Skip to content
LITHOEN

Geological process

Element partitioning

The division of an element between coexisting phases — crystal and melt, mineral and fluid. It is the mechanism by which Earth becomes chemically heterogeneous, and it is a property of a cation in a particular site under particular conditions, not a fixed label on an element.

A schematic with a crystal on the left containing sized lattice sites, a melt on the right, arrows exchanging ions between them, and the definition of the partition coefficient D as concentration in crystal divided by concentration in melt.
SchematicWhether an element enters a growing crystal or stays in the melt depends on how well its charge and radius fit the lattice site on offer. The partition coefficient D expresses that as a ratio — but it is a ratio for one cation, one site and one set of conditions, not a property of the element.
Full description of this figure

On the left, a crystal is drawn with three lattice sites of fixed size, each holding a cation. A cation whose charge and radius fit a site is taken into the crystal and is called compatible, with a partition coefficient greater than one. On the right, a melt is drawn as a disordered field able to accommodate cations of any size; a cation that fits the crystal sites poorly is left there and is called incompatible, with a partition coefficient below one. Arrows run in both directions between the two. The partition coefficient D is defined as the concentration in the crystal divided by the concentration in the melt. The figure is labelled schematic and carries the caution that compatibility is a property of a cation in a particular site under particular conditions.

Original Lithoen diagram · LITHOEN-ORIGINAL

How this record is known

3
Settled consensus
Cited as the accepted position of the discipline.
1
Interpretation
Reached by reasoning from evidence, or produced by a named model.

4 of 4 claims on this page cite at least one registered source. Counts describe how each statement is known, not how likely it is to be true.

What Lithoen records

Each claim states how it is known and cites its evidence.

EstablishedGoverned by cation size and charge against the size and elasticity of the receiving lattice site.

The partitioning of any series of isovalent cations can be rationalised by the size and elasticity of the crystal lattice site that receives them, with site elasticity varying linearly with the formal charge of the cation. Partitioning is a property of a cation and a site together, not of an element alone.

  • model: The lattice-strain model of Blundy & Wood (1994), which predicts partitioning from the physical characteristics of cation sites in the crystal.
  • precision note: The model was demonstrated on 15 elements partitioning between silicate minerals and coexisting melts.

Evidence support: Supported by the cited evidence one source

Evidence: Blundy 1994 Peer-reviewed

InferredCompatible and incompatible are behaviours under stated conditions, not intrinsic labels.

Compatibility is not a permanent property of an element. Whether an element is taken into a crystal or left in the melt depends on which crystal, which melt, and under what pressure, temperature and oxidation state — and therefore changes from setting to setting.

  • method: Follows from the lattice-strain result: if behaviour is set by the fit between a cation and a particular site, then changing the host phase changes the behaviour.

Evidence support: Supported by the cited evidence one source

Evidence: Blundy 1994 Peer-reviewed

EstablishedPrediction from first principles was not available before the lattice-strain treatment.

Before the lattice-strain model, quantitative prediction of crystal–melt partition coefficients from thermodynamic principles had not been possible; partition coefficients were measured case by case rather than derived.

Evidence support: Supported by the cited evidence one source

Evidence: Blundy 1994 Peer-reviewed

EstablishedPartitioning between coexisting crystal and liquid is what governs magmatic and planetary differentiation.

Many geochemical processes — the crystallisation of silicate magmas, planetary differentiation — cannot be understood without knowing how elements divide between coexisting crystal and liquid phases.

Evidence support: Supported by the cited evidence one source

Evidence: Blundy 1994 Peer-reviewed

In the knowledge graph

Record last updated 2026-09-06. Corrections follow the published corrections policy; superseded claims are retained, never silently edited.