Semi-automated bathymetric spectral decomposition delineates the impact of mass wasting on the morphological evolution of the continental slope,offshore Israel     

Omri Gadol  Gideon Tibor  Uri ten Brink  John K. Hall  Gavrielle Groves-Gidney  Gideon Bar-Am  Christian Hübscher  Yizhaq Makovsky 《Basin Research》2020,32(5):1156-1183

Understanding continental-slope morphological evolution is essential for predicting basin deposition. However, separating the imprints and chronology of different seafloor shaping processes is difficult. This study explores the utility of bathymetric spectral decomposition for separating and characterizing the variety of interleaved seafloor imprints of mass wasting, and clarifying their role in the morphological evolution of the southeastern Mediterranean Sea passive-margin slope. Bathymetric spectral decomposition, integrated with interpretation of seismic profiles, highlights the long-term shape of the slope and separates the observed mass transport elements into several genetic groups: (1) a series of ~25 km wide, now-buried slide scars and lobes; (2) slope-parallel bathymetric scarps representing shallow faults; (3) slope-perpendicular, open slope slide scars; (4) bathymetric roughness representing debris lobes; (5) slope-confined gullies. Our results provide a multi-scale view of the interplay between sediment transport, mass transport and shallow faulting in the evolution of the slope morphology. The base of the slope and focused disturbances are controlled by ~1 km deep salt retreat, and mimic the Messinian base of slope. The top of the open-slope is delimited by faults, accommodating internal collapse of the margin. The now-buried slides were slope-confined and presumably cohesive, and mostly nucleated along the upper-slope faults. Sediment accumulations, infilling the now-buried scars, generated more recent open-slope slides. These latter slides transported ~10 km³ of sediments, depositing a significant fraction (~3 m in average) of the sediments along the base of the studied slope during the past < 50 ka. South to north decrease in the volume of the open-slope slides highlight their role in counterbalancing the northwards diminishing sediment supply and helping to maintain a long-term steady-state bathymetric profile. The latest phase slope-confined gullies were presumably created by channelling of bottom currents into slide-scar depressions, possibly establishing incipient canyon headword erosion.  相似文献   

Equations of state of magnesium silicates anhydrous B and superhydrous B     

W. A. Crichton  N. L. Ross  T. Gasparik 《Physics and Chemistry of Minerals》1999,26(7):570-575

High-pressure single crystal X-ray diffraction experiments of phase anhydrous B and superhydrous B have been carried out to 7.3 and 7.7?GPa, respectively, at room temperature. Fitting a third-order Birch-Murnaghan equation of state to the P-V data yields values of V ₀?=?838.86?±?0.04?ų, K_T,0?=?151.5?±?0.9?GPa and K′?=?5.5?±?0.3 for Anhy-B and V ₀?=?624.71?± 0.03?ų, K_T,0?=?142.6?±?0.8?GPa and K′?=?5.8?±?0.2 for Shy-B. A similar analysis of the axial compressibilities in Anhy-B reveals that the c-axis is most compressible (K_c?=?137?±?3?GPa), the b-axis is least compressible (K_b?=?175?±?4?GPa), and the a-axis is intermediate (K_a?=?148?±?1?GPa). In Shy-B, the a-axis is most compressible (K_a?=?135?±?1?GPa), followed by the b- and c-axes which have similar compressibilities (K_b?=?146?±?3?GPa; K_c?=?148?±?3?GPa). The fact that the b-axis of Shy-B is approximately 16% more compressible than Anhy-B is primarily due to differences in the O-T layer in which the H atoms are located and the linkages with the adjacent O layers. The rigid edge-sharing chains of MgO₆ and SiO₆ octahedra in the O layer control compressibility along the a- and c-axes in both structures. The net result is a reduction in the overall anisotropic compression from ～22% in Anhy-B to ～9% in Shy-B.  相似文献   

Geochemical,mineralogical and magnetic characteristics of vertical dust deposition in urban environment   总被引：1，自引：0，他引：1  

Péter Sipos  Emő Márton  Zoltán May  Tibor Németh  Viktória Kovács Kis 《Environmental Earth Sciences》2014,72(3):905-914

Studies on composition and distribution of dust deposition are necessary for the risk assessment of dust to atmospheric quality. We studied the vertical distribution pattern of dust and metal (Cu, Fe, Pb, Zn) deposition up to 33 m height in urban environment. Integrated geochemical, mineralogical and magnetic study of the seasonally sampled dust helped to specify our knowledge on the use of magnetic susceptibility for tracking its deposition. Harmful dust and metal deposition may occur even at great heights and at the low-traffic side of buildings. Re-suspension of local surface materials dominates the dust deposition primarily in summer and spring due to weather conditions, and it may overwrite the influence of recent anthropogenic activities on dust composition. The accepted air-flow models should be modified by taking the local conditions (weather, morphology, etc.) into account. All studied metals showed strong enrichment in the dust and could be characterized by similar vertical deposition pattern to dust. The total susceptibility was found to be much more useful proxy for tracking dust and metal deposition than mass-specific susceptibility. Using the former, potential errors arising from sampling practice of settled dust could be eliminated. The most important heavy-metal-bearing phases were iron oxides and clay minerals. Their different behavior during the dust deposition is reflected by the vertical metal distribution patterns. Clay minerals originate primarily from re-suspension and may be one of the most important sources of potentially mobile heavy metals in such materials.  相似文献   

