bluuebunny/crossref_metadata_2025_split huggingface dataset:
Letters concerning the Cambrian-Silurian controversy of 1852
Authors: CRAIG GORDON YOUNGER 
Published: December 2007

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Murchison died 100 years ago. One of the last political acts of his busy life was to provide an endowment of £6,000 to the University of Edinburgh in 1870 so that a Chair of Geology might be founded. At the same time he ensured that his protégé Archibald Geikie was appointed to the post in 1871. Among Geikie's correspondence, now in the library of the University, are letters on the notorious Cambrian-Silurian controversy involving Murchison and Council members of the Geological Society of London. The letters followed the publication of Sedgwick's paper on the classification and nomenclature of the Lower Palaeozoic rocks of England and Wales in the Quarterly Journal of the Society in 1852. For good measure there is also a document by Murchison setting out his considered views on the controversy and an earlier letter written but never sent to Sedgwick in which Murchison comments candidly on his mother-in-law and his religious creed.

The main story spans the life of two Councils of the Geological Society—those of 1851 and 1852—but the events themselves are crowded into the period February to June 1852. The Council for 1852 consisted of: D. T. Ansted W.J. Hamilton (Secretary) Lt.-Coh Portloek R. A. C. Austen J. D. Hooker S.P. Pratt J. J. Bigsby W. Hopkins (President) J. L. Prevost J. S. Bowerbank L. Horner A.C. Ramsay C. J. F. Bunbury C. Lyell D. Sharpe E. Forbes G.A. Mantell W.W. Smyth G. B. Greenough R.I. Murchison
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The Devonian successions in the Padstow area, North Cornwall
Authors: GAUSS GARRY ALLAN , HOUSE MICHAEL ROBERT 
Published: December 2007

Two different successions of Middle and early Upper Devonian rocks are described from the north coast of Cornwall around Padstow. These have been named the Trevone and Pentire successions. The former is seen especially south and west of Camel Estuary and is characterised by a tectonic style of overturned or recumbent folds facing north. The Pentire succession seen north and east of the outer part of the Camel Estuary shows greater tectonic complexity with a southward facing recumbent fold style. A correlation of these successions with each other has been attempted and faunas enable correlation with the international scale. Some interpretation of the depositional environments is given and estimates of the thickness of units have been made. The axis of the St. Minver synclinorium of the literature approximately separates the two successions.
The Trevone Succession in order of deposition comprises Trevose Slates (upper Eifelian and Givetian and at least 490 m thick), Marble Cliff Beds of turbiditic limestones (lowest Frasnian and at least 67 m thick), Longcarrow Cove Beds of grey slates with agglomerates and tufts (probably low Frasnian and perhaps as much as 300 m thick), Merope Island Beds of goniatite-bearing grey slate (mid Frasnian and some 60 m in thickness), Harbour Cove Slates of grey slate with purple bands and many goniatite beds (mid Frasnian of about 580 m thickness), Polzeath Slates of colourful purple and green slate (presumed late Frasnian and earliest Famen-nian seen to 120 m).
The Pentire Succession shows closely similar Trevose Slates and Polzeath Slates, the latter seen to some 200 m. Marked differences are shown by the intervening sequence which appears complete and comprises the Pentire Pillow Lava Group some 450 m thick, comprising slates, pillow lavas, volcanic tilloids and tufts, the Pentire Slates some 340 m thick, the Gravel Caverns Conglomerate, a remarkable group some 90 m in thickness of slates, mud flow conglomerates and volcanics with mid Frasnian goniates. The latter is overlain by the Polzeath Slates.
Tectonic juxtaposition of two essentially deep water argillite successions is invoked to explain the present proximity of the two differing successions. Some comparisons are made with equivalent successions in South Cornwall and South Devon.
Major structures in Morar and Knoydart, NW Scotland
Authors: POOLE ALAN B. , SPRING JOHN S. 
Published: December 2007

