The nature of dark-etching rims in meteoritic taenite

Taenite fields when etched develop a cloudy brown rim with approximate compositional limits of 25 and 40 per cent Ni. In iron meteorites this cloudy zone is only a few microns wide, with a sharp, high-Ni edge about 1 μm from the kamaciteinterface and a diffuse edge several microns from the central plessite. It is always present in irons unless the meteorite has been cosmically or terrestrially reheated.X-Ray and electron diffraction of grains scratched from exceptionally large areas of cloudy taenite in the mesosiderite Estherville show that this etching zone contains a fine exsolution of kamacite. Electron microscopy reveals a cellular structure with kamacite walls surrounding taenite volumes about 1000 Å in diameter; about one-third of the total volume is kamacite. Electron diffraction from a thin foil of Tazewell indicates that for several microns the cloudy border consists of a single crystal of kamacite interpenetrating a single crystal of taenite.Detailed electron-probe investigations of taenite in Estherville show that there is a step in the M-shaped Ni profile at the sharp, high-Ni edge of the cloudy region, the Ni dropping suddenly from approximately 45 to 42 per cent. It is proposed that exsolution in the cloudy region effectively froze in the Ni profile at that temperature. On subsequent cooling only the clear outer taenite continued to equilibrate with the kamacite matrix producing the kink in the M profile.Cloudy taenite is therefore a variety of plessite differing from the usual varieties in that it forms at lower temperatures in areas much richer in Ni, and the morphology is not crystallographically oriented. Its absence can provide a sensitive indication of reheating.     

The chemical classification of iron meteorites—VII. A reinvestigation of irons with Ge concentrations between 25 and 80 ppm

We report Ni, Ga, Ge and Ir concentrations for 193 irons. The compositional trends in groups IIIA and IIIB are redefined, and the suggestion by Wasson and Kimberlin that they represent a single fractionation sequence (group IIIAB) is confirmed. A new group, HIE, is similar in its properties to group IIIA but distinguished by lower Ga/Ni and Ge/Ni ratios, larger bandwidths and the formation of haxonite (Fe, Ni)₂₃C₆ in each of its members. A sixth member, Hassi-Jekna, has been added to group IIIC, extending its Ge range up to 70 ppm. The characteristics of these groups can be summarized as follows:

     

983.

Man and his physical environment: Gary D. McKenzie and Russell O. Utgard (Editors): Readings in Environmental Geology. Burgess Publishing Company,Minneapolis. 338 pp. Price $4.95     

Edward D Goldberg 《Geochimica et cosmochimica acta》1973,37(1):171

     

984.

The Permian Huangshanxi Cu–Ni deposit in western China: intrusive–extrusive association,ore genesis,and exploration implications     

Mingjie Zhang  Chusi Li  Piaoer Fu  Peiqing Hu  Edward M. Ripley 《Mineralium Deposita》2011,46(2):153-170

The Permian Huangshanxi Cu–Ni deposit is the second largest magmatic sulfide deposit discovered to date in a major Ni–Cu province related to protracted basaltic magmatism in eastern Xinjiang, China. It is hosted by a small mafic–ultramafic intrusion comprised predominantly of lherzolites, olivine websterites, gabbronorites, and gabbros. The Huangshanxi intrusion is coeval with Permian basalts of tholeiitic and alkaline affinities in the Tuha and Tarim basins, respectively. To evaluate a possible genetic relationship between the Huangshanxi intrusion and a specific type of coeval basalt in the region, as well as ore genesis in the intrusion, we have carried out an integrated mineralogical, petrological, and geochemical study. Our data reveal that the Huangshanxi intrusive rocks are characterized by relatively flat chondrite-normalized REE patterns, depletion in Nb and Ta, and elevated εNd values varying between 6 and 10. These features are similar to those of coeval tholeiitic basalts in the nearby Tuha basin, but are significantly different from those of coeval alkaline basalts in the relatively remote Tarim basin. The geochemical similarities and differences suggest that the Huangshanxi intrusion is genetically related to the tholeiitic basalts in the Tuha basin, not to the alkaline basalts in the Tarim basin, as suggested previously by some researchers. This implies that regional exploration for the Huangshanxi-type Cu–Ni deposits should be centered in the Tuha basin instead of the Tarim basin. More specifically, the uplifted areas around the Tuha basin where similar intrusions may have been brought close to the surface should be carefully examined for mineralization potential. Intrusive relations and mass balance constraints from incompatible trace elements and sulfide abundances suggest that the Huangshanxi intrusion represents a dynamic magma conduit through which multiple pulses of magma ascended to higher levels or to the surface. Numerical simulation of magma evolution and mixing calculations using Sr–Nd isotopes indicate that selective assimilation of S-bearing crustal materials is important for sulfide saturation during the early stages of magma evolution when lherzolites formed. Fractional crystallization may have also played a role in the attainment of sulfide saturation during the later stages of magma evolution when olivine websterites and gabbronorites formed. In both cases, immiscible sulfide droplets were retained in the conduit to form disseminated sulfide lenses while the fractionated silicate liquids and buoyant phases such as plagioclase continued to ascend. Extremely low PGE tenors in the sulfide ores of the Huangshanxi deposit suggest that the parental magma was highly depleted in chalcophile elements possibly due to previous sulfide segregation at depth.     

