Shear strength characteristics of Irbid clayey soil mixed with iron filling and iron filling–cement mixture

Iron filling and iron filling–cement mixture were used to improve the shear strength characteristics of Irbid clayey soil. For this purpose, five types of Irbid clay soils were obtained and mixed with iron filling and iron filling–cement mixture at different percentages. Two sets of prepared samples were mixed with the admixture. The first set was prepared by mixing the soil samples with iron filling alone at 2.5, 5.0, 7.5, and 10% by dry weight of the soil. The second set was prepared by mixing with iron filling–cement mixture at equal ratio of the same percentages of the first set. An unconfined compression test was performed in this study to measure the shear strength properties of the soils. The test results showed that the increase in the percentages of the iron filling and iron filling–cement mixture up to 10% will result in increasing the maximum dry density of the soil and increase the unconfined compressive strength and the secant of modulus of elasticity of the clayey soil. Also, the addition of iron filling–cement mixture increased the unconfined compressive strength and secant modulus of elasticity of the clayey soil higher than the addition of iron filling alone.     

Reactivity of aquatic iron(III) oxyhydroxides—implications for redox cycling of iron in natural waters

The reactivity of iron(III) oxyhydroxides as reflected by their tendency to dissolve is of great importance in the redox cycling of iron and the bioavailability of iron to phytoplankton in natural waters. In this study, various iron(III) oxyhydroxides were produced by oxygenation of iron(II) in the presence of solutes, such as phosphate, sulfate, bicarbonate, valeric acid, TRIS, humic and fulvic acids, and in the presence of minerals, such as bentonite and δ-Al₂O₃ under conditions encountered in aquatic systems. The reactivity of the different iron(III) oxyhydroxides was subsequently assessed by means of a reductive dissolution using ascorbate and non-reductive dissolution using HQS (8-hydroxyquinoline-5-sulfonic acid) or oxalate. The experimental results show that the iron(III) oxyhydroxides with a low degree of polymerization exhibit higher reactivity than those with a high degree of polymerization or with high crystallinity. The quantity of active surface sites and the coordination arrangement of the functional groups at the surface of the iron(III) oxyhydroxides, especially the extent of the endstanding -OH groups per iron(III) ion determine the reactivity of iron(III) oxyhydroxides toward dissolution.Surfaces, such as clay and aluminum oxides, not only accelerate the oxygenation reaction of iron(II), but also induce the formation of iron(III) oxyhydroxides which are more active toward the dissolution reactions. Polymerization of iron(III) oxyhydroxides on the surfaces occurs predominantly in two dimensions rather than in three dimensions.In a laboratory experiment, the iron(III) oxyhydroxide formed in the presence of TRIS can be reduced by fulvic acid in a closed system under the following conditions: Fe(OH)₃(s) 0.01 g/l, fulvic acid 5 mg/l, pH 7.5, 20°C. The kinetics of the reaction depend on the reactivity of iron(III) oxyhydroxide and reducing power of fulvic acid. Although reductants other than fulvic acid may be of importance in antural waters, this result provides the laboratory evidence that the >Fe^III-OH/Fe(II) is able to act as an electron transfer mediator for the oxidation of natural organic substances, such as fulvic acid, by molecular oxygen either in the absence of microorganisms or as a supplement to microbial activity.     

The Bedded Chert,banded iron‐formation problem

The characteristics of Bedded Cherts and Banded Iron‐Formations are summarised. As, following O'Rourke's work, the latter are considered as not confined to the Precambrian, the only significant difference between the two formations is shown to be the low iron content of Bedded Cherts. This difference it is suggested is due to Bedded Cherts having been deposited in a virtually continuously acid to weakly alkaline environment, whereas Banded Iron‐Formation was precipitated under an alternation of acid and alkaline conditions yielding siliceous and iron‐rich layers respectively. Such chemical precipitation of either Bedded Chert or Banded Iron‐Formation was in some examples of each type of formation rhythmically interrupted by the deposition of clastic sediment.     

