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1.
G. T. Skublov Yu. B. Marin S. G. Skublov E. V. Vasil’ev I. M. Gembitskaya E. S. Nechaeva Yu. N. Tarasenko 《Geology of Ore Deposits》2009,51(8):698-711
Kirishites are highly carbonaceous hairlike fibers 30–100 μm in thickness and 3–30 mm long, which jut out as bunches on the
surface of cinder and shungite fragments associated with volkhovites (Holocene tectitelike glasses corresponding to the rocks
of kimberlite-lamproite-carbonatite series in composition). Kirishite fibers are zonal. Their inner (axial) zone is composed
of high-nitrogen proteinlike compounds, whereas the outer zone is essentially carbonaceous, with a high content of organoelemental
complexes (Si, Fe) and numerous micrometer-sized anomalies of major, volatile, trace, and ore elements. Longitudinal zoning
is established in aposhungite kirishites: the consecutive change of maximum concentrations—K, Na, Cl, C, Mn → C, S, V, Ni,
Cu, Zn → S, N, Ba, Te, Pb, Bi, Nd—is traced from the roots of fibers to their ends. It is suggested that as volkhovites were
forming, fragments of cinder and shungite underwent partial melting. The highly carbonaceous compounds released due decompression
and explosion were squeezed out from fragments and solidified as fibers during fall of fragments on the Earth’s surface. 相似文献
2.
The study of amino acids in the Precambrian shungite rocks of Karelia showed that their contents vary within 25–89 μg/g depending
on proportions between shungite and mineral components. It was established that the amino acids exhibit an excess of L-enantiomers.
In the shungite rocks, they form organomineral complexes with silica and aluminosilicates, being built in the globular structure
of shungite matter. There are several sources of amino acids in shungites: secondary synthesis, microbial pollution, and original
amino acids of organic matter in shungite rocks. 相似文献
3.
Barbara Kwiecinska Slawomira Pusz Marta Krzesinska Barbara Pilawa 《International Journal of Coal Geology》2007,71(4):455-461
This paper presents the results of physical parameters such as bulk porosity, true density, optical reflectance, dynamic elastic moduli, X-ray diffractograms and EPR spectra, determined for shungite. All shungite samples studied are considerably denser materials than anthracite — high rank coal with similar carbon content. Bright shungites were porous with the very dense matrix, while the dull shungite is compact, almost non-porous material. Elastic moduli of the dull shungite are generally higher than those of bright shungites and anthracite. All shungites studied (including anthracite) exhibit the directional dependence of elasticity. The maximum reflectance values of bright shungites are higher than those for dull shungite and anthracite. That corresponds with the denser matrix of these samples and suggests the greatest ordering of graphene layers in the case of bright shungites and also suggests some similarity to meta-anthracite from Paleozoic basins. Reflectance anisotropy of shungites studied are generally lower than that of anthracite. Ordering of graphene layers in bright shungite, as a high rank coal variety, is obvious, but lower anisotropy than that of anthracite is a surprise. X-ray studies confirm a high density of bright shungite. Interplanar distances dhkl of the shungite (d002 = 3.48 Å) are closer to those of anthracite (d002 = 3.52 Å) than to those of graphite (d002 = 3.35 Å). All results described here show the differences in molecular structure and degree of graphitisation of carbonaceous matter in bright, semi-bright and dull varieties of shungite. Our data could play a key role in production of materials composed of carbon nanoparticles. 相似文献
4.
M. T. Krupenin A. V. Maslov I. D. Tsybulenko R. A. Nafikov V. G. Petrishcheva 《Lithology and Mineral Resources》2000,35(3):267-277
A property of swelling on heating to yield firm lightweight granules has first been revealed for lowcarbonaceous shales (LCS)
from the Riphean stratotype in the Bashkirian Megaanticlinorium, Southern Urals. These granules possess all technological
properties of “keramzite” or claydite (an artificial, expanded clayey material) and can successfully substitute this material.
