Iron metal production in silicate melts through the direct reduction of Fe(II) by Ti(III), Cr(II), and Eu(II)     

Henry D. Schreiber  G.Bryan Balazs  Andrew P. Shaffer  P.Lynne Jamison 《Geochimica et cosmochimica acta》1982,46(10):1891-1901

The production of metallic iron in silicate melts by the chemical reactions, 2Ti³⁺_(melt) + Fe²⁺_(melt) → 2Ti⁴⁺_(melt) + Fe⁰_(crystal)2Cr²⁺_(melt) + Fe²⁺_(melt) → 2Cr³⁺_(melt) + Fe⁰_(crystal)2Eu²⁺_(melt)+ Fe²⁺_(melt) → 2Eu³⁺_(melt) + Fe⁰_(crystal) has been demonstrated under experimental conditions in a simplified basaltic liquid, Such reactions may occur in lunar basalts and other reduced systems, and, thus, may aid in the understanding of the reduced nature of lunar basalts. The reactions were studied in a glass-forming Na-Ca-Mg-Al-silicate composition at a melt temperature of 1250°C and an imposed oxygen fugacity at the C/CO buffer (1 atm total pressure). Microtitrations of individually-doped samples were used in the quantitative assessment of their redox ratios and for the calibration of visible and near-infrared spectral absorptions. These spectral absorptions were then applied to the evaluation of the mutual redox interactions in dual-doped samples.  相似文献   

${}^{40}\text{Ar}{}^{39}\text{Ar}$ and KAr dating of altered glassy volcanic rocks: the Dabi Volcanics,P.N.G.     

David A. Walker  Ian McDougall 《Geochimica et cosmochimica acta》1982,46(11):2181-2190

KAr and ${}^{40}\text{Ar}{}^{39}\text{Ar}$ ages have been determined for altered submarine tholeiitic and boninite (high-Mg andesite) lavas from the Dabi Volcanics, Cape Vogel Peninsula, Papua New Guinea. ${}^{40}\text{Ar}{}^{39}\text{Ar}$ whole rock total fusion and plateau ages identify a Late Paleocene age for the tholeiitic lavas (58.9 ± 1.1 Ma) and also for the boninitic lavas (58.8 ± 0.8 Ma). Apparent KAr ages for the same samples range from 27.2 ± 0.7 to 63.9 ± 4.5 Ma, and young KAr ages for glassy boninites are probably due to variable radiogenic ⁴⁰Ar (⁴⁰Ar¹) loss. These new ages effectively reconcile previously ambiguous age data for the Dabi Volcanics and indicate contemporaneous tholeiitic and boninitic volcanism occurring in southeast PNG during the Late Paleocene.Smectites, developed as alteration products after glass in oceanic lavas commonly do not retain ³⁹Ar during or subsequent to irradiation, but in some cases may contain ⁴⁰Ar1. In the absence of other factors modifying K and Ar contents, samples which have not lost ⁴⁰Ar¹ from smectite and suffer ³⁹Ar loss only, are interpreted to have been altered immediately subsequent to the crystallization of the lava; whereas samples which have lost ⁴⁰Ar¹ as well as ³⁹Ar may be the result of either recent alteration, or of continuous ⁴⁰Ar¹ loss since the time of crystallization.  相似文献   

F-OH exchange equilibria between mica-amphibole mineral pairs     

Henry R. Westrich 《Contributions to Mineralogy and Petrology》1982,78(3):318-323

Fluoride-hydroxyl exchange equilibria between phlogopite-pargasite and phlogopite-tremolite mineral pairs were experimentally determined at 1,173K, 500 bars and 1,073–1,173 K, 500 bars respectively. The distribution of fluorine between phlogopite and pargasite was found to favor phlogopite slightly, G _ex ^. (1,173 K)=–1.71 kJ anion^–1, while in the case of phlogopite-tremolite, fluorine was preferentially incorporated in the mica, G _ex ^. (1,073)=– 5.67 kJ anion^–1 and G _ex ^. (1,173K)=–5.84 kJ anion^–1. These results have yielded new values of entropy and Gibbs energy of formation for fluortremolite, S _f =–2,293.4±16.0JK^–1 mol^–1 and G _f = –11,779.3±25.0 kJ mol^–1, respectively. In addition, F-OH mineral exchange equilibria support a recent molten oxide calorimetric value for the Gibbs energy of fluorphlogopite, G _f =–6,014.0±7.0 kJ mol^–1, which is approximately 40 kJ mol^–1 more exothermic than the tabulated value.This work performed in part at Sandia National Laboratories supported by the U.S. Department of Energy, DOE, under contract number DE-AC04-76DP00789  相似文献   

