bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dust deposition in the central Mediterranean (Tyrrhenian and Adriatic Seas): Relationships with marine sediments and riverine input
Authors: Correggiari A. , Guerzonid̊ S. , Lenazd̊ R. , Quarantottod̊ G. , Rampazzo G. 
Published: July 2007

ABSTRACTMajor (Al, Ca, Fe, Mg, Mn, Si) and minor (Cd, Pb, Zn) elements of aeolian dust samples collected onboard ship around Italy were analysed, and the concentrations of metal in the dusts were in good agreement with previously published data from the Mediterranean Sea.The elemental composition of dust samples collected in four subareas (Adriatic, Ionian, Tyrrhenian, and Sicily Channel) was compared with the composition of marine deep sediments obtained in the same regions: Mn, Al, Cd and Zn contents differentiated between the four areas in both sets of samples, suggesting a possible ‘geochemical signature’ of the atmospheric crustal contribution in marine deep sediments.An estimate of the relative contribution of atmospheric dry deposition of Cd, Pb and Zn and riverine discharge indicates that: (a) the metals deposited from the atmosphere to the Adriatic basin are a small fraction (2–5%) of those discharged by the Po and Adige rivers; (b) almost the same amounts of Cd, Pb and Zn are delivered to the Tyrrhenian Sea by the atmosphere and by the Arno and Tiber Rivers.
Carbon isotopes and Precambrian—Cambrian boundary geology, South Australia: ocean basin formation, seawater chemistry and organic evolution
Authors: Tucker Maurice E. 
Published: July 2007

ABSTRACTA carbon isotope stratigraphy from the lowest Cambrian strata in the Adelaide fold belt of South Australia is interpreted in terms of the geological context of the sequence: major transgression, developing circulation patterns and upwelling resulting from an adjacent opening ocean, and biomass increases stemming from the Cambrian radiation event. There is also evidence from the textures of ooids and cements in late Precambrian‐Cambrian strata for subtle variations in seawater chemistry across the boundary and these may well have been instrumental in the development of calcareous skeletons in the early metazoans.
A geological transect from Kun Lun to Karakorum (Sinkiang, China): the western termination of the Tibetan Plateau. Preliminary note
Authors: Gaetani Maurizio , Gosso Guido , Pognante Ugo 
Published: July 2007

ABSTRACTA geological‐geophysical expedition (Ev‐K2–CNR 1988) visited the area from West Kun Lun to Karakorum (K2–Gasherbrum). Seven tectonic units including sedimentary, magmatic and metamorphic rocks were distinguished in this area; the northernmost are suggested to belong to the Kun Lun and Qiangtang Microplates. The sedimentary sequence of Shaksgam is proved to extend from the Permian to the Jurassic, with Carboniferous and Cretaceous ages more doubtful. This sequence shows intermediate affinities between the Karakorum and the Qiangtang. The two southernmost units belong to the Karakorum Microplate. The Karakorum Fault Zone comprises a complex pattern of faults and thrusts, with brittle deformation and uplifting of granitoid bodies.
Numerical basin modelling of the Sleipner field, North Sea
Authors: Wei Z.P. , Hermanrud C. , Lerche I. 
Published: July 2007

ABSTRACTBoth one‐dimensional (1‐D) and two‐dimensional (2‐D) basin modelling has been carried out in the Sleipner area in the North Sea. Thermal refraction by salt and more minor convection by fluid transport combine to provide a temperature regime which is hotter at the Sleipner East field relative to the Sleipner West field by approximately 5°C at the same sub‐surface depth. These results are obtained only with 2‐D modelling, and show that such simulations are necessary to explain the spatial variations of temperature distribution at the least.Modelling of hydrocarbon generation in the Sleipner kitchen shows that the source rocks are presently in a late gas generation state, and that a gas‐condensate is to be expected in fields draining this kitchen. Such hydrocarbon phases are encountered in the Sleipner field, confirming that the model can simulate satisfactorily hydrocarbon generation in the Sleipner area.
Persistence of quartz disequilibrium in groundwater flows
Authors: de Caritat Patrice 
Published: July 2007

