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Heat flow and gas hydrates of the Baikal Rift Zone 总被引:3,自引:0,他引:3
A. Y. Golmshtok A. D. Duchkov D. R. Hutchinson S. B. Khanukaev 《International Journal of Earth Sciences》2000,89(2):193-211
Multi-channel seismic studies (MCS), performed during a Russian expedition in 1989 and a joint Russian-American expedition
in 1992, have for the first time revealed a “bottom simulating reflector” (BSR) in Lake Baikal. These data have shown that
gas hydrates occur in the southern and central basins of Lake Baikal in those places where the water depth exceeds 500–700 m.
Four types of tectonic influence on the distribution of the gas hydrate were revealed: (a) Modern faults displace the BSR
as they do with normal seismic boundaries. (b) Older faults displace normal reflectors, whereas the BSR is not displaced.
(c) Modern faults form zones, where the BSR has been totally destroyed. (4) Processes that occur within older fault zones
situated close to the base of the hydrated sediment layer lead to undulations of the BSR. The thickness of the hydrate stability
field (inferred from seismic data) ranges between 35 and 450 m. Heat-flow values determined from BSR data range from 48 to
119 mW/m2. A comparison between heat-flow values from BSR data and values measured directly on the lake bottom shows an overall coincidence.
Changes in water level and bottom-water temperature that occurred in the past have had no noticeable influence on the present
BSR depths or heat-flow values. Determination of deep heat flow from BSR data is in this case more reliable than by direct
measurements.
Received: 10 December 1998 / Accepted: 15 November 1999 相似文献
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Alexandr A. Nikitin Alexandr S. Serdyukov Anton A. Duchkov 《Computational Geosciences》2018,22(3):775-787
Numerical solution of the eikonal equation is frequently used to compute first-arrival travel times for a given velocity model in seismic applications. Computations for large three-dimensional models become expensive requiring the use of efficient parallel solvers. We present new parallel implementations of the fast sweeping and locking sweeping methods optimized for shared memory systems such as multicore CPUs; we call them block fast sweeping method (BFSM) and block locking sweeping method (BLSM). Proposed methods are based on the domain decomposition approach with a special attention paid to high efficiency of the cache utilization and task execution synchronization. Performance tests on realistic models show high parallel efficiency of 85–95% on modern multicore CPUs and require the same number of iterations to converge as do the serial sweeping methods. We also highlight the importance of properly selecting the stopping criterion in the iterative sweeping methods aiming for a balance between computational time and accuracy of the result required by an application. In particular, we show that in seismic applications one can reach reasonable accuracy of computed travel times while dramatically reducing the number of iterations compared to the case of using the full convergence stopping criterion. 相似文献
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A. D. Duchkov N. A. Golikov A. A. Duchkov A. Yu. Manakov M. E. Permyakov A. N. Drobchik 《Seismic Instruments》2016,52(1):70-78
Equipment for simulation in laboratory conditions of hydrate-containing artificial samples and measuring their acoustic properties (wave velocities, absorption and attenuation) at different temperature and pressures is designed and constructed. The plant consists of a high-pressure chamber (up to 45 MPa), a measuring system intended for the excitation and reception of acoustic waves, systems for temperature and pressure control (axial and lateral) and for gas/liquid delivery into the sample. The measurements are performed on cylindrical samples with a 30-mm diameter and height of 10–50 mm. A set of successful test experiments was performed, including measurements of acoustic velocities of consolidated (plexiglas, sandstone, and frozen sand) and unconsolidated (dry and wet quartz sand) samples and formation of methane-hydrate bearing samples. 相似文献
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Dunite samples from a borehole drilled in the platiniferous concentrically-zoned Kondyor Massif are studied by electron spin
resonance (ESR). The spectrum profiles, relative intensities I, and volume magnetic susceptibilities κ are analyzed. These values experience strong irregular variations, sometimes by an
order of magnitude, in the upper and medium parts of the column, at depths from 100 to 400 m; and the variations decay at
greater depths. The magnetic properties of the samples are determined by iron (II) ions in the olivine lattice and by iron