985.

Strontium-90 in surface and groundwater of the reclamation systems at the Chernobyl exclusion zone     

Alex Shevchenko  Vadym Gudzenko  Igor Nasedkin  Edward Panasevitch 《Environmental Geology》2001,40(10):1177-1184

The left bank of the Pripiat' river, opposite of the Chernobyl Nuclear Power Plant (ChNPP) is covered with a developed network of drainage canals, built for the reclamation of the swampy floodplain. This area is highly contaminated after the disaster in 1986. Concentrations of the most mobile radionuclide, ⁹⁰Sr, are comparable with ¹³⁷Cs, and reach many MBq m^-2. Their ratio in the upper 10 cm of soil is about 1. The high surface contamination as well as precipitation and flooding have been responsible for the water pollution in this area. Some specifics of ⁹⁰Sr behaviour in surface and groundwater, controlled by the hydrological regime, are described.     

986.

Exponential Gaussian approach for spectral modeling: The EGO algorithm I. Band saturation     

Loredana Pompilio  Giuseppe Pedrazzi  Edward A. Cloutis  Ted L. Roush 《Icarus》2009,201(2):781-794

Curve fitting techniques are a widespread approach to spectral modeling in the VNIR range [Burns, R.G., 1970. Am. Mineral. 55, 1608-1632; Singer, R.B., 1981. J. Geophys. Res. 86, 7967-7982; Roush, T.L., Singer, R.B., 1986. J. Geophys. Res. 91, 10301-10308; Sunshine, J.M., Pieters, C.M., Pratt, S.F., 1990. J. Geophys. Res. 95, 6955-6966]. They have been successfully used to model reflectance spectra of powdered minerals and mixtures, natural rock samples and meteorites, and unknown remote spectra of the Moon, Mars and asteroids. Here, we test a new decomposition algorithm to model VNIR reflectance spectra and call it Exponential Gaussian Optimization (EGO). The EGO algorithm is derived from and complementary to the MGM of Sunshine et al. [Sunshine, J.M., Pieters, C.M., Pratt, S.F., 1990. J. Geophys. Res. 95, 6955-6966]. The general EGO equation has been especially designed to account for absorption bands affected by saturation and asymmetry. Here we present a special case of EGO and address it to model saturated electronic transition bands. Our main goals are: (1) to recognize and model band saturation in reflectance spectra; (2) to develop a basic approach for decomposition of rock spectra, where effects due to saturation are most prevalent; (3) to reduce the uncertainty related to quantitative estimation when band saturation is occurring. In order to accomplish these objectives, we simulate flat bands starting from pure Gaussians and test the EGO algorithm on those simulated spectra first. Then we test the EGO algorithm on a number of measurements acquired on powdered pyroxenes having different compositions and average grain size and binary mixtures of orthopyroxenes with barium sulfate. The main results arising from this study are: (1) EGO model is able to numerically account for the occurrence of saturation effects on reflectance spectra of powdered minerals and mixtures; (2) the systematic dilution of a strong absorber using a bright neutral material is not responsible for band deformation. Further work is still required in order to analyze the behavior of the EGO algorithm with respect to the saturation phenomena using more complex band shapes than pyroxene bands.     