ABSTRACTThis paper shows how constraints can be placed on the prediction of quartz equilibration distance in subsurface water flows. This is achieved here by coupling kinetic equations for the simple (SiO2(quartz)‐H2O(water)) system to various groundwater flow parameters (compaction flow, aquifer, convection flow, and hydrothermal system). This approach determines: (1) the order of magnitude of the downstream distance necessary for equilibrium to be attained, when a flowing solution is initially out of equilibrium; and (2) the minimum flow velocity required to sustain a sufficient quartz undersaturation or oversaturation over a given distance. Geological conditions under which specific water‐rock interactions take place can be constrained with those calculations. Water flow in most subsurface environments, as idealized here, tends to equilibrate with the quartz‐rich hosting medium on a very short distance (≤ 1 m). Major exceptions are: (1) the topmost part of a compacting pile, (2) shallow and fast‐flowing aquifers, and (3) most hydrothermal systems.
The MAR‐Vema Fracture Zone intersection surveyed by deep submersible Nautile
Authors: Auzende Jean‐Marie , Bideau Daniel , Bonatti Enrico , Cannat Mathilde , Honnorez José , Lagabrielle Yves , Malavieille Jacques , Mamaloukas‐Frangoulis Vassilios , Mével Catherine 
Published: July 2007

ABSTRACTOne of the two objectives of the Vemanaute cruise of the French deep submersible Nautile, was the geological study of the eastern intersection area between the Mid‐Atlantic Ridge (MAR) and the Vema Fracture Zone in the equatorial Atlantic. Fourteen dives were conducted that allowed detailed geological survey and sampling of the main morphostructural units of this area: the northern and southern walls of the fracture zone, the median ridge, the northern and southern troughs and the nodal basin. In situ observations of recent tectonic features such as furrows, ridges and circular depressions, concentrated within the southern trough, allowed us to establish the location and the size of the present‐day displacement zone. Geological investigations have shown that the nodal basin is entirely floored by basalts thus contrasting with other equivalent areas such as the Kane and Oceanographer fracture zone‐MAR eastern intersections. Finally, this study stresses the great opposition between the relatively old and tectonically inactive northern part of the fracture, and the southern part which shows active tectonics and recent volcanic activity.
The effect of Rayleigh degassing of magma on sulphur isotope composition: a quantitative evaluation
Authors: Zheng Y‐F. 
Published: July 2007

ABSTRACTThe effect of Rayleigh distillation by outgassing of SO2 and H2O on the isotopic composition of sulphur remaining in silicate melts is quantitatively modelled. A threshold mole fraction of sulphur in the sulphide component of the melts is reckoned as being critically important in shifting the δ34S value of degassed melts with respect to the original magmas. During the outgassing, melts above the threshold are depleted in 34S, whereas melts below the threshold are enriched in 34S. In particular, the outgassing of SO2 above the sulphide threshold can produce large negative δ34S values in the degassed melts, whereas the outgassing of H2S below the threshold will strongly drive the δ34S value of the melts in the positive direction. The correlation between δ34S value and sulphur content of total sulphur in the solidified rocks is indicative of the Rayleigh‐type degassing.
Uranium at the Cretaceous‐Tertiary boundary in Denmark
Authors: Kunzendorf Helmar , Gwozdz Rajmond , Hansen Hans Jørgen 
Published: July 2007

ABSTRACTUranium is significantly enriched (up to two orders of magnitude) in the Danish Cretaceous‐Tertiary boundary beds relative to the underand overlaying sediments. Both the predominant oxic and some anoxic deposits have a high uranium content. To investigate the geochemical behaviour of the element, a series of sections was analysed for uranium by means of the delayed‐neutron counting technique.Uranium contents in the carbonate rocks from different parts of the Danish Sub‐basin are generally low but show slight regional trends. Experiments that involve cold acid extractions suggest that uranium is associated with the non‐carbonate residues.The uranium distribution with depth in the offshore drill core from the Central Graben area (North Sea) suggests that the element is associated with clay in the Danian part.Cretaceous‐Tertiary boundary beds from Stevns Klint and other localities in the Danish sub‐basin have anomalously high uranium contents compared with the values for chalk. Uranium is not correlated with iron, non‐carbonate carbon or aluminium. The highest uranium values within boundary sections are not found in the lower part of the sections as is the case for iridium.The only boundary beds that show typical anoxic depositional affinity have a total uranium accumulation that is one order of magnitude lower than that found in the oxic sections.High amounts of uranium within Cretaceous‐Tertiary boundary beds are suggested to be related to diagenetic processes such as compaction and dehydration.Uranium is thought not to cause the extinctions at the Cretaceous‐Tertiary boundary because of the relatively low contents found at the actual extinction level.
Heat production and seismic velocity of crustal rocks
Authors: Stegena Lajos G. , Meissner Rolf O. 
Published: July 2007

