bluuebunny/crossref_metadata_2025_split huggingface dataset:
The chemistry of geothermal waters: its effects on exploitation
Authors: Czernichowski‐Lauriol I. , Fouillac C. 
Published: July 2007

ABSTRACTThe aim of this paper is to demonstrate all aspects of the way in which chemistry affects exploitation of geothermal fluids: through scaling and corrosion and their treatment, through its influence on production characteristics, environmental considerations and also in the possible recovery of valuable by‐products. It is therefore essential that the chemical characteristics and behaviour of fluids are evaluated fully in order to optimize the design, operating conditions and management of a commercial geothermal system. Careful sampling and accurate measurements are thus indispensable. Chemical computer models are shown to be valuable tools for studying the chemical behaviour of a fluid in various situations; a brief illustration using the TPDEGAZ code is given.
Sulphur isotopic fractionation between sulphate and sulphide in hydrothermal ore deposits: disequilibrium vs equilibrium processes
Authors: Zheng Yong‐Fei 
Published: July 2007

ABSTRACTCorrelative fractionation relationships of sulphur isotope data for coexisting sulphate and sulphide pairs from hydrothermal ore deposits on δ38S versus Δ34S diagrams are deciphered theoretically. Taking into account dissolved H2S and SO42‐ in hydrothermal fluids during precipitation of both sulphate and sulphide minerals, a 4‐species closed system is suggested for describing the conservation of mass among all sulphur‐bearing species on the δ‐Δ diagrams. The covariation in the δ34S values of both sulphate and sulphide is ascribed to isotopic exchange between oxidized and reduced sulphur species during mineral precipitation. The isotopic exchange could be a thermodynamic process due to simple cooling of high temperature fluids, which results in an equilibrium fractionation, or a kinetic process due to mixing of two sulphur reservoirs, which leads to a disequilibrium fractionation. The δ34S value of total sulphur in a hydrothermal system could change due to the precipitation of minerals, or due to the escape of H2S and/or SO42‐. Sulphur isotope data for anhydrite and pyrite pairs from the Luohe porphyrite iron deposit in the Yangtze River Valley is used to illustrate the mixing responsible for the disequilibrium fractionation.
Seismicity and volcanism of Jan Mayen Island
Authors: Havskov J. , Atakan K. 
Published: July 2007

ABSTRACTThe small, arctic Jan Mayen Island, site of the World's northernmost active volcano, Beerenberg, is part of the mid‐Atlantic ridge system and located along the Jan Mayen Fracture Zone (JMFZ). Recent data from the local seismic network, and fault plane solutions from the global network, indicate that the island is located at a ridge‐crest intersection, which might explain the origin of the island and the associated volcanism. Moreover, the new data suggest a series of offset segments of the Mohn's Ridge, overlapping in an en echelon pattern.In January 1985, a flank eruption was for the first time observed with the local seismic network. Volcanic tremors and low‐frequency events were observed on 5 January at 2230 h and 10 hours later the first large earthquake occurred. No visual confirmation of the eruption was made until 6 January at 1630 h. The seismic observations rule out the possibility that the large earthquake caused the eruption; it seems more likely that the changes in local stress conditions triggered the earthquake and that the eruption started before the first large earthquake. Recent observations show that the local network provides an efficient tool for monitoring and warning of volcanic activity. However, since there was no change in the local seismicity in the days or months before the 1985 eruption, it seems to be difficult to make long‐term predictions of Beerenberg flank eruptions without using other techniques such as observations of tilt.
Seismotectonic significance of the 29 January 1989 Etne earthquake, SW Norway
Authors: Karpuz M. Ridvan , Gabrielsen Roy H. , Engell‐Sørensen Lisbeth , Anundsen Karl 
Published: July 2007