The Moine and Lewisian rocks of Morar and Knoydart on the west coast of Scotland have been involved in at least three major deformation phases. The earliest folds, in which Lewisian rocks form the cores of anticlines, and the youngest Moine formation the cores of synclines, are perfectly isoclinal. The second phase has produced a major recumbent fold, essentially a westward closing antiform, which refolds the previous structural succession. This recumbent fold, which is termed the Knoydart Fold, is underlain by a clearly recognized slide of approximately the same age which is called the Knoydart Slide.
It is proposed that the axial plane of the Knoydart Fold is cut at a small angle by the slide, so that the fold and its closure have two main outcrops, one below the slide in the west and another above the slide in the east. The whole assemblage is finally refolded into the more open Morar Antiform in the west and the Ben Sgriol Synform in the east. The proposed structure implies that the Lewisian outcrops around the Morar Antiform are on the lower limb of the Knoydart Fold and root eastwards. These rocks may be traced round the hinge of Knoydart Fold and are represented on the upper limb by the Lewisian in east Morar, which consequently roots westwards.
Interpretation of geophysical observations between the Orkney and Shetland Islands
Authors: BOTT M. H. P. , BROWITT C. W. A. 
Published: December 2007

A N.–S. orientated region of low gravity adjacent to the W. coast of the S. Shetland mainland is partly caused by a basin of probable Mesozoic age, as indicated by seismic refraction, sparker and bathymetric observations. The floor of the basin is estimated to be up to 2.3 km deep. The sediments of the western part of the basin are thin and of variable dip, but the eastern part takes the form of an eastward dipping sediment wedge or synclinal structure truncated on the east side by a normal boundary fault of contemporaneous or later age. The basin divides at its southern end into two tongues. The gravity low is also partly attributed to low density basement rocks such as granite, both at its north end and in the vicinity of Fair Isle, and to westward thickening of upper Palaeozoic (O.R.S.?) strata beneath the basin.
The postulated Mesozoic basin appears to be a subsidence structure along a major underlying dislocation approximately continuing the line of the Walls boundary fault. The new evidence is consistent with this being the Great Glen fault or a splay of it and interpretation of the linear magnetic gradient coinciding with the eastern tongue supports this hypothesis. The eastern boundary fault of the basin, however, appears to be normal. Tertiary transcurrent movement along the line appears to be improbable.
A strain study of a granite–granite gneiss transition and accompanying schistosity formation in the Betic orogenic zone, SE. Spain
Authors: BORRADAILE GRAHAM J. 
Published: December 2007

An allochthonous granite-bearing tectonic unit in the Alpine mountain belt of SE. Spain shows all transitions from meta-granites with original igneous textures to granite-gneisses with a single, regionally subhorizontal schistosity. Locally, the transition may be recognized in ‘shear zone’ type structures and this is suspected on a regional scale. In some out-crops of deformed meta-granite, large feld-spar phenocrysts show preferred orientation with maximum pole densities of (010) faces perpendicular to schistosity. The symmetrical arrangement of the poles with respect to the tectonic fabric elements, and increasing preferred orientation with schistosity development favour an absence of preferred orientation prior to deformation. The minimum strain responsible for the preferred orientation may be determined by progressively "undeforming" the orientations of the phenocrysts until the assumed, original random distribution is achieved. In this way strains in excess of +150% within the schistosity, and more than −77% normal to the schistosity have been found.
The large strains associated with a sub-horizontal schistosity could account for a considerable part of the displacements between flat-lying tectonic units of different competence. Furthermore, the large strain differences between different lithologies might account for the initiation of tectonic contacts and individualisation of nappes.
Aspects of materials science of interest to tectonic studies
Authors: ATKINSON B. K. 
Published: December 2007

Of The current research trends in tectonophysics, the study of deformation mechanisms and of relations quantifying their characteristic stress-strain-time behaviour (constitutive equations) should produce some of the most significant improvements in the interpretation of the structures and fabrics of deformed rocks. Such studies can shed light on phenomena as widely disparate in scale as the extent to which geologically significant flow occurs in the Earth's mantle, and the nature of preferred orientation in tectonites. They deal with phenomena that are of fundamental importance in attempts to model the structural evolution of the Earth's crust, either by computer studies or by scaled physical analogues of rock behaviour. In model studies the behaviour of real rock is assumed to follow a specific constitutive equation, i.e. a deformation mechanism is assumed. Yet many geologists are unfamiliar with the physics and chemistry of deformation processes, and even those researching these fields rarely have the time to take full advantage of the enormous quantities of pertinent literature produced by materials scientists.
Geologists and materials scientists both face similar problems in studying the phenomena of flow and fracture. Moreover, the increasing industrial concern with ceramics as new engineering materials means that scientists working in these two fields are interested in the deformation properties of often very similar materials. Meetings designed to promote an exchange of ideas can thus be of benefit to both disciplines. An important role of such meetings is to serve as the extent to which geologically significant flow occurs in the Earth's mantle,
Volcanic processes in ore genesis
Authors: GASS I. G. 
Published: December 2007