Timing and setting of skarn and iron oxide formation at the Smältarmossen calcic iron skarn deposit, Bergslagen, Sweden

Abundant iron oxide deposits including banded iron formations, apatite iron oxide ores, and enigmatic marble/skarn-hosted magnetite deposits occur in the Palaeoproterozoic Bergslagen region, southern Sweden. During the last 100 years, the latter deposit class has been interpreted as contact metasomatic skarn deposits, metamorphosed iron formations, or metamorphosed carbonate replacement deposits. Their origin is still incompletely understood. At the Smältarmossen mine, magnetite was mined from a ca. 50-m-thick calcic skarn zone at the contact between rhyolite and stratigraphically overlying limestone. A syn-volcanic dacite porphyry which intruded the footwall has numerous apophyses that extend into the mineralized zone. Whole-rock lithogeochemical and mineral chemical analyses combined with textural analysis suggests that the skarns formed by veining and replacement of the dacite porphyry and rhyolite. These rocks were added substantial Ca and Fe, minor Mg, Mn, and LREE, as well as trace Co, Sn, U, As, and Sr. In contrast, massive magnetite formed by pervasive replacement of limestone. Tectonic fabrics in magnetite and skarn are consistent with ore formation before or early during Svecokarelian ductile deformation. Whereas a syngenetic–exhalative model has previously been suggested, our results are more compatible with magnetite formation at ca. 1.89 Ga in a contact metasomatic skarn setting associated with the dacite porphyry.     

Lower Ordovician iron ooids and associated oolitic clays in Russia and Estonia: a clue to the origin of iron oolites?

On the Baltic platform a lower Llanvirn (Ordovician) iron oolite can be traced for a distance of 1200 km from Norway to the east of Lake Ladoga in Russia. This oolite is usually thin (seldom exceeding 0.5 m) and is dominated by goethite (limonite) type ooids. The easternmost part of the oolite, from Tallinn to Ladoga, is examined here. The oolitic limestone is intercalated with oolitic clay beds. The mineralogical, chemical and isotopic composition and other indicators point to volcanic ash being the source for the clay. Similarities in REE distribution patterns and immobile element contents between ooids and the oolitic clay suggest that the ooids were also formed from volcanic ash.     

Can fly-ash extend bentonite binder for iron ore agglomeration?

There is great incentive to reduce bentonite use in iron ore pelletization by improving its effectiveness. In order to make bentonite more effective, it is necessary to understand the actual binding mechanisms so that they can be properly taken advantage of. Bentonite use could also be reduced by replacing bentonite with even lower-cost binders, such as high-carbon fly-ash based binder (FBB). While FBBs can be used alone as binders, it was considered possible that mixtures of FBB and bentonite could exhibit superior binding properties. In this study, it was found that bentonite bonds by a physical mechanism, while FBB bonds by a chemical mechanism. These mechanisms were determined to be incompatible. Mixtures of the two binders resulted in reduced dry magnetite concentrate pellet compressive strengths below the industrially acceptable value of 22 N (5 lbf). Activators and accelerators, which were necessary components of the FBB, deactivated the bentonite. The compatibilities and mechanisms of the two binders are explained in this paper. The classical theory of the binding mechanism of bentonite binder is challenged by the bentonite fiber mechanism that was recently identified by the authors.     

Oldest volcanic-hosted submarine iron ores in South China: Evidence from zircon U–Pb geochronology and geochemistry of the Paleoproterozoic Dahongshan iron deposit

The Dahongshan iron deposit is hosted in the Paleoproterozoic submarine metavolcanic rocks of the Dahongshan Group in the Yangtze Block, South China. LA-ICP-MS dating of hydrothermal zircon grains from the genetically associated albitite and dolomite albitite show ca. 2008 Ma ages that are consistent with the zircon ages from the host metavolcanic rocks (ca. 2012 Ma), and postdated the post-ore diabase dike (ca. 1724 Ma), marking the Dahongshan iron deposit as the oldest submarine volcanic-hosted deposit so far as known. The ore-hosting metavolcanic rocks in the Dahongshan deposit have low Ni (9.1–77.4 ppm), Cr (1.0–63.0 ppm) and Co contents (5.6–62.9 ppm), suggesting the fractionation of olivine, clinopyroxene and plagioclase within the magma chamber. The major and trace element features of the alkaline to tholeiitic metavolcanic rocks are consistent with high-degree partial melting of the mantle wedge metasomatized by melts enriched in high field strength elements (HFSEs), which were derived from the subducted slab in volcanic arc setting. Based on an evaluation of the morphology of orebody, ore fabrics, petrology and melt-fluid inclusions, as well as the geochemical characteristics of the major ore mineral (magnetite), we correlate the iron mineralization in the Dahongshan deposit with hydrothermal process induced by the high-temperature, high-salinity and Fe-rich brines derived through magmatic exsolution. The similar characteristic of Ce and Eu anomalies of the Dahongshan iron deposit and banded iron formations (BIFs) suggest that the Dahongshan deposit was formed in reducing environment, although the two types of iron ores were generated through distinct processes with hydrothermal processes dominating for the submarine volcanic-hosted iron deposits whereas the BIFs were formed through chemical precipitation.     