ABSTRACTHeat production of the continental crust can be determined from the seismic velocity structure. There is, however, a significant scatter in the determination, partly caused by the quality of geothermal data and partly by the fact that seismic velocity and radiogenic heat production are not uniquely related to each other by the chemical composition of rocks.
Tracing Chernobyl's Fallout
Authors: Gould Peter R. 
Published: July 2007

ABSTRACTWhen the third angel blew his trumpet a great star flaming like a torch descended from the sky, falling upon the third part of the rivers and upon the sources of water. The star is called wormwood. The third part of the waters turned to wormwood, and great numbers of men died from drinking the waters because they had been poisoned.
An analysis of the variation in delta architecture
Authors: Postma George 
Published: July 2007

ABSTRACTThe architecture and sedimentary facies of a delta during its steady‐state development varies with the type of distributary system, the basin water depth, and the different ways of sediment diffusion at the delta front. Analysis of these variables has resulted in twelve prototype deltas, which are postulated as sedimentological norms to facilitate comparisons of both modern and ancient delta systems.
Stratigraphy and K‐Ar ages of the Diego Hernández wall and their significance on the Las Cañadas Caldera formation (Tenerife, Canary Islands)
Authors: Marti J. , Mitjavila J. , Villa I.M. 
Published: July 2007

ABSTRACTThe Las Canadas Caldera corresponds to a volcanic caldera formed after a long period of explosive activity. The structural and lithological variations which can be observed in the caldera wall make clear the complexity of the original Las Canadas Edifice in which different eruptive centres existed. The stratigraphic and structural reconstruction of the Las Canadas Caldera indicates that the Diego Hernández wall, located at the eastern side of the caldera wall, comprises the youngest pre‐caldera deposits. Determination of their K‐Ar ages has provided the maximum age for the formation of the Las Canadas caldera. The results are internally consistent with stratigraphic relationships and allow two pre‐caldera volcanic cycles in the Diego Hernández wall to be differentiated in accordance with geological evidence. The first cycle shows imprecise age limits. The second cycle ranges from 0.35 to 0.17 Ma. This upper pre‐caldera age suggests that the Las Canadas caldera and the Teide‐Pico Viejo were formed more recently than was previously assumed.
The origin of magnesite deposits from the Polish Foresudetic Block ophiolites: preliminary δ13C and δ18O investigations
Authors: Jedrysek M. Orion , Halas Stanislaw 
Published: July 2007

ABSTRACTTwenty‐three magnesite samples from vein deposits, found in ultramafic rocks related to ophiolites in the north‐east Bohemian Massif, have been examined for carbon and oxygen isotope ratios. In these rocks two stages of antigorite serpentinization took place prior to magnesite precipitation. δ18OSMOW in magnesites ranges from 24.5 to 27.9%o (corrected for acid fractionation factor) which leads us to conclude a meteoric origin of the ore‐forming solution. This inference is further supported by δ13C values (−18.7 to −4.4%o) which point to a biogenic origin of carbon in the magnesites.
Resolution of gravimagnetic and radiometric signals by Hilbert Transform
Authors: Ramadass G. 
Published: July 2007

ABSTRACTRegional gravity, magnetic and radiometric surveys were conducted in the Sunkalagaripalle–Rekhalakunta area of the Cuddapah basin, Andhra Pradesh, India. Since the Geophysical anomalies of this area are of very low amplitude, a new filter Mj, was generated, using the Hilbert Transform in order to enhance the signal from its noisy background. Filter Mj is the summation of the multiplied values of the horizontal derivative of the anomaly and its corresponding Hilbert Transform (or vertical gradient), computed three at a time (three point data window) starting from one end of the profile. The process was repeated by sliding the data window along the entire profile, the Filter Mj was convolved with the first horizontal derivative (Mj×A) and with its Hilbert Transform (Mj, ×H). Resolved gravimagnetic and radiometric signals were then correlated with contacts and faults etc. Such studies are shown to be of value for the qualitative interpretation of noisy geophysical data.
Gold‐antimony mineralization at Loddiswell, Devon, UK
Authors: Stanley C.J. , Halls C. , Camm G.S. , James J. 
Published: July 2007