ABSTRACTThe integrated analysis of geological, seismological and field observations with lineament data derived from satellite images allows the identification of a possible seismogenic fault zone for an earthquake which occurred near Etne in southwestern Norway, on 29 February 1989. The hypocentre of the earthquake was located at the mid‐crust at a depth of 13.8±0.9 km which is typical of small intraplate earthquakes. The Etne earthquake occurred as a result of normal faulting with a dextral strike‐slip component on a NW–SE trending fault. Available geological and lineament data indicate correlation of the inferred seismogenic fault with the NW–SE trending Etne fault zone. An aeromagnetic anomaly related to the Etne fault zone forms a regional feature intersecting both Precambrian basement and allochthonous Caledonian rocks. Based on these associations the occurrence of the Etne event is ascribed to the reactivation of a zone of weakness along the Etne fault zone. Slope‐instabilities developed in the superficial deposits during the Etne event demonstrate the existence of potentially hazardous secondary‐effects of such earthquakes even in low seismicity areas such as southwestern Norway.
PETROLEUM GEOLOGY OF THE SOUTHEASTERN PART OF THE PANNONIAN BASIN
Authors: Šarković Miodrag , Stanković Srboljub , Miloslavljević Stanislav 
Published: July 2007

ABSTRACTThe large Pannonian Basin is one of the most prospective European regions for petroleum. This paper considers the geological framework and tectonic relations of the southeastern part of the basin, its generative potential for oil and gas, and some physico‐chemical descriptions of the oil and gas fields so far identified.
Hydrogen in petroleum geochemistry
Authors: Levshounova S.P. 
Published: July 2007

ABSTRACT950 samples were analysed to study the possibility of using information on hydrogen in the evaluation of regional, zonal and local hydrocarbon potential. The main method for identifying that hydrogen is of natural origin is by comparison with the δD of hydrogen of technical origin that is −792‰. As an added criterion for recognizing the origin of hydrogen in wells the investigation of changes in gas composition within the borehole section is proposed. The distribution of hydrogen in the free and adsorbed states and the role of hydrogen in hydrocarbon gas formation have been evaluated. These data combined with tests on hydrogen absorption establish a difference between oil and gas generation in terrigenous and carbonate rocks caused by different types of organic matter and by the ability of hydrogen to be preserved in the crystal lattice of carbonate minerals. This absorbed hydrogen promotes HC generation and also changes the physical properties of limestones producing fundamentally different styles of fracture genesis.
Neptunian dykes along a drowned carbonate platform margin: an indication for recurrent extensional tectonic activity?
Authors: Lehner Benedikt L. 
Published: July 2007

ABSTRACTThree successive Mesozoic neptunian dyke generations and related unconformities suggest recurrent extensional fracturing and periods of relative sea‐level rise along the NW Trento Plateau margin in the Southern Alps, Italy. The first neptunian dyke generation was induced by NNW–SSE directed extension of Early Jurassic skeletal oolitic periplatform deposits generating micritic early Middle Liassic neptunian dykes with orthogonal orientation. The second generation of neptunian dykes was possibly caused by marginal extension at the drowned platform edge penetrating Late Jurassic, red pelagic limestones with a pelagic matrix of Albian/Cenomanian age and nearly orthogonal fracture orientation. The third generation of neptunian dykes occurred after a prolonged period of submarine exposure and erosion (Aptian/Albian to Late Maastrichtian) during the rapid burial of the submarine Trento Plateau margin relief. The Late Maastrichtian neptunian dykes were caused by extension of Early to Middle Jurassic oolitic periplatform limestones along steep (inclination > 10°) submarine slopes.Generally successive neptunian dyke generations along drowned carbonate platform margins could be caused by repeated extensional brittle fracturing of lithified periplatform deposits and the filling of micritic matrix derived from overlying pelagic sediment sequences under substantial hydrostatic pressure. This would suggest that recurrent extensional fracturing is continuously recorded by neptunian dyke formation which could be used to indicate extensional tectonic activity at a foundering deep‐marine carbonate platform edge.
Strike‐slip faults parallel to crustal spreading axes: data from Iceland and the Afar Depression
Authors: Passerini Pietro , Marcucci Marta , Sguazzoni Giovanni , Zan Leonardo , Haga Abdourahman Omar 
Published: July 2007

