bluuebunny/crossref_metadata_2025_split huggingface dataset:
Scorpions from the Viséan of East Kirkton, West Lothian, Scotland, with a revision of the infraorder Mesoscorpionina
Authors: Jeram Andrew J. 
Published: November 2011

ABSTRACTScorpions from East Kirkton Quarry are represented by abundant cuticle fragments and rarer articulated specimens. Cuticles isolated from their matrix are exquisitely preserved, permitting this fauna to be described in more detail than other Carboniferous scorpion faunas. Most of the material is attributed to Pulmonoscorpius kirktonensis n. gen. n. sp. Specimens possibly indicating the presence of two additional Pulmonoscorpius species are referred to under open nomenclature. Rare fragments of an aquatic ‘archaeoctonoid’, and an orthostern scorpion, also occur. Most specimens of Pulmonoscorpius are juveniles. The range of taphonomic effects observed in these and larger individuals suggests that, as a consequence of poor preservation, the morphology of some Upper Palaeozoic scorpions has been misinterpreted by previous workers. Within the infraorder Mesoscorpionina two groups are recognised. These are distinguished by the position of the posterior pair of coxae. Pulmonoscorpius n. gen. belongs to group A, in which the posterior coxae abut the sternum. This group includes the known Lower Carboniferous mesoscorpions and ranges from the Upper Devonian to the Upper Carboniferous. All group-A mesoscorpions are reviewed here. In group-B mesoscorpions the posterior pair of coxae apparently abut the genital opercula, but confirmation of this derived character and formal taxonomic recognition of these groupings must await a restudy of the group-B mesoscorpions, which are known from the Upper Carboniferous and Triassic.
Eurypterids from the Viséan of East Kirkton, West Lothian, Scotland
Authors: Jeram Andrew J. , Selden Paul A. 
Published: November 2011

ABSTRACTThe hibbertopteroid eurypterid genera Hibbertopterus, Dunsopterus, and Cyrtoctenus occur in the East Kirkton Limestone of Bathgate, West Lothian. Most specimens are fragmentary and appear to have been washed into the depositional area with plant debris and tuffaceous sediment. Nearly all of the identifiable material can be attributed to Hibbertopterus scouleri (Hibbert), but two isolated Cyrtoctenus combs, and a femur comparable with Dunsopterus have also been recognised.New material of Hibbertopterus scouleri (Hibbert) reveals that the posterior legs and telson resemble those of the cyrtoctenids more closely than was previously thought. It is possible that Hibbertopterus, Dunsopterus, and Cyrtoctenus are indistinguishable except by relatively minor characteristics, and that all of the material from East Kirkton Quarry might be derived from a single eurypterid species. However, associations of the diagnostic sclerites which would demonstrate that these taxa are either cogeneric or distinct have not yet been found.
Myriapodous arthropods from the Viséan of East Kirkton, West Lothian, Scotland
Authors: Shear William A. 
Published: November 2011

ABSTRACTSeveral specimens of myriapodous arthropods have been discovered at the early Carboniferous East Kirkton site near Bathgate, West Lothian, Scotland. None is particularly well preserved, but they are the earliest known Carboniferous myriapods, filling the time gap between the Old Red Sandstone of the early Devonian and the abundant myriapod faunas of the late Carboniferous (Pennsylvanian). One of the specimens, a milliped, provides the earliest evidence for both ozopores (repugnatorial gland openings) and spiracles. A second milliped specimen has some characteristics of the living Order Glomeridesmida, and hence of Enghoff's (1990) ‘ground plan’ of chilognathan millipeds. Aspects of these forms and a third suggest a novel early Carboniferous fauna clearly different from both earlier and later ones. The taxon name ‘Myriapoda’ should be abandoned, since it covers a group now recognised as paraphyletic. ‘Archipolypoda’ is probably synonymous with Order Euphoberiida, Class Diplopoda.
Silvanerpeton miripedes, a new anthracosauroid from the Viséan of East Kirkton, West Lothian, Scotland
Authors: Clack J. A. 
Published: November 2011

