Processes governing the carbon chemistry during the SAGE experiment

Measurements of pCO₂, pH and alkalinity in the surface waters of an iron fertilised patch of sub-Antarctic water were made during SAGE (SOLAS SAGE: Surface-Ocean Lower Atmosphere Studies Air-Sea Gas Experiment). The iron addition induced a minor phytoplankton bloom, however the patch dynamics were dominated by physical processes which suppressed and masked the biological effects. The Lagrangian nature of the experiment allowed the carbonate chemistry in the patch to be followed for 15.5 days, and the relative importance of the biological and physical factors influencing the surface water pCO₂ was estimated. The pCO₂ of the surface waters of the patch increased from 327 ??atm prior to iron addition to 338 ??atm on Day 14, effects of vertical and horizontal mixing offset the 15 ??atm drawdown that would have occurred had the induced biological uptake been the sole factor to influence the pCO₂. The air-sea carbon flux calculated using the measured skin temperature and a piston velocity parameterisation determined during SAGE (Ho et al., 2006) was 98.5% of the flux determined using conventional bulk temperature measurement and the Wanninkhof (1992) piston velocity parameterisation. The skin temperature alone contributed to an 8% increase in the flux compared with that determined using bulk temperature.     

Sunset on Heimdall's Stones. A View from Archaeology and Archaeoastronomy of the Ravlunda 169 Iron Age Cemetery

Salt, A. and Rundkvist, M., 2011. Letter to the editor: Sunset on Heimdall's stones. A view from archaeology and archaeoastronomy of the Ravlunda 169 Iron Age cemetery. Geografiska Annaler: Series A, Physical Geography, 93, 193–196. DOI: 10.1111/j.1468‐0459.2011.00428.x     

Spectral characterization of weathering products of elemental iron in a Martian atmosphere: Implications for Mars hyperspectral studies

Visible and near-infrared spectroscopic properties have been measured on elemental iron experimentally weathered in simulated Martian atmosphere and correlated to mineralogical compositions determined by X-ray diffraction. Two main features are observed in the reflectance spectra, corresponding to two deep bands located at 0.9 and 3.1 μm, respectively the iron band and the hydration band. In early weathering stages both Fe²⁺ and Fe³⁺ bands are identified. In addition, whereas the water band position does not change with time, the Fe²⁺ band disappears, and the Fe³⁺ band shifts towards longer wavelength (from 0.88 to 0.92 μm) because of transition from Fe²⁺ phases (siderite) to Fe³⁺ phases (ferrihydrite and goethite). Apart from these spectral signatures, other bands more specific of each phase are not clearly evidenced, especially for siderite. This is due to relatively low abundance of siderite (<20 wt%), but also to the very small grain size of secondary phase as well as surface coatings of iron (oxy)hydroxides. Therefore, our results suggest that carbonates, even if not detected, could be present in the form of very small grains in the surface of Mars.     

The nature of iron and manganese species in dam waters

The molecular weight (M. W.) distributions of iron and manganese species in dam water samples were investigated by use of gel filtration, while the ion-exchangeable and non-ion-exchangeable fractions of these metals were also analysed by ion-exchange chromatography. For the samples studied, more than 96 per cent of the manganese species present were found to be ion-exchangeable, whilst less than 35 per cent of iron species were ion-exchangeable. These results correlated with the finding that all the manganese species had molecular weights less than 700, but that the molecular weights of the iron species were mostly in excess of 5000. Electron paramagnetic resonance (EPR) spectroscopy has been used to support the finding that manganese is almost totally present in the form of simple aquated Mn(II) ions.     

Coprecipitation with Cu(II)‐4‐(2‐Pyridylazo)‐resorcinol for Separation and Preconcentration of Fe(III) and Ni(II) in Water and Food Samples

The coprecipitation method is widely used for the preconcentration of trace metal ions prior to their determination by flame atomic absorption spectrometry (FAAS). A simple and sensitive method based on coprecipitation of Fe(III) and Ni(II) ions with Cu(II)‐4‐(2‐pyridylazo)‐resorcinol was developed. The analytical parameters including pH, amount of copper (II), amount of reagent, sample volume, etc., were examined. It was found that the metal ions studied were quantitatively coprecipitated in the pH range of 5.0–6.5. The detection limits (DL) (n = 10, 3s/b) were found to be 0.68 µg L^?1 for Fe(III) and 0.43 µg L^?1 for Ni(II) and the relative standard deviations (RSD) were ≤4.0%. The proposed method was validated by the analysis of three certified reference materials (TMDA 54.4 fortified lake water, SRM 1568a rice flour, and GBW07605 tea) and recovery tests. The method was successfully applied to sea water, lake water, and various food samples.     