Speciation of adsorbed arsenate on the surface of hydrous iron oxide

Adsorption of arsenate on hydrous iron oxide is an important process controlling geochemical cycling of arsenic in environment as well as the fate of arsenic-bearing mining wastes. The widely accepted view on the mechanism of adsorption is that arsenate is adsorbed via bidentate binuclear inner-sphere complexation. In this study, we characterized the arsenate-hydrous iron oxide sorption solids synthesized at pH=3-8 using Fourier transformed infrared spectroscopy （FTIR） and X-ray diffraction （XRD）. It has been determined that poorly crystalline ferric arsenate developed on the surface of iron oxide when arsenate was sorbed at acidic pH, while at alkaline pH the adsorption of arsenate was via bidentate complexation.     

Optical and Mössbauer spectroscopy of iron in rock-forming silicates

The inner nebula out to ~3 A.U. was depleted in volatile elements that included potassium and manganese at a very early stage of solar-system history. The inner planets and many meteorites inherited this element signature, the cause of which probably was early violent solar activity. Because of this evidence for elemental depletions correlated with volatility, one might also expect to find examples of fractionation, particularly among lower mass elements. Here we discuss the search for such effects among the isotopes of K, Mg, Si, and Ca in a wide variety of terrestrial, lunar, and meteoritic samples. We examine examples of vaporization without isotope fractionation, and a comparison of the effects expected between distillation and condensation. Effects attributable both to evaporation and condensation are observed in refractory inclusions (CAIs) in meteorites and reflect localized events in the early nebula. However, the lack of isotopic fractionation that is observed among a wider variety of presolar-system materials rules out the general operation of Rayleigh-type fractionation on primitive solar-nebular material. We conclude with a discussion of volatileelement behavior during the giant Moon-forming impact that shows that the material in the Moon was not subjected to Rayleigh-type distillation.     

Equation of state of iron–silicon alloys to megabar pressure

The stability and pressure–volume equation of state of iron–silicon alloys, Fe-8.7 wt% Si and Fe-17.8 wt% Si, have been investigated using diamond-anvil cell techniques up to 196 and 124 GPa, respectively. Angular–dispersive X-ray diffractions of iron–silicon alloys were measured at room temperature using monochromatic synchrotron radiation and an imaging plate (IP). A bcc–Fe-8.7 wt% Si transformed to hcp structure at around 1636 GPa. The high-pressure phase of Fe-8.7 wt% Si with hexagonal close-packed (hcp) structure was found to be stable up to 196 GPa and no phase transition of bcc–Fe-17.8 wt% Si was observed up to 124 GPa. The pressure–volume data were fitted to a third-order Birch–Murnaghan equation of state (BM EOS) with zero–pressure parameters: V₀=22.2(8) ų, K₀=198(9) GPa, and K₀=4.7(3) for hcp–Fe-8.7 wt% Si and V₀=179.41(45) ų, K₀=207(15) GPa and K₀=5.1(6) for Fe-17.8 wt% Si. The density and bulk sound velocity of hcp–Fe-8.7 wt% Si indicate that the inner core could contain 3–5 wt% Si.     