ABSTRACTSilvanerpeton miripedes gen. et sp. nov. is a small gracile anthracosauroid. The holotype is an almost complete articulated specimen in black shale. Its anthracosaur characters include tabular-parietial contact, with a tabular horn and a moderate surangular crest indicating relationship with the embolomeres. It has gastrocentrous vertebrae with poorly ossified centra and neural arches, and the presacral vertebral count is estimated to be over 30. There are a number of apparently primitive characters as found in other anthracosauroids include a closed palate, mobile basal articulation, and an intertemporal. It differs from the other recognised species of anthracosaur at East Kirkton, Eldeceeon rolfei, in vertebral count, number of ribs, interclavicle shape, relative limb length, and in having an unossified tarsus, and a pedal phalangeal count of 23455.Disarticulated bones from East Kirkton including large limb and vertebral elements may belong to this taxon, to Eldeceeon rolfei or to as yet unidentified taxa.
Evaluation of geological age and environmental factors in changing aspects of the terrestrial vertebrate fauna during the Carboniferous
Authors: Carroll Robert L. 
Published: November 2011

ABSTRACTOf all the localities that have yielded a diversity of Carboniferous tetrapods, the fossil assemblage at East Kirkton most closely resembles that of the Joggins locality in Nova Scotia. Both assemblages are dominated by dendrerpetontid temnospondyls and a smaller number of small anthracosaurs, which are thought to have been primarily terrestrial in habits. Both localities lack adelogyrinids and lysorophids, and such presumably deep water genera as Crassigyrinusand large embolomeres. The East Kirkton Limestone differs in the presence of aïstopods and a possible nectridean, which are associated with a shallow-water environment in other localities. The absence of amniotes and microsaurs may be explained by the later evolution of these groups, their limited geographical distribution, or the lack of any aspects of the depositional environment that would preferentially select primarily terrestrial animals.
Bradoriida (Arthropoda) from the early Cambrian of North Greenland
Authors: Siveter David J. , Williams Mark , Peel John S. , Siveter Derek J. 
Published: November 2011

ABSTRACTMarine shelf siliciclastics of the early Cambrian Buen Formation of North Greenland have yielded the earliest abundant, well localised Bradoriida (Arthropoda) from the Laurentian part of North America: the shelf-dwellingPetriannagen. nov.Petriannaapparently has a fairly rigid, phosphatic shell. Its assignment to the Cambriidae, a family markedly dissimilar morphologically from the phosphatocopines (the only Bradoriida hitherto regarded as having a primary phosphatic shell), implies rejection of the criterion of carapace composition in the ordinal/subordinal classification of Bradoriida.Petriannaconfirms the Bradoriida as a consistent component of the earliest arthropod faunas. Cambriids are currently known only from the early Cambrian of Greenland, Siberia and China and offer potential for correlation. Cambriid occurrences span parts of the Redlichiid, Olenellid and Bigotinid trilobite faunal realms but are known only from tropical/subtropical regions, thus indicating possible palaeolatitudinal controls on their distribution.
Fertility of crustal rocks during anatexis
Authors: Thompson Alan Bruce 
Published: November 2011

ABSTRACT:After many years of systematic experimental investigations, it is now possible to quantify the conditions for optimum fertility to melt production of most common crustal rock types as functions of temperature andto about 30 kbar pressure. Quartzo-feldspathic melting produces steady increases in melt proportion with increasing temperature. The exact melt fraction depends on the mineral mode relative to quartz-feldspar eutectics and the temperatures of mica dehydration melting reactions. Mica melting consumes SiO2from residual quartz during the formation of refractory Al2SiO5, orthopyroxene, garnet or cordierite.A simple graphical interpretation of experimental results allows a deduction of the proportions of mica and feldspar leading to optimum fertility. In effect, the mica dehydration melting reactions, at specific pressure andare superimposed on quartz-feldspar melting relations projected onto Ab-An-Or. Fertility to melt production varies with the mica to feldspar ratio and pressure. Pelites are more fertile than psammites at low pressures (e.g. 5 kbar), especially if they contain An40to An50plagioclase. At higher pressure (e.g. 10-20 kbar) and for rocks containing albitic plagioclase, psammites are more fertile than pelites. For a typical pelite (e.g. with An25at 20 kbar), the cotectic with muscovite lies at higher(≍·) andXAb(≍0·42) than with biotite:≍0·35;XAb(≍·), thus dehydration melting of muscovite requires 10% more plagioclase for fertility than does biotite.The first melts from dehydration melting of muscovite (with Plg + Qtz) are more sodic and form at lower temperatures than the first melts from Bio + Plg + Qtz. With increasing pressure, to at least 30 kbar, granite minimum and mica dehydration melts become more sodic. This indicates thatof such melts is greater than 0·3.
Dynamic model of dehydration melting motivated by a natural analogue: applications to the Ivrea–Verbano zone, northern Italy
Authors: Barboza Scott A. , Bergantz George W. 
Published: November 2011