Review of geology, alteration and origin of iron oxide–apatite deposits in the Cretaceous Ningwu basin, Lower Yangtze River Valley, eastern China: Implications for ore genesis and geodynamic setting

In the Cretaceous Ningwu volcano-sedimentary basin in the Yangtze River Valley metallogenic belt, eastern China, there are three areas with a dense distribution of magnetite or hematite deposits: the Meishan deposit in the north; Washan, Nanshan and Taocun deposits in the center; and the Zhongjiu and Gushan deposits in the south. The mineralization in the Ningwu basin is associated mainly with subvolcanic intrusions, consisting of gabbro–diorite porphyry and/or gabbro–diorite. Alteration zoning of these deposits is pronounced, and includes: (1) an upper light colored zone of argillic, kaolinite, silica, carbonate and pyritic alteration (2) a middle dark colored zone of diopside, fluorapatite–magnetite, phlogopite, and garnet with fluorapatite–magnetite; (3) a lower light colored zone of extensive albitic alteration. However, at the Gushan iron deposit, the lower light colored zone and the middle dark colored zone are absent, whereas the principal alteration is represented by silicification, kaolinization, and carbonatization.The iron oxide–apatite deposits in the Ningwu basin are typically magmatic–metasomatic origin and are similar to the Kiruna-type deposits in Scandinavia, particularly with respect to mineral assemblages, fabric and structure of the iron ores, occurrence of the orebodies and wall rock alteration. The iron oxide–apatite deposits of the Ningwu basin contain magnetite and/or hematite, with diopside or actinolite and apatite gangue. They were formed in a rift or extensional environment and the mineralization is associated with alkaline magmatism. The time interval between magmatism and related mineralization is very short.     

格尔木市扎日玛日那西铁矿矿床地质特征及找矿前景分析

格尔木市扎日玛日那西铁矿属小型铁多金属矿床,矿区内目前已探测出13条铁矿体和4条锌矿体。通过对矿区内矿床地质特征、矿石特征、磁异常特征、控矿因素等进行研究分析,认为该矿床为矽卡岩型矿床,NW向断裂和接触带是重要的导矿、控矿因素,铁矾帽、磁异常、矽卡岩、颜色为重要的找矿标志,该矿床具有较好的找矿前景。     

Iron-Molybdenum Isotopes and the Chemical Evolution of Ancient-Oceans

Iron(Fe) is abundant in nature while molybdenum(Mo) is the most abundant transition metal in seawater. Due to their high sensitivity to the redox state of the environment, the isotopic compositions of Fe and Mo as well as variations have been widely used to probe the redox conditions and the evolution of ancient ocean chemistry in favor of improved analytical techniques. Here, we summarized isotopic fractionation mechanisms and natural distribution of both iron and molybdenum isotopes, and further we summarized and partially reinterpreted the redox evolution of ancient oceans through time based on available Fe-Mo data compiled in this study. The process that causes the largest iron isotope fractionation is redox reaction and the iron in oxidation state is generally enriched in ⁵⁶Fe. Biotic and abiotic pyrite formations also produce a large Fe isotope fractionations. Isotopic fractionation of molybdenum in seawater is mainly caused by the adsorption process of dissolved Mo onto ferromanganese oxides or hydroxides in sediments. Fe-Mn (hydro)oxides tend to adsorb isotopically light molybdenum resulting in the isotopic composition of Mo in seawater heavier. However, the Mo sinks in euxinic settings cause almost no molybdenum isotope fractionation. The Fe Mo isotope isotopic records through geological timegenerally suggest similar ocean redox evolution: Oceans older than 2.3 Ga was mainly dominated by ferruginous condition, and there was a slight increase in oxygen content between 2.6 and 2.5 Ga. Earth’s surface was initially oxidized during 2.3 to 1.8 Ga, during which euxinic deposition of sulfide was elevated. Euxinic waters may have expanded greatly between 1.8 and 0.8 Ga, and after that, Earth’s surface had being gradually oxidized and the euxinic waters shrank substantially.Finally, suggestions are proposed for further work on the Fe-Mo isotope research in the context of ancient ocean chemistry.     

The role of iron sources and transport for Southern Ocean productivity

Iron has been found to limit primary productivity in high nutrient, low chlorophyll regions of the oceans, including the Southern Ocean. Here we assess the relative magnitudes and geographical distributions of the sources of iron (sedimentary, atmospheric, icebergs and sea ice) to the Southern Ocean, and their impact on productivity. We present an iron cycling model, based on the assumptions of iron and light limitation of primary production, which is embedded in an eddy resolving ocean general circulation model. We find that the injection depth of the various iron inputs determines their availability for driving production because dissolved iron may be scavenged prior to it entering the illuminated mixed layer where it can drive primary production. The model suggests that production is predominantly regulated by sediment-derived iron sources rather than icebergs, sea ice or atmospheric dust. We note non-linear response in productivity to changes in the strength of one or more iron sources due to scavenging. Sea ice influences productivity by modifying the timing of iron supply to the euphotic zone. We also show that in the Scotia Sea the majority of productivity is driven by sediment-sourced iron from the Antarctic Peninsula, with additional local hotspots driven by island sources.     

沂水县北躲庄铁矿地质特征

山东省沂水县北躲庄矿区处于汞丹山凸起之上,其西侧为马站-苏村凹陷,东侧为莒县凹陷。区域地层分布较齐全,构造复杂,岩浆岩发育。该矿区地层简单,只出露新太古代泰山岩群柳杭组地层包体和新生代第四纪松散堆积物;构造有韧性剪切带和脆性断裂构造2种;岩浆岩发育,主要分布有古元古代条花峪单元、松山单元、三官寨单元。铁矿体赋存于泰山岩群柳杭组的顶部,共圈定了7个矿体,矿体呈层状产出,倾向110°~120°,倾角47°~82°。TFe品位29%~37%。其矿体成因为沉积变质型铁矿。