G. Morin, V. Noël, N. Menguy, J. Brest, B. Baptiste, M. Tharaud, G. Ona-Nguema, M. Ikogou, E. Viollier, F. Juillot
Chemical and isotopic compositions of pyrites are used as biogeochemical tracers in Archean to modern sediments. Moreover, pyrite formation from monosulphide precursors has been proposed to be involved in prebiotic chemistry. However, the factors controlling pyrite formation and distribution in the sedimentary record are incompletely understood. Read more
Z. Liu, T. Ishii, T. Katsura
Rapid decrease of MgAlO2.5 component in bridgmanite with pressure.
The solubility of the MgAlO2.5 component in bridgmanite was measured at pressures of 27, 35 and 40 GPa and a temperature of 2000 oK using an ultra-high pressure multi-anvil press. Compositional analysis of recovered samples demonstrated that the MgAlO2.5 component decreases with increasing pressure, and approaches virtually zero at 40 GPa. Read more
R. Arató, A. Audétat
The oxidation state of magmas is a key parameter that is notoriously difficult to reconstruct. The most common approach is via magnetite–ilmenite oxybarometry. However, many natural magmas do not contain ilmenite, preventing application of this technique. Here we present a new method that allows fO2 to be reconstructed based on the partitioning of Fe and Ti between magnetite and silicate melt. Read more
B.J. Peters, J.M.D. Day
Geodynamical models of mantle plumes often invoke initial, high volume plume ‘head’ magmatism, followed by lower volume plume ‘tails’. However, geochemical links between plume heads, represented by flood basalts such as the Deccan Traps, and plume tails, represented by ocean islands such as La Réunion, are ambiguous, challenging this classical view of mantle plume theory. Read more
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