bluuebunny/crossref_metadata_2025_split huggingface dataset:
Stratigraphic and sedimentological constraints on the age and tectonic evolution of the Neotethyan ophiolites along the Yarlung Tsangpo suture zone, Tibet
Authors: Aitchison Jonathan C. , Davis Aileen M. , Abrajevitch Alexandra V. , Ali Jason R. , Badengzhu  , Liu Jianbing , Luo Hui , McDermid Isabella R. C. , Ziabrev Sergey V. 
Published: April 2008

Abstract
Ophiolitic rocks distributed along the Yarlung Tsangpo suture zone in southern Tibet are the few remaining fragmentary remnants of many thousands of kilometres of the ocean space that formerly existed between India and Eurasia. Portions of mid-Jurassic and mid-Cretaceous intra-oceanic island arcs can be recognized amongst those rocks that have been studied in detail. Complete suprasubduction zone ophiolite successions are preserved in the Dazhuqu terrane, which crops out both east and west of Xigaze. Radiolarians in inter-pillow cherts and immediately overlying sedimentary rocks indicate a Barremian ophiolite generation event. Palaeomagnetic data show that this ophiolite formed at equatorial latitudes south of the Lhasa terrane before its south-directed emplacement onto the northern margin of India. Highly refractory ultramafic rocks in the Luobusa ophiolite appear to be of Mid-Jurassic age and are potentially related to intra-oceanic island arc remnants in the nearby Zedong terrane. Ophiolitic massifs along the suture in western Tibet are thrust southwards onto northern India and record Late Jurassic ocean-floor development. Miocene north-directed back-thrusting associated with India-Asia collision has further complicated interpretation of regional geology. The ophiolitic rocks of the Yarlung Tsangpo suture zone provide evidence for the former existence of multiple oceanic island arc segments within Neotethys and suggest that consumption of the oceanic space between India and Asia was more complicated than has been predicted by existing models.
Geodynamic patterns of ophiolites and marginal basins in the Indonesian and New Guinea regions
Authors: Harris Ron 
Published: April 2008

AbstractAnalysis of spatial, temporal, geological and geochemical patterns of ophiolites in the Indonesian and New Guinea region indicates a strong correlation with marginal basin development and closure. The spatial distribution of ophiolites is mostly linked with marginal basin producing zones of oblique convergence and collision. Strain partitioning in these zones creates a series of ephemeral plate boundaries between several independently moving lithospheric blocks. Repeated disruption of the diffuse boundaries between the blocks by changes in plate motion and collision-induced mantle extrusion creates space that is rapidly filled by new ocean basins in the upper plate of subduction zones. Suprasubduction zone (SSZ) spreading of these basins is enhanced by episodic extrusion of asthenosphere escaping collisional suture zones. Various closure events and global plate motion changes are reflected in the temporal distribution of marginal basin and ophiolite ages. Most ophiolite slabs in the Indonesian and New Guinea region represent fragments of oceanic lithosphere with a subduction zone component, as indicated by the common refractory petrochemistry of the mantle sequence and occurrence of boninite. Age and compositional heterogeneity may indicate that some ophiolite bodies are composite terranes. Collisions with buoyant lithosphere transform parts of these ocean basins into ophiolites. The connection between ophiolites and marginal basins is strongest where parts of actively spreading SSZ basins are partially represented as ophiolites in collision zones.
Controls on back-arc crustal accretion: insights from the Lau, Manus and Mariana basins
Authors: Martinez Fernando , Taylor Brian 
Published: April 2008