Moreover, the procedure of their manufacture, analogous to the manufacture of “shungizite” (an artificial carbonaceous-clayey
material) from Lower Proterozoic clayey rocks of Karelia, is more economical than that for keramzit. Productive beds of the
homogeneous LCS make up extended bodies tens of meters thick. At the present time, they can be used as cover rocks during
the exploitation of the Bakal siderite deposits. The LCS represent fine-grained quartz-chlorite-sericite aggregates (with
variable relationships between the major components), bearing fine-dispersed shungite in amounts of 0.5–1.0%. High-quality
raw material of this kind is characterized by a fine-dispersed admixture of a mixed-layer clayey material bearing montmorillonite
and vermiculite. Geological, lithological, mineralogical, and chemical prognostic criteria have been developed for the shungizite
raw material. It has been concluded that this construction material, new for the Urals, is promising for industrial use 相似文献
5.
This paper examines the surface sediments collected from Dongping Lake in China for speciation and distribution of toxic heavy metals (Cu, Pb, Ni, Cd) in different grain size fractions, and for the factors that need to be considered in potential hazard of metals to the environment. Four grain size fractions (<63, 63–78, 78–163 and 163–280 μm), divided in wet condition, and bulk samples less than 280 μm in diameter were analyzed for their distribution, density and appearance. A three-stage extraction procedure following the BCR protocol was used to chemically fractionate metals into “acid soluble”, “reducible”, “oxidizable” and “residual” fractions. Correlation analysis was used to analyze the datasets. The results showed that <63 μm grain size part constitutes the major proportion of the sediments, but its density is the smallest among the four grain size fractions. In general, the metal content curve against grain size presents “S” distribution, and the highest concentrations do not exist in <63 μm grain size. Appearance observation indicates that the adsorbed substance increases gradually along with the decreasing grain size. The dominant speciation of elements and the extent of pollution are responsible for the metal distribution in different grain size sediments. While studying bioavailability and mobilization of metals, it is advisable to take metal speciation, grain size distribution and density into consideration. 相似文献
6.
During the late Early Cretaceous, the shallow-water domains of the western Tethys are characterized by the widespread deposition
of Urgonian-type carbonates rich in rudists, corals and other oligotrophic, shallow-marine organisms. In the Helvetic Alps,
the Urgonian occurrences have been dated by ammonite biostratigraphy as Late Barremian and Early Aptian. For the more proximal
occurrences in the western Swiss Jura, a recent age model based on bio-, chemo- and sequence stratigraphy has been proposed,
which allows for an improved correlation with the Helvetic counterparts. In order to corroborate the recently proposed age
model for the Jura, a set of well-preserved rhynchonellids collected from five different lithostratigraphical formations and
members (“Marnes bleues d’Hauterive”, “Marnes d’Uttins”, basal marly layers within the “Urgonien Jaune”, “Marnes de la Russille”,
“Urgonien Blanc”) has been analysed for its strontium–isotope ratios (87Sr/86Sr). In addition, K–Ar dating was performed on well-preserved glauconite grains from two different levels (“Marnes d’Uttins”
and a basal layer within the “Urgonien Jaune”). The correlation of the Sr–isotope data set with a belemnite-based, ammonite-calibrated
reference curve provides an age model which is coherent with recently published ages based on calcareous nannofossil biostratigraphy
and the correlation of trends in chemo- and sequence stratigraphy. K–Ar dating on well-preserved glauconite grains from the
“Marnes d’Uttins” and lowermost part of the “Urgonien Jaune” delivered ages of 127.5 ± 2.3 and 130.7 ± 2.6 Ma, respectively.
Whereas the age of the glauconitic level near the base of the “Urgonien Jaune” is chronostratigraphically meaningful, the
K–Ar age of the “Marnes d’Uttins” appears too young relative to the presently used time scale. This may be related to rejuvenation
of the K–Ar chronometer due to post-depositional Ar loss, most likely during hardground formation. The ages obtained here
confirm the Late Barremian age for the onset of the Urgonian platform, an age which is conform with ages obtained in the Helvetic
Alps and elsewhere along the northern Tethyan margin. 相似文献
7.
