Alkuainejakaumaa

Alkuainejakaumaa is a concept used in geochemistry, cosmochemistry, and planetary science to describe the distribution of chemical elements and their isotopes within a defined reservoir or system. The term combines alkuaine (element) and jakauma (distribution) in Finnish, reflecting its etymology. An alkuainejakaumaa covers both the relative abundances of elements by weight or mole fraction and the isotopic composition, and it can be specified for global, regional, or local contexts.

Data are obtained through laboratory measurements such as mass spectrometry, inductively coupled plasma techniques, and X-ray fluorescence, as well as through analysis of meteorites, lunar samples, and planetary spectra. The concept is used to model how planetary differentiation, crust formation, evaporation and condensation, or stellar nucleosynthesis shape the observed abundances.

In practice, the Earth's crust shows a characteristic order of abundance with oxygen, silicon, aluminum, iron, calcium, sodium, potassium, and magnesium among the most abundant elements; actual percentages vary by rock type. Alkuainejakaumaa is subject to uncertainties and natural variability between reservoirs, and it is often complemented by isotopic fractionation data to trace processes such as weathering, melting, or planetary accretion.

Related topics include the overall abundance of the chemical elements, cosmochemistry, and isotopic geology.