ABSTRACT:Dehydration melting of crustal rocks may commonly occur in response to the intrusion of mafic magma in the mid- or lower crust. However, the relative importance of melt buoyancy, shear or dyking in melt generation and extraction under geologically relevant conditions is not well understood. A numerical model of the partial melting of a metapelite is presented and the model results are compared with the Ivrea-Verbano Zone in northern Italy. The numerical model uses the mixture theory approach to modelling simultaneous convection and phase change and includes special ramping and switching functions to accommodate the rheology of crystal-melt mixtures in accordance with the results of deformation experiments. The model explicitly includes both porous media flow and thermally and compositionally driven bulk convection of a restitecharged melt mass. A range of melt viscosity and critical melt fraction models is considered. General agreement was found between predicted positions of isopleths and those from the Ivrea-Verbano Zone. Maximum melt velocities in the region of porous flow are found to be 1 × 10−7 and 1 × 10−1m per year in the region of viscous flow. The results indicate that melt buoyancy alone may not be a sufficient agent for melt extraction and that extensive, vigorous convection of partially molten rocks above mafic bodies is unlikely, in accord with direct geological examples.
Controls on the trace element composition of crustal melts
Authors: Bea F. 
Published: November 2011

ABSTRACT:The behaviour of trace elements during partial melting depends primarily on their mode of occurrence. For elements occurring as trace constituents of major phases (e.g. Li, Rb, Cs, Eu, Sr, Ba, Ga, etc.), slow intracrystalline diffusion (D ≍ 10−16 cm2 s−1) at the temperature range of crustal anatexis causes all effective crystal-melt partition coefficients to have a value close to unity and impedes further melt-restite re-equilibration. Usually, therefore, the trace element composition of crustal melts simply depends on the mass balance between the proportion and composition of phases that melt and the proportion and composition of newly formed phases. The behaviour of trace elements occurring as essential structural components in accessory phases (e.g. P, La-Sm, Gd-Lu, Y, Th, U, Zr, Hf, etc.) depends on the solubility, solution kinetics, grain size and the textural position of accessory phases. In common crustal protoliths a significant mass fraction of monazite, zircon, xenotime, Th-orthosilicates, uraninite; etc.—but not apatite—is included within other major and accessory phases. During low melt fraction anatexis the amount of accessory phases available for the melt is not sufficient for saturation, thus producing leucosomes with concentrations of La-Sm, Gd-Lu, Y, Th, U and Zr lower than expected from solubility equations. Low concentrations of these elements may also occur if the melt is prevented from reaching equilibrium with the accessories due to fast segregation. However, the first mechanism seems more feasible as leucosomes that are undersaturated with respect to monazite and zircon are frequently saturated, even oversaturated, with respect to apatite.
Water contents of felsic melts: application to the rheological properties of granitic magmas
Authors: Holtz F. , Scaillet B. , Behrens H. , Schulze F. , Pichavant M. 
Published: November 2011