Abstract
Together, the Lau, Manus and Mariana basins encompass a broad range of conditions of back-arc basin development. Marine surveys have determined the tectonic setting and reconnaissance-scale geophysical and geochemical properties of the extension axes in these basins. We review these data to examine crustal accretion characteristics in the back-arc setting. In each basin magmatism is enhanced in spreading centres near the arc volcanic front, but decreases becoming ‘deficient’ in axes further from the arc. In the Lau and Manus basins the axes extend far behind the arc and develop typical mid-ocean ridge (MOR)-like characteristics. We propose that these variations are controlled by the subducting slab, which shapes composition and flow within the mantle wedge: water released from the slab lowers the mantle solidus and increases in concentration toward the volcanic arc. Spreading centres near the arc advect the hydrated mantle material, enhancing melt production. Slab-induced flow carries melt-depleted mantle material back beneath the basin where it mixes with ambient mantle. Spreading centres further from the arc advect this mantle mixture and produce thinner than normal crust. Far from the arc, spreading centres advect essentially mid-ocean ridge basalt (MORB)-source mantle and their characteristics are MOR-like. Thus, in addition to spreading-rate effects on mantle melting that predominate at MORs, in back-arc basins the subducting slab introduces additional systematic effects.
The subduction factory: its role in the evolution of the Earth’s crust and mantle
Authors: Tatsumi Yoshiyuki , Kogiso Tetsu 
Published: April 2008

Abstract
Subduction zones are major sites of magmatism on the Earth. Dehydration processes and associated element transport, which take place in both the subducting lithosphere and the down-dragged hydrated peridotite layer at the base of the mantle wedge, are largely responsible for the following characteristics common to most subduction zones: (1) the presence of dual volcanic chains within a single volcanic arc; (2) the negative correlation between the volcanic arc width and the subduction angle; (3) selective enrichment of particular incompatible trace elements; and (4) systematic across-arc variations in incompatible trace element concentrations. The occurrence of two types of andesites, calcalkalic and tholeiitic, typifies magmatism in subduction zones. Examination of geochemical characteristics of those andesites in the NE Japan arc and bulk continental crust reveals marked compositional similarity between calc-alkalic andesites and continental crust. One of the principal mechanisms of generation of calc-alkalic andesites, at least those on the NE Japan arc, is the mixing of two magmas, having basaltic and felsic compositions and being derived from partial melting of the mantle and the overriding basaltic crust, respectively. It may be thus suggested that this process would also have contributed greatly to continental crust formation. If this is the case, then the melting residue after extraction of felsic melts should be removed and delaminated from the initial crust into the mantle in order to form ‘andesitic’ crust compositions. These processes cause accumulation in the deep mantle of residual materials, such as delaminated crust materials and dehydrated, compositionally modified subducted oceanic crusts and sediments. Geochemical modelling suggests that such residual components have evolved to form enriched mantle reservoirs.
The Bouma Sequence (1962) and the resurgence of geological interest in the French Maritime Alps (1980s): the influence of the Grès d’Annot in developing ideas of turbidite systems
Authors: Bouma Arnold H. , Ravenne Christian 
Published: April 2008

Abstract
The two authors explain how and why the Grès d’Annot successions were chosen for their influential studies in the context of the 1960s and the 1980s. Arnold Bouma explains the origin of the Bouma Sequence in the 1960s, while Christian Ravenne focuses on the significance of the area as analogues of deep-sea fans and seismic stratigraphy in the 1980s. Ravenne recalls the main results obtained at that time: palaeogeographical maps, interpretative and synthetic sections, the spectacular onlap relationships at Chalufy, the strong interaction between seismic interpretation and field data, and the importance of large failures/collapses on the continental slope for the initiation of density surges.
Confined turbidite systems
Authors: Lomas Simon A. , Joseph Philippe 
Published: April 2008

Abstract
Deep-water sedimentation is currently a major focus of both academic research and industrial interest. Recent studies have emphasized the fundamental influence of seafloor topography on the growth and morphology of submarine ‘fans’: in many turbidite systems and turbidite hydrocarbon reservoirs, depositional system development has been moderately to strongly confined by pre-existing bounding slopes. This publication examines aspects of sediment dispersal and accumulation in deepwater systems where basin-floor topography has profoundly affected deposition, and the associated controls on hydrocarbon reservoir architecture and heterogeneity. The papers herein offer a global perspective which is wide-ranging in terms of both approach and location, including contrasting case studies of outcrop, subsurface, modern and experimental systems.
Timing, geodynamic setting and character of Permo-Carboniferous magmatism in the foreland of the Variscan Orogen, NW Europe
Authors: Timmerman Martin Jan 
Published: April 2008