(III) ions in the magnetite and pyrrhotite microphases and in the products of breakdown of the solid solution: chromiferous
magnetite, chromoferrite, etc. The I and κ values are directly related: κmax = 27.8 × 10−3 SI units, κmin=2.63 × 10−3 SI units, and κmean = 12.7 × 10−3 SI units. The maximum κ values are found in the zones with elevated contents of magnetite and pyrrhotite particles, and the
minimum ones, in zones with few medium and small clusters with Fe3+ ions. The uneven distributions of solid solutions and magnetic phases over depths are suggested to be related to the disturbances
in the conditions of crystallization. 相似文献
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The concentration of rock-forming elements, the static magnetic susceptibility κ, spectra of electron paramagnetic resonance, and their relative intensities I are studied in samples from a borehole drilled in Cenozoic sedimentary deposits of southern Western Siberia. All measured values experience appreciable irregular variations with depth. A linear dependence exists between κ and I within the range of their medium and large values; κ and I have maximum values in the same sample, and κmax = 1920 × 10?6SI, κmin = 210 × 10?6 SI, and κav = 630 × 10?6 SI. The magnetic properties of the samples are controlled by Fe2+ ions present in clastic material and by microphases (clusters) with Fe3+ ions of the goethite and lepidocrocite type present in the cement. The theoretically possible magnetic susceptibility of the Fe2+ ion system (provided that all iron exists in this form) is quite comparable with κmin but, even with very high concentrations of Fe2+, does not reach half of κav: (154 < κ(Fe2+) < 254) × 10?6 SI. Anomalously high values of κ are due to a large number of clusters with Fe3+ ions if structural units FeOOH do not dissociate and the interaction of the clusters with hydroxides of aluminum and precipitation medium impedes the process of their coagulation. Otherwise, the cluster sizes gradually increase, an antiferromagnetic structure develops in clusters, and the magnetic susceptibility decreases. 相似文献
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Eleven new estimates of heat flow (q) from the southern Altai-Sayan Folded Area (ASFA) have provided update to the heat flow map of Gorny Altai. Measured heat flow in the area varies from 33 to 90 mW/m2, with abnormal values of >70 mW/mq at four sites. The anomalies may have a deep source only at the Aryskan site in the East Sayan (q = 77 mW/m2) while high heat flows of 75–90 mW/m2 obtained for the Mesozoic Belokurikha and Kalguty plutons appear rather to result from high radiogenic heat production in granite, which adds a 25–30 W/m2 radiogenic component to a deep component of 50–60 mW/m2. The latter value is consistent with heat flow estimates derived from helium isotope ratios (54 mW/m2 in both plutons). Heat flow variations at other sites are in the range from 33 to 60 mW/m2. The new data support the earlier inferences of a generally low heat flow over most of ASFA (average of 45–50 mW/m2) and of a “cold” Cenozoic orogeny in the area (except for southeastern ASFA), possibly driven by shear stresses associated with India indentation into Eurasia. 相似文献
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We formulate the fundamentals of the geothermal method for determining the hydrate saturation of bottom sediments. According to laboratory experiments (A.A. Trofimuk Institute of Petroleum Geology and Geophysics, A.V. Nikolaev Institute of Inorganic Chemistry), detecting gas hydrates in bottom sediments requires measurement of thermal conductivity at least twice at one bottom site, using a cylindrical probe with different heater power values. Changing the latter permits controlling gas hydrate stability and instability. A low-power probe does not destroy gas hydrates and permits measuring the true thermal conductivity of the sediments. Increasing heater power destroys gas hydrates near the probe and drastically increases effective thermal conductivity. Comparison between true and effective thermal conductivity clearly shows the presence of gas hydrates in the sample or their absence from it. A technique was proposed for the quantitative interpretation of changes in the temperature field of a cylindrical probe. It permits quite a precise determination of the mass of gas hydrate that decomposed in the layer surrounding the probe over a certain period. Also, it permits a rough estimation of the gas hydrate content of the sediments. Thermal conductivity can be measured in the field with submersible multichannel thermoprobes, which are commonly used for studying the heat flow through the bottom of water basins. Now it is important to perform field experiments, so that we gain the necessary experience with the geothermal method. 相似文献