Reply to A.Y. Glikson     

E.G. Nisbet  D. Walker 《Earth and Planetary Science Letters》1983

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Organochlorine residues in whales landed at Durban,South Africa     

John Henry  Peter B Best 《Marine pollution bulletin》1983,14(6):223-227

The levels of DDT and its metabolites found in the blubber of 29 minke, 6 fin and 1 sei whale landed at the Durban whaling station in 1974 were on average much lower than those found in baleen whales from the North Atlantic, but of the same order as those measured from the Antarctic and North Pacific. In 12 sperm whales examined at Durban the levels of DDT and its metabolites in the blubber were substantially lower than in any other locality so far examined, including the Antarctic, but this may partly reflect the comparative youth of the animals sampled. Low levels of Dieldrin were found in some minke whales only. No PCB could be detected in any of the whales examined.  相似文献   

Quantimet image analysis of soil pore geometry: Comparison with tracer breakthrough curves     

P. J. C. Walker  S. T. Trudgill 《地球表面变化过程与地形》1983,8(5):465-472

The relationships between two-dimensional image analysis of soil thin-sections and tracer breakthrough curves has been studied for a silty clay loam brown earth soil under saturated conditions. Initial tracer breakthrough is well in advance of one pore volume. Discrepancies between Quantimet image analysis and breakthrough curve characterization were related by inference to the role of infrequently occurring macropores not necessarily sampled on the two-dimensional images. A fundamental difficulty found in the use of image analysis is the uncertain nature of the relationship between the two-dimensional image and the three-dimensional pore system. Caution is needed in using Quantimet image analysis to describe gross properties of the three-dimensional pore system.  相似文献   

Rates of cave and landform development in the Yorkshire Dales from speleothem age data     

Melvyn Gascoyne  Derek C. Ford  Henry P. Schwarcz 《地球表面变化过程与地形》1983,8(6):557-568

Uranium-series ages have been obtained for 87 speleothems collected from nine major cave systems in the Craven district of northern England. Large systems such as Ease Gill Caverns, the West Kingsdale caves, and Gaping Gill-Ingleborough Cave, which contain relict high-level tunnels, are found to be older than 350,000 years (the limit of the ²³⁰Th/²³⁴U dating method). There is little evidence to indicate a significant enlargement of these passages since this time. Estimates of the age of Victoria Cave from ²³⁴U/²³⁸U isotopic ratios suggest that the cave has been fully relict for more than 500,000 years. Ages of in situ speleothems immediately adjacent to local base level cave streams show that mean maximum downcutting rates in limestone channels are about 2 to 5 cm 1000 yr. These rates are significantly lower than those obtained from direct measurements on limestone bedrock in stream channels but are comparable to areal denudation rates based on solute budgets. Using the present elevation of caves with respect to adjacent valley floor levels, mean maximum valley entrenchment rates are found to range between 5 cm/ky and < 20cm/ky, which corresponds to 6 m to < 24 m of lowering per glacial/interglacial cycle. These rates suggest that upper beds of the limestone were incised to form the Yorkshire Dales between 1 and 2 million years ago. The results indicate that the erosional effects of individual glaciations are not as severe as previously proposed in the literature.  相似文献   

Stream-sediment geochemical prospecting for uranium in the paleozoic of the Belgian ardennes     

