L. R. Danielson

Redox variations in the inner solar system with new constraints from vanadium XANES in spinels

Abstract Many igneous rocks contain mineral assemblages that are not appropriate for application of common mineral equilibria or oxybarometers to estimate oxygen fugacity. Spinel-structured oxides, common minerals in many igneous rocks, typically contain sufficient V for XANES measurements, allowing use of the correlation between oxygen fugacity and V K pre-edge peak intensity. Here we report V pre-edge peak intensities for a wide range of spinels from source rocks ranging from terrestrial basalt to achondrites to oxidized chondrites. The XANES measurements are used to calculate oxygen fugacity from experimentally produced spinels of known fo2

The W-WO2 oxygen fugacity buffer (WWO) at high pressure and temperature: Implications for fO2 buffering and metal-silicate partitioning

{f_{{{\rm{o}}_2}}}

High Pressure Effects on the Iron-Iron Oxide and Nickel- Nickel Oxide Oxygen Fugacity Buffers

. We obtain values, in order of increasing fo2

Experimental evidence for sulfur-rich martian magmas: Implications for volcanism and surficial sulfur sources

{f_{{{\rm{o}}_2}}}

Flux of carbonate melt from deeply subducted pelitic sediments: Geophysical and geochemical implications for the source of Central American volcanic arc

, from IW-3 for lodranites and acapulcoites, to diogenites, brachinites (near IW), ALH 84001, terrestrial basalt, hornblende-bearing R chondrite LAP 04840 (IW+1.6), and finally ranging up to IW+3.1 for CK chondrites (where the ΔIW logfo2

Experimental determination of the metal/silicate partition coefficient of Germanium: Implications for core and mantle differentiation

\log {f_{{{\rm{o}}_2}}}

Experimental studies of metal–silicate partitioning of Sb: Implications for the terrestrial and lunar mantles

of a sample relative to the logfo2

Valence and metal/silicate partitioning of Mo: Implications for conditions of Earth accretion and core formation

\log {f_{{{\rm{o}}_2}}}

Highly Siderophile Elements in the Terrestrial Upper Mantle Require a Late Veneer? New Results for Palladium

of the IW buffer at specific T). To place the significance of these new measurements into context we then review the range of oxygen fugacities recorded in major achondrite groups, chondritic and primitive materials, and planetary materials. This range extends from IW-8 to IW+2. Several chondrite groups associated with aqueous alteration exhibit values that are slightly higher than this range, suggesting that water and oxidation may be linked. The range in planetary materials is even wider than that defined by meteorite groups. Earth and Mars exhibit values higher than IW+2, due to a critical role played by pressure. Pressure allows dissolution of volatiles into magmas, which can later cause oxidation or reduction during fractionation, cooling, and degassing. Fluid mobility, either in the sub-arc mantle and crust, or in regions of metasomatism, can generate values >IW+2, again suggesting an important link between water and oxidation. At the very least, Earth exhibits a higher range of oxidation than other planets and astromaterials due to the presence of an O-rich atmosphere, liquid water, and hydrated interior. New analytical techniques and sample suites will revolutionize our understanding of oxygen fugacity variation in the inner solar system, and the origin of our solar system in general.

Core-Mantle Partitioning of Volatile Elements and the Origin of Volatile Elements in Earth and Moon

Abstract Synchrotron X-ray diffraction data were obtained to simultaneously measure unit-cell volumes of W and WO2 at pressures and temperatures up to 70 GPa and 2300 K. Both W and WO2 unit-cell volume data were fit to Mie-Grüneisen equations of state; parameters for W are KT = 307 (±0.4) GPa, KT′ = 4.05(±0.04)