Two major themes pervaded this joint meeting of the Volcanic Studies Group and the Institute of Mining and Metallurgy. On the one hand were the ‘academics’ who, using trace element and isotope geochemistry and even naked thermodynamics, erected hypotheses and models for the tectonic setting, origin and circulation of ore forming fluids. At the other extreme were those who provided the critical evidence as to whether these data applied to a particular ore deposit. Fortunately, speakers such as J. P. Hunt, T. Sato and G. Constantineou with experience in both areas more than adequately bridged the all-too-common gulf between the two.
Stable isotope studies strongly suggest that the origin of the ore-carrying solutions was either sea-water, in the case of the massive sulphides formed at or near constructive margins, or meteoric waters for ore bodies such as porphyry coppers, emplaced above subduction zones. The role of magmatic waters is minimal in the former and minor in the latter; magmatic processes seem to provide the thermal energy and very little else. Both thermodynamic models of geothermal systems (J. W. Elder), or modification of stable isotope ratios (E. T. G. Spooner & T. H. E. Heaton) indicate that the circulation of the solutions that cause mineralization follow immediately after the magmatic thermal event and that they are short-lived in terms of thousands rather than millions of years and vigorous. There are therefore signs of a semi-quantitative breakthrough in the understanding of geothermal processes. This has been brought about by the use of
Remanent magnetism of middle Old Red Sandstone lacustrine and fluviatile sediments from the Orcadian basin, Scotland
Authors: TURNER P. 
Published: December 2007

A palaeomagnetic survey has been made of fluviatile red beds and lacustrine flagstones in the Orcadian Basin. The results from five facies are all different in important respects and this suggests that the palaeomagnetic history is strongly influenced by short-term and long-term diagenetic processes. Red beds from below the Caithness Flagstones retain much of their original magnetization, probably due to the protection of quartz cementation. Red beds from above the Caithness Flagstones have stable magnetizations but they are apparently random in direction. This is because these porous sandstones were not protected by extensive cementation and had a long history of magnetization due to the continuous penetration of oxidizing agents.
The Caithness Flagstones had varied palaeomagnetic histories and demonstrate the importance of early diagenetic events. Siltstones and dolostones in the lower Caithness Flagstones are unstable due to the presence of normal and reversed components with similar blocking temperatures. The Achanarras Limestone, a carbonate laminite deposited under strongly reducing conditions, has a stable magnetization but this is of post-Palaeozoic age and there is no original magnetization preserved. Flagstones of the Spital Group in the upper Caithness Flagstones have stable magnetizations carried by authigenic pseudo single-domain (PSD) magnetite apparently produced during early diagenesis. Throughout the Caithness Flagstones both normal and reversed components are present in many individual specimens. This makes it extremely difficult to obtain palaeomagnetically ‘clean’ directions and casts doubt on the use of the Caithness Flagstones for precise palaeomagnetic work.
Chemistry, thermal gradients and evolution of the lower continental crust
Authors: TARNEY J. , WINDLEY B. F. 
Published: December 2007