Abstract
In the early Carboniferous, final subduction of the Rhenohercynian Ocean, accretion of a magmatic arc and docking of microcontinents caused fault reactivation, extension and fault-controlled basin formation in the foreland of the Variscan Orogen. Lithospheric stretching resulted in generally mildly alkaline basaltic volcanism that peaked in the Visean. In the internal Variscides, rapid uplift and granitoid plutonism shortly followed collision and was probably due to slab detachment(s) or removal of orogenic root material. A regional-scale, E-W-oriented stress field was superimposed on a collapsing orogen and its foreland from the Westphalian onwards. In the Stephanian-Early Permian, a combination of outward-propagating collapse, mantle or slab detachment and the regional stress field resulted in widespread formation of fault-controlled basins and extensive magmatism dated at 290-305 Ma. In the foreland, large amounts of felsic volcanic rocks erupted in northern Germany, accompanied by mafic-felsic volcanics and intrusions in the Oslo Rift, and dolerite sills and dyke swarms in Britain and Sweden. In the internal Variscides, mafic rocks are rare and felsic-intermediate compositions predominate. Their apparent subduction-related signature may have been inherited from metasomatized mantle sources or caused by extensive assimilation of continental crust.
New40Ar/39Ar ages and geochemistry of late Carboniferous-early Permian lamprophyres and related volcanic rocks in the Saxothuringian Zone of the Variscan Orogen (Germany)
Authors: von Seckendorff V. , Timmerman M. J. , Kramer W. , Wrobel P. 
Published: April 2008

Abstract40Ar/39Ar step-heating dating of mineral separates from a series of lamprophyre dykes in the Saxothuringian Zone of the Variscan Orogen yielded Viséan-Namurian (334–323 Ma) and Stephanian-early Permian (297–295 Ma) crystallization ages indicating magma generation over a period of 30 Ma. In many cases, dyke emplacement was controlled by faults. Many are composite or show evidence for mingling of primitive and evolved magmas, and, to a certain degree, contamination with crustal melts. The high MgO (6–7 wt%), Ni (75–270 ppm) and Cr (140–1250 ppm) contents and mafic phenocryst assemblage are evidence for derivation from a mantle source. Kersantites and minettes have similar incompatible trace-element and rare earth element (REE) patterns (light REE (LREE)- and medium REE (MREE)-enriched and heavy REE (HREE)-depleted) and high, but varying Th, Zr and Hf contents. Positive Ni v. Mg# (FeO=FeOtot) correlations suggest early fractionation of olivine, and the general absence of negative Eu anomalies makes feldspar fractionation improbable. For the lamprophyres of the Spessart, the variations of Ba, Rb and TiO2indicate phlogopite fractionation. Negative Ta, Nb and Ti anomalies are common, and may be an artefact of the high large ion lithophile element (LILE) and REE contents, but are more likely to reflect derivation from a mantle source that was metasomatized during a previous (Devonian?) subduction event. The generation of the parent melts was possibly triggered by partial melting of metasomatized mantle due to lithosphere detachment, removal and replacement of metasomatized lithospheric mantle by upwelling hot asthenospheric mantle. Compared to the spessartites, the minettes and kersantites appear to have originated by partial melting of deeper-mantle sources. Lithospheric mantle detachment may have caused post-collisional Namurian uplift and cooling of the crust, and facilitated emplacement of lamprophyre dykes along fault zones at high crustal levels.
Ductile shearing, hydrous fluid channelling and high-pressure metamorphism along the basement-cover contact on Sikinos, Cyclades, Greece
Authors: Gupta S. , Bickle M. J. 
Published: April 2008

Abstract
On the island of Sikinos in the Cyclades a schistose carapace separates a marble-blueschist cover sequence from underlying basement rocks. The basement ‘core’, comprising metapelitic gneisses, biotite-bearing granodiorites and aplites, becomes increasingly strained towards the carapace with progressive obliteration of earlier structures and intensification of a mylonitic foliation that becomes pervasive within the carapace. Granodiorites in the ‘core’ can be traced into microcline schists within the carapace, whereas metapelitic gneisses are converted to garnet-mica schists. The carapace is therefore a simple shear zone comprising basement rocks mylonitized during overthrusting of the cover.
Biotite clusters in granodiorites of the basement ‘core’ are partially altered to phengite, whereas plagioclase shows incipient sericitization. In more strained rocks these hydration reactions show enhanced progress, until biotite and plagioclase are finally eliminated in the carapace. Rare glaucophane and chloritoid inclusions within garnets of metapelitic gneisses adjacent to the carapace are also attributed to hydration reactions. The association of higher strain with increased hydration in the basement suggests localization of fluids in the strained carapace zone, with limited percolation into underlying rocks. The restricted availability of water outside the carapace may be responsible for preservation of pre-Alpine assemblages in large parts of the Cycladic basement.
Shear zone folds: records of flow perturbation or structural inheritance?
Authors: Alsop G. I. , Holdsworth R. E. 
Published: April 2008