ABSTRACTSlickenside studies in regions of crustal spreading such as Iceland and the Afar Depression, East Africa, reveal that a significant number of faults parallel and close to rift axes are strike‐slip rather than normal. Therefore, the pattern of brittle deformation in these regions does not conform to the classic two‐dimensional schemes of oceanic tectonics and pre‐oceanic rifting. Dip‐slip and strike‐slip faulting presumably alternated along or in the vicinity of spreading axes, indicate a varying stress field and a combination of transverse and longitudinal movements.In Iceland, strike‐slip faults parallel to rifts are observed both west and east of the rift system as well as in a median area between overlapping rifts; the mechanisms proposed for their origin include accommodation of oblique convergence or divergence of crustal sections due to variations of spreading directions along axis and the interaction of overlapping rifts. In the Afar Depression this kind of fault is recorded west of the rift of Asal and can be imputed to reflect an interaction among rifts in the vicinity of the Afar triple junction.Rift‐parallel strike‐slip faults cannot however be assumed to be a feature of all crustal spreading axes due to the peculiarity of the examined regions: both of them are hot‐spot areas and the Afar Depression lies at a triple junction.
Debris‐flow phenomena in the Central Apennines of Italy
Authors: Guzzetti Fausto , Cardinali Mauro 
Published: July 2007

ABSTRACTThe results of a research project on the extent of debris‐flow processes in the Monti Sibillini area (Central Italy) are presented. Debris flows have greatly contributed in shaping the landscape of the Monti Sibillini territory. Based on the dominant active process they can be subdivided into three sections: a source area, a transport area and a depositional area. Four environments can be identified as source areas: landslide deposits, highly fractured rocks, scree or talus deposits, and glacial deposits. The evolution of some of the largest features present in the area is examined. These may have developed from an initial stage of mostly gully erosion and minor landsliding, through an intermediate stage characterized by extensive mass‐movement, to a final stage dominated by fluvial processes. Lastly, generalizations on the debris‐flow hazard in the study area are made.
Chaotic fault interactions: implications for seismic hazard in New Zealand
Authors: Hodder A.P.W. 
Published: July 2007

ABSTRACTA chaotic fault interaction model previously developed for the San Andreas Fault System and the Nankai Trough (examples of transform fault and subduction dominated tectonic regimes, respectively) is here applied to the large‐event seismicity in the New Zealand region, where the interacting blocks of the model are taken to be those parts of the Indo‐Australian plate boundary that are, from north‐east to southwest, subduction dominated, ‘transpressional’, and transform‐fault dominated. The model suggests a shorter term recurrence of large events than do simple seismic cycle approaches.
A facies geological test of stable isotope interpretation of the Upper Permian depositional environment in West Spitsbergen
Authors: Malkowski Krzysztof , Gruszczyński Michal , Hoffman Antoni 
Published: July 2007

ABSTRACTLithofacies analysis of two transgressive sequences within the Kapp Starostin Formation (Upper Permian, West Spitsbergen), indicates considerable differences in seawater chemistry between their depositional environments. The onshore part of the sequence represented in the Vøringen and Svenskeegga Members is largely calcareous, with allochthonous and corroded siliceous materials. In contrast, in the equivalent sequence within the Hovtinden Member, silica is ubiquitous whereas carbonate materials include mainly corroded bioclasts. These differences are consistent with predictions of the oceanographic model of ‘overfed’ and ‘hungry’ oceans proposed previously on the basis of carbon and oxygen stable isotope analysis.
Oversized U‐shaped canyon development at the edge of rotating blocks due to wrench faulting on margins of the Dead Sea graben
Authors: Gilat Arieh 
Published: July 2007

ABSTRACTStrike‐slip fault systems on the western margin of the Dead Sea active pull‐apart basin (central part of the Dead Sea Transform) have been mapped in detail in the vicinity of the Ya'elim Valley, in the southeastern Judean Desert.Compressional, tensional and strike‐slip shearing features are described and the geomorphology of the valley (which changes over a 6 km long segment from a mature meandering valley to a deep and narrow canyon, and then to an oversized, very deep and very wide U‐shaped canyon), is elucidated using profiles and superimposed cross‐sections.A kinematic model for the Formation of the Ya'elim Valley is proposed, reflecting dextral shearing on the margins of counterclockwise rotating blocks. In the same area Subrecent‐Recent spreading of tensional fractures has occurred, separating sections of blocks which protrude eastward into the deepest on‐land depression.The large‐width of shear zones sub‐perpendicular to the Transform may relate to repeated reversals in the sense of rotation of second‐order (rigid block) domains, caused by rotations of neighbouring first order domains due to earthquake ruptures on individual parallel faults of the Transform.
Seismotectonic evidence of an active normal fault beneath Thessaloniki (Greece)
Authors: Hatzidimitriou P.M. , Hatzfeld D. , Scordills E.M. , Papadimitriou E.E. , Christodoulou A.A. 
Published: July 2007