Precambrian granulites are representative of the lower continental crust. They are, relative to upper crustal gneisses, refractory and low in heat-producing elements, being 'depleted' in K, Rb, Cs, U and Th; they have normal or even higher than normal abundances of Zr, Sr, and Ba, highly fractionated REE patterns and high Ba/Rb, Ba/Sr, Ce/Yb, K/Cs and K/Rb ratios. Having low Rb/Sr, U/Pb and Sm/Nd ratios they are likely to be unradiogenic with respect to Sr, Pb and Nd isotopes. They do not seem to have marked positive Eu anomalies which might compensate for the significant negative Eu anomalies observed in upper crustal granitic rocks and sediments. The granulites formed largely under an intermediate goethermal gradient with P of 7–12 kbar and T of 700–1000°C.
The continental crust completed a substantial part of its growth by 2500 Ma ago. We suggest that growth took place at Cordillerantype continental margins with underthrusting of oceanic crust, generation and underplating of extensive calc-alkaline tonalitic-granodioritic material containing early remnants of hornblende gabbro/calcic anorthosite complexes, and that it was associated with widespread nappe stacking and imbricate interthrusting. This crustal generation process culminated in the granulite metamorphism deep in the tectonically and magmatically thickened continents.
The influence of erosion upon the mineral fades of rocks from different metamorphic environments
Authors: ENGLAND P. C. , RICHARDSON S. W. 
Published: December 2007

Metamorphism of tectonically thickened continental crust or subducted sediment wedges is likely to take place in a thermal regime where temperature increases by conductive relaxation whilst concurrently pressure decreases by erosion of the pile. The mineral facies of rocks reaching the surface do not reflect any one geotherm through the pile but lie on a locus of P–T conditions, the metamorphic geotherm, which will generally be concave towards the temperature axis. Maximum pressures on the metamorphic geotherm are significantly less than maximum pressures experienced by rocks during the early stages of recrystallization. The metamorphic geotherm is polychrome, points at lower temperatures reflecting conditions earlier in the development than those at higher temperature; crustal melts are developed after low-medium temperature metamorphism and the amount of such melts could be significant.
Blueschists develop on the low temperature end of the metamorphic geotherm and are succeeded in exposure at the surface by greenschist- or amphibolite-facies rocks; the time-scale for this process is consistent with the virtual absence of Precambrian blueschists. Crust thickened by addition of hot magma is likely to yield a metamorphic geotherm convex towards the temperature axis. Recognition of differently curving metamorphic geotherms can be used to assess the part played by magmatic activity in older metamorphic terrains.
Mesozoic–Cenozoic metallogenesis in Iran
Authors: Förster H. 
Published: December 2007

A short description of the regional geology of Iran is followed by new data concerning grade of metamorphism, palaeomagnetism, continental drift and radiometric age determinations.
Mineralization in Iran is considered in terms of four metallogenic epochs: Lower and mid-Cretaceous lead-zinc deposits in limestones, late Cretaceous chromium, copper and manganese associated with ophiolites, early Tertiary copper veins, skarns and porphyries and late Tertiary and Pleistocene porphyry copper deposits and lead-zinc veins.
Eight areas are examined as regional exploration targets. In the Yazd-Golpaigan area Lower and mid-Cretaceous stratabound lead-zinc ores of Mississippi Valley type are associated with magmatism related to the initial rifting of Gondwanaland. In western Azerbaijan Upper Cretaceous chromite ores in serpentinised dunite are regarded as part of a plate boundary environment. In northern Azerbaijan Oligocene granodiorite intrusions, related to porphyry copper deposits in Russia, have given rise to copper-molybdenum skarns. The Sabzevar zone is thought to be a 200 km wide area of oceanic crust. Cretaceous ophiolites with chromite deposits occur in its northern part, while the southern part contains chalcopyrite and pyrolusite ores in submarine lavas and sediments and low grade copper ores associated with Eocene island arc volcanism. Eastern Lut contains Cretaceous chromite deposits and lead-zinc-copper-gold veins possibly related to Plio-Pleistocene intrusions. The Neogene-Pleistocene portion of the central Iranian volcanic belt is a chain of large stratovolcanoes and granodiorite intrusions, apparently fault-controlled, which includes important porphyry copper deposits. The Oligocene volcanics of western Alborz contain veins with galena, sphalerite and chalcopyrite and a large hydrothermal alunite deposit. The flows and tuffs are intruded by granodiorite, granite and monzonite, with potential for porphyry-type copper ores.
Emplacement and crystallisation of minor intrusives
Authors: Upton B. G. J. 
Published: December 2007

