Final answer:
Lanthanides are used in geochemical studies to analyze high temperature igneous systems and date rocks from Earth, Moon, and the Solar System, by acting as tracers and through radiometric dating techniques.
Step-by-step explanation:
The lanthanides, also known as rare earth elements, are used in geochemical studies to analyze high temperature igneous systems and date rocks from the Earth, Moon, and Solar System.
In geochemical studies, lanthanides can be used as tracers to understand the processes occurring in high temperature igneous systems such as volcanic eruptions.
They are also used in dating rocks through radiometric dating techniques, especially in lunar and planetary samples obtained from missions like the Apollo program.