No iron isotope fractionation between molten alloys and silicate melt to 2000 °C and 7.7 GPa: Experimental evidence and implications for planetary differentiation and accretion

Hydrous silicate melts appear to have greater compressibility relative to anhydrous melts of the same composition at low pressures (<2 GPa); however, at higher pressures, this difference is greatly reduced and becomes very small at pressures above 5 GPa. This implies that the pressure effect on the partial molar volume of water in silicate melt is highly dependent on pressure regime. Thus, H 2 O can be thought of as the most compressible ‘liquid oxide’ component in silicate melt at low pressure, but at high pressure its compressibility resembles that of other liquid oxide components. A best-fit curve to the data on from various studies allows calculation of hydrous melt compression curves relevant to high-pressure planetary differentiation. From these compression curves, crystal–liquid density crossovers are predicted for the mantles of the Earth and Mars. For the Earth, trapped dense hydrous melts may reside atop the 410 km discontinuity, and, although not required to be hydrous, atop the core–mantle boundary (CMB), in accord with seismic observations of low-velocity zones in these regions. For Mars, a density crossover at the base of the upper mantle is predicted, which would produce a low-velocity zone at a depth of approximately 1200 km. If perovskite is stable at the base of the Martian mantle, then density crossovers or trapped dense hydrous melts are unlikely to reside there, and long-lived, melt-induced, low-velocity regions atop the CMB are not predicted.

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A sulfide perspective on iron isotope fractionation during ocean island basalt petrogenesis

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2018.10.015 ◽

2019 ◽

Vol 245 ◽

pp. 59-78 ◽

Cited By ~ 4

Author(s):

Bradley J. Peters ◽

Anat Shahar ◽

Richard W. Carlson ◽

James M.D. Day ◽

Timothy D. Mock

Keyword(s):

Isotope Fractionation ◽

Ocean Island Basalt ◽

Iron Isotope ◽

Ocean Island ◽

Island Basalt

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Evidence for equilibrium iron isotope fractionation by nitrate-reducing iron(II)-oxidizing bacteria

Geochimica et Cosmochimica Acta ◽

10.1016/j.gca.2010.02.017 ◽

2010 ◽

Vol 74 (10) ◽

pp. 2826-2842 ◽

Cited By ~ 47

Author(s):

A. Kappler ◽

C.M. Johnson ◽

H.A. Crosby ◽

B.L. Beard ◽

D.K. Newman

Keyword(s):

Isotope Fractionation ◽

Iron Isotope

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A tandem-column extraction chromatography for Nd separation: minimizing mass-independent isotope fractionation for ultrahigh-precision Nd isotope-ratio analysis

Journal of Analytical Atomic Spectrometry ◽

10.1039/d1ja00365h ◽

2022 ◽

Author(s):

Da Wang ◽

Richard Carlson

Keyword(s):

Solar System ◽

Extraction Chromatography ◽

Isotope Ratio ◽

Isotope Fractionation ◽

Ratio Analysis ◽

Nd Isotope ◽

Planetary Differentiation ◽

Isotope Ratio Analysis ◽

Isotope System ◽

Column Extraction

The short-lived 146Sm-142Nd isotope system traces key early planetary differentiation processes that occurred during the first 500 million-years of solar system history. The variations of 142Nd/144Nd in terrestrial samples, typically...

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