987.

On the observability of extrasolar planetary systems     

Edward Argyle 《Icarus》1974,21(2):199-201

An unresolved companion to a variable star can in principle be detected by taking the apparent autocovariance function of a suitable photometric record of the system.     

988.

Controls on the organic chemical composition of settling particles in the Northeast Atlantic Ocean     

Konstadinos Kiriakoulakis  Edward Stutt  Steven J. Rowland  Annick Vangriesheim  Richard S. Lampitt  George A. Wolff   《Progress in Oceanography》2001,50(1-4)

The organic matter of sinking particulate material collected in the Northeast Atlantic Ocean (ca. 49°N, 16°W) was investigated in order to determine temporal and depth-related variability in its composition. Three sediment traps were deployed at nominal depths of 1000 m (below the permanent thermocline), 3000 m (representing the deep-water fluxes) and at 4700 m, about 100 m above the seafloor (just above the benthic boundary layer). The samples span a 28-month sampling period from October 1995 until February 1998, each sample representing a period of between 7 and 28 days.Total organic carbon and total nitrogen contents decrease with depth, as did the absolute concentrations of most biochemicals measured in this study, such as intact proteins and individual lipids. However, concentrations of proteins relative to total organic carbon and total nitrogen did not show any significant change with depth, implying that they are not being rapidly degraded and so may provide an important supply of nitrogen to the benthos. Fluxes of protein, TN and TOC are significantly correlated at all depths.Lipid compositions vary temporally. During periods of high flux, particularly in the summer, the lipids are richer in ‘labile components’, namely unsaturated fatty acids and low molecular weight alcohols. During periods of low flux other compounds, such as sterols, steroidal ketones and a trisnorhopan-21-one are more abundant. One sample, taken close to the seafloor, was highly enriched in lipids, sterols and fatty acids in particular; this may represent detritus derived from bottom-dwelling invertebrates.     

989.

Effects of Direct Ocean CO<Subscript>2</Subscript> Injection on Deep-Sea Meiofauna     

James P. Barry  Kurt R. Buck  Chris F. Lovera  Linda Kuhnz  Patrick J. Whaling  Edward T. Peltzer  Peter Walz  Peter G. Brewer 《Journal of Oceanography》2004,60(4):759-766

Purposeful deep-sea carbon dioxide sequestration by direct injection of liquid CO₂ into the deep waters of the ocean has the potential to mitigate the rapid rise in atmospheric levels of greenhouse gases. One issue of concern for this carbon sequestration option is the impact of changes in seawater chemistry caused by CO₂ injection on deep-sea ecosystems. The effects of deep-sea carbon dioxide injection on infaunal deep-sea organisms were evaluated during a field experiment in 3600 m depth off California, in which liquid CO₂ was released on the seafloor. Exposure to the dissolution plume emanating from the liquid CO₂ resulted in high rates of mortality for flagellates, amoebae, and nematodes inhabiting sediments in close proximity to sites of CO₂ release. Results from this study indicate that large changes in seawater chemistry (i.e. pH reductions of ∼0.5–1.0 pH units) near CO₂ release sites will cause high mortality rates for nearby infaunal deep-sea communities. This revised version was published online in July 2006 with corrections to the Cover Date.     

990.

Lagrangian modelling studies of Antarctic krill (Euphausia superba) swarm formation     

Hofmann  Eileen E; Haskell  A.G.Edward; Klinck  John M; Lascara  Cathy M 《ICES Journal of Marine Science》2004,61(4):617-631

     

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Group	Structure	Ni%	Ga(ppm)	Ge(ppm)	Ir(ppm)
IIIA	Om	7.1–9.3	7–23	32–47	0.17–19
IIIB	Om	8.4–10.5	16–21	27–46	0.014–0.17
IIIC	Off-Of	10.5–13.0	11–27	8.6–70	0.08–0.6
IIIE	Og	8.2–8.9	17–19	34–37	0.05–0.6 The Ge-Ni correlation is positive in IIIA, negative in IIIB and IIIC, and there is no significant correlation in IIIE. San Cristobal is identified as a member of group IAB, thereby extending the Ge and Ni range of this group to 25 ppm and 25 per cent, respectively. Previous reports of wide cooling-rate variations in group IIIAB are not substantiated, and current evidence favors a core over a raisin-bread model for this group. There appears to be no genetic relationship between group IIIAB and either the pallasites or the mesosiderites

