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1.
Temperature was monitored in two boreholes in Kamchatka (Russia) in years 2001–2003. Ten-min reading (sampling) interval was selected for the first half-year run followed by shorter (12 days) experiment with 5-s reading interval. A similar experiment was repeated later in the test borehole Sporilov (Prague, Czech Republic), where four temperature–time series were performed with reading intervals varying from 1 to 20 s. All temperature–time series (except the record from the bottom of the hole) displayed intermittent, non-periodic oscillations of temperature of up to several hundredths of degree with sharp gradients and large fluctuations over all observed time intervals. No such oscillation was detected at the bottom of the hole. The spectral analysis revealed a high level of stochasticity in the measured signal. Calculated spectra showed “band-pass” behavior without any definite peaks, which might characterize certain periodicity. Local growth of the second moment technique revealed the presence of at least two distinct temperature-forming processes. One of them can be related to heat transfer in the structurally and compositionally complex subsurface. The second process, which presents the bulk of the measured signal, probably reflects certain intra-hole convection. We hypothesized that the oscillatory regime of such convection is responsible for the stochastic nature of measured temperatures. Results of numerical modeling describing the fluctuation of water-cells in a vertical slot support the idea of thermally unstable water column in a hole, the instability of which produces a complex oscillation system. Model solutions and their discussion is presented in Part II of this work.  相似文献   

2.
In the previous part of this work (Cermak, Safanda and Bodri, this volume p.MMM) we have described experimental data and quantified the heterogeneity features of the microtemperature time series. The spectral analysis and the local growth of the second moment technique revealed scaling structure of all observed time series generally similar and suggested the presence of two temperature forming processes. The longer-scale part can be attributed to the heat conduction in compositional and structural heterogeneous solid rocks, further affected by various local conditions. Short-scale temperature oscillations are produced by the intra-hole fluid convection due to inherent instability of water column filling the hole. Here we present how the observational evidence is supported by the results of the computer simulations. The exact modes of intra-hole convection may be different, ranging from quasi-periodic (“quiescent”) state to close of turbulence. As demonstrated by numerical modeling and referred on laboratory experiments, at higher Rayleigh numbers the periodic character of oscillation characteristic for “quiescent” regime is superseded by stochastic features. This so called “oscillatory” convection occurs due to instability within the horizontal boundary layers between the individual convectional cells. In spite of the fact that the basic convective cell motion is maintained and convection is characterized by slow motion, the oscillatory intra-hole flow and corresponding temperature patterns exhibit typical features of turbulence. The idea of boundary layer instability as a source of stochastic temperature fluctuations could explain many distinct features of borehole temperatures that previously cannot be interpreted.  相似文献   

3.
Coastal flooding occurs due to storm surges generated by tropical and extra-tropical cyclones on the globe. The meteorological forcing fields for the generation of storm surges are the tangential surface wind stress on the ocean surface and the normal atmospheric pressure gradients associated with the weather systems. The large scale forcing from the cyclones is referred to as the synoptic scale and storm surge prediction from synoptic scale forcing is well developed and is reasonably satisfactory around the world. However, coastal flooding also occurs from weather systems, with forcing on a meso-scale and also from remote forcing. It is proposed here that the term “Storm surge” be used to only refer to coastal flooding from synoptic scale forcing and the terminology “Rissaga” be used for coastal flooding from meso-scale forcing. For flooding due to remote forcing, a new term “Kallakkadal” is proposed.  相似文献   

4.
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5.
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   