H. Martin  J.P. Lefin  L. Dejonghe  J. Henry 《Journal of Geochemical Exploration》1983,19(1-3)

During the years 1979 and 1980, a preliminary program of uranium exploration in the Paleozoic of the Belgian Ardennes was carried out under the sponsorship of the Commission of European Communities. The Laboratory of Mineralogy of the Polytechnic Faculty of Mons was charged with the radiometric section of the program, the Geochemistry Laboratory of the Free University of Brussels with the hydrogeochemical exploration, and the Geochemistry Laboratory of the University of Louvain with the stream sediment exploration. The Geological Survey of Belgium had the responsibility for coordinating the three programs, the statistical and computer treatment of the data, and the compilation of the different maps.Orientation studies at the Geochemistry Laboratory of the University of Louvain showed that a positive geochemical response for uranium could be obtained with bank sampling, which consists of collecting colluvium and alluvium on both sides of the rivers. This necessitates a large sampling density of about one sample per km² (10 205 samples from an area of 11 000 km²).The frequency distribution of the values of uranium follows the lognormal law with a geometric mean of 1.06 ppm and a threshold of 2.36 ppm (P= 0.954). The anomalies (> 3 ppm) fall into three main areas each in a different geological setting: (1) at the periphery of the Cambro-Silurian Massif of Stavelot; (2) within the transition beds between the Visean and Namurian; and (3) in the lower Devonian of the central Ardennes.The first two areas coincide with zones of known radiometric anomalies and of the occurrence of uraniferous minerals.In the third zone, follow-up work has led to the discovery of a uraniferous mineral assemblage consisting of a weathered mass of iron oxide, leucoxene and phosphates.Statistical analyses of the results indicate no significant relationship between U and either organic carbon or Mn, a negative correlation between U and carbonate and pH, and a good positive correlation between U and Cu, V and Fe. The last correlation may indicate an association of U, V, and Cu with iron oxides formed during meteoric alteration.  相似文献   

Subliquidus glass-glass immiscibility along the albite-diopside join     

D.J. Henry  I.D.R. Mackinnon  I. Chan  A. Navrotsky 《Geochimica et cosmochimica acta》1983,47(2):277-282

A calorimetric study has shown that glasses along the albite-diopside join in the system albiteanorthite-diopside have positive enthalpies of mixing. Thermodynamic calculations based on these data describe a nearly symmetric, metastable, subliquidus irascibility gap along the join with a critical temperature at 910 K. The existence of the miscibility gap was tested experimentally by annealing an Ab₅₀Di₅₀ glass at 748 K and 823 K. Annealed glasses were examined by optical microscopy and by scanning and transmission electron microscopy. The glasses showed morphological and chemical features consistent with unmixing of two glass phases. The apparent mechanism of phase separation involves initial spinodal decomposition followed by coarsening to produce 0.1 μm–0.3 μm spherical glass phases.  相似文献   

High-Resolution Seismic Reflection Evidence for Middle Holocene Environmental Change, Owasco Lake, New York   总被引：2，自引：0，他引：2  

Henry T. Mullins  John D. Halfman 《Quaternary Research》2001,55(3):322

Approximately 70 km of new decimeter-resolution seismic reflection profile data from Owasco Lake, New York define a middle Holocene (4600 ¹⁴C yr B.P.) erosion surface in the north end of the lake at water depths as great as 26 m. Beneath the lake, post-glacial sediments are up to 9 m thick and represent about 10% of the total sediment fill. Early to middle Holocene sediments, 6 m thick, contain biogenic gas at the south end of the basin and a large (4 km×300 m×15 m) subaqueous slide deposit along the east-central portion of the lake. Late Holocene sediments are thinner or absent, particularly at the north end of the lake. The middle Holocene erosion surface may have been produced by a drop in lake level. Alternatively, it may represent a change in climate during the transition between the relatively warm Holocene hypsithermal and cool neoglacial. At this time (4600 ¹⁴C yr B.P.) circulation in Owasco Lake appears to have evolved from sluggish to active. The increased circulation, which persists today, probably resulted from atmospheric cold fronts with strong southwesterly winds that piled up water at the north end of the lake. The increased water circulation may have been ultimately driven by decreasing insolation, which produced an increased pole-to-equator thermal gradient and, thus, stronger global winds that began at the transition between the hypsithermal and neoglacial.  相似文献