Compatibility (geochemistry)

Compatibility is a term used by geochemists to describe how elements partition themselves in the solid and melt within Earth's mantle.

For instance, olivine (an abundant mineral in the upper mantle) has the chemical formula (Mg,Fe)2SiO4.

Nickel, with very similar chemical behaviour to iron and magnesium, substitutes readily for them and hence is very compatible in the mantle.

Compatible elements are depleted in the crust and enriched in the mantle, with examples nickel and titanium.

There are still uncertainties in the understanding of the lower crust and upper mantle region of Earth's interior.

In addition, numerous studies have focused on looking at the partition coefficients of certain elements in the basaltic magma to characterize the composition of oceanic crust.

[1] This constant can be used to describe how individual elements in a mineral is concentrated in two different phases.

During chemical fractionation, certain elements may become more or less concentrated, which can allow geochemists to quantify the different stages of magma differentiation.

[4] Ultimately, these measurements can be used to provide further understanding of elemental behavior in different geologic settings.

One of the main sources of information about the Earth's composition comes from understanding the relationship between peridotite and basalt melting.

This ultimately changes the chemical composition of the melt as different minerals begin to crystallize.

Fractional crystallization of elements in basaltic liquids has also been studied to observe the composition of lava in the upper mantle.

[5] This concept can be applied by scientists to give insight on the evolution of Earth's mantle and how concentrations of lithophile trace elements have varied over the last 3.5 billion years.

[6] Previous studies have used compatibility of trace elements to see the effect it would have on the melt structure of the peridotite solidus.

[7] In such studies, partition coefficients of specific elements were examined and the magnitude of these values gave researchers some indication about the degree of polymerization of the melt.

One of the parameters used to characterize and describe the crustal structure in this region was compatibility of various element pairs.

[8] Essentially, studies like this showed how compatibility of certain elements can change and be affected by the chemical compositions and conditions of Earth's interior.

The oceanic crust, which is rich in basalts from volcanic activity, show distinct components that provides information about the evolution of the Earth's interior over the geologic timescale.

Incompatible trace elements become depleted when mantle melts and become enriched in oceanic or continental crust through volcanic activity.

These phenomena can be quantified by looking at radioactive decay records of isotopes in these basalts, which is a valuable tool for mantle geochemists.