The Permian Huangshanxi Cu–Ni deposit in western China: intrusive–extrusive association,ore genesis,and exploration implications

The Permian Huangshanxi Cu–Ni deposit is the second largest magmatic sulfide deposit discovered to date in a major Ni–Cu province related to protracted basaltic magmatism in eastern Xinjiang, China. It is hosted by a small mafic–ultramafic intrusion comprised predominantly of lherzolites, olivine websterites, gabbronorites, and gabbros. The Huangshanxi intrusion is coeval with Permian basalts of tholeiitic and alkaline affinities in the Tuha and Tarim basins, respectively. To evaluate a possible genetic relationship between the Huangshanxi intrusion and a specific type of coeval basalt in the region, as well as ore genesis in the intrusion, we have carried out an integrated mineralogical, petrological, and geochemical study. Our data reveal that the Huangshanxi intrusive rocks are characterized by relatively flat chondrite-normalized REE patterns, depletion in Nb and Ta, and elevated εNd values varying between 6 and 10. These features are similar to those of coeval tholeiitic basalts in the nearby Tuha basin, but are significantly different from those of coeval alkaline basalts in the relatively remote Tarim basin. The geochemical similarities and differences suggest that the Huangshanxi intrusion is genetically related to the tholeiitic basalts in the Tuha basin, not to the alkaline basalts in the Tarim basin, as suggested previously by some researchers. This implies that regional exploration for the Huangshanxi-type Cu–Ni deposits should be centered in the Tuha basin instead of the Tarim basin. More specifically, the uplifted areas around the Tuha basin where similar intrusions may have been brought close to the surface should be carefully examined for mineralization potential. Intrusive relations and mass balance constraints from incompatible trace elements and sulfide abundances suggest that the Huangshanxi intrusion represents a dynamic magma conduit through which multiple pulses of magma ascended to higher levels or to the surface. Numerical simulation of magma evolution and mixing calculations using Sr–Nd isotopes indicate that selective assimilation of S-bearing crustal materials is important for sulfide saturation during the early stages of magma evolution when lherzolites formed. Fractional crystallization may have also played a role in the attainment of sulfide saturation during the later stages of magma evolution when olivine websterites and gabbronorites formed. In both cases, immiscible sulfide droplets were retained in the conduit to form disseminated sulfide lenses while the fractionated silicate liquids and buoyant phases such as plagioclase continued to ascend. Extremely low PGE tenors in the sulfide ores of the Huangshanxi deposit suggest that the parental magma was highly depleted in chalcophile elements possibly due to previous sulfide segregation at depth.     

Strontium-90 in surface and groundwater of the reclamation systems at the Chernobyl exclusion zone

The left bank of the Pripiat' river, opposite of the Chernobyl Nuclear Power Plant (ChNPP) is covered with a developed network of drainage canals, built for the reclamation of the swampy floodplain. This area is highly contaminated after the disaster in 1986. Concentrations of the most mobile radionuclide, ⁹⁰Sr, are comparable with ¹³⁷Cs, and reach many MBq m^-2. Their ratio in the upper 10 cm of soil is about 1. The high surface contamination as well as precipitation and flooding have been responsible for the water pollution in this area. Some specifics of ⁹⁰Sr behaviour in surface and groundwater, controlled by the hydrological regime, are described.     