ABSTRACT:New experimental determinations of water solubility in haplogranitic melts (anhydrous compositions in the system Qz-Ab-Or and binary joins) and of the viscosity of hydrous Qz28Ab38Or34 melts (normative proportions) and natural peraluminous leucogranitic melt (Gangotri, High Himalaya) are used to constrain the evolution of viscosity of ascending magmas, depending on their P-T paths.At constant pressure, in the case of fluid-absent melting conditions, with water as the main volatile dissolved in the melts, the viscosity of melts generated from quartzo-feldspathic protoliths is lower at low temperature than at, high temperature (difference of 1-2 log units between 700 and 900°C). This is due to the higher water contents of the melts at low temperature than at high temperature and to the fact that decreasing temperature does not counterbalance the effect of increasing melt water content. In ascending magmas generated from crustal material the magma viscosity does not change significantly whatever the P-T path followed (i.e. path with cooling and crystallisation; adiabatic path with decompression melting) as long as the crystal fraction is low enough to assume a Newtonian behaviour (30-50% crystals, depending on size and shape). Comparison of the properties of natural and synthetic systems suggests that both water solubility and the viscosity of multicomponent natural felsic melts (with less than 30-35% normative Qz) can be extrapolated from those of the equivalent synthetic feldspar melts.
Granite and granitic pegmatite melts: volumes and viscosities
Authors: Dingwell D. B. , Hess K.-U. , Knoche R. 
Published: November 2011

ABSTRACT:Progress in the understanding of the volumes and viscosities of granitic and related pegmatitic melts generated by experimental studies are reviewed. The results of a series of investigations of the volumes and viscosities of melts derived from a haplogranitic base composition, HPG8, located near the 2 kbar water-saturated minimum melt composition in the albite—orthoclase—silica system are discussed. Melt volumes, obtained using a combination of dilatometric and calorimetric methods at 1 atm and relatively low temperatures yield an internally consistent set of partial molar volumes for 18 components in granitic melts. These partial molar volumes, combined with an estimate for water, allow the estimation of melt densities for granitic and related pegmatitic magmas.Melt viscosities, obtained using a combination of high and low range viscometry techniques, provide a template for the estimation of melt viscosities in more complex natural systems. The parameterisation of the non-Arrhenian temperature-dependence of the viscosity of such melts is presented, together with some structural implications of the variation of melt viscosity with temperature and composition. Outstanding questions related to the PVT equation of state of granitic melts and to the mechanical response to shear stresses are discussed, with an outlook for the experimental solutions to those questions in the next few years.
Melt segregation in the lower crust: how have experiments helped us?
Authors: Rushmer Tracy 
Published: November 2011

ABSTRACT:The rheological and chemical behaviour of the lower crust during anatexis has been a major focus of geological investigations for many years. Modern studies of crustal evolution require significant knowledge, not only of the potential source regions for granites, but also of the transport paths and emplacement mechanisms operating during granite genesis. We have gained significant insights into the segregation and transport of granitoid melts from the results of experimental studies on rock behaviour during partial melting. Experiments performed on crustal rock cores under both hydrostatic conditions and during deformation have led, in part, to two conclusions. (1) The interfacial energy controlling melt distribution is anisotropic and, as a result, the textures deviate significantly from those predicted for ideal systems—planar solid-melt interfaces are developed in addition to triple junction melt pockets. The ideal dihedral angle model for melt distribution cannot be used as a constraint to predict melt migration in the lower crust. (2) The ‘critical melt fraction’ model, which requires viscous, granitic melt to remain in the source until melt fractions reach >25 vol%, is not a reliable model for melt segregation. The most recent experimental results on crustal rock cores which have helped advance our understanding of melt segregation processes have shown that melt segregation is controlled by several variables, including the depth of melting, the type of reaction and the volume change associated with that reaction. Larger scale processes such as tectonic environment determine the rate at which the lower crust heats and deforms, thus the tectonic setting controls the melt fraction at which segregation takes place, in addition to the pressure and temperature of the potential melting reactions. Melt migration therefore can occur at a variety of different melt fractions depending on the tectonic environment; these results have significant implications for the predicted geochemistry of the magmas themselves.
Status of thermobarometry in granitic batholiths
Authors: Anderson J. Lawford 
Published: November 2011