Hydrochemistry and Classification of Groundwater Resources of Ishwardi Municipal Area,Pabna District,Bangladesh 总被引:2,自引:0,他引:2
Golzar Hossain M. Farhad Howladar Lutfun Nessa Syed Samsuddin Ahmed Chowdhury Quamruzzaman 《Geotechnical and Geological Engineering》2010,28(5):671-679
The chemical property of groundwater depends largely on the mineralogical composition of the rocks through which the water
has moved and the rate of movement and these characteristics of surface water depend on organic and inorganic reactions, industrial
effluents, rainfall and temperature etc. The underground water tends to contain more dissolved materials than those in surface
water because of their more intimate and longer contact with organic materials of soil and rock particles. The groundwater
of the studied area is dominant of alkaline earth’s (Ca2+ and Mg2+) and weak acids (HCO3
−) which may be classified as Magnesium-Bicarbonate and Calcium Carbonate types. Genetically, the groundwater of the area belongs
to both “Normal Chloride” “Normal Sulphate” and “Normal Carbonate” to “Super Carbonate” group. Based on EC, SAR and RC, the
groundwater of the area varies from good–excellent quality for irrigation purposes with low alkali hazard and medium salinity
hazard. 相似文献
8.
Indrajit Pal Sankar Kumar Nath Khemraj Shukla Dilip Kumar Pal Abhishek Raj K. K. S. Thingbaijam B. K. Bansal 《Natural Hazards》2008,45(3):333-377
An earthquake hazard zonation map of Sikkim Himalaya is prepared using eight thematic layers namely Geology (GE), Soil Site
Class (SO), Slope (SL), Landslide (LS), Rock Outcrop (RO), Frequency–Wavenumber (F–K) simulated Peak Ground Acceleration (PGA),
Predominant Frequency (PF), and Site Response (SR) at predominant frequencies using Geographic Information System (GIS). This
necessitates a large scale seismicity analysis for seismic source zone classification and estimation of maximum earthquake
magnitude or maximum credible earthquake to be used as a scenario earthquake for a deterministic or quasi-probabilistic seismic
scenario generation. The International Seismological Center (ISC) and Global Centroid Moment Tensor (GCMT) catalogues have
been used in the present analysis. Combining b-value, fractal correlation dimension (Dc) of the epicenters and the underlying tectonic framework, four seismic source zones
are classified in the northeast Indian region. Maximum Earthquake of M
W 8.3 is estimated for the Eastern Himalayan Zone (EHZ) and is used to generate the seismic scenario of the region. The Geohazard
map is obtained through the integration of the geological and geomorphological themes namely GE, SO, SL, LS, and RO following
a pair-wise comparison in an Analytical Hierarchy Process (AHP). Detail analysis of SR at all the recording stations by receiver
function technique is performed using 80 significant events recorded by the Sikkim Strong Motion Array (SSMA). The ground
motion synthesis is performed using F–K integration and the corresponding PGA has been estimated using random vibration theory
(RVT). Testing for earthquakes of magnitude greater than M
W 5, a few cases presented here, establishes the efficacy and robustness of the F–K simulation algorithm. The geohazard coverage
is overlaid and sequentially integrated with PGA, PF, and SR vector layers, in order to evolve the ultimate earthquake hazard
microzonation coverage of the territory. Earthquake Hazard Index (EHI) quantitatively classifies the terrain into six hazard
levels, while five classes could be identified following the Bureau of Indian Standards (BIS) PGA nomenclature for the seismic
zonation of India. EHI is found to vary between 0.15 to 0.83 quantitatively classifying the terrain into six hazard levels
as “Low” corresponding to BIS Zone II, “Moderate” corresponding to BIS Zone III, “Moderately High” belonging to BIS Zone IV,
“High” corresponding to BIS Zone V(A), “Very High” and “Severe” with new BIS zones to Zone V(B) and V(C) respectively. 相似文献
9.
