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Determination of Aggregate Surface Morphology at the Interfacial Transition Zone ITZ
Published on: December 16, 2019
Primordial and recycled helium isotope signatures in the mantle transition zone
S Timmerman1, M Honda2, A D Burnham2
1Research School of Earth Sciences, Australian National University, 142 Mills Road, Acton, ACT 2601, Australia. suzette.timmerman@anu.edu.au.
Abstract:
Isotope compositions of basalts provide information about the chemical reservoirs in Earth's interior and play a critical role in defining models of Earth's structure. However, the helium isotope signature of the mantle below depths of a few hundred kilometers has been difficult to measure directly. This information is a vital baseline for understanding helium isotopes in erupted basalts. We measured He-Sr-Pb isotope ratios in superdeep diamond fluid inclusions from the transition zone (depth of 410 to 660 kilometers) unaffected by degassing and shallow crustal contamination. We found extreme He-C-Pb-Sr isotope variability, with high 3He/4He ratios related to higher helium concentrations. This indicates that a less degassed, high-3He/4He deep mantle source infiltrates the transition zone, where it interacts with recycled material, creating the diverse compositions recorded in ocean island basalts.
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