Environmental geology problems caused by mining activities in Panzhihua iron mine

The Panzhihua iron mine, a famous V-Ti magnetite mine in our country, is composed of the Jianshan, Lanjiahuoshan and Zhujiabaobao ore areas. It has caused many ecological problems in the Panzhihua iron mine after nearly 40 years of mining, which has severe impact on safe mining and has brought huge economic losses. This paper begins with the environmental geological problems caused by unloading （mining） and loading （mine dump） that is then resulted from mining activities. The paper then analyses and studies the cause and development of every environmental geological problem as well as the formation of geological disasters （landslip, coast and landslide） from two aspects： geological disasters and environmental geological problems caused by mining activities. Meanwhile, the paper puts forward suggestions about prevention and management of mine. It is found that material unloading in the Panzhihua iron mine has made the originally stable geological body be less stable, and has formed much disastrous slope. The resulted geological disasters include landslip, landslip, etc. Material loading, i.e. mine dump, has caused a huge artificial loose stack piled up in valleys. The steep slopes can easily result in geological disasters, such as landslip, landslide, debris flow, etc. Till now, there have been over10 times geological disasters caused by material unloading, and over 20 times caused by material loading. The economic loss has been over 0.1 billion yuan RMB. It is also found that the major impact of mining on environment is the pollution of soil and water caused by heavy metals. Besides this, powder is also another source of pollution.     

As (V) adsorption characteristics of iron oxide coated sands

The presence of arsenic has been great concern because of its toxicity for human health. Generally As forms stable solids in the presence of Ba and has strong affinity for sulfur. The purpose of the study is to compare the As (V) adsorption capacities of …     

Hydrothermal titanite from the Chengchao iron skarn deposit: temporal constraints on iron mineralization,and its potential as a reference material for titanite U–Pb dating

Mineralogy and Petrology - Uranium–lead isotopes and trace elements of titanite from the Chengchao iron skarn deposit (Daye district, Eastern China), located along the contact zones between...     

Phase relations of iron–silicon alloys at high pressure and high temperature

The phase relations of Fe-6.4 wt% Si and Fe-9.9 wt% Si have been investigated up to 130 GPa and 2,600 K based on in situ synchrotron X-ray diffraction measurements in a laser-heated diamond-anvil cell along with chemical analysis of the quenched samples using a field-emission electron probe microanalyzer. We found that the maximum solubility of silicon in solid hcp-iron increases with increasing pressure. Linear extrapolation of the phase boundary between hcp + B2 and hcp phases for Fe-9.9 wt% Si suggests that the solid hcp-iron can include more than 9.9 wt% Si at the Earth’s inner-core conditions. If silicon is a major light element in the outer core, a substantial amount of silicon may be incorporated into the inner core during inner-core solidification.     

Spherules with pure iron cores from Myanmar jadeitite: Type-I deep-sea spherules?

Here we report spherules in Myanmar jadeitite, a rock forming from jadeitic fluids within mantle-derived serpentinized rocks in subduction zones under high-pressure conditions (>1.0 GPa) and rather low temperatures of about 250-370 °C. The spherules have off-centre iron nuclei and dendritic wüstite cortexes, with tiny wüstite crystals perpendicular to the surface of iron core. Within the spherules are vesicles occupied by calcite, jadeite, albite? or mixtures of these phases, and the cortexes contain about 10 wt.% SiO₂ + Al₂O₃ + Na₂O filling materials within wüstite. The spherules are in direct contact with jadeite crystals. Contrasting patterns of some individual spherules are obvious between a front area with a crowd of hill-like prominences and a rear zone with one or more rings on the surface. Such surface features and internal textures suggest that they experienced movement at high temperature and then rapid cooling. Chemical compositions of the nuclei are homogenous and consist of nearly pure iron with minor Cr (<0.05 wt.%), Mn (<0.80 wt.%), and Ni (0.142-0.23 wt.%), and a trend of Ni decreasing and Cr increasing from core to cortex. Mn in the cortex (up to about 2.00 wt.%) is far more enriched than the nucleus. The bulk ratios (average) of δ⁵⁶Fe and δ⁵⁷Fe in the core and cortex are 0.51and 0.78, respectively. Such features suggest that there is a very low possibility of origin associated with volcanic explosive eruption, impact ejecta, chemical reduction or oxidation of iron on seafloor. Since biological reduction processes are not significant under high P/T condition in subduction zones, this origin is excluded. Considering their low Ni contents, it is more likely that they belong to the minor type-I deep-sea cosmic spherules/dusts of low isotope fractionation. This discovery shows that such spherules could remain stable under low-temperature and high-pressure conditions during recycling processes, and therefore could be found in rocks related to slab-derived sediments within subduction zones. This also suggests that subducted oceanic slab sediments contribute to the formation of jadeitite, coupled with dehydration of sediments and altered oceanic crust.     

