HIgh temp geochem - isotopes

Stable isotope

Isotope that does not undergo radioactive decay.

Isotope fractionation

Separation of isotopes during physical or chemical processes.

Delta notation (δ)

Expression of isotope ratios relative to a standard in ‰ (per mil).

Fractionation factor (α)

Ratio describing isotope partitioning between phases.

High-T fractionation

Small differences in isotope ratios at high temperature.

Low-T fractionation

Larger isotope differences at low temperature (e.g.

Country rock assimilation

Mixing of magma with surrounding rock; identified using isotope shifts.

Radiogenic isotope

Isotope formed by radioactive decay of another isotope.

Parent isotope

Original unstable isotope before decay.

Daughter isotope

Product of radioactive decay.

Half-life

Time required for half of parent isotopes to decay.

Alpha decay

Emission of 2 protons + 2 neutrons (He nucleus).

Beta-minus decay

Neutron → proton + electron (β⁻).

Beta-plus decay

Proton → neutron + positron (β⁺).

Gamma decay

Release of energy as gamma radiation from excited nuclei.

Electron capture

Proton captures an electron → neutron.

Spontaneous fission

Heavy nucleus splits into two large fragments.

Decay equation

N = N₀ e^(−λt)

Isochron

Plot used to determine age and initial isotopic composition.

Geochronology

Dating rocks using radiogenic isotope systems.