Siderite elements

Iron is a relatively abundant element in the universe. It is found in the sun and many types of stars in considerable quantity. Its nuclei are very stable. Iron is a principal component of a meteorite class known as siderites and is a minor constituent of the other two meteorite classes. The core of the earth — 2150 miles in radius — is thought to be largely composed of iron with about 10 percent occluded hydrogen. The metal is the fourth most abundant element, by weight that makes up the crust of the earth. 

Occurrence and Recovery. Rhenium is one of the least abundant of the naturally occurring elements. Various estimates of its abundance in Earth s cmst have been made. The most widely quoted figure is 0.027 atoms pet 10 atoms of silicon (0.05 ppm by wt) (3). However, this number, based on analyses for the most common rocks, ie, granites and basalts, has a high uncertainty. The abundance of rhenium in stony meteorites has been found to be approximately the same value. An average abundance in siderites is 0.5 ppm. In lunar materials, Re, when compared to Re, appears to be enriched by 1.4% to as much as 29%, relative to the terrestrial abundance. This may result from a nuclear reaction sequence beginning with neutron capture by tungsten-186, followed by p-decay of of a half-hfe of 24 h (4) (see Extraterrestrial materials). 

The nuclei of iron are especially stable, giving it a comparatively high cosmic abundance (Chap. 1, p. 11), and it is thought to be the main constituent of the earth s core (which has a radius of approximately 3500 km, i.e. 2150 miles) as well as being the major component of siderite meteorites. About 0.5% of the lunar soil is now known to be metallic iron and, since on average this soil is 10 m deep, there must be 10 tonnes of iron on the moon s surface. In the earth s crustal rocks (6.2%, i.e. 62000ppm) it is the fourth most abundant element (after oxygen, silicon and aluminium) and the second most abundant metal. It is also widely distributed. 

In the wetlands of Idaho, the formation of an Fe(III) precipitate (plaque) on the surface of aquatic plant roots (Typha latifolia, cat tail and Phalaris arundinacea, reed canary grass) may provide a means of attenuation and external exclusion of metals and trace elements (Hansel et al, 2002). Iron oxides were predominantly ferrihydrite with lesser amounts of goethite and minor levels of siderite and lepidocrocite. Both spatial and temporal correlations between As and Fe on the root surfaces were observed and arsenic existed as arsenate-iron hydroxide complexes (82%). 

Mojzsis SJ, Arrhenius G, McKeegan KD, Harrison TM, Nutman AP, Friend CRL (1996) Evidence for life on Earth before 3,800 million years ago. Nature 384 55-59 Mozely PS (1989) Relationship between depositional environment and the elemental composition of early diagenetic siderite. Geology 17 704-706... 

Mozley PS, Carothers WW (1992) Elemental and isotopic compositions of siderite in the Kuparuk formation, Alaska effect of microbial activity and water/sediment interaction on early pore-water chemistry. J Sed Pet 62 681-692... 

The major components CaO and MgO in dolomite have a minimal range indicative of very small variation in Ca/(Ca+Mg+Fe) ratios, whereas the minor elements such as SrO and MnO have a wide variation. Therefore trace components in carbonate minerals can be used as discriminant parameters to determine the origin of the carbonate rocks (cf. Yang LeBas 2004). Compositional variation of carbonate minerals from Chehelkureh on the basis of MnO or SrO (wt%) versus [Ca/(Ca+Mg+Fe)j (atoms per formula unit, a.f.u.) diagrams (Fig. 4) show that the MnO and SrO contents in dolomite-ankerite are higher than those in siderite-magnesite and accessory calcite. 

Key indicators of alteration and proximity to ore are increased K2O (particularly in the shale component) near complete loss of Na20 increased FeO (particularly in the siltstone-sandstone component) and increased CO2 in shale. These changes reflect the development of iron carbonate (siderite and ankerite) by carbonate introduction and some alteration of existing calcic carbonate in siltstone-sandstone samples. Destruction of albite, absence of chlorite and increased abundance of muscovite due to potassic alteration, are the other major mineral alteration effects in the altered host rocks. Trace elements enriched in the primary dispersion zone are Zn, Pb, Ag, Sb, As, Rb, and TI. Antimony provides the most consistent and extensive trace element dispersion halo around the deposit and is also preserved in most of... 

Hematitic iron ores of hydrothermal-sedimentary origin and Palaeozoic in age, are those of the Lahn-Dill-type in West and Central Europe (Harder, 1964). Hydro-thermal solutions associated with submarine volcanic activities have transported Fe (as FeCl3) into a marine environment, where after hydrolysis, hematite was formed (via ferrihydrite) at the margin of the basin, whereas siderite (after reduction) was formed in its centre. These ores are - in contrast to true sedimentary ores - low in Al,Ti and trace elements, which betrays their volcanic origin. 