6.
The Pleistocene Incapillo Caldera and Dome Complex (5,570 m) marks the southernmost siliceous center of the Andean Central Volcanic Zone (~28°S), where the steeply dipping (~30°) segment of the subducting Nazca plate transitions into the Chilean “flatslab” to the south. The eruption of the Incapillo Caldera and Dome Complex began with a 3–1 Ma effusive phase characterized by ~40 rhyodacitic dome eruptions. This effusive phase was terminated by an explosive “caldera-forming” event at 0.51 Ma that produced the 14 km3 Incapillo ignimbrite. Distinctive and virtually identical chemical signatures of the domes and ignimbrites (SiO2 = 67–72 wt%; La/Yb = 37–56; Ba/La = 16–28; La/Ta = 30–50; 87Sr/86Sr = 0.70638–0.70669; ε Nd = −4.2 to −4.6) indicate that all erupted lavas originated from the same magma chamber and that differentiation effects between units were minor. The strong HREE depletion (Sm/Yb = 6–8) that distinguishes Incapillo magmas from most of the large ignimbrites of the Altiplano–Puna plateau can be explained by the extent and degree of partial melting at lower crustal depths (>40 km) in the presence of garnet. At upper crustal depths, this high-pressure residual geochemical signature, also common to adjacent late Miocene/Pliocene Pircas Negras andesites, was partially overprinted by shallow-level assimilation and fractional crystallization processes. Energy-constrained AFC modeling suggests that incorporation of anatectic upper crustal melts into a fractionated “adakite-like” dacitic host best explains the petrogenesis of Incapillo magmas. The diminution of the sub-arc asthenospheric wedge during Nazca plate shallowing left the Incapillo magma chamber unreplenished by both mafic mantle-derived and lower crustal melts and thus stranded at shallow depths within the Andean crust. Based on its small size and distinctive high-pressure chemical signature, the Incapillo Caldera and Dome Complex provides an endmember model for an Andean caldera erupting within a waning magmatic arc over a shallowing subduction zone.  相似文献   

7.
The study presents the result of continuous temperature monitoring in a 300 m deep borehole located on the Pacific coast of the Kunashir Island. Temperature variations at of 20–240 m depths with periods from a few tens of minutes to a few tens of days and amplitudes in the order of thousandths to tenths of degree are found to result from three main causes: tidal variations of groundwater level in the borehole, natural convection in the borehole, and nonperiodic and spatially heterogeneous changes of the pore pressure resulting in the appearance of an anomalous subsurface fluid regime and generating crossflow between the different aquifers through the annular space. Joint analysis of temperature and seismic data revealed that shallow-focus (up to 30 km) earthquakes with M > 5 occurred southeast of the seismic station created more expressed temperature response at 240 m depth. This response has the form of a 0.05–0.3 K temperature drop, which precedes a seismic event within a period of a few hours to a few days. Tidal analysis of borehole temperature measurements can be used to calculate the strain sensitivity and the method of borehole temperature monitoring can be used to investigate the tectonic regime of the Earth’s crust.  相似文献   

8.
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   

9.
Durability is one of the most important engineering properties of weak and clay-bearing rocks. Weathering can induce a rapid change in rock material from initial properties to soil-like properties. The sensitivity of a rock type against weatherability is usually described by a durability parameter, such as the slake durability index. However, marl resistance is not detected satisfactorily by the durability indices by using slake durability test as suggested by ISRM for two wetting–drying cycles. The results of this study are obtained from samples of compact or laminated eocene marls from region of Dalmatia, Croatia. The samples were subjected to 4 cycles of slake durability, point load tests, determination of dry density, determination of carbonate content and absorption of water. The scatter of data suggests that strength probably has no influence on the durability of marls. On the other hand a separate group of marl samples have a second-cycle slake durability index higher than approximately 85%, and the durability of these samples is classified as “medium-high” to “high”, although the visual inspection of samples after testing, suggests that they should have “medium” to “low” durability classification. According to obtained results these samples of marl fulfil the criterions for the durability classification: a carbonate content lower than approximately 65%, a dry density lower than 2.4 Mg/m3, and values of water absorption higher than 5%.  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.
The simulated annealing algorithm has been applied successfully to conditional simulation of categorical variables (e.g., rock or facies units) with the objective of improving the match between measured and modeled spatial variability. In some implementation schemes, however, spurious features termed “artifact discontinuities” may occur near conditioning data, especially during the “zero- temperature” case referred to as simulated quenching. This paper shows that artifact discontinuities can be avoided by considering the anisotropy of the spatial variability model, reducing the number of lag vectors used in the objective function, and providing a rudimentary initial configuration. Results from several test cases suggest that the artifact discontinuities might be caused by overly precise fitting of measured to modeled spatial variability.  相似文献   