N. A. Gnatus’ M. D. Khutorskoy V. K. Khmelevskoi 《Moscow University Geology Bulletin》2011,66(3):151-157
The geological-geophysical, methological, and economic aspects of extraction and utilization of petrothermal resources (“hot
dry rock thermal”) for thermal and electric energy production were considered. Heat collectors are hydraulic fracturing zones
of natural or artificially made cracks in the crystalline rocks of the basement; these rocks have higher temperature and can
be a kind of “thermal cauldron.” Detection of such “collectors” can be carried out by geophysical methods. When pumped out
of wells and warmed to 100–300°C, waters function as a heat transfer for thermal energy supply and electric energy generation.
If the technical problem of the rapid drilling of 6–10 km wells could be solved, then petrothermal energy will become competitive
with the traditional types of energy production and supply. 相似文献
10.
Summary ?Data from secondary fluid inclusions in barite and quartz occurring in strongly silicified lithologies (“Quarzite”) along
the inter-Ordovician unconformity in SW Sardinia suggest that two distinct fluids are recorded in the mineral phases. (A),
a high temperature (250–360 °C) – low salinity (0–6% NaCl equiv.) fluid, measured in quartz, (B), a high salinity (6–20% NaCl
equiv.) – low temperature (<80–200 °C) fluid, measured in barite. Fluid (B), though less abundant than A, has also been recorded
in quartz, whereas traces of fluid (A) were found in barite. The characteristics of fluid (B) make it akin to the well known
saline formation waters responsible for the deposition of the post-Variscan barite and galena ores in SW Sardinia.
It is inferred that at least two distinct post-depositional hydrothermal events took place, with fluids circulating along
the inter-Ordovician unconformity. Fluid (A) is related to the last phases of Variscan tectonics, whereas the timing of the
second hydrothermal event (fluid B) spans the interval from Permian to Mesozoic.
Due to the lack of measurable primary inclusions and to the ubiquitous evidence for the stratigraphic control of the silicification,
as well as to the marked deformation of the “Quarzite” horizon, it cannot be excluded that at least part of this hydrothermal
event could have taken place in pre-Variscan (Silurian?) times.
An alternative model is to consider the deposition of the “Quarzite” to be unrelated to pre-Variscan hydrothermal events,
but to fluid circulation along Late-Variscan structures.
Received July 12, 2001; revised version accepted March 11, 2002 相似文献
11.
Chemodynamics of trace metal fractions in surface sediments of the Pandoh Lake,Lesser Himalaya,India
Anshumali A. L. Ramanathan Gurdeep Singh Gurmeet Singh Rajesh Ranjan Parijat Tripathi 《Environmental Geology》2009,57(8):1865-1879
The seasonal variation in the trace metals’ concentrations (Cd, Co, Cu, Fe, Mn, Ni, Pb, and Zn) were investigated in surface
sediments of the Pandoh Lake. The horizontal distribution of TC, TN, and TP reflects spatial and temporal differences in sedimentary
organic production. The chemical sequential extraction of heavy metals was carried out by seven-step fractionation scheme
(Leleyter and Probst in Int J Environ Chem 73:109–128, 1999). The significant concentrations of Ni and Cd were associated with “water soluble (Eua)” fraction in the monsoon and winter,
respectively, while “exchangeable (Exch)” and “carbonate-bound (Carb)” fractions for Ni and Cd were abundant in winter and
summer. The Cd, Cu, and Pb associated with “Exch” fraction in the summer season support their availability on exchange sites
due to oxidized nature of surface sediments. Enrichment of Co, Fe, Mn, and Zn in “AFeO” fraction showed poor bioavailability,
while Cd, Cu, and Mn in the monsoon, Co in the winter and summer, and Zn in the winter season showed significant “organically
bound (Org)” fraction. The ANOVA was significant for chemical fractions of trace elements except “Carb” fraction of Pb and
Zn and “CFeO” fraction of Pb. Factor analysis revealed that the “Eua”, “Exch”, and “Carb” fractions together control the metal
enrichment of “MnO”, “AFeO”, and “CFeO” fractions in the summer season. 相似文献
12.