The abundance of nickel in the earth s crust is only 84 mg/kg, the 24 most abundant element. It is found in most meteorites, particularly in the iron meteorites or siderites, alloyed with iron. Its average concentration in seawater is 0.56 pg/mL. Nickel is one of the major components of the earth s core, comprising about 7%. 

Coal contains detrital minerals that were deposited along with the plant material, and authigenic minerals that were formed during coalification. The abundance of mineral matter in coal varies considerably with its source, and is reported to range between 9.05 and 32.26 wt% (Valkovic 1983). Minerals found in coal include (Table 2) aluminosilicates, mainly clay minerals carbonates, such as, calcite, ankerite, siderite, and dolomite sulphides, mainly pyrite (FeS2) chlorides and silicates, principally quartz. Trace elements in coal are commonly associated with one or more of these minerals (see Table 2). 

The -pH relations for the important iron-water system at 25 °C are summarized in Fig. 15.3 with some simplifications. First, it is assumed that no elements other than Fe, O, and H are involved in a natural water system, the presence of C02 would oblige us to include FeCC>3 (siderite), and sulfur compounds could lead to precipitation of iron sulfides in certain Eh-pH regimes. As it is, the only Fe-O-H solids we have considered are Fe metal, Fe(OH)2, and Fe(OH)3, whereas in practice magnetite (Fe30,i), hematite (a-Fe2C>3), goethite [a-FeO(OH)], and other Fe-O-H phases could be present. Indeed, our choice of solubility products for Fe(OH)2 and... 

Arsenic is very widely distributed in Nature, but seldom in abundance. The element occurs in the free state, but in too small a quantity to be of economic importance. It is found more frequently in combination with sulphur and as metallic arsenides, sulpharsenides, arsenites and arsenates. The presence of arsenic in the sun has not been observed,1 but it is frequently detected in meteorites,2 and has been separated from siderites occurring in Mexico and Ontario.3... 

Elemental iron, the major element in Earth s core, is the fourth most abundant element in Earth s crust (about 5.0% by mass overall, 0.5%-5% in soils, and approximately 2.5 parts per billion in seawater.) In the crust, iron is found mainly as the oxide minerals hematite, Fe203, and magnetite, Fe304. Other common mineral forms are siderite, FeC03, and various forms of FeO(OH). Iron is an essential element in almost all living organisms. In the human body, its concentration ranges between 3 and 380 parts per million (ppm) in bone, 380-450 ppm in blood, and 20-1,400 ppm in tissue. 

Iron is the second most abundant metal after A1 and the fourth most abundant element in the earth s crust. The earth s core is believed to consist mainly of iron and nickel, and the occurrence of iron meteorites suggests that it is abundant throughout the solar system. The major iron ores are hematite (Fe203), magnetite (Fe304), limonite [FeO(OH)], and siderite (FeC03). 

It will be observed that all of the meteorites contain, in addition to nickel, a small quantity of cobalt, whilst the carbon content is extremely small. Carbon is sometimes present in meteoric iron in the form of minute diamonds.2 The Rowton specimen is interesting as being the first sidente observed to fall in Great Britain, and may be seen in the Natural History Museum, South Kensington. The Perryville siderite is the first recorded instance of the presence of ruthenium in meteoric iron. In addition to traces of this element, traces of iridium, palladium, and platinum were detected. 

The redox state of the mineralized brines, which in turn is reflected in whether the ore fluid is dominated by sulfate (oxidized) or sulfide (reduced), is important for controlling minor element associations in Sedex deposits. Cooke et al. (2000) point out that weakly acidic to weakly alkaline oxidized brines can precipitate siderite... 

Iron is often described as a ubiquitous element since it forms numerous stable compounds with S and with silicates. Iron represents about 5.0% of the earth s crust, occurring as hematite, magnetite, limonite, siderite, and pyrite. 

The sample suite from each core can be divided into four factors on the basis of similarities in chemical compositions as defined by Q-mode factor modeling. Factor-1 samples are rich in trace metals due to adsorption onto clay, altered tuffaceous material, and (or) organic matter and precipitation as sulfides. The relatively high concentration of boron is probably related to its inclusion in authigenic feldspars. Factor-2 samples are rich in elements commonly associated with minerals of detrital or volcanic origin. These samples contain relatively high concentrations of analcime, dawsonite, and (or) potassium feldspar, all of which are associated with alteration of tuffaceous material. Siderite and ferroan or ankeritic... 

Minerals. Few analyses of the mineral contents are available despite the abundance of elemental analyses expressed as oxides of high temperature ashes (71,72). Sprunk and O Donnell (30) described and illustrated the microscopic occurrences of minerals in many U.S. coals, especially kaolinite, pyrite, calcite, siderite, and quartz. O Gorman and Walker (2 ) quantitatively identified 14 different mineral phases in dull durain and clarain layers in 12 samples from mines in Kentucky, Pennsylvania, West Virginia, North Dakota, and Wyoming. 

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