scholarly journals Oxidation State of the Lithospheric Mantle Beneath Komsomolskaya–Magnitnaya Kimberlite Pipe, Upper Muna Field, Siberian Craton

Minerals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 740 ◽  
Author(s):  
Anna Dymshits ◽  
Igor Sharygin ◽  
Zhe Liu ◽  
Nester Korolev ◽  
Vladimir Malkovets ◽  
...  
Keyword(s):  
Oxygen Fugacity ◽  
Oxidation State ◽  
Siberian Craton ◽  
Lithospheric Mantle ◽  
Redox State ◽  
Kimberlite Pipe ◽  
Good Explanation ◽  
Redox Conditions ◽  
Lateral Heterogeneity ◽  
Physical Processes

The oxidation state of the mantle plays an important role in many chemical and physical processes, including magma genesis, the speciation of volatiles, metasomatism and the evolution of the Earth’s atmosphere. We report the first data on the redox state of the subcontinental lithospheric mantle (SCLM) beneath the Komsomolskaya–Magnitnaya kimberlite pipe (KM), Upper Muna field, central Siberian craton. The oxygen fugacity of the KM peridotites ranges from −2.6 to 0.3 logarithmic units relative to the fayalite–magnetite–quartz buffer (∆logfO2 (FMQ)) at depths of 120–220 km. The enriched KM peridotites are more oxidized (−1.0–0.3 ∆logfO2 (FMQ)) than the depleted ones (from −1.4 to −2.6 ∆logfO2 (FMQ)). The oxygen fugacity of some enriched samples may reflect equilibrium with carbonate or carbonate-bearing melts at depths >170 km. A comparison of well-studied coeval Udachnaya and KM peridotites revealed similar redox conditions in the SCLM of the Siberian craton beneath these pipes. Nevertheless, Udachnaya peridotites show wider variations in oxygen fugacity (−4.95–0.23 ∆logfO2 (FMQ)). This indicates the presence of more reduced mantle domains in the Udachnaya SCLM. In turn, the established difference in the redox conditions is a good explanation for the lower amounts of resorbed diamonds in the Udachnaya pipe (12%) in comparison with the KM kimberlites (33%). The obtained results advocate a lateral heterogeneity in the oxidation state of the Siberian SCLM.

Earth’s Electrodes

Elements ◽  
2020 ◽  
Vol 16 (3) ◽  
pp. 157-160 ◽  
Author(s):  
Maria Rita Cicconi ◽  
Roberto Moretti ◽  
Daniel R. Neuville
Keyword(s):  
High Temperature ◽  
Low Temperature ◽  
Redox Potential ◽  
Oxygen Fugacity ◽  
Oxidation State ◽  
Redox State ◽  
Fluid Phase ◽  
Phase Relations ◽  
Geochemical Evolution ◽  
Oxidation Reduction

The oxidation–reduction (‘redox’) state is an important intensive property of any geologic system and is typically measured (and reported) as either the redox potential (Eh) or the oxygen fugacity (fO2). These two concepts cover the whole spectrum of geologic systems: from low-temperature aqueous and sedimentary systems to high-temperature rock-forming environments. The redox state determines the speciation of a fluid phase and exercises fundamental controls on phase relations and geochemical evolution. Here, we review the concepts that underpin the redox state and outline a framework for describing and quantifying the concept of the oxidation state.

Spectroscopic evidence of the origin of brown and pink diamonds family from Internatsionalnaya kimberlite pipe (Siberian craton)

2020 ◽  
Vol 47 (4) ◽  
Author(s):  
Olga P. Yuryeva ◽  
Mariana I. Rakhmanova ◽  
Dmitry A. Zedgenizov ◽  
Viktoria V. Kalinina
Keyword(s):  
Siberian Craton ◽  
Kimberlite Pipe ◽  
Spectroscopic Evidence

scholarly journals Redox state of southern Tibetan upper mantle and ultrapotassic magmas

Geology ◽  
2020 ◽  
Vol 48 (7) ◽  
pp. 733-736 ◽  
Author(s):  
Weikai Li ◽  
Zhiming Yang ◽  
Massimo Chiaradia ◽  
Yong Lai ◽  
Chao Yu ◽  
...  
Keyword(s):  
Upper Mantle ◽  
Lithospheric Mantle ◽  
Redox State ◽  
Volcanic Rocks ◽  
Mantle Xenoliths ◽  
Continental Plate ◽  
Cratonic Mantle ◽  
Tectonic Settings ◽  
Mantle Condition ◽  
Typical Range

Abstract The redox state of Earth’s upper mantle in several tectonic settings, such as cratonic mantle, oceanic mantle, and mantle wedges beneath magmatic arcs, has been well documented. In contrast, oxygen fugacity () data of upper mantle under orogens worldwide are rare, and the mechanism responsible for the mantle condition under orogens is not well constrained. In this study, we investigated the of mantle xenoliths derived from the southern Tibetan lithospheric mantle beneath the Himalayan orogen, and that of postcollisional ultrapotassic volcanic rocks hosting the xenoliths. The of mantle xenoliths ranges from ΔFMQ = +0.5 to +1.2 (where ΔFMQ is the deviation of log from the fayalite-magnetite-quartz buffer), indicating that the southern Tibetan lithospheric mantle is more oxidized than cratonic and oceanic mantle, and it falls within the typical range of mantle wedge values. Mineralogical evidence suggests that water-rich fluids and sediment melts liberated from both the subducting Neo-Tethyan oceanic slab and perhaps the Indian continental plate could have oxidized the southern Tibetan lithospheric mantle. The conditions of ultrapotassic magmas show a shift toward more oxidized conditions during ascent (from ΔFMQ = +0.8 to +3.0). Crustal evolution processes (e.g., fractionation) could influence magmatic , and thus the redox state of mantle-derived magma may not simply represent its mantle source.

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