Pyrrhotite-silicate melt partitioning of rhenium and the deep rhenium cycle in subduction zones

The Re-Os isotopic system serves as an important tracer of recycled crust in Earth's deep mantle because of the large Re/Os ratios and time-integrated enrichment of radiogenic Os in Earth's crust. However, the Re distribution in Earth's known reservoirs is mass imbalanced, and the beh...

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Bibliographic Details
Published in:Geology (Boulder) 2022-02, Vol.50 (2), p.232-237
Main Authors: Xue Shuo, Xue Shuo, Li Yuan, Li Yuan
Format: Article
Language:English
Subjects:
Basalt
basalts
Coefficients
crust
Earth crust
Earth mantle
Fayalite
Fugacity
geochemical cycle
Geochemistry
Geology
Geophysics
histograms
igneous and metamorphic rocks
igneous rocks
Iron content
Iron silicates
isotope ratios
Isotopes
Laboratory experiments
Magnetite
mantle
Mass balance
melting
melts
metals
osmium
Oxygen
P-T conditions
partition coefficients
partitioning
Petrology
plate tectonics
platinum group
Pyrrhotite
radioactive isotopes
Re-187/Os-188
Rhenium
Sediments
silicate melts
Silicates
slabs
solid Earth (tectonophysics)
stable isotopes
statistical analysis
Storage
Subduction
Subduction (geology)
Subduction zones
sulfides
Tracers
volcanic rocks
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Summary:The Re-Os isotopic system serves as an important tracer of recycled crust in Earth's deep mantle because of the large Re/Os ratios and time-integrated enrichment of radiogenic Os in Earth's crust. However, the Re distribution in Earth's known reservoirs is mass imbalanced, and the behavior of Re during subduction remains little understood. We performed laboratory experiments to determine the partition coefficients of Re between pyrrhotite and silicate melt (DRepo/sm) at 950-1080°C, 1-3 GPa, and oxygen fugacities (in log units relative to the fayalite-magnetite-quartz [FMQ] buffer) of FMQ -1.3 to FMQ +2. The obtained DRepo/sm values are 200-25,000, which increase with decreasing oxygen fugacity and the total iron content (FeOtot) of silicate melt but decrease with increasing temperature or decreasing pressure. Applying DRepo/sm to constrain the behavior of Re during slab melting demonstrates that slab melts contribute minimal Re to the sub-arc mantle, with most Re dissolved in sulfides subducted into Earth's deep mantle. Deep storage of recycled oceanic basalts and sediments can explain the mass imbalance of Re in Earth's primitive mantle, depleted mantle, and crust.
ISSN:0091-7613
1943-2682
DOI:10.1130/G49374.1