12.
Spatial pattern analysis of marine terrace elevations from 40–30 thous. years BP was used to reconstruct sea level/geoid surface and geoid parameters during that time. The polar flattening of geodetic ellipsoid was lower than its present value (1/298.81 and 1/298.26) respectively because of glacial-induced mass redistribution. Increase in polar stress occurred during the last 30 thous. years was possibly driven by pertubation brought to the gravitational field by disintegration of polar ice sheets in the Northern hemisphere. But the polar flattening value becomes only half-restored during the last deglacial hemicycle. So repetitive glacial advances during Pleistocene acted as a global “pump” for uncondensed zones at the upper/lower mantle boundary. Dissipation of tidal energy is an order of magnitude less intensive in its Earth's rotation effect. A contribution to the International Geological Correlation Programme Project JGCP — 274 “Coastal Evolution in the Quaternary”.  相似文献   

13.
The extraction and transfer of uranium was modeled in the “granite-water” system at 800–100°C and 700–3000 bar. It was shown that the scale of ore accumulation depends on T,P parameters of source and amount of hydrothermal fluid that infiltrated through ore precipitation zone. The modeling results give further arguments that granitoid-associated uranium mineralization was derived from high temperature source.  相似文献   

14.
During the Mesozoic, the epicontinental Germanic Basin and the Regensburg Strait the latter being an embayment of the Tethys Ocean that had subsided into the Moldanubian Zone of the Central European Variscides were filled with terrigenous continental-marine sediments. Both sediments’ heavy mineral (HM) grains and aggregates have been studied in a drill section in the Wackersdorf area, SE Germany. The majority of them belong to the (semi)opaque group of Fe–Ti minerals. In Wackersdorf, the entire stratigraphy of the basin fill, which occurred between the Triassic and the Late Cretaceous, is well exposed. In addition to the chemical composition of HM, the morphology and texture of zircon, apatite and Fe–Ti compounds have been studied in a provenance-related mineral classification. Provenance analysis has yielded five discrete source rock lithologies: (1) Moldanubian H-T-metamorphics, (2) late Paleozoic (sub)volcanic rocks, (3) gneisses of the Tepla-Barrandian unit, (4) ophiolites of the Tepla-Barrandian unit, (5) silicified shear zones and quartz cores of pegmatites. The detrital minerals include zircon, tourmaline (dravite-schoerl), apatite, monazite (Ce–Th–La–Nd), xenotime, biotite, rutile, ilmenite, “nigrine” (ilmenite-rutile intergrowth), sphene, amphibole, staurolite, garnet and spinel (Cr–Mg–Al). Based on the allogenic Ti and Fe minerals, a magnetite-type source area (Eh > 0, near-surface felsic to intermediate (sub)volcanic rocks) was distinguished from an ilmenite-type source area (Eh < 0), deeply eroded crystalline basement rocks (gneiss, granite, shear zones). The latter may be subdivided into “nigrine –I” (deep) and “nigrine-II” (intermediate) subtypes, according to the level of erosion in the source area. At the Jurassic–Cretaceous transition, extrabasinal erosion provoked a noticeable variation of allogenic heavy minerals with the incisions of rivers into source rock lithologies (4) and (5). Uplift and erosion along the western edge of the Bohemian Massif took place contemporaneously with spreading and closure in the central parts of the adjacent Tethys Ocean.  相似文献   

