Siderophile Element

siderophile element

[′sid·ə·rə‚fīl ′el·ə·mənt]
(chemistry)
An element with a weak affinity for oxygen and sulfur and that is readily soluble in molten iron; includes iron, nickel, cobalt, platinum, gold, tin, and tantalum.

Siderophile Element

 

any of a group of transition elements belonging for the most part to group VIII (3d-5d) of the periodic system of elements (Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt) but also including certain neighboring elements (Mo, Re). Sometimes Au, P, As, C, Ge, Ga, Sn, Sb, and Cu are also classed as siderophile elements. Siderophile elements are located at the minima on the curve showing the dependence of the atomic volume of elements on the atomic number. The similar chemical and physical properties of the atoms, caused largely by the structure of outer electron subshells, suggests a common natural origin.

In the earth’s crust, siderophile elements occur either in the native state (native platinum, iridosmine group) or in lower-valence compounds. Siderophile elements exhibit a special chemical affinity for arsenic (arsenides of Pt, Co, Ni, Fe) and a slightly lesser one for sulfur (primarily Mo and Re, also Pd, inferior quantities of Fe, Co, Ru, Pt). With the exception of Fe, which is extremely widespread in the earth’s crust, and the much less abundant elements Ni and Co, the siderophile elements have very low clarkes. Platinum metals have a reduced capacity for geochemical migration.

References in periodicals archive ?
Among their topics are experimental results on fractionation of the highly siderophile elements at variable pressures and temperatures during planetary and magmatic differentiation, nucleosynthetic isotope variations of siderophile and chalcophile elements in the solar system, the distribution and processing of highly siderophile elements in cratonic mantle lithosphere, chalcophile and siderophile elements in mantle rocks: trace elements controlled by trace minerals, petrogenesis of the platinum-group minerals, and highly siderophile and strongly chalcophile elements in magmatic ore deposits.
Today, roughly 98 percent of Earth's highly siderophile elements are tucked away in its iron-rich core.
Most researchers think the highly siderophile elements joined with iron and sank into the core as it formed in the first tens of millions of years of Earth's history.
High-pressure experiments involving molten iron and sulfur showed that sulfur could have triggered the highly siderophile elements to eventually separate out, closer to the core.
Thus, density varies in relation to the presence of siderophile elements.
Third, the chalcophile (Cu, Pb, Zn, Cd, Mo, As, Ag, Bi) and siderophile elements (Ni, Co) form a large group occupying the middle of the diagram.
Why are certain siderophile elements like molybdenum, which have a natural affinity for iron, even rarer in lunar material than in the Earth's mantle?
Platinum and gold are among eight occupants of the periodic table belonging to the category known as the highly siderophile elements.
The siderophile elements tend not to ally themselves with the oxygen- and silicon-based compounds that form the bulk of Earth's crust.
Because highly siderophile elements are relatively abundant in the core and scarce in the mantle and crust, they help scientists trace how Earth's insides have evolved over time.
For instance, Walker and his colleagues have explored siderophile elements in some of the oldest rocks on Earth.
Creaser titled "A review of the Rhenium-Osmium (Re-Os) isotope system with application to organic-rich sedimentary rocks" emphasizes the importance of the Re-Os isotope system to the direct dating of sedimentary rocks, particularly black shales in which these broadly chalcophile and siderophile elements are concentrated by reductive extraction from seawater.