The structure, isostasy and gravity field of the Levant continental margin and the southeast Mediterranean area   总被引：1，自引：0，他引：1  

Amit Segev  Michael Rybakov  Vladimir Lyakhovsky  Avraham Hofstetter  Gidon Tibor  Vladimir Goldshmidt  Zvi Ben Avraham   《Tectonophysics》2006,425(1-4):137-157

A 3-D layered structure of the Levant and the southeastern Mediterranean lithospheric plates was constructed using interpretations of seismic measurements and borehole data. Structural maps of three principal interfaces, elevation, top basement and the Moho, were constructed for the area studied. This area includes the African, Sinai and Arabian plates, the Herodotus and the Levant marine basins and the Nile sedimentary cone. In addition, an isopach map of the Pliocene sediments, as well as the contemporaneous amount of denuded rock units, was prepared to enable setting up the structural map of the base Pliocene sediment. Variable density distributions are suggested for the sedimentary succession in accord with its composition and compaction. The spatial density distribution in the crystalline crust was calculated by weighting the thicknesses of the lower mafic and the upper felsic crustal layers, with densities of 2.9 g/cm³ and 2.77 g/cm³, respectively. Results of the local (Airy) isostatic modeling with compensation on the Moho interface show significant deviations from the local isostasy and require variable density distribution in the upper mantle. Moving the compensation level to the base of the lithosphere ( 100 km depth) and adopting density variations in the mantle lithosphere yielded isostatic compensation (± 200 m) over most of the area studied. The spatial pattern obtained of a density distribution with a range of ± 0.05 g/cm³ is supported by a regional heat flux. Simulations of the flexure (Vening Meinesz) isostasy related to the Pliocene to Recent sedimentary loading and unloading revealed concentric oscillatory negative and positive anomalies mostly related to the Nile sedimentary cone. Such anomalies may explain the rapid subsidence in the Levant Basin and the arching in central Israel, northern Sinai and Egypt during Pliocene–Recent times. Comparison between the observed (Bouguer) gravity and the calculated gravity for the constructed 3-D lithospheric structure, which has variable density distributions, provided a good match and an independent constraint for the large-scale structure suggested and confirmed an oceanic nature for the Levant Basin lithosphere.  相似文献   

Oligocene to Present kilometres scale subsidence and exhumation of the Ligurian Alps and the Tertiary Piedmont Basin (NW Italy) revealed by apatite (U–Th)/He thermochronology: correlation with regional tectonics     

Giovanni Bertotti  Pietro Mosca  Joaquim Juez  Riccardo Polino  Tibor Dunai 《地学学报》2006,18(1):18-25

The Ligurian Alps segment of the Alpine–Apennine orogen in NW Italy is unconformably covered by Upper Eocene to Holocene sediments in the Tertiary Piedmont Basin (TPB) and Po Plain. These sediments dip towards the north demonstrating the erosional nature of the southern border of the succession and implying that the adjacent orogenic belt formed the substratum rather than the margin of the sedimentary basin. Apatite (U–Th)/He and fission track thermochronology shows that the orogen first subsided and was buried at >4 km from 30 to 26 Ma and began its exhumation thereafter. From 26 Ma to present, this upward movement was contemporaneous with subsidence in the northern TPB. The couple exhumation in the S and subsidence in the N migrated northwards through time. Vertical movements in the area are similar to those reconstructed in Corsica. In both cases, the onset of exhumation becomes younger away from the Ligurian‐Provençal basin and has little correlation with the opening of the surrounding oceanic basins.  相似文献   

Enstatite-jadeite join and its role in the Earth's mantle   总被引：4，自引：0，他引：4  

Tibor Gasparik 《Contributions to Mineralogy and Petrology》1992,111(3):283-298

Phase relations on the enstatite-jadeite join were experimentally determined at solidus temperatures and 90–152 kb, and at 1400–2050°C/175–219 kb, with a split-sphere anvil apparatus (USSA-2000). New findings include immiscibility in garnet and determination of the stability of NaAlSiO₄ (calcium ferrite structure) with stishovite. A thermodynamic model for the enstatite-jadeite join was developed to calculate a complete phase diagram for the join at 500–2500°C and 0–270 kb. The results indicate that the two major discontinuities in the Earth's mantle at 400 and 670 km depths could correspond respectively to the formation and the breakdown of garnet with a pyroxene composition. A model for a chondritic upper mantle is proposed in which large-scale chemical and mineral layering was produced by fractionation of liquidus phases in a magma ocean. Solidification was completed at 400 km depth by crystallization of sodium-enriched residual melts, which produced a pyroxene layer at 300–400 km depths.  相似文献   

Carbonatite melt inclusions in coexisting magnetite,apatite and monticellite in Kerimasi calciocarbonatite,Tanzania: melt evolution and petrogenesis   总被引：1，自引：0，他引：1  

