocks—the Loch Tay inversion—which forms the lower limb of the Tay (fold) nappe. The early-formed Tay nappe, nucleated at a relatively high tectonic level, was translated as a result of movements within the deeper rotation zone progressively towards the SE principally by simple shear. The core of the Tay nappe is recognised within the Highland Border steep belt at Aberfoyle, but does not root within the deeper levels of the Central Highlands Dalradian. The Highland Border steep belt at Dunkeld was formed by late orogenic downbending of the previously flat-lying inverted limb of the Tay nappe probably resulting from sub-vertical movements within the basement along the ancestral line of the Highland Boundary fault. A kinematic model explains the nappe geometry by density inversion of the Dalradian succession consequent on the pre-orogenic evolution of the Dalradian (marginal) basin.
The Tarfside succession and the structure and stratigraphy of the eastern Scottish Dalradian rocks
Authors: Harte Ben 
Published: May 2008

Summary
Limestones and quartzites within the Tarfside culmination of Glen Esk (Angus) are correlated with the upper part of the Dalradian Argyll Group, and form part of a right way up succession extending upwards into the Southern Highland Group. This correlation makes the Tarfside limestones stratigraphically equivalent to the Loch Tay and Deeside limestones in the inverted flat belt of the Tay nappe. The zone of inversion between the Tarfside succession and that of Deeside and Loch Tay lies in the headwaters of Glen Esk and further south; the Tarfside succession occupies the structural position of the right way up limb of the Pitlochry-Kirkmichael recumbent syncline beneath the Tay nappe. The actual inversion is thought to take place across a slide which also causes the sudden disappearance of the Green Beds. Evidence for sedimentary facies variation in the Tarfside rocks and their stratigraphical equivalents supports the interpretation of some of Read’s Boyne Line phenomena (in Aberdeenshire and Banffshire) as being sedimentary facies variations.
Pre-tectonic reconstruction of the Islay anticline: implications for the depositional history of Dalradian rocks in the SW Highlands
Authors: Borradaile Graham J. 
Published: May 2008

Summary
The shape and orientation of the finite strain ellipsoid has been determined at more than 50 locations around the Islay anticline. Restoration of the ellipsoids to their original spherical form with the appropriate adjustments in orientations and positions of parts of the Anticline allow it to be ‘unfolded’. Original stratigraphical thicknesses were generally twice present day values and constant across the area with the exception of those of the Jura Quartzite which had much more marked thickness variations than are now observed. These probably resulted from syndepositional normal faulting with NE-SW crustal tension (a similar stress system controlled the intrusion of the Jura epidiorite dykes subsequently). This unstable phase in the depositional environment interrupted the otherwise uniform subsidence during Argyll Group deposition. A NE-SW striking (Caledonide) palaeostope did not develop until the close of the Argyll Group with the very energetic deposition of the Crinan Grit turbidites.
Palaeocurrent data, especially for the less competent lithologies, are unreliable unless the suggested corrections are made for the effects of penetrative tectonic strain.
Dalradian structure in the Creeslough area, NW Donegal, Ireland
Authors: Hutton D. H. W. 
Published: May 2008

Summary

The principal structure of the Appin Group metasediments in the Creeslough area is a series of D
2
NW-facing recumbent folds and two important slides that are thrusts (to the northwest). D
3
produces large open folds that face to the southeast. D
4
is associated with a major synform and shear zone in the aureole of the Main Donegal granite. No major F
1
fold hinges are present, although D
1
faces northwest. It is concluded that of the early deformations in Donegal, D
2
can be regarded as the Caledonian thrust front.
Structure and stratigraphy of the Dalradian rocks of the Bennabeola area, Connemara, Eire
Authors: Tanner Peter William Geoffrey , Shackleton Robert Milner 
Published: May 2008

