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691.
Andrei V. Sharygin Robert H. Wood Victor N. Balashov 《Geochimica et cosmochimica acta》2006,70(20):5169-5182
The electrical conductivities of aqueous solutions of Li2SO4 and K2SO4 have been measured at 523-673 K at 20-29 MPa in dilute solutions for molalities up to 2 × 10−2 mol kg−1. These conductivities have been fitted to the conductance equation of Turq, Blum, Bernard, and Kunz with a consensus mixing rule and mean spherical approximation activity coefficients. In the temperature interval 523-653 K, where the dielectric constant, ε, is greater than 14, the electrical conductance data can be fitted by a solution model which includes ion association to form , , and , where M is Li or K. The adjustable parameters of this model are the first and second dissociation constants of the M2SO4. For the 673 K and 300 kg m−3 state point where the Coulomb interactions are the strongest (dielectric constant, ε = 5), models with more extensive association give good fits to the data. In the case of the Li2SO4 model, including the multi-ion associate, , gave an extremely good fit to the conductance data. 相似文献
692.
Francesco Stoppa Adrian P. Jones Victor V. Sharygin 《Central European Journal of Geosciences》2009,1(2):131-151
Vulture volcano displays a wide range of mafic to alkaline, carbonate-, and/or CaO-rich volcanic rocks, with subvolcanic and plutonic rocks together with mantle xenoliths in pyroclastic ejecta. The roles of magmatic volatiles such as CO2, S, and Cl have been determined from compositions and trapping temperatures of inclusions in phenocrysts, which include the Na-K-Ca-carbonate nyerereite within melilite. We surmise that this alkali carbonate crystallised from an appropriate carbonatitic melt at relatively high temperature. Carbonatitic metasomatic features are traceable throughout many of the mantle xenoliths, and various carbonatitic components are found in the late stage extrusive suite. There is no evidence that alkali carbonatite developed as a separate magma, but it may have been an important evolutionary stage. We compare the rare occurrence of nyerereite at Vulture with other carbonatites and with an unaltered kimberlite from the Udachnaya pipe. We review the evidence at Vulture for associated carbonatitic metasomatism in the mantle, and we suggest that low viscosity alkali carbonatitic melts may have a primary and much deeper origin than previously considered. 相似文献
693.
Cabral Victor Carvalho Reis Fábio Augusto Gomes Vieira D’Affonseca Fernando Mazo Lucía Ana dos Santos Corrêa Claudia Vanessa Veloso Vinicius Gramani Marcelo Fischer Ogura Agostinho Tadashi Lazaretti Andrea Fregolente Vemado Felipe Pereira Filho Augusto José dos Santos Claudia Cristina Lopes Eymar Silva Sampaio Rabaco Lis Maria Reoni do Carmo Giordano Lucilia Zarfl Christiane 《Natural Hazards》2021,108(3):3021-3043
Natural Hazards - Debris flows represent great hazard to humans due to their high destructive power. Understanding their hydrogeomorphic dynamics is fundamental in hazard assessment studies,... 相似文献
694.
Victor Balagansky Andrey Shchipansky Alexander I. Slabunov Il’ya Gorbunov Sergey Mudruk Mikhail Sidorov 《International Geology Review》2015,57(11-12):1543-1565
This paper addresses the relationships between relic amphibole-eclogite facies (AE) eclogites and their host units, Archaean amphibolites, enveloped by Archaean tonalite–trondhjemite–granodiorite (TTG) gneisses, in the Kuru-Vaara study area in the northern Belomorian Province. According to observational constraints, the crystallization of the relic peak omphacite + Mg-garnet ± kyanite assemblage and the subsequent replacement of omphacite by clinopyroxene–plagioclase symplectite occurred before the earliest deformational, metamorphic, and migmatization events that are recorded in the amphibolites. The amphibolites and their TTG hosts have a shared deformational and metamorphic history that is composed of the Archaean and Palaeoproterozoic periods. This history favours the conclusion that the AE metamorphism recorded in the relic eclogites within the amphibolites occurred during the Mesoarchaean to Neoarchaean periods. The deformation and metamorphism of the amphibolite facies of the second period resulted from the Lapland–Kola collisional orogeny at 1.91–1.93 Ga, which led to eclogite–high-pressure granulite (E–HPG) facies conditions in the lowermost portions of the over-thickened crust in Belomorian Province (the southwestern foreland of the Lapland–Kola collisional orogen). The Palaeoproterozoic E–HPG overprint was reported from the Palaeoproterozoic Gridino mafic dikes. Although the ages of the oldest low Th/U zircons are close to the time of the Lapland–Kola collision, the low Th/U 1.9–1.8 Ga zircons reflect a zircon response to regional fluid infiltration in the eclogites during slow exhumation following the Lapland–Kola orogeny and do not record any metamorphic event. Contrary to the Palaeoproterozoic E–HPG overprint, the areal occurrence of the 2.7–2.8 Ga AE eclogites with mid-ocean ridge basalt-like chemistry and their paragenetic link with the TTG gneisses suggest a tectonic regime that involves subduction. This research favours concepts suggesting that the modern-style plate tectonics has operated in some places, at least since the late Mesoarchaean. 相似文献
695.