Tibor Guzmics  Roger H. Mitchell  Csaba Szabó  Márta Berkesi  Ralf Milke  Rainer Abart 《Contributions to Mineralogy and Petrology》2011,161(2):177-196

Kerimasi calciocarbonatite consists principally of calcite together with lesser apatite, magnetite, and monticellite. Calcite hosts fluid and S-bearing Na–K–Ca-carbonate inclusions. Carbonatite melt and fluid inclusions occur in apatite and magnetite, and silicate melt inclusions in magnetite. This study presents statistically significant compositional data for quenched S- and P-bearing, Ca-alkali-rich carbonatite melt inclusions in magnetite and apatite. Magnetite-hosted silicate melts are peralkaline with normative sodium-metasilicate. On the basis of our microthermometric results on apatite-hosted melt inclusions and forsterite–monticellite phase relationships, temperatures of the early stage of magma evolution are estimated to be 900–1,000°C. At this time three immiscible liquid phases coexisted: (1) a Ca-rich, P-, S- and alkali-bearing carbonatite melt, (2) a Mg- and Fe-rich, peralkaline silicate melt, and (3) a C–O–H–S-alkali fluid. During the development of coexisting carbonatite and silicate melts, the Si/Al and Mg/Fe ratio of the silicate melt decreased with contemporaneous increase in alkalis due to olivine fractionation, whereas the alkali content of the carbonatite melt increased with concomitant decrease in CaO resulting from calcite fractionation. Overall the peralkalinity of the bulk composition of the immiscible melts increased, resulting in a decrease in the size of the miscibility gap in the pseudoquaternary system studied. Inclusion data indicate the formation of a carbonatite magma that is extremely enriched in alkalis with a composition similar to that of Oldoinyo Lengai natrocarbonatite. In contrast to the bulk compositions of calciocarbonatite rocks, the melt inclusions investigated contain significant amount of alkalis (Na₂O + K₂O) that is at least 5–10 wt%. The compositions of carbonatite melt inclusions are considered as being better representatives of parental magma composition than those of any bulk rock.  相似文献   

К воззванию американских ученых о прекращении испытаний атомного оружия     

Tibor Kolbenheyer 《Studia Geophysica et Geodaetica》1958,2(4):303-305

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Biogeochemistry of trace metals (Mn, Sr, Rb, Ba, Cu, Zn, Pb and Cd) in a river-wetland-lake system (Balaton Region, Hungary)     

Françoise Elbaz-Poulichet  Attila Nagy  Tibor Cserny  Piroska Pomogyi 《Aquatic Geochemistry》1996,2(4):379-402

Mn, Sr, Ba, Rb, Cu, Zn, Pb and Cd concentrations have been measured seasonally in the water and deposited sediments of the system comprising: Zala river (main input) — Lakes Kis-Balaton 1 and 2 (small artificial lakes created in a former bay of Lake Balaton) — Keszthely bay (hypertrophic part of Lake Balaton). The concentrations of the trace elements together with pH, alkalinity, dissolved cations (Ca²⁺, Mg²⁺, Na⁺, and K⁺), dissolved inorganic ligands (Cl^–, SO₄ ^2–), particulate Al, Ca, inorganic and organic carbon are used to assess the contamination of the study area and biogeochemical processes controlling trace element concentrations. Thermodynamic speciation calculations have also been utilized to enhance our understanding of the system. In the sediments Rb, Ba, Cu and Zn concentrations were mainly controlled by the abundance of the aluminosilicate fraction. Strontium was mainly associated with the calcium carbonate fraction. The aluminosilicate fraction constitutes a major sink for Mn and Cd but the concentration of these elements are also strongly related to calcite precipitation. The main processes that control the dissolved distribution of trace elements in the Balaton system were: solid phase formation (carbonate) for Mn; coprecipitation with calcite for Sr, Ba, Rb and possibly Mn and Cd; adsorption/desorption processes (pH dependent) for Zn and Pb; solubilization of Mn and precipitation of Cd and Cu in reed covered wetland areas where anoxic conditions were probably existing during the warm season. A preliminary budget of atmospheric and river input to Lake Balaton has also been outlined. Although Lake Balaton, is subjected to anthropogenic inputs mainly from agricultural and domestic activities, their impact on trace element concentrations in the Balaton system is very limited due to the efficiency of removal processes (i.e. adsorption and co-precipitation) and to high sedimentation rates and strong sediment re-suspension. Anthropogenic inputs are only detected for Pb.  相似文献   

On one method of solving the three-dimensional direct magnetic problem     

Tibor Kolbenheyer  Reviewer M. Burda 《Studia Geophysica et Geodaetica》1977,21(3-4):316-320

Summary The solution of the direct magnetic problem is derived for three-dimensional bodies under the assumption that the components of the magnetization vector are analytical functions of the co-ordinates within the body being considered. The solution to the problem is given in the form of Green-type integrals and, much like with gravitational fields of inhomogeneous bodies, it may serve the purpose of solving the problem of the analytical continuation of the external field into the body.  相似文献