A joint Tectonic Studies Group and Volcanic Studies Group meeting was held at the Department of Geology, University of Edinburgh on 20 May 1977, for the purpose of exploring the common ground between structural and petrological/volcanological interests in the subject of minor intrusives.
In the course of the eleven papers presented a wide range of ground was covered although, not surprisingly, the problems associated with the intrusion and congelation of basic magmatic sheets occupied the greater part of the meeting. By way of contrast, however, two of the papers presented were directed towards the deformation phenomena within and around granitic intrusions.
Basic sheet swarms were considered from a diversity of viewpoints ranging from petrochemical to structural. G. P. Durant highlighted the wide compositional range from transitional basalt to trachyte within the Islay and Jura dyke swarms and concentrated on their penological relationships. T. J. Halsall demonstrated that, from a detailed study of the south Arran dyke swarm, it is possible to recognise a sequence of emplacement episodes within which the change of magma type is a reflection of changing stress patterns. M. K. Wells, speaking of the Centre 2 intrusions of Ardnamurchan, indicated how the processes of cone-sheet intrusion, gabbro emplacement and updoming were intimately inter-related processes associated with the lateral spread of magma from a central feeder system. In a detailed treatment of the emplacement and crystallisation of a single sheet intrusion (the Dippin sill, Arran), F. G. F. Gibb and C. M. B. Henderson discussed the role of crystal fractionation
Late Precambrian sedimentary rocks in East Finnmark, north Norway and their relationship to the Trollf jord-Komagelv fault
Authors: Johnson H. D. , Levell B. K. , Siedlecki S. 
Published: December 2007

The late Precambrian sedimentary rocks of the Varanger Peninsula, north Norway, occur in the Tanafjord–Varangerfjord (autochthonous) and Barents Sea (allochthonous) regions. The autochthonous region includes 4-5 km of shallow water clastic sediments with subordinate carbonates and also tillites, of late Precambrian (Upper Riphean) to Tremadocian age. The allochthonous region includes about 14 km of deep and shallow water clastic sediments with subordinate carbonates, all of Precambrian age. On Varanger Peninsula these two regions are always separated by a major strike-slip tectonic disturbance, the Trollfjord–Komagelv fault. This is a single, high-angle fault in Inner Varanger Peninsula, but in the Trollfjordalen–Lille Molvik area a braided fault pattern occurs in which an early trace of the Trollfjord-Komagelv fault has been later folded and faulted. Some structural observations support strike-slip movement along the Trollfjord-Komagelv fault, while comparison with recent strike-slip fault zones suggests that the folded fault in the Trollf jordalen-Lille Molvik area represents an inactive, curved fault trace which was abandoned and subsequently tightened by (? Caledonian) folding.
Stratigraphic and structural data support recent geochronological and palaeomagnetic results which suggest the geological separation of the two regions during their deposition and perhaps during their principal deformations.
Ore forming processes
Authors: Evans A. M. 
Published: December 2007

THE MINERAL DEPOSITS STUDIES GROUP held its third residential conference at Sheffield University from 10 to 14 December 1977. Following two days' field excursions examining mineralization in northern Derbyshire twenty papers were presented by Group members. All but two were dominantly concerned with ore genesis and the majority of these dealt with deposits in the British Isles, four of them with Irish mineralization. A. M. Boast presented textural and isotopic evidence showing that much of the material, particularly the sulphur, of the Tynagh deposit was of synsedimentary origin. The weight of evidence for this and similar Irish ores undoubtedly suggests a very early time of deposition and M. J. Russell favoured a synsedimentary origin for all the larger Irish base metal deposits in the Lower Carboniferous. He discussed a mechanism whereby circulating sea water could have leached the metals from buried Lower Palaeozoic rocks. J. P. N. Badham put forward a fresh interpretation of the stratigraphy of the mineralized zones at Avoca and suggested that the stockwork feeder zone, a further possible orebody, has yet to be found. P. McArdle's work on Donegal base metal mineralization also suggests a revision of exploration philosophy in that he demonstrated that deposits in the Dalradian were originally of stratiform type.
Rock alteration processes in two very different environments and their relationship to mineralization were discussed by five workers. D. H. M. Alderton presented an excellent documentation of wall rock alteration assemblages developed in the Cornish granites. He made considerable use of isotopic and