Summary

The geology of an area of 400 sq km of Lower and Middle Dalradian rocks is described. It consists mainly of rocks belonging to the Appin and Argyll Groups which have been strongly deformed during four stages (F
1
–F
4
) with the major development of tectonic slides occurring before F
3
. Eighteen major F
3
folds, whose geometry is described, are correlated across the Connemara antiform (F
4
); they refold an earlier nappe-like (? F
2
) antiform, the Derryclare fold. All of the Appin Group rocks and the Cleggan Boulder Bed Formation are contained within the core of the Derryclare fold, which locally has attenuated limbs. A zone of vertical foliation, the ‘steep belt’, is present in the south of the area. It is superimposed upon the originally steeply inclined, south-facing Derryclare fold and appears to have developed during F
4
.
Strain adjacent to the Iapetus suture in Ireland
Authors: Phillips W. E. A. , Flegg A. M. , Anderson T. B. 
Published: May 2008

Summary

The Iapetus suture, extending northeastwards through Silvermines and Navan, separates distinct structural provinces of the paratectonic Caledonides. On the north side, F
2
and F
3
folds and a shallow pitching stretching lineation become increasingly important southwards over a zone up to 50 km wide. S
1
cleavage here shows an anomalous relationship to F
1
folds, with a consistent clockwise offset of cleavage strike away from F
1
axial planes. Dextral simple shear along strike appears to have been important during ductile deformation in this zone. South of the suture, upright F
1
folds of varied plunge are the dominant ductile structures. Strain varies from pure flattening to often a component of down dip extension. Within 50 km on either side of the suture, analysis of faulting suggests control by dextral simple shear parallel to the suture. Outside this zone a different ‘intra-plate’ conjugate system is developed.
A structural profile of Caledonian deformation in Down
Authors: Anderson T. B. , Cameron T. D. J. 
Published: May 2008

Summary
Coastal exposure in County Down provides an almost complete cross section of the continuation of the Southern Uplands fold belt in Ireland. Intensely folded Ordovician and Silurian turbidite successions are segmented by at least ten major strike parallel faults. In each segment the fold envelope descends northward but the strike faults throw up progressively younger sediments to the south. A system of upright folds, with slaty cleavage axial plane, but locally transecting, becomes progressively complicated southward by the clear development of two further phases of folding and cleavage with constant geometry and opposing vergence. The chronology of cleavage, folding, later kink-band and brittle deformation is punctuated by successive late Caledonian lamprophyre dyke swarms. The total structure is consistent with a model of diachronous deformation and northward translation and rotation at a destructive plate margin.
Structure of the Southern Uplands of Scotland
Authors: Eales Martin H. 
Published: May 2008

Summary
In the Moffat Shale lithology of the Southern Uplands, the primary Caledonian structure consists of thrusting at a low angle to the bedding. Thrusting was associated with minor and large scale folding and northwesterly rotation of beds and thrust planes. Wrench faulting is considered as the final major Caledonian event. All these structural phases were caused by similar principal stress orientations. The primary thrusting is best studied in the Moffat Shale inliers where stratigraphical control is excellent. It is possible that these beds overlie a major plane of décollement.
Thrusting is less conspicuous in the overlying greywacke sequence where the beds are more competent, and the stratigraphy is less well defined. Otherwise, the Caledonide structural evolution of the greywacke is essentially the same as that in the underlying pelagic sequence. Consequently it is suggested that nearly all the Caledonian structures of the Southern Uplands can be broadly explained by a common but evolving stress system.
A strain section across part of the Caledonian orogen in W Ireland
Authors: Kelly Thomas J. , Max Michael D. 
Published: May 2008

Summary
Quantitative strain analysis supports the concept of tectonic compartmentation within the western Irish Caledonides. Older rocks do not always show higher strains and this may be due to each compartment’s particular response to stress. Strain variation also occurs within individual tectonic compartments.
Caledonian thrusting in NW Scotland
Authors: Mendum J. R. 
Published: May 2008