The impact of atmospheric circulation fluctuations (Vangengeim’s classification) on the zoobenthos dynamics in the Sea of
Azov was studied. The “western” circulation processes lead to zoobenthos biomass decrease, and the opposite pattern was observed
when “eastern” circulation processes prevail. A quasiperiodicity with 3–7 to 10–15 year cycles is revealed for the zoobenthos
biomass dynamics. These changes are closely connected with the climatically induced increase of the zoobenthos biomass in
the Sea of Azov. 相似文献
13.
Maria Aldona Augustyniak-Jabłokow Yurii V. Yablokov Bartłomiej Andrzejewski Wojciech Kempiński Szymon Łoś Krzysztof Tadyszak Mikhail Y. Yablokov Valentin A. Zhikharev 《Physics and Chemistry of Minerals》2010,37(4):237-247
The X-band EPR and magnetic susceptibility in the temperature range 4.2–300 K study of the shungite-I, natural nanostructured
material from the deposit of Shunga are reported. Obtained results allow us to assign the EPR signal to conduction electrons,
estimate their number, N
P, and evaluate the Pauli paramagnetism contribution to shungite susceptibility. A small occupation (~5%) of the localized
nonbonding π states in the zigzag edges of the open-ended graphene-like layers and/or on σ (sp
2+x
) orbitals in the curved parts of the shungite globules has been also revealed. The observed temperature dependence of the
EPR linewidth can be explained by the earlier considered interaction of conduction π electrons with local phonon modes associated
with the vibration of peripheral carbon atoms of the open zigzag-type edges and with peripheral carbon atoms cross-linking
different nanostructures. The relaxation time T
2 and diffusion time T
D are found to have comparable values (2.84 × 10−8 and 1.73 × 10−8 s at 5.2 K, respectively), and similar dependence on temperature. The magnetic measurements have revealed the suppression
of orbital diamagnetism due to small amount of large enough fragments of the graphene layers. 相似文献
14.
Hualing Wei Nianqiao Fang Xuan Ding Lanshi Nie Xiuming Liu 《Frontiers of Earth Science》2008,2(2):162-169
This paper presents pelagic records of planktic foraminifera, as well as data of stable isotope stratigraphy and carbonate
stratigraphy since 3.5 Ma B.P. from site ODP758 in the Ninetyeast Ridge of the Indian Ocean. Based on these data, manifestations
and related mechanisms of major tectonic and environmental events such as the rapid uplift of the Himalaya Mountains, “middle
Pleistocene climatic transition” and “mid-Brunhes dissolution event” in the region are discussed. According to the analysis
and comparison of various indices and changes in terms of foraminifera assemblage, paleotemperature, paleosalinity and themocline
from site ODP758, the authors deduce that the paleoclimatic changes might correlate with the mid-Pleistocene transition at
1.4–1.7 Ma B.P. The changes of CaCO3, mass accumulation rates (MAR) of CaCO3 and non- CaCO3 MAR indicate that the loaded terrigenous sediments increased at 1.7 Ma, which is in agreement with the uplift history of
the Qinghai-Tibet plateau as shown by the available data. The last two changes coincide with the uplift of the Qinghai-Tibet
plateau, hence they are called “Qinghai-Tibet movement” (1.7 Ma), and the “Kunlun-Yellow River movement” (1.2–0.6 Ma). The
changes of the CaCO3 content, coarse fraction (> 150 μm) content and planktonic foraminifera biostratigraphy show that strong dissolution of abyssal
CaCO3 occurred in the study region during 0.5–0.4 Ma. The event was consistent with the “mid-Brunhes dissolution event” in the
sedimentary records of the Atlantic Ocean, Pacific Ocean, Indian Ocean and Nansha sea area of the South China Sea.
__________
Translated from Geological Bulletin of China, 2007, 26(12): 1627–1632 [译自: 地质通报] 相似文献
15.
Sophie Decrée Étienne Deloule Gilles Ruffet Stijn Dewaele Florias Mees Christian Marignac Johan Yans Thierry De Putter 《Mineralium Deposita》2010,45(7):621-629
The Katanga province, Democratic Republic of Congo, hosts world-class cobalt deposits accounting for ~50% of the world reserves.