ABSTRACT:Most granitic batholiths contain plutons which are composed of low-variance mineral assemblages amenable to quantification of the P– conditions that characterise emplacement. Some mineral thermometers, such as those based on two feldspars or two Fe–Ti oxides, commonly undergo subsolidus re-equilibration. Others are more robust, including hornblende–plagioclase, hornblende–clinopyroxene, pyroxene–ilmenite, pyroxene–biotite, garnet–hornblende, muscovite-biotite and garnet–biotite. The quality of their calibration is variable and a major challenge resides in the large range of liquidus to solidus crystallisation temperatures that are incompletely preserved in mineral profiles. Further, the addition of components that affect Kd relations between non-ideal solutions remains inadequately understood. Estimation of solidus and near-solidus conditions derived from exchange thermometry often yield results >700°C and above that expected for crystallisation in the presence of an H2O-rich volatile phase. These results suggest that the assumption of crystallisation on an H2O-saturated solidus may not be an accurate characterisation of some granitic rocks.Vapour undersaturation and volatile phase composition dramatically affect solidus temperatures. Equilibria including hypersthene–biotite–sanidine–quartz, fayalite–sanidine–biotite, and annite–sanidine–magnetite (ASM) allow estimation of Estimates by the latter assemblage, however, are highly dependent on . Oxygen fugacity varies widely (from two or more log units below the QFM buffer to a few log units below the HM buffer) and can have a strong affect on mafic phase composition. Ilmenite–magnetite, quartz–ulvospinel–ilmenite–fayalite (QUILF), annite–sanidine–magnetite, biotite–almandine–muscovite–magnetite (BAMM), and titanite–magnetite–quartz (TMQ) are equilibria providing a basis for the calculation of .Granite barometry plays a critical part in constraining tectonic history. Metaluminous granites offer a range of barometers including ferrosilite–fayalite–quartz, garnet–plagioclase–hornblende–quartz and Al-in-hornblende. The latter barometer remains at the developmental stage, but has potential when the effects of temperature are considered. Likewise, peraluminous granites often contain mineral assemblages that enable pressure determinations, including garnet–biotite–muscovite–plagioclase and muscovite–biotite–alkali–feldspar–quartz. Limiting pressures can be obtained from the presence of magmatic epidote and, for low-Ca pegmatites or aplites, the presence of subsolvus versus hypersolvus alkali feldspars.As with all barometers, the influence of temperature, , and choice of activity model are critical factors. Foremost is the fact that batholiths are not static features. Mineral compositions imperfectly record conditions acquired during ascent and over a range of temperature and pressure and great care must be taken in properly quantifying intensive parameters.
Lachlan Fold Belt granitoids: products of three-component mixing
Authors: Collins W. J. 
Published: November 2011

ABSTRACT:The paradox of Lachlan Fold Belt (LFB) granitoids is that although contrasted chemical types (S- and I-types) imply melting of distinct crustal sources, the simple Nd–Sr–Pb–O isotopic arrays indicate a continuum, suggesting mixing of magmatic components. The paradox is resolved by the recognition that the previously inferred, isotopically primitive end-member is itself a crust-mantle mix, so that three general source components, mantle, lower crust and middle crust, comprise the granitoids. Based on Nd isotopic evidence, mantle-derived basaltic magmas melted and mixed with Neoproterozoic-Cambrian, arc-backarc-type material to produce primitive I-type, parental granitoid magmas in the lower–middle crust. Ordovician metasediment, locally underthrust to mid-crustal levels, was remobilised under the elevated geotherms and is most clearly recognised as diatexite in the Cooma complex, but it also exists as gneissic enclaves in S-type granites. The diatexite mixed with the hybrid I-type magmas to produce the parental S-type magmas. Unique parent magma compositions of individual granite suites reflect variations within any or all of the three major source components, or between the mixing proportions. For example, chemical tie-lines between Cooma diatexite and mafic I-type Jindabyne suite magma encompass almost all mafic S-type granites of the vast Bullenbalong supersuite, consistently in the proportion Jindabyne: Cooma, 30:70. The modelling shows that LFB S-type magmas are heavily contaminated I-type magmas, produced by large-scale mixing of hot I-type material with lower temperature diatexite in the middle crust. The model implies a genetic link between migmatite and pluton-scale, crustally derived (S-type) granites.Given the chemical and isotopic contrasts of the crustally derived source components, and their typically unequal proportions in the magmas, it is not surprising that the LFB granitoids are so distinctive and have been categorised as S- and I-type. The sublinear chemical trends of the granitoid suites are considered to be secondary effects associated with crystal fractionation of unique parental magmas that were formed by three-component mixing. The model obviates the necessity for multiple underplating events and Proterozoic continental basement, in accordance with the observed tectonostratigraphy of the Lachlan Fold Belt.