Summary

Several major thrusting events, ranging in age from Precambrian to Middle Devonian, have affected the Moine assemblage and adjacent foreland. An early thrusting event is primarily responsible for the emplacement of lenticular Lewisian Gneiss inliers within the Moines. The main Caledonian (
sensu stricto
) event (F
2
) at about 480 Ma was complex in nature with widespread marginal and internal ductile thrusting, related recumbent folding, metamorphism and locally migmatisation. Later open to tight folding (F
3
, F
4
) and minor ductile thrusting (F
3
) modified this pattern. Subsequently in Silurian to Lower Devonian times marginal major brittle thrusting, and internal faulting, minor thrusting and uplift, occurred.
Pelite facies series and the temperatures and pressures of Dalradian metamorphism in E Scotland
Authors: Harte Ben , Hudson Neil F. C. 
Published: May 2008

Summary
An attempt is made to synthesise data on the regional metamorphism of pelites in the eastern Scottish Dalradian. Zonal sequences (facies series) of mineral assemblages are presented and variants of the traditionally recognised Barrovian and Buchan metamorphism are separated. A Schreinemakers net and petrogenetic grid for the system KFMASH is presented and fixed in P-T space using experimental data. The P-T data for the various facies series are used in conjunction with other constraints to develop a model of isotherm and isobar distribution in the region, and the effects of post metamorphic folding of the isopleths are noted. P-T gradients normal to isobars suggest overall ‘geothermal’ gradients for most of the area to be convex to the T-axis, and it is suggested that they result from magma intrusion at depth. The region adjacent to the Highland Boundary fault shows strong horizontal and vertical temperature gradients which are tentatively interpreted to indicate the presence of a synmetamorphic tectonic boundary to the Dalradian metamorphic belt.
Thermal evolution of metamorphic rocks in the Central Highlands of Scotland
Authors: Wells P. R. A. , Richardson S. W. 
Published: May 2008

Summary
Conditions of the metamorphic maxima in lower Dalradian kyanite zone pelites from Kinloch Rannoch, Schichallion, Glen Tilt, Glen Ey and Glen Avon are calculated from analyses of coexisting kyanite, garnet, biotite, plagioclase and quartz (staurolite or chlorite also coexist in some samples). Temperatures of 550–620°C were reached at pressures of 9–12 kb corresponding to depths of burial of 35–40 km. Compositional gradients in zoned garnets indicate that pressures were falling at the time maximum temperatures were reached. The high values of pressure are confirmed by observations of the sub-assemblages kyanite-zoisite (not anorthite-margarite) and kyanite-garnet-chlorite-quartz (not staurolite or chloritoid). The pressure of intrusion of a Newer Igneous complex in upper Glen Tilt is 5–6 kb. The present results are contrasted with conditions at a similar structural/stratigraphical level 50 km WNW where comparable temperatures were reached at depths around 20 km. It is concluded that either erosion rates early during metamorphism were lower or the tectonic cover was greater in the Central Highlands than to the west.
Migmatisation, deformation and porphyroblast growth in the Dalradian of Tayside, Scotland
Authors: Bradbury Harry J. 
Published: May 2008

Summary
In Tayside, migmatisation of kyanite zone Argyll and Southern Highland Dalradian metasediments occurred between the regional D2 and D3 episodes in the Grampian orogeny. The U-Pb zircon age for the emplacement of the ‘Older’ Ben Vuirich Granite (514 + 6/ − 7 Ma), which intervenes between D2 and D3, provides an approximate age for migmatisation. This is significantly younger than recent isotopic ages of migmatites from the W Scottish Highlands with which the Tayside migmatites were previously correlated. In Tayside, migmatisation largely post dated the development of the Tay nappe but pre-dated the late-stage modification of the Tummel steep belt and the Loch Tay inversion. Textural evidence indicates that migmatisation was broadly coeval with the climactic Barrovian metamorphism, the age of which is discussed.
Textural and mineralogical evolution of migmatites
Authors: Ashworth J. R. 
Published: May 2008