Amartya K. Saha Christopher S. Moses René M. Price Victor Engel Thomas J. SmithIII Gordon Anderson 《Estuaries and Coasts》2012,35(2):459-474
Water budget parameters are estimated for Shark River Slough (SRS), the main drainage within Everglades National Park (ENP)
from 2002 to 2008. Inputs to the water budget include surface water inflows and precipitation while outputs consist of evapotranspiration,
discharge to the Gulf of Mexico and seepage losses due to municipal wellfield extraction. The daily change in volume of SRS
is equated to the difference between input and outputs yielding a residual term consisting of component errors and net groundwater
exchange. Results predict significant net groundwater discharge to the SRS peaking in June and positively correlated with
surface water salinity at the mangrove ecotone, lagging by 1 month. Precipitation, the largest input to the SRS, is offset
by ET (the largest output); thereby highlighting the importance of increasing fresh water inflows into ENP for maintaining
conditions in terrestrial, estuarine, and marine ecosystems of South Florida. 相似文献
696.
正1.Introduction In response to the proposal by the Earth Science community of China,we are delighted to organize this special issue of Geoscience Frontiers(GSF)in honor of the work by Xuanxue Mo,Professor of Petrology and Geochemistry of China University of Geosciences(Beijing)and Academician of the Chinese Academy of Sciences,as a tribute to him on his 80th birthday.In his over 50 years of profes- 相似文献
697.
Michael V. Kurgansky Aldo Montecinos Victor Villagran Stephen M. Metzger 《Boundary-Layer Meteorology》2011,138(2):285-298
We report on field observations in January 2009 (austral summer) of atmospheric dust devils in the northern part of the Atacama
Desert in South America (≈20◦S). An extremely high level of dust-devil activity over the study site has been observed, dependent on local meteorological
conditions. We found a high correlation between the dust-devil frequency of occurrence and the Obukhov length scale, L, calculated from meteorological gradient measurements, with a clear tendency for this frequency to increase with decreasing
−L. The upper threshold values of −L ≈ 20–30 m, and the 2-m mean wind speed, V
2 ≈ 8m s−1, for dust-devil occurrence have been found, but the minimal V
2 threshold was not observed. Parallel routine meteorological measurements enabled us to calculate the main constituents of
the surface energy balance, to obtain direct estimates of the surface albedo (α ≈ 0.21 at the solar noon) and to summarize the local conditions. 相似文献
698.
Marked, 19th‐century kiln bricks and rocks from Caledonia Springs (CS) have black glass coatings that can easily be mistaken for glass produced at the elusive CS glassworks (c. 1844–1846). The glass‐on‐brick material, however, is more aluminous (nearly 20% Al2O3) than virtually any analyzed historical glass, and the glass‐on‐rock is compositionally similar to the rock itself, which shows clear signs of having undergone extensive melting. Mineral thermometry (Cpx‐Ol, Pl‐melt) indicates that parts of the kiln‐achieved temperatures of approximately 1200–1300°C. The CS samples show that caution must be exercised when identifying seemingly obvious waste glass near defunct glassworks sites. © 2005 Wiley Periodicals, Inc. 相似文献
699.
The major stochastic elements in the fission track dating method are (i) the number of spontaneous fission tracks (N
s
) in a sample, and (ii) the number of induced tracks (N
i
) observed when the sample is irradiated with neutrons. The foundations for the statistical uncertainty in these measures are of two kinds: (i) there exists a definite probability of uranium fission by means of natural decay and by neutron activation, and (ii) within a crystal the distribution of uranium is not uniform and perhaps follows something like a Poisson law. In any event, the natural logarithm of the ratio (N
s
/N
i
) is proportional to age. A plausible statistical fission track dating model should, therefore, start by considering the joint distribution of N
s
and N
i
. In this paper a joint bivariate normal model is described which allows the rigorous definition of the probability distributions of Ns, N
i
, the ratio N
s
/N
i
, and age itself. A general computer program (FISSION) has been developed to perform all the necessary computations. By accounting for the correlation between N
s
and N
i
, the statistical model here ascribes smaller standard errors to N
s
/N
i
(and therefore age) than do previous methods. In addition, the error associated with neutron flux is a significant factor in the age relationships and has been incorporated into the model. 相似文献
700.
Victor Szebehely 《Celestial Mechanics and Dynamical Astronomy》1978,18(4):383-389
A quantitative measure of stability based on Hill's definition is evaluated for direct and retrograde satellite orbits. These orbits are known as Poincaré's first kind in the restricted problem of three bodies. Onsets of possible instabilities and captures are established. A critical (maximum) value of the satellite's orbital radius is found for stability as a remarkably simple function of the massparameter. The results are applied to the natural satellites of the solar system. 相似文献