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71.
Tamás Vigh Tibor Kovács János Somlai Norbert Kávási Márta Polgári Lóránt Bíró 《Acta Geophysica》2013,61(4):831-847
Previously, little attention has been paid to terrestrial radioisotopes (U, Th, 40K) occurring in manganese ores, despite the fact that the biogeochemical relationship between Mn and U is versatile. Occurrence of terrestrial radioisotopes in great amounts during mining on a long-term causes significant radiation exposure. It is important to inspect black shale-hosted manganese ores from this aspect, as black shales are typically potential U-rich formations. Despite the increased radon concentration in the mine, based on the detailed major elements, trace elements and gamma spectroscopy inspection of the rock types of deposit, the U, Th enrichment was undetectable. However, the U and Th content of about average terrestrial abundance of the great ore amount may be in the background of the increased radon concentration level. This Mn-carbonate ore deposit in spite of the low U content exhibit potential radon danger for miners, which can be eliminated with intensive air change only. 相似文献
72.
Imprints of hydrocarbon-bearing basinal fluids on a karst system: mineralogical and fluid inclusion studies from the Buda Hills,Hungary 总被引:1,自引:1,他引:0
Zsófia?PorosEmail author Andrea?Mindszenty Ferenc?Molnár Jacques?Pironon Orsolya?Gy?ri Paola?Ronchi Zoltán?Szekeres 《International Journal of Earth Sciences》2012,101(2):429-452
Calcite veins and related sulphate–sulphide mineralisation are common in the Buda Hills. Also, abundant hypogenic caves are
found along fractures filled with these minerals pointing to the fact that young cave-forming fluids migrated along the same
fractures as the older mineralising fluids did. The studied vein-filling paragenesis consists of calcite, barite, fluorite
and sulphides. The strike of fractures is consistent—NNW–SSE—concluding a latest Early Miocene maximum age for the formation
of fracture-filling minerals. Calcite crystals contain coeval primary, hydrocarbon-bearing- and aqueous inclusions indicating
that also hydrocarbons have migrated together with the mineralising fluids. Hydrocarbon inclusions are described here for
the first time from the Buda Hills. Mixed inclusions, i.e., petroleum with ‘water-tail’, were also detected, indicating that
transcrystalline water migration took place. The coexistence of aqueous and petroleum inclusions permitted to establish the
entrapment temperature (80°C) and pressure (85 bar) of the fluid and thus also the thickness of sediments, having been eroded
since latest Early Miocene times, was calculated (800 m). Low salinity of the fluids (<1.7 NaCl eq. wt%) implies that hydrocarbon-bearing
fluids were diluted by regional karst water. FT-IR investigations revealed that CO2 and CH4 are associated with hydrocarbons. Groundwater also contains small amounts of HC and related gases on the basin side even
today. Based on the location of the paleo- and recent hydrocarbon indications, identical migration pathways were reconstructed
for both systems. Hydrocarbon-bearing fluids are supposed to have migrated north-westward from the basin east to the Buda
Hills from the Miocene on. 相似文献
73.
Saman Tavakoli Mahdieh Dehghannejad María de los Ángeles García Juanatey Tobias E. Bauer Pär Weihed Sten-Åke Elming 《Acta Geophysica》2016,64(6):2171-2199
Multi-scale geophysical studies were conducted in the central Skellefte district (CSD) in order to delineate the geometry of the upper crust (down to maximum ~ 4.5 km depth) for prospecting volcanic massive sulphide (VMS) mineralization. These geophysical investigations include potential field, resistivity/induced polarization (IP), reflection seismic and magnetotelluric (MT) data which were collected between 2009 and 2010. The interpretations were divided in two scales: (i) shallow (~ 1.5 km) and (ii) deep (~4.5 km). Physical properties of the rocks, including density, magnetic susceptibility, resistivity and chargeability, were also used to improve interpretations. The study result delineates the geometry of the upper crust in the CSD and new models were suggested based on new and joint geophysical interpretation which can benefit VMS prospecting in the area. The result also indicates that a strongly conductive zone detected by resistivity/IP data may have been missed using other geophysical data. 相似文献
74.
