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Updated: Aug 5, 2026
06:04
Simulation of the Planetary Interior Differentiation Processes in the Laboratory
Published on: November 16, 2013
Osmium isotopes and mantle convection
1Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Rd NW, DC 20015, USA. hauri@dtm.ciw.edu
Summary
The rhenium-187 to osmium-187 decay system tracks mantle evolution. Ancient mantle lithosphere and recycled oceanic crust reveal distinct isotopic signatures, explaining mantle heterogeneity and ocean island basalt sources.
Area of Science:
- Geochemistry
- Isotope Geology
- Mantle Petrology
Background:
- The rhenium-187 (Re) to osmium-187 (Os) decay system offers a powerful tool for tracing mantle evolution due to its long half-life.
- Subcontinental mantle lithosphere exhibits low Re/Os and (187)Os/(188)Os ratios, indicative of ancient melt depletion events dating back as far as 3.2 billion years.
- Subduction of crustal materials introduces radiogenic (187)Os into the mantle, creating isotopic heterogeneity.
Purpose of the Study:
- To investigate the isotopic fingerprint of Re-Os decay in tracing crustal and mantle evolution.
- To understand the role of melt extraction and crustal subduction in creating mantle heterogeneity.
- To identify the source reservoirs responsible for the geochemical signatures observed in ocean island basalts (OIBs).
Main Methods:
- Analysis of Re/Os and (187)Os/(188)Os ratios in various mantle lithologies, including peridotites and eclogites.
- Comparison of isotopic signatures between subcontinental lithospheric mantle, convecting mantle, and abyssal peridotites.
- Mass balance calculations to reconcile rhenium depletion in the upper mantle with potential crustal reservoirs.
Main Results:
- Peridotites and eclogites show distinct partitioning of Re/Os and (187)Os/(188)Os ratios, with peridotites being low and eclogites high.
- The convecting mantle displays Os-isotopic heterogeneity influenced by convective mixing.
- Abyssal peridotites indicate prior melt depletion events in the upper mantle.
- A significant rhenium depletion in the upper mantle suggests a missing reservoir, likely recycled mafic oceanic crust.
Conclusions:
- Ancient subcontinental lithosphere and recycled oceanic crust are key components controlling mantle isotopic heterogeneity.
- The mantle sources of OIBs are enriched in mafic material, consistent with recycled ancient oceanic lithosphere.
- The Re-Os system provides crucial insights into the long-term cycling of materials between the crust and mantle over geological timescales.
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