15.
Three generations of tourmaline have been identified in propylite in the Vetka porphyry copper-molybdenum deposit of the Chukchi Peninsula of Russia. Tourmaline-I is characterized by its Fetot/(Fetot + Mg) value, which ranges from 0.33 to 0.49. Tourmaline-II, which crystallizes at a lower temperature, overgrowing tourmaline-I or occurring as isolated crystals, is distinguished by a higher Fetot/(Fetot + Mg), which varies from 0.46 to 0.72. The Fetot/(Fetot + Mg) ratio in tourmaline-III, which overgrows tourmaline-II is lower (0.35–0.49), and is identical to that of the first tourmaline generation. This is probably caused by the beginning of sulfide deposition. Tourmalines in the deposit characterized by complex isomorphic substitutions can be attributed to the intermediate members of the dravite—“hydroxy-uvite”-“oxy-uvite” and schorl-“hydroxy-feruvite”-“oxy-feruvite” series. Tourmaline starts to crystallize at temperatures above 340°C. The fluid responsible for the tourmaline deposition was magmatic, with a significant admixture of meteoric water (δ18OH 2O = −0.85 to −0.75‰). The high Fe3+/Fetot ratio (0.50) indicates high oxygen activity when the tourmaline precipitated. It has been established that the isomorphic substitution Fetot → Al is typomorphic of tourmalines from porphyry copper deposits worldwide.  相似文献   

16.
This paper discusses the largest electrum units precipitated in calcite of the final (“nonproductive”) stage of ore formation. Notably, during examination of the chemical composition of these gold grains, sphalerite and other minerals belonging to the early (“productive”) association have been found. The results of thermo- and cryometric investigations of fluid inclusions in calcite of the Agatovskoe deposit have indicated that in the composition of two-phase fluid solutions of admixtures, NaCl, KCl, and MgCl dominated. This is evidenced by chloride eutectics of the admixture solutions in the temperature interval from −35 to −39°C. The complete homogenization of the fluid admixtures takes place in a narrow temperature interval (from 206 to 213°C) and concentration of salts is 3.7–6.0 mass % in NaCl equivalent. The density of the fluid changes starting from 0.88–0.89 g/cm3. The derived homogenization temperatures correspond to the temperatures of gold deposition, since the pressure during formation of gold veins in the deposit was small.  相似文献   

17.
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   

18.
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   

19.
Internal Wave (IW) characteristics and the impact of IW on acoustic field have been studied utilizing the hourly time series of temperature and salinity data collected at a coastal site off Paradeep (north Bay of Bengal) during 24–25 October 2008. The IW characteristics, viz. period (t per ), velocity (C vel ), wavelength (L), and wave numbers (k), are found to be 2.133–34.72 h, 0.135 km h−1, 0.37–6.2 km and 2.70–0.16 cycles km−1, respectively. The semi-diurnal tidal forces are predominant than diurnal as well as at other frequencies and its contribution is about 64% towards the total potential energy (E 0 = 3.34 J m−2). Sound velocity perturbations with space and time in the presence of IW field are examined from Garrettt-Munk (GM) model. Transmission loss anomaly for optimized source-receiver configuration at the depth of 53 m and range of 9 km has been computed from acoustic modelling. The loss in the acoustic transmission is found to be 38.4 dB in the presence of low-frequency IW field.  相似文献   

20.
Horizontal, vertical and temporal distribution of a cyclonic (counterclockwise) eddy, where biological productivity is high, downstream of the Tsushima Islands in the eastern channel of the Tsushima Straits in November 2007 was revealed using conductivity–temperature–depth and acoustic Doppler current profiler data. The eddy had a horizontal scale of approximately 40–60 km, and the accompanying baroclinic current was more than 15 cm s−1 at the edge of the eddy. The island-induced cyclonic eddy moved east-northeastward at about 10 km day−1 (∼10 cm s−1) along the Tsushima Warm Current and was intensified by the barotropic instability in the current shear. The cyclonic eddy with high surface chlorophyll a concentrations intensified in the vicinity of the Tsushima Islands and was advected by the Tsushima Warm Current towards the southwestern Japan Sea.  相似文献   

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