Abstract

Deformation within shear zones can be both temporally and spatially variable, resulting in multiple generations of folds which display a range of scales and overprinting relationships in mylonitic rocks associated with high strain zones. Despite such complexities, two main fold associations are broadly recognized in many shear zone settings: early tight to isoclinal sheath folds, often with mylonitic limbs that are post-dated by one or more local generations of synshearing folds which are preserved within, or root downwards into mylonitic high strain zones. These latter structures locally fold the mylonitic foliation and lineation whilst displaying geometric characteristics that are kinematically compatible with the movement regime of the major shear zone. Using examples related to ductile thrusting in Moine metasediments of north Scotland, we show that both types of fold display predictable geometric patterns on fabric topology plots. Fold axes and axial surfaces display consistent changes in asymmetry and sense of obliquity relative to local, transport-parallel mineral lineations that can be used to map out a series of culminations and depression zones. The sheath folds preserve more acute, but almost identical geometric patterns compared to the later synshearing folds, with culmination and depression zones often coinciding in location and scale. Detailed analysis also demonstrates that the distribution of finite strain is systematically linked to the architecture of all folds and that clear and predictable relationships exist between the fabric topologies of both the sheath folds and synshearing folds. These consistent topological relationships could be explained in terms of a
fold evolution model
, where sheath folds represent a more highly deformed and evolved variety of synshearing folds originally generated during perturbations in ductile flow. However, an alternative
fold inheritance model
predicts that the gross structural architecture generated during sheath folding may subsequently control the geometry and govern the orientation of the synshearing folds. Both models may be widely applicable in a broad range of shear zone environments.
Crenulation-slip development in a Caledonian shear zone in NW Ireland: evidence for a multi-stage movement history
Authors: Chew D. M. , Daly J. S. , Flowerdew M. J. , Kennedy M. J. , Page L. M. 
Published: April 2008

Abstract

In Scotland and Ireland, a Laurentian passive margin sequence, the Dalradian Supergroup, was deformed during the
c.
470–460 Ma Grampian orogeny, resulting in the formation of crustal-scale recumbent nappes. In Ireland, this passive margin sequence is in general bounded to the SE by the Fair Head-Clew Bay Line (FHCBL), a segment of a major lineament within the Caledonides. Adjacent to the FHCBL, Dalradian metasediments in two separate inliers have undergone post-Grampian strike-slip movement, with the initially flat-lying Grampian nappe fabric acting as a décollement-like slip surface in both cases. As the orientation of these foliation slip surfaces was oblique to the local shear plane in both inliers, displacement along these pre-existing foliation surfaces was also accompanied by crenulation slip. However, the crenulation-slip morphologies produced imply the opposite sense of movement in the two inliers.
40
Ar-
39
Ar dating of muscovite defining the crenulation-slip surfaces indicates that post-Grampian dextral displacement took place along the FHCBL at 448 ± 3 Ma. A subsequent phase of sinistral movement along the FHCBL took place at
c.
400 Ma, based on previously published Rb-Sr muscovite ages for synkinematic pegmatites. The kinematic information obtained from crenulationslip morphologies combined with geochronology can thus be used to constrain the reactivation history of a major crustal-scale shear zone.
200 years of British hydrogeology — an introduction and overview
Authors: Mather J. D. 
Published: April 2008

