Answer:
Tracing mantle sources: Isotopic ratios of elements like neodymium and strontium can tell us where rocks in the mantle come from. By comparing these ratios to known values, scientists can figure out the origins of different rocks and how mantle materials mix together.
Isotopic signatures of mantle processes: Certain isotopes, like helium-3 and lead-206, show us the involvement of ancient materials and the recycling of crustal materials into the mantle. By studying these isotopic signatures, we can learn about the movements and activities of the mantle, including the impact of mantle plumes.
Mantle melting and differentiation: Isotopic ratios of elements like osmium and helium give us insights into how the mantle melts and forms magma. By examining the isotopic compositions of rocks created through mantle melting, we can understand how much melting occurs, how different magma types form, and how they differentiate.