Exponential Gaussian approach for spectral modeling: The EGO algorithm I. Band saturation

Curve fitting techniques are a widespread approach to spectral modeling in the VNIR range [Burns, R.G., 1970. Am. Mineral. 55, 1608-1632; Singer, R.B., 1981. J. Geophys. Res. 86, 7967-7982; Roush, T.L., Singer, R.B., 1986. J. Geophys. Res. 91, 10301-10308; Sunshine, J.M., Pieters, C.M., Pratt, S.F., 1990. J. Geophys. Res. 95, 6955-6966]. They have been successfully used to model reflectance spectra of powdered minerals and mixtures, natural rock samples and meteorites, and unknown remote spectra of the Moon, Mars and asteroids. Here, we test a new decomposition algorithm to model VNIR reflectance spectra and call it Exponential Gaussian Optimization (EGO). The EGO algorithm is derived from and complementary to the MGM of Sunshine et al. [Sunshine, J.M., Pieters, C.M., Pratt, S.F., 1990. J. Geophys. Res. 95, 6955-6966]. The general EGO equation has been especially designed to account for absorption bands affected by saturation and asymmetry. Here we present a special case of EGO and address it to model saturated electronic transition bands. Our main goals are: (1) to recognize and model band saturation in reflectance spectra; (2) to develop a basic approach for decomposition of rock spectra, where effects due to saturation are most prevalent; (3) to reduce the uncertainty related to quantitative estimation when band saturation is occurring. In order to accomplish these objectives, we simulate flat bands starting from pure Gaussians and test the EGO algorithm on those simulated spectra first. Then we test the EGO algorithm on a number of measurements acquired on powdered pyroxenes having different compositions and average grain size and binary mixtures of orthopyroxenes with barium sulfate. The main results arising from this study are: (1) EGO model is able to numerically account for the occurrence of saturation effects on reflectance spectra of powdered minerals and mixtures; (2) the systematic dilution of a strong absorber using a bright neutral material is not responsible for band deformation. Further work is still required in order to analyze the behavior of the EGO algorithm with respect to the saturation phenomena using more complex band shapes than pyroxene bands.     

On the observability of extrasolar planetary systems

An unresolved companion to a variable star can in principle be detected by taking the apparent autocovariance function of a suitable photometric record of the system.     

Controls on the organic chemical composition of settling particles in the Northeast Atlantic Ocean

The organic matter of sinking particulate material collected in the Northeast Atlantic Ocean (ca. 49°N, 16°W) was investigated in order to determine temporal and depth-related variability in its composition. Three sediment traps were deployed at nominal depths of 1000 m (below the permanent thermocline), 3000 m (representing the deep-water fluxes) and at 4700 m, about 100 m above the seafloor (just above the benthic boundary layer). The samples span a 28-month sampling period from October 1995 until February 1998, each sample representing a period of between 7 and 28 days.Total organic carbon and total nitrogen contents decrease with depth, as did the absolute concentrations of most biochemicals measured in this study, such as intact proteins and individual lipids. However, concentrations of proteins relative to total organic carbon and total nitrogen did not show any significant change with depth, implying that they are not being rapidly degraded and so may provide an important supply of nitrogen to the benthos. Fluxes of protein, TN and TOC are significantly correlated at all depths.Lipid compositions vary temporally. During periods of high flux, particularly in the summer, the lipids are richer in ‘labile components’, namely unsaturated fatty acids and low molecular weight alcohols. During periods of low flux other compounds, such as sterols, steroidal ketones and a trisnorhopan-21-one are more abundant. One sample, taken close to the seafloor, was highly enriched in lipids, sterols and fatty acids in particular; this may represent detritus derived from bottom-dwelling invertebrates.     

Effects of Direct Ocean CO<Subscript>2</Subscript> Injection on Deep-Sea Meiofauna

Purposeful deep-sea carbon dioxide sequestration by direct injection of liquid CO₂ into the deep waters of the ocean has the potential to mitigate the rapid rise in atmospheric levels of greenhouse gases. One issue of concern for this carbon sequestration option is the impact of changes in seawater chemistry caused by CO₂ injection on deep-sea ecosystems. The effects of deep-sea carbon dioxide injection on infaunal deep-sea organisms were evaluated during a field experiment in 3600 m depth off California, in which liquid CO₂ was released on the seafloor. Exposure to the dissolution plume emanating from the liquid CO₂ resulted in high rates of mortality for flagellates, amoebae, and nematodes inhabiting sediments in close proximity to sites of CO₂ release. Results from this study indicate that large changes in seawater chemistry (i.e. pH reductions of ∼0.5–1.0 pH units) near CO₂ release sites will cause high mortality rates for nearby infaunal deep-sea communities. This revised version was published online in July 2006 with corrections to the Cover Date.