ABSTRACTDuring 3 weeks in 1985, we operated a dense network of portable seismological stations around the city of Thessaloniki, in Northern Greece, where a destructive earthquake had occurred in 1978. We recorded 282 microearthquakes, with magnitudes ranging between ‐0.2 to 3.0, and we computed 22 Fault Plane Solutions.The experiment was designed to map the stress pattern west of the 1978 shock, and to study the Asvestohorio fault. Around this fault, located near Thessaloniki, Mercier et al. (1983) observed a few cracks during the 1978 shock.The seismicity shows the same scattered pattern seen through the whole Chalkidiki region. We observe also a dense cluster around Asvestohorio, but this cluster is probably related to explosions in nearby mines. After filtering the data from possible explosions we found evidence of seismic activity. The earthquakes are dipping toward the NE, suggesting that the Asvestohorion fault is active. The Fault Plane Solutions do not help in defining the geometry of the fault but the P and T‐axes are consistent with the regional stress pattern.
Seismic image of undercrusted serpentinite beneath a rifted margin
Authors: Boillot Gilbert , Beslier Marie‐Odile , Comas Maria 
Published: July 2007

ABSTRACTDuring the continental rifting the upper mantle was unroofed, and the mantle rocks were transformed into serpentinite at the ocean‐continent transition of the west Galicia margin (Spain). The serpentinite layer, several km thick, extends probably eastwards, beneath the highly thinned continental crust of the margin.The serpentinite layer was recently imaged by seismic reflection. It is discontinuously and deeply layered. As serpentinized peridotite can have densities and seismic velocities comparable to those of the lower continental crust, we suggest that undercrusting by serpentinite can play a part in building the lower seismic crust in highly stretched continental rifted areas.
Generation and metamorphism of new crust in magmatic arcs: a case study from northern Chile
Authors: Lucassen F. , Franz G. 
Published: July 2007

ABSTRACTIn a deep section of the Jurassic Andean arc, coastal Cordillera of northern Chile, south of Antofagasta, basic magmas from a mantle source accreted large masses of crust in an early stage of arc development. These gabbroic intrusions were isochemically metamorphosed at moderate pressures (≤ 5 kbar) and high temperatures (∼ 800°C) into uniform garnet‐absent dino+ortho‐pyroxene gneisses (granulites). Subsequently they were partly transformed into amphibolites (T≤ 700°C) during tectonically controlled access of fluid without major changes in whole rock chemistry. Locally migmatization occurs in the amphibolites. The metamorphic unit was diversified by enduring magmatic activity in the form of chemically distinct gabbroic and quartz dioritic intrusions. Formation and composition of continental crust might be a typical example for the deeper plutonic sections of this continental magmatic arc.
The nature and geological history of the deep crust under the Eifel, Germany
Authors: Stosch H.‐G. , Schmucker A. , Reys Ch. 
Published: July 2007

ABSTRACTThe crust ≈ 10–20 km under the Eifel is composed of amphibolite‐facies metasediments and meta‐igneous rocks of tonalitic to granodioritic composition; mafic granulites occupy the base of the crust down to a Moho depth between about 29 and 34 km. The meta‐granodiorites and meta‐tonalites have I‐type chemical characteristics and appear to have formed approximately 400 Myr ago by partial melting of a lower crustal source. Amphibolite‐facies metamorphism probably followed within the same orogeny. During the Quaternary, many amphibolite‐facies rocks were subjected to contact heating in crustal magma chambers and/or during transport to the earth's surface. Contact heating is also recorded in radiogenic isotope compositions of minerals from one xenolith. A genetic link between meta‐igneous amphibolites and the deeper crustal mafic granulites can neither be proven nor discounted by the isotope data. If there is a genetic relationship, it requires fractionation of a mafic magma in the lower crust and assimilation of metasediments and separation of a highly evolved melt.
3D seismic study of a ductile shear zone from laboratory and petrofabric data (Saint Barthélémy Massif, Northern Pyrenees, France)
Authors: Barruol Guilhem , Mainprice David , Kern Hartmut , de Saint Blanquat Michel , Compte Patrick 
Published: July 2007