ABSTRACTNative gold, in association with tetrahedrite, bournonite, bismuthian jamesonite, antimonian bismuth, chalcopyrite, sphalerite, gersdorffite, galena, covelline, yarrowite and acanthite occurs in a NW‐SE trending quartz carbonate vein which cuts folded Lower Devonian slates of the Meadfoot Group. The locality, 2.5 km north of the village of Loddiswell, lies in a belt of Devonian thrust and nappe terrain with a roughly E‐W trend. The host‐rocks are muddy turbiditic sediments interbedded with spilitic lavas, keratophyres and tuffs, together with intrusive dolerites (greenstones) which were deformed together during the Variscan orogeny.The deposit was worked briefly in the nineteenth century but little ore was raised and it is doubtful whether any gold was recovered. Analysis of samples collected in the present study revealed gold values of 5‐10 ppm and silver values of 1000‐2000 ppm.The relationship between gold‐antimony mineralization, the basic igneous rocks in the nappe sequence, and their intersection by a series of major NW‐SE fracture zones is discussed in the context of the regional metallogenic evolution of SW England. The mineralization is considered to be the result of fluid extraction during shear movements on the NW‐SE structures and shows features in common with mesothermal gold‐bearing sulphide veins in other Palaeozoic provinces.
The Archaean gold mineralization in Rämepuro, llomantsi greenstone belt, Eastern Finland
Authors: Ojala V.J. , Pekkarinent L.J. , Piirainen T. , Tuukki P.A. 
Published: July 2007

ABSTRACTThe Rämepuro gold mineralization is situated in the Hattu sub‐belt of the Archaean Ilomantsi greenstone belt, Eastern Finland. It consists of gold‐bearing quartz veins located mainly within the shear zone contact between felsic volcanics and sedimentary rocks. The quartz veins cutting all the types of Archaean rocks are composed mainly of quartz and tourmaline and minor amounts of pyrite, pyrrothite, chalcopyrite, sphalerite, siderite, hedleyite, native bismuth and gold. The highest amounts of gold are found in the quartz‐tourmaline veins, with abundant chalcopyrite and sphalerite. Gold has its best correlation with Bi, Te, S, Zn and Cu. The minor mineralogical alterations (sericirization, saussuritizarion, chloritization) are connected with variations in some major elements. The quartz veins were emplaced under greenschist facies conditions after the peak in the lower amphibolite facies metamorphism.
The gold area of Jales (northern Portugal)
Authors: Neiva J.M. Cotelo , Neiva A.M.R. 
Published: July 2007

ABSTRACTThe hydrothermal gold quartz veins of Jales cut Hercynian granitic rocks, Pre‐Ordovician, Ordovician and Silurian schists. They occur along Hercynian NNE‐SSW, NE‐SW and WNW‐ESE faults and are probably related to the Jales granite. Some are over 2 km long and have a thickness of 0.02–2 m. The only exploited quartz veins are from Campo and Desvio which contain several ore‐shoots (25t Au exploited since 1933). The veins from Jales area also have good Au reserves.Quartz and arsenopyrite dominate in the gold quartz veins with a banded structure. Electrum and gold are included in sulphides, sulphosalts and quartz and also in veinlets cutting these minerals. Silver occurs in electrum, argentite, galena, freibergite and polyargyrite. Several minerals were analysed by electron microprobe. The primary minerals, some showing recurrences, belong to six paragenetic stages formed between 550 and 30°C and separated by faulting.
A granite window to the lower electrical crust and upper mantle
Authors: Beamish David 
Published: July 2007

ABSTRACTThe structure and properties of the deep crust and upper mantle can be investigated using magnetotelluric observations. Near‐surface and upper crustal complexities may distort or limit the capability of the data to adequately resolve deep structure. Granite batholiths have been regarded as windows into the lower crust in the context of seismic reflection data although the granite bodies themselves are not usually detected. Magnetotelluric data from SW England are here used to demonstrate that, in addition to imaging the internal structure and base of a granite, the batholith itself provides a suitable environment for the effective estimation of the resistivity structure to lower crustal and upper mantle depths.
Evolution of the Western Amazon Lowland Relief: impact of Andean foreland dynamics
Authors: Räsänen M.E. , Salo J.S. , Jungnert H. , Pittman L. Romero 
Published: July 2007