They originated from sediment-hosted stratiform copper and cobalt sulfide deposits within Neoproterozoic metasedimentary rocks.
Heterogenite, the main oxidized cobalt mineral, is concentrated as “cobalt caps” along the top of silicified dolomite inselbergs.
The supergene cobalt enrichment process is part of a regional process of residual ore formation that also forms world-class
“manganese cap” deposits in western Katanga, i.e., the “black earths” that are exploited by both industrial and artisanal
mining. Here, we provide constraints on the genesis and the timing of these deposits. Ar–Ar analyses of oxidized Mn ore and
in situ U–Pb SIMS measurements of heterogenite yield Mio–Pliocene ages. The Ar–Ar ages suggest a multi-phase process, starting
in the Late Miocene (10–5 Ma), when the metal-rich substratum was exposed to the action of meteoric fluids, due to major regional
uplift. Further oxidation took place in the Pliocene (3.7–2.3 Ma) and formed most of the observed deposits under humid conditions:
Co- and Mn-caps on metal-rich substrata, and coeval Fe laterites on barren areas. These deposits formed prior to the regional
shift toward more arid conditions in Central Africa. Arid conditions still prevailed during the Quaternary and resulted in
erosion and valley incision, which dismantled the metal-bearing caps and led to ore accumulation in valleys and along foot
slopes. 相似文献
16.
Hydrochemical framework of the aquifer in and around East Kolkata Wetlands,West Bengal,India 总被引:1,自引:0,他引:1
The area lies between Hugli river in the northwest and Bidyadhari river in the east and includes the East Kolkata Wetlands.
The East Kolkata Wetlands is included in the List of Wetlands of International Importance (“Ramsar List”), as per the Convention
on Wetlands signed in Ramsar, Iran, in 1971. This wetland has been declared as a Ramsar site on the 19th August 2002 (Ramsar
site no. 1208) and therefore has acquired an international status. The area is a part of the lower deltaic plain of the Bhagirathi–Ganga
river system and is generally flat in nature. The sub-surface geology of the area is completely blanketed by the Quaternary
fluviatile sediments comprising a succession of clay, silty clay, sand and sand mixed with occasional gravel. The Quaternary
aquifer is sandwiched between two clay sequences. The confined aquifer is made up of moderately well sorted sand and reflects
fluviatile environment of deposition. The regional groundwater flow direction is from east to west. Detailed geochemical investigations
of 40 groundwater samples along with statistical analysis (for example, correlation and principal component analysis) on these
chemical data reveal: (i) four types of groundwater quality, for example, good, poor, very poor and water unsuitable for drinking
purpose, (ii) four hydrochemical facies which may be assigned to three broad types such as “fresh”, “blended”, and “brackish”
waters, (iii) the evolution of the “blended” water is possibly due to hydraulic mixing of “fresh” and “brackish” waters within
the aquifer matrix and/or in well mixing, and (iv) absence of Na–Cl facies indicates continuous flushing of the aquifer. 相似文献
17.
M. Tischler H. R. Gröger B. Fügenschuh S. M. Schmid 《International Journal of Earth Sciences》2007,96(3):473-496
The interplay between the emplacement of crustal blocks (e.g. “ALCAPA”, “Tisza”, “Dacia”) and subduction retreat is a key
issue for understanding the Miocene tectonic history of the Carpathians. Coeval thrusting and basin formation is linked by
transfer zones, such as the Mid-Hungarian fault zone, which seperates ALCAPA from Tisza-Dacia. The presented study provides
new kinematic data from this transfer zone. Early Burdigalian (20.5 to ∼18.5 Ma) SE-directed thrusting of the easternmost
tip of ALCAPA (Pienides), over Tisza-Dacia is linked to movements along the Mid-Hungarian fault zone and the Periadriatic
line, accommodating the lateral extrusion of ALCAPA. Minor Late Burdigalian (∼18.5 to 16 Ma) NE-SW extension is interpreted
as related to back-arc extension. Post Burdigalian (post-16 Ma) NE–SW shortening and NW–SE extension correlate with “soft
collision” of Tisza-Dacia with the European foreland coupled with southward migration of active subduction. During this stage
the Bogdan-Voda and Dragos-Voda faults were kinematically linked to the Mid-Hungarian fault zone. Sinistral transpression
(16 to 12 Ma) at the Bogdan-Voda fault was followed by sinistral transtension (12–10 Ma) along the coupled Bogdan-Dragos-Voda
fault system. During the transtensional stage left-lateral offset was reduced eastwards by SW trending normal faults, the
fault system finally terminating in an extensional horse-tail splay. 相似文献
18.