Summary
Textures and muscovite compositions in regional migmatites from the Central Highlands of Scotland are compared with those of the Huntly-Porsoy area, where early retrograde muscovite retains compositions appropriate to the sillimanite-potash feldspar zone. In samples from the upper Findhorn area, textural relics from this zone are found, even though textures are strongly modified by recrystallisation, and sillimanite no longer coexists with potash feldspar. Muscovite composition varies within a leucosome, between compositions appropriate to the sillimanite zone and others adjusted to much lower grade. In samples from mid-Strathspey, mineralogy is low-grade and textural modification profound, despite relatively little deformation. The grade at which these latter samples were migmatised is difficult to deduce from internal evidence.
Time, space and intensity relationships of the Precambrian and lower Palaeozoic metamorphisms of the Scottish Highlands
Authors: Lambert R. St J. , Winchester J. A. , Holland J. G. 
Published: May 2008

Summary
Isotopic evidence suggests that a complex sequence of events, collectively known to us as the Morarian event, affected the Morar and Glenfinnan divisions of the Moine from 1000 to 750 Ma. A regional thermal anticline, with a minimum age of 750 Ma, extends north from Ardgour to northern Ross-shire: it probably extends southwards under the eastern Dalradian. This thermal anticline is cut across and shifted westwards south of Monar by the Sgurr Beag slide, on which up to 25 km thrust movement is estimated. The Loch Eil Division lacks old isotopic ages; it appears to be structurally and metamorphically simpler than the Morar and Glenfinnan divisions and it also differs from them geochemically. The simplest explanation of these facts is that Loch Eil Division rests unconformably on the metamorphosed Glenfinnan Division. The Central Highland Group (including the Monadhliath Schists) is presumed to occupy the same tectono-stratigraphical niche as the Loch Eil Division. Grampian events (510-480 Ma) produced three thermal highs of sillimanite grade: one in the Monadhliaths, the second in the NE Grampians, and the third affecting E Sutherland. Throughout most of the area under consideration, Grampian age isograd surfaces appear to dip at low angles.
Patterns of metamorphism in the Ox Mountains and adjacent parts of Western Ireland
Authors: Yardley Bruce W. D. , Long C. Barry , Max Michael D. 
Published: May 2008

Summary
Three types of regional metamorphism are present in the Ox Mountains inlier. High pressure granulites occur in the northeast, but elsewhere most Ox Mountains rocks show a single progressive Barrovian metamorphism from garnet zone to kyanite zone. Conditions of metamorphism for the kyanite zone were near 600°C and 6–7 kbar total pressure. Regional retrogression occurs principally in the north central Ox and affects both granulites and the lower grade metasediments. The tectonic contact between granulites and Barrovian kyanite zone rocks in the Ox is analogous to that in southern Donegal and the conditions of metamorphism of the (Dalradian) staurolite-kyanite schists are the same in both areas.
Oxide-sulphide-silicate mineral phase relations in some thermally metamorphosed graphitic pelites from Co. Donegal, Eire
Authors: Atkin B. P. 
Published: May 2008

Summary
A chemical control over the oxide-sulphide-silicate phase relations of the graphitic pelites from the aureoles of Donegal granites is demonstrated. Kyanite-bearing rocks (M/FM ratio >0.54) have the ore assemblage of rutile + pyrite or pyrrhotite and kyanite-free rocks have the assemblage ilmenite + pyrrhotite. The stabilisation, during prograde metamorphism of pyrrhotite over pyrite and ilmenite over rutile accompanied by an increase in the Mg content of ferromagnesium phases is also demonstrated. Phase relations between oxide and silicate phases are illustrated by AFMT(i); tetrahedral diagrams and sulphide-silicate phases by AFMS tetrahedral diagrams. Retrograde reactions especially the replacement of ilmenite by rutile and pyrrhotite by marcasite are also described.