Anomalous iron distribution in shales as a manifestation of “non-clastic iron” supply to sedimentary basins: relevance for pyritic shales,base-metal mineralization,and oolitic ironstone deposits

In previous investigations, nearshore pyritic shale horizons in the Mid-Proterozoic Newland Formation were interpreted to be due to non-clastic colloidal iron supply by streams. New data on the chemical composition of shales in the Newland Formation support this interpretation. In these shales, Fe and Al show a positively correlated trend that intercepts the Fe axis above the origin. These relationships suggest control of Fe by clays (via iron oxide coatings on clay minerals), and the presence of an additional, non-clastic iron component. Shales from stratigraphic intervals during which pyritic shale horizons were deposited plot above the Fe/Al trend typical for the remainder of the Newland Formation.Pyritic shale horizons in sediments are favourable hosts for base-metal deposits of the pyrite-replacement type. Fe/Al relationships as found in the Newland Formation may help to identify stratigraphic horizons in other sedimentary basins that contain pyritic shale horizons and potentially base-metal mineralization.     

The effect of nitrogen on the compressibility and conductivity of iron at high pressure

Although nitrogen in the Earth’s interior has attracted significant attention recently,it remains the most enigmatic of the light elements in the Earth’s core.In this work,synchrotron X-ray diffraction(XRD)and electrical conductivity experiments were conducted on iron nitrides(Fe₂N and Fe₄N)in diamond anvil cells(DACs)up to about 70 GPa at ambient temperature.These results show that iron nitrides are stable up to at least 70 GPa.From the equation of state(EOS)parameters,iron nitrides are more compressible than iron carbides.Moreover,using the van der Pauw method and Wiedemann-Franz law,the electrical and thermal conductivity of samples were determined to be much lower than that of iron carbides.The conductivities of Fe₂N and Fe₄N were similar at 20–70 GPa,suggesting no evident effects by varying the N stoichiometries in iron nitrides.Iron nitrides are less dense and conductive but more compressible than carbides at 0–70 GPa.This study indicates that less nitrogen than carbon can explain geophysical phenomena in the deep Earth,such as the density deficit.     

Is iron redox cycling in a high altitude watershed photochemically or thermally driven?

Many studies have shown that the concentration of aqueous Fe²⁺ increases in surface waters during exposure to sunlight and attribute this phenomenon either to photoreductive dissolution of ferric minerals/colloids or to ligand-to-metal charge transfer within organic complexes of Fe³⁺. In a multi-summer study of iron redox cycling in a relatively high pH stream (Middle Crow Creek, MCC) that drains a mostly-granitic watershed at an altitude of 2400 m, aqueous Fe³⁺ (not Fe²⁺) concentrations were correlated with both sunlight and temperature. A steady state model fails to explain the [Fe²⁺] and [Fe³⁺] data from this stream. However, Fe²⁺ concentrations can be explained using a simple kinetic model in which rate constants for oxidation and reduction were obtained by fitting data from in situ oxidation experiments, including first-order thermal (nonphotochemical) reduction of Fe³⁺. Rate constants obtained from experiments in the dark result in too much Fe²⁺ to match the data from illuminated experiments, requiring a net photooxidation process to explain [Fe³⁺] measured in MCC. The organic content of MCC results in high concentrations of Fe–DOM complexes that not only act as a reservoir contributing to daily changes in [Fe_tot] as measured by our methods, but whose photochemistry may contribute highly oxidizing reactive oxygen species to the stream. In situ studies suggest that photochemical reduction of organically bound Fe³⁺ occurs, followed by thermal release of Fe²⁺ to the water column and subsequent rapid re-oxidation.