Vladimir Cermak Jan Safanda Louise Bodri 《International Journal of Earth Sciences》2010,99(6):1437-1451
Observational evidence proved that even when a borehole is in “fully” stabilized conditions, temperature data may exhibit
certain unrest resembling irregular oscillations in the order of hundredths or (in the extreme case) even tenths of degree.
Temperature was monitored in complicated hydrogeological conditions in the Yaxcopoil-1 hole (Chicxulub impact structure, Mexico).
Two experiments are reported: (a) 20-day monitoring when a logger was located in the center of the high temperature gradient
anomaly produced by the cold wave slowly propagating downwards and (b) simultaneous three-loggers 18-day monitoring with loggers
located above, in and below the anomaly. All observed temperature–time series displayed intermittent oscillations of temperature
with sharp gradients and large fluctuations over all observed time scales. While the “upper” and “lower” records revealed
quasi-periodic temperature variations, the “central” record shows fast temperature oscillations with strong up-and-down reversals,
all with amplitudes up to a few tenths of degree. The observed temperature–time series were processed by recurrence and recurrence
interval quantification as well as by spectral analyses. It is shown that fluid in a borehole, subject to thermal gradient,
is stable, as far as the gradient remains below a certain critical value. At higher Rayleigh numbers, the periodic character
of oscillations typical for “quiescent” regime is superseded by stochastic features. This “oscillatory” convection occurs
due to instability of the horizontal boundary layers. In the specific case of the Yaxcopoil hole, the time series above and
below the cold wave (characterized by relatively lower temperature gradients between 20 and 50 mK/m) contain a clear low frequency
component produced by tidal forcing. This component dominates over the high frequency domain (periods from 10–15 to 1 min),
which exhibit a scaling behavior. This pattern conspicuously changes in the center part of the cold wave, where the local
temperature gradient exceeds 200 mK/m and where tidal forcing composes only ~3% of the signal. 相似文献
19.
In this report, we present the situation in Slovenia, Europe with regard to natural hazards, emphasizing land-sliding problems.
Furthermore, we shortly present the University of Ljubljana and the Faculty of Civil and Geodetic Engineering as the new member
of the ICL that was selected to be the World Center of Excellence on Landslide Risk Reduction for the period of 2008–2013
with the project entitled “Mechanisms of landslides in over-consolidated clays and flysch” in the Activity scale and targeted
region as “National.” Some preliminary results of this project are shortly presented at the end. 相似文献
20.
Fritz A. Pfaffl 《International Journal of Earth Sciences》2010,99(4):949-954
Alfred E. Bergeat, originated from a family, who produced gold-glance in a factory (porcelain painting), studied mineralogy
and geology at the University of Munich from 1886 to 1892. Due to the results of his habilitation work on the volcanism of
island arcs, especially of the Stromboli volcanic island in the Tyrrhenian Sea, he became a recognized volcanologist and specialist
in volcanic petrography. He further became an explorer of syngenetic, epigenetic and deuterogenic ore deposits at the mining
academies (Bergakademien) of Freiberg (Saxony) and Clausthal (Harz mountains). He described these ore deposits in a two-volume
manual (1904–1906) which was summarized again in 1913. After his early death in 1924, the two manuals “Die Vulkane” (1925) and “Vulkankunde” (1927) were posthumously published by his colleague and friend Karl Sapper (1866–1945). 相似文献