ABSTRACTIn order to constrain interpretations of seismic reflection records more effectively, the seismic properties of a middle crustal section exposed in the Saint Barthélémy Massif have been determined. The massif, transected by a 200 m thick shear zone has been systematically sampled for density measurements and modal analysis has been performed in order to define the spatial variations of physical properties. Seismic velocities (Vp, VS, shear wave birefringence), have been measured on five representative samples to 600 MPa and 600°C simultaneously in the three structural directions (X, Y and Z). For two samples, the experimental data have been compared with calculated values, based on petrofabric analyses. The Lattice Preferred Orientation (LPO) is determined using universal stage, electron channelling microscopy and neutron diffraction goniometry. Using the experimental and calculated velocity data, we establish a lateral homogeneous anisotropic model.
A seismic reflection‐refraction experiment across the exposed lower crust in Calabria (southern Italy): first results
Authors: Lüschen E. , Nicolich R. , Cernobori L. , Fuchs K. , Kern H. , Kruhl J.H. , Persoglia S. , Romanelli M. , Schenk V. , Siegesmund S. , Tortorici L. ,   (Italian‐German Lower Crust Group)
Published: July 2007

ABSTRACTExposed crystalline basement of the Serre Mountains in Calabria presents a tilted block of a nearly complete section of the Hercynian continental lower crust (HCLC). In addition to petrological and structural data from surface mapping, and petrophysical data from the laboratory, a seismic reflection‐refraction experiment was conducted in May 1990. This consisted of a 40 km long N‐S profile crossing the HCLC and of four short transverse profiles, each recorded using 3‐component receivers with an 80 m spacing and explosive sources.The reflectivity of the outcropping lower crustal units is lower than theoretically predicted from the observed compositional layering. A low‐velocity zone, outcropping in the north, and dipping to the south, marks the contact between the HCLC and the underlying Alpine metamorphic units. Below this zone, the deeper crust appears well‐structured by strong and continuous, discrete reflections down to 6.5–8 s t.w.t. (presumably the crust‐mantle boundary at 19–24 km depth) with a dominant dip toward the south.Analysis of refracted‐wave velocities reveals values systematically lower by up to 30% than laboratory data on rock samples or calculated data from modal analysis. This discrepancy can only partly be explained by the effect of microcracks (10%), the underestimation of the amount of leucosomes (2–5%) and the effect of seismic anisotropy (0–5%). The remaining discrepancy must be attributed to large scale alteration of the rocks due to Apennine tectogenetic events.
Evolution of the petrological and seismic Moho‐implications for the continental crust‐mantle boundary
Authors: Mengel K. , Kern H. 
Published: July 2007

ABSTRACTThe chemical and petrological composition of mafic rocks from the lower continental crust are discussed by comparing mafic granulites and meta‐gabbroic rocks from the Ivrea Zone and the Northern Hessian Depression (NHD) xenolith suite. Both regions contain contrasting types of meta‐mafic lithologies (i) former basaltic rocks with trace element patterns ranging from MORB‐Iike to subduction‐related or intra‐plate tholeütes and (ü) Ca‐and Al‐enriched, plagiodase‐dominated gabbroic rocks showing positive Eu‐anomalies generated by complex deep crustal magmatic processes such as fractionation, accumulation of plagiodase and pyroxene, and crustal contamination. The absence of typical garnet‐omphadte parageneses in these rocks indicates that the eclogite stability field was not reached during Palaeozoic orogenic processes.A compilation of experimentally determined P‐wave velocities and densities for mafic granulites, gabbroic rocks, eclogites and peridotites is used to evaluate key physical properties of lower crustal mafic rocks during crystal thickening caused by continent‐continent collision. In a step‐by‐step scenario it is demonstrated that the position of the seismic Moho (defined as a first‐order velocity discontinuity) and the petrological Moho (defined as the boundary between non‐peridotitic crustal rocks and olivine‐dominated rocks) is not identical for the case that mafic rocks are transformed into edogites at the base of orogenically thickened crust. P‐wave velocities of eclogites largely overlap with those of peridotites, although their densities are significantly higher than common upper mantle rocks.As a consequence, refraction seismic field studies may not detect edogites as crustal rocks. This means that the seismic Moho detected by refraction seismic field studies appears at the upper boundary between edogites and overlying crustal units. Since edogites generally have higher densities than peridotites, they might be recycled into the deeper lithosphere thereby transferring excess Eu into the upper mantle. This process could be a due for understanding the negative Euanomaly in the upper continental crust which is apparently not balanced quantitatively by the abundance of common mafic crustal rocks.