Abstract
In the early years of the 19th century William Smith and his pupil John Farey began to apply stratigraphic principles to the sinking of water wells. Between 1840 and 1870 engineers, such as Robert Stephenson, and geologists, such as James Clutterbuck, Joseph Prestwich and David Ansted began to make systematic observations. After 1870 Geological Survey officers, particularly William Whitaker, Joseph Lucas and Charles de Rance, became involved in groundwater work. Lucas introduced the term hydrogeology and produced the first British hydrogeological maps. The first half of the 20th century was a period of missed opportunities with the significant advances in hydrogeology taking place in mainland Europe and North America. The Water Act of 1945 marked the start of a new era in which the Geological Survey and, after 1965, the Water Resources Board led the way. Hydrogeology is now a mainstream branch of geology in Britain and interest in the subject is such that the Hydrogeological Group of the Geological Society has a membership of around 1050.
The contribution of geologists to the development of emergency groundwater supplies by the British army
Authors: Rose Edward P. F. 
Published: April 2008

Abstract
During the 19th Century, the British military pioneered geological mapping and teaching, and the operational use of Norton tube wells. In the First World War, the British army appointed its first military hydrogeologist to serve as such, to develop water-supply maps for Belgium and northern France and guide deployment of Royal Engineer units drilling boreholes into the Cretaceous Chalk of the Somme region and Tertiary sands beneath the Flanders plain. Similar well-boring units were also deployed with geological guidance in the northeastern Mediterranean region. All military geologists were demobilized after hostilities ceased, but wartime experience was quickly drawn together in the first Royal Engineer textbook on water supply. During the Second World War, several British military well-drilling units were raised and deployed, notably to East Africa and North Africa as well as northern France, normally with military geological and sometimes (in Africa) with military geophysical technical direction. A reduced well-drilling capability has since been retained by the British army, through the Cold War to the present day, supported by a small group of reserve army geologists to contribute basic hydrogeological expertise to the armed forces for peace-time projects and war-related operations.
Tectonic evolution of Palaeozoic terranes in West Junggar, Xinjiang, NW China
Authors: Buckman Solomon , Aitchison Jonathan C. 
Published: April 2008

Abstract
Nine separate Cambrian to Carboniferous terranes are recognized in West Junggar, northwest China. They were amalgamated as part of the Central Asian Orogenic Belt which records accretion of continental, island-arc and oceanic terranes to Archaean-Proterozoic continental nuclei. Tangbale, Kekesayi, Ebinur and Mayila terranes (Cambrian-Silurian) evolved in intra-oceanic settings and docked, along a series of north-dipping subduction zones, on to the Laba terrane to their south. This southern continent was contiguous with lithosphere of the Kulumudi Ocean to the north. Devonian subduction on the northern edge of this ocean resulted in formation of a continental arc (Toli terrane) and accretionary complex (Kulumudi terrane). The Karamay terrane formed as an accretionary complex during the Carboniferous. The ophiolitic Sartuohai terrane was emplaced as mélange between Kulumudi and Karamay terranes during the Late Carboniferous. Subduction migrated southward, continuing beneath these terranes, resulting in the intrusion of I-type granites into the Toli, Kulumudi, Sartuohai and Karamay terranes. These granites are closely associated with epithermal and porphyry-style gold mineralization. Composite terranes either side of the Kulumudi Ocean collided in the Late Carboniferous, marking the final consolidation of Central Asia. Collision was accompanied by anorogenic granite and diabase dyke intrusion, followed by widespread latest Carboniferous to Permian extension, and subsequently the formation of the Junggar Basin. West Junggar has been further disrupted by Cenozoic strike-slip faulting along Junggar and Dalabute faults.
Some ichnological concepts, methodologies, applications and frontiers
Authors: McIlroy Duncan 
Published: April 2008

Abstract
Ichnology straddles the boundary between palaeontology and sedimentology, and is becoming an increasingly important tool in both fields. For the palaeontologist, trace fossils allow insight into behaviour and biomechanics of animals that would otherwise be the subject of conjecture. For the sedimentologist, trace fossils have a marked impact on the interpretation of sedimentary rocks in that they destroy primary sedimentary structures, but can also reveal subtle palaeoenvironmental information beyond the resolution attainable by analysis of primary physical sedimentary structures. This contribution aims to review the major developments in the field of ichnology, and to highlight some of the tools and approaches currently used by ichnologists. A personal ethos for the study of trace fossils in core is outlined as a model ichnological protocol, and some of the frontiers of the science as a whole are briefly discussed.