Gbor Újvri Gyula Mentes Lszl Bnyai Jnos Kraft Attila Gyimthy Jnos Kovcs 《Geomorphology》2009,109(3-4):197-209
The banks of the River Danube are one of the most susceptible areas to mass wasting in Hungary. In 2007, a large slump began to develop along the Danube at Dunaszekcső and jeopardized properties on land and navigation in the river. Several factors such as geological, hydrogeological and morphological conditions, recurrent flooding and erosion by the Danube led to a gradual development of the large rotational slide. Slope failure has been monitored using GPS, precise levelling techniques and tiltmeters since October 2007. The expected location of the maximum lateral displacement and extrusion was indicated by GPS measurements from the middle of November 2007. The main phase of the slope failure evolution, i.e. the rapid movement on 12 February 2008 was indicated by accelerated tilting of the southern moving block prior to slumping. Small rise of the relatively stable part of the slope was measured after the rapid movements, which may be explained either by the elastic rebound along the slip surface, or by the intrusion of some plastic material into the lower section of the slope.Comparison of geodetic datasets and field observations with the timing of rainfall and water level changes of the Danube suggested that hydrological properties (subsurface flow processes, soil physical properties, infiltration, and perched water table) were primarily responsible for initiation of the studied slump. A model of slope failure evolution is proposed here based on the monitoring and field observations. 相似文献
75.
76.
Summary ?Evapotranspiration characteristics on the point-scale (several hundred square meters) and the local scale (several square
kilometers) are analysed by comparing a deterministic and a statistical – deterministic surface energy balance model. The
vegetation surface variability is represented by both the surface heterogeneity and inhomogeneity. Heterogeneity means the
mosaic of wet (wif ≠ 0) and dry (1-wif) fractions of vegetation surface, while inhomogeneity addresses small scale variations of soil moisture content.
The microscale characteristics of evapotranspiration are considered in terms of analysing evapotranspiration E
v
versus soil moisture content θ, relative frequency distribution characteristics of E
v
(θ) and the aggregation algorithms for its estimation. The analyses are performed for loam soil type under different atmospheric
forcing conditions.
The main result is as follows: For dry vegetation surface (wif = 0), the relationship between the aggregated (θagg) and the area-averaged (θ
m
) soil moisture content is nonlinear and depends on both the states of the surface and the atmospheric forcing conditions.
In the study, we assumed that there are no advective effects and mesoscale circulation patterns induced by surface discontinuities.
Based on this fact it seems unlikely to be able to construct an aggregation algorithm for calculating θagg without inclusion of the atmospheric forcing conditions. This means that it will be difficult to construct a simple formula
for calculating area-averaged transpiration, if it is possible at all.
Received May 3, 2001; revised May 31, 2002; accepted June 3, 2002 相似文献
77.
Lenin Ávila-Barrientos Carlos Valdés-González David A. Novelo-Casanova 《Natural Hazards》2011,59(2):655-664
Acceleration and velocity data of large earthquakes recorded by the Mexican National Broadband Seismological Network were
used to generate isoseismal maps for Mexico. The seismic data consist of 99 events recorded at 27 seismic stations located
in the southern and northern regions of Mexico from 2004 to 2009. The magnitude (Mw) of these events ranged from 4.1 to 7.1.
Peak ground velocity values (PGV) and peak ground accelerations (PGA) were estimated, and velocity-derived peak ground accelerations
(PGAv) were calculated. No important differences between PGAv and PGA values were found; thus, both parameters were used in
the isoseismal determination. The generated synthetic isoseismal maps were compared with those from an existing catalog for
large earthquakes in Mexico. Using empiric relations between PGA and MMI (modified Mercalli intensity) and PGV and MMI, the
obtained simulated intensity maps showed similar behavior to those reported in the catalog. The results indicate that the
PGAv values can be used to determine intensities when acceleration records (PGA) are unavailable. 相似文献
78.
79.
80.
This work is the continuation of the search for such a cosmological model using which the observed redshift distribution of galaxies in the sample of Broadhurstet al. (1990) turns out to be maximally periodic in the calculated spatial distance. In a previous work, Paálet al. (1992) have demonstrated that among theflat models with non-negative cosmological constant (e.e., vacuum density) the one with a vacuum: dust ratio 2:1 provides the optimum. Now we extend that study to the case of arbitrary space curvature and find equally good periodicity in a surprisingly wide range of models. By use of the dimensionless parameters 0=
0/
crit and
0=/3H
0
2
acceptable periodicity is obtained forall points of the parameter plane within the strip between the parallel lines 0.830–0.30<
0(0)<0.830+0.85(0<1.8), whilst the best periodicities appear along the line
0=0.830+0.39 fitting to the previous optimum at 0=1/3,
0=2/3. Any nonpositive value of
0 gives bad periodicity unless the space curvature is strongly negative and 0<0.4. Fairly good periodicity is observed only in the range of the deceleration parameter –1.2q
0<0.2, corresponding to a small or even negative total gravitational attraction and an expansion time-scale longer than usually expected. 相似文献