ABSTRACTThe congruency in the depositional origin and age of the uppermost sedimentary strata forming non‐flooded rainforest ground (terra firme) in the western and central Amazon lowlands is a much debated subject. Here we conclude from the study of remote sensing imagery that active Andean foreland dynamics have played a major role in the evolution of the Plio‐Pleistocene fluvial landscape in the westernAmazon. Foreland dynamics have resulted in a terra firme composed of late Tertiary alluvium and younger alluvial terraces and plains. In Peru, thermoluminescence and 14C dating show local aggradation of this younger alluvium between 180 and 30 ka. The documented high age heterogeneity of the terra firme has implications for considerations of the biogeography of the Amazon forest.
Lithospheric extension and the opening of the Red Sea: sediment‐basalt relationships in Yemen*
Authors: Menzies Martin , Bosence Dan , El‐Nakha Hamed A. , Al‐Khirbash Salah , Al‐Kadasi Mohamed A. , Subbary Abdulkarim Al 
Published: July 2007

ABSTRACTThis paper analyses new field and radiometric age data on the timing of extension, sedimentation and magmatism related to the opening of the Red Sea. The first evidence of widespread extension is found in synsedimentary fissures in the fluviatile to shallow marine Tawilah Formation of Cretaceous to early Tertiary age. The first indication of magmatism is the eruption of alkaline basalts (43.5–21.2 Ma) on to marine and non‐marine sandstones of lower to middle Tertiary age. The lack of an angular unconformity at the sediment‐basalt contact, over a period of 25 Myr, corroborates a diachronous relationship between the Tawilah sandstones and the Yemen Volcanics. These data also indicate that the onset of volcanism in Yemen was in the Eocene, as is the case in Ethiopia and Saudi Arabia. A passive rifting model is supported by early extension and sedimentation followed by syn‐ and post‐tectonic magmatism.
Reflection and refraction seismics in areas of complex geology. An example in the Northern Apennines
Authors: Cassinis R. , Lozej A. , Tabacco I. , Gelati R. , Biella G. , Scarascia S. , Mazzotti A. 
Published: July 2007

ABSTRACTAn experimental survey, employing refraction wide‐angle reflection seismic techniques (DSS: deep seismic soundings) was carried out in the Northern Apennines (North Italy).The main objective of the experiment was the application of DSS to better‐define the structure of the upper crust, down to about 15 km depth, in the crucial Alps–Apennines boundary zone. A second objective was to understand the potential of DSS as a complementary tool in areas of complex geology, where the results of near vertical reflection (NVR) are generally poor.The results of the experiment show that DSS, if properly planned, can continuously follow deep markers, and therefore impart a greater significance to faint and discontinuous NVR, as well as data on the P– wave velocity of the seismic units.
A new ophiolite occurrence in NW Sudan – constraints on Late Proterozoic tectonism
Authors: Rahman E.M. Abdel , Harms U. , Schandelmeier H. , Franz G. , Darbyshire D.P.F. , Horn P. , Müller‐Sohnius D. 
Published: July 2007

ABSTRACTMafic–ultramafic sequences in the Jebel Rahib fold‐and‐thrust belt of NW Sudan comprise the metamorphosed equivalents of obducted oceanic lithosphere. Primary features like pillow‐structures, quenchtextures, igneous layering and primary minerals like chromian spinels and pyroxenes are partly preserved. Geochemical investigations confirm the field evidence and reveal the occurrence of harzburgites, ophiolitic chromites, gabbros, gabbroic cumulates and basalts of primitive tholeiitic compositions resembling transitional MORBs. The age of low‐grade overprint of the basaltic rocks can be limited to 860–740 Myr (K–Ar). The existence of an ophiolite, as well as its close interfingering with highly deformed basin sediments, provides unambiguous evidence for a cycle of extensional and compressional tectonics in NW Sudan during Pan‐African times. Consequently, the concept of an older, stable Proterozoic, or even Archaean, ‘African Craton’onto which the juvenile Pan‐African Nubian Shield assemblages were accreted, needs revision.
Elastic and isostatic subsidence of the Blåsjø artificial lake, Southern Norway
Authors: Fjeldskaar Willy 
Published: July 2007

ABSTRACTWhen a load is applied to the surface of the Earth, there is an immediate elastic deformation followed by a time‐dependent isostatic subsidence. The two processes on the Blåsjø artifical lake, Southern Norway are modelled. The isostatic subsidence turns out to be negligible. A comparison of the modelled elastic deformation and the relative land levelling data gives valuable information about the elastic properties of the Earth's upper layers. The elastic parameters inferred from this study are lower than those from seismic investigations, and more in accordance with laboratory experiments.