petrology Petrology () is the branch of geology that studies rocks and the conditions under which they form. Petrology has three subdivisions: igneous, metamorphic, and sedimentary petrology. Igneous and metamorphic petrology are commonly taught together ...

and geochemistry, an incompatible element is one that is unsuitable in size and/or charge to the

cation An ion () is an atom or molecule with a net electrical charge. The charge of an electron is considered to be negative by convention and this charge is equal and opposite to the charge of a proton, which is considered to be positive by convent ...

sites of the minerals of which it is included. It is defined by the partition coefficient between rock-forming minerals and

melt Melt may refer to: Science and technology * Melting, in physics, the process of heating a solid substance to a liquid * Melt (manufacturing), the semi-liquid material used in steelmaking and glassblowing * Melt (geology), magma ** Melt inclusions, ...

being much smaller than 1. During the

fractional crystallization Fractional crystallization may refer to: * Fractional crystallization (chemistry), a process to separate different solutes from a solution * Fractional crystallization (geology) Fractional crystallization, or crystal fractionation, is one of the ...

of magma and magma generation by the partial melting of the Earth's

mantle A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...

and crust, elements that have difficulty in entering cation sites of the minerals are concentrated in the melt phase of magma (liquid phase). Two groups of incompatible elements that have difficulty entering the solid phase are known by acronyms. One group includes elements having large ionic radius, such as potassium,

rubidium Rubidium is the chemical element with the symbol Rb and atomic number 37. It is a very soft, whitish-grey solid in the alkali metal group, similar to potassium and caesium. Rubidium is the first alkali metal in the group to have a density higher ...

caesium Caesium (IUPAC spelling) (or cesium in American English) is a chemical element with the symbol Cs and atomic number 55. It is a soft, silvery-golden alkali metal with a melting point of , which makes it one of only five elemental metals that a ...

strontium Strontium is the chemical element with the symbol Sr and atomic number 38. An alkaline earth metal, strontium is a soft silver-white yellowish metallic element that is highly chemically reactive. The metal forms a dark oxide layer when it is ex ...

barium Barium is a chemical element with the symbol Ba and atomic number 56. It is the fifth element in group 2 and is a soft, silvery alkaline earth metal. Because of its high chemical reactivity, barium is never found in nature as a free element. Th ...

(called LILE, or large-ion lithophile elements), and the other group includes elements of large ionic valences (or high charges), such as zirconium,

niobium Niobium is a chemical element with chemical symbol Nb (formerly columbium, Cb) and atomic number 41. It is a light grey, crystalline, and ductile transition metal. Pure niobium has a Mohs hardness rating similar to pure titanium, and it has sim ...

, hafnium, rare-earth elements (REE), thorium, uranium and tantalum (called HFSE, or high-field-strength elements). Another way to classify incompatible elements is by mass (l anthanide series): light rare-earth elements (LREE) are La, Ce, Pr, Nd, and Sm, and heavy rare-earth elements (HREE) are Eu– Lu. Rocks or magmas that are rich, or only slightly depleted, in light rare-earth elements are referred to as "fertile", and those with strong depletions in LREE are referred to as "depleted".

References

Geochemistry Igneous petrology {{Geology-stub

See also

References