Siderophiles

Sideringelb, n. siderin yellow, siderophil, a. (.Petrog.) siderophilic. file, pron. she, her, it, they, them. 

Note It is sometimes convenient to describe the element distribution between sulfides and oxides as chalcophiles (occurring in the Earth s crust as sulfides) and lithophiles (predominating as oxides and halides in the Earth s crust) (see Fig. 1.5). This geochemical classification includes also the siderophiles (remaining as metals or alloys, especially in the Earth s core) and the atmophiles (which occurs largely in volatile form in the atmosphere and dissolved in the oceans). 

Siderophile elements in the zonal structure of ore geochemical systems ... 

Within the limits of the positive anomalies of the ore-forming elements the siderophile... 

Detailed mineralogical studies have shown that pyrite of different generations is the main form containing siderophile elements, and their zonal distribution is connected both to the position of wall rock pyritization zones and to the concentration changes of these elements within the pyrites. 

The presentation on sections, plans and 3-D models provides examples of the distribution of siderophile element. 

Keywords exploration, geochemical, system, siderophile, anomaly... 

A model of an ore geochemical system has been developed (Goldberg et al, 2003), which can be applied to ore entities of various categories ore bodies, deposits and ore regions. The nuclear section of the system contains a zone of accumulation of the principal ore and associated elements. The peripheral areas contain zones of depletion of ore-forming elements. Anomalies of siderophile elements (Ni, Co, Mn, Ti, V, Cr), which are the subject of this paper, are located on the periphery of the nuclear sections of these systems. 

In areas of accumulation of ore-forming elements the siderophile elements, as a rule, form zones of lower concentrations relative to the background concentration. Experience shows that these zones most probably contain ore bodies and deposits... 

This example shows possible mineral forms of occurrence of siderophile elements in ores and ore-surrounding zones. 

Barnes, S.J., Prichard, H.P., Cox, R.A., Fisher, P.C., Godel, B. 2008. The location of the chalcophile and siderophile elements in platinum-group elements ore deposits (a textural, microbeam and whole rock geochemical study) Implication for the formation of ore deposits. Chemical Geology, 248, 295-317. 

The analysis of rock samples was conducted in the chemical laboratory in Ust-Kamenogorsk, Kazakhstan. by inductively coupled plasma mass spectrometry, and the equipment used was an ELAN-6100 (US) mass spectrometer. In the present abstract the distribution of two elements zinc (as the basic ore-forming element) and titanium (of the siderophile element) is examined. The sensitivity of the analysis is 5 ppm for Zn and 0.05% for Ti. The analytical results for Zn and Ti are presented on contoured... 

Glikson A. and Allen C. (2004) Iridium anomalies and fractionated siderophile element patterns in impact ejecta, Brockman Iron Formation, Hamersley Basin, Western Australia evidence for a major asteroid impact in simatic crustal regions of the early pro-terozoic Earth. Earth Planet. Sci. Lett. 220, 247-264. 

Iron oxides present in coal are generally stable for the relatively short period of time that they are exposed to combustion temperatures. Therefore, siderophile elements (e.g., Ni, Co, Mo, Pt, Pd, Au) that are incorporated within iron oxides are also expected to remain stable, and escape any significant thermal transformation reactions (Bums 2003). Similarly, lithophile elements (e.g., Ba, B, Cr, Mn, Sr, V) that are initially found in association with silicates and aluminosilicates in coal are expected to be incorporated within the glassy fraction of coal ash upon thermal transformation of their parent minerals (Bums 2003). 

A cosmochemical periodic table, illustrating the behavior of elements in chondritic meteorites. Cosmic abundances are indicated by symbol sizes. Volatilities of elements reflect the temperatures at which 50°/o of each element would condense into a solid phase from a gas of solar composition. As in Figure 1.2, the chemical affinities of each element, lithophile for silicates and oxides, siderophile for metals, and chalcophile for sulfides, are indicated. Some of the most highly volatile phases may have remained uncondensed in the nebula. Stable, radioactive, and radiogenic isotopes used in cosmochemistry are indicated by bold outlines, as in Figure 1.2. Abundances and 50% condensation temperatures are from tabulations by Lodders and Fegley (1998). 

Distinguish between the following terms lithophile, siderophile, chalcophile, atmophile. 

Two different kinds of metals are found in chondrites. Small nuggets composed of highly refractory siderophile elements (iridium, osmium, ruthenium, molybdenum, tungsten, rhenium) occur within CAIs. These refractory alloys are predicted to condense at temperatures above 1600 from a gas of solar composition. Except for tungsten, they are also the expected residues of CAI oxidation. 

The most abundant mineral in aubrites is coarse-grained orthopyroxene (as it is in enstatite chondrites), and only a small amount of plagioclase is present. Aubrites are commonly brecciated, and several clasts of related basalt have been observed. The aubrites are depleted in siderophile and chalcophile elements relative to chondritic abundances,... 

Iron meteorites offer the unique opportunity to examine metallic cores from deep within differentiated bodies. Most of these samples were exposed and dislodged when asteroids collided and fragmented. Although irons constitute only about 6% of meteorite falls, they are well represented in museum collections. Most iron meteorites show wide variations in siderophile-element abundances, which can be explained by processes like fractional crystallization in cores that mimic those in achondrites. However, some show perplexing chemical trends that may be inconsistent with their formation as asteroid cores. 

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