Shock wave equation of state of serpentine to 150 GPa: Implications for the occurrence of water in the Earth's lower mantle

Tyburczy, J. A.; Duffy, Thomas S.; Ahrens, Thomas J.; Lange, Manfred A.

doi:10.1029/91jb01573

Cited by 55 publications

(58 citation statements)

References 49 publications

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“…Comparison of anhydrous and hydrous magnesium silicates by density Т а б л и ц а 2. Сравнительные данные по плотности безводных и водосодержащих силикатов магния П р и м е ч а н и е. Данные по плотности силикатов магния взяты из работ : Liu [1987]; Tyburczy et al [1991]; Frost and Fei [1998].…”

Section: Involvement Of Molecular Hydrogen and The Role Of Water In unclassified

Seismic Evidence for Partial Melt at the Base of Earth's Mantle

Williams

Garnero

1996

Science

533

406

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Abstract:The content of hydrogen in the outer core of the Earth is roughly quantified from the dependence of the density of iron (viewed as the main component of the core) on the amount of hydrogen dissolved in the core, with account of the most likely presence of iron hydrogen in the outer core, and the matter's density jumps at the boundaries between the outer liquid core and the internal solid core (that is devoid of hydrogen) and the mantle. Estimations for the outer liquid core show that the hydrogen content varies from 0.67 wt. % at the boundary with the solid inner core to 3.04 wt. % at the boundary with the mantle.Iron occlusion is viewed as the most likely mechanism for the iron-nickel core to capture such a significant amount of hydrogen. Iron occlusion took place at the stage of the young sun when the metallic core emerged in the cooling protoplanetary cloud containing hydrogen in high amounts, and non-volatile hydrogen was accumulated. Absorption (occlusion) of molecular hydrogen was preceded by dissociation of molecules into atoms and ionization of the atoms, as proved by results of studies focused on Fe-H2 system, and hydrogen dissipation was thus prevented. The core matter was subject to gravitational compression at high pressures that contributed to the forced rapprochement of protons and electrons which interaction resulted by the formation of hydrogen atoms. Highly active hydrogen atoms reacted with metals and produced hydrides of iron and nickel, FeH and NiH. While the metallic core and then the silicate mantle were growing and consolidating, the stability of FeH and NiH was maintained due to pressures that were steadily increasing. Later on, due to the impacts of external forces on the Earth, marginal layers at the mantle-core boundary were detached and displaced, pressures decreased in the system, and iron and nickel hydrides were decomposed to produce molecular hydrogen. Consequences of the hydrides transformation into molecular hydrogen are important in terms of petrology, mineralogy and geodynamics. At high temperatures, molecular hydrogen can be involved in redox reactions with iron silicates and carbonaceous gases (CO and CO2), and the synthesis of water becomes possible throughout the entire mantle. It is known that water can significantly reduce the temperature of rock melting, which leads to partial melting of the rocks and pluming in the asthenosphere (in the D" layer) at the bottom of the mantle, and causes the hydrolysis of magnesium silicates, which results in the chemically bound state (hydroxyl ions). Highly ductile hydroxyl-containing magnesium silicates can alter rheological properties of the rocks. A combination of rheologically weak areas in the mantle rocks and the external cosmic effects can cause significant impacts on the tectonic activity and facilitate its manifestation throughout the entire mantle. GEODYNAMICS & TECTONOPHYSICS P U B L I S H E D B Y T H E I N S T I T U T E O F T H E E A R T H ' S C R U S T S I B E R I A N B R A N C H O F R U S S I A N A C A D E M Y O...

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Section: Involvement Of Molecular Hydrogen and The Role Of Water In unclassified

Seismic Evidence for Partial Melt at the Base of Earth's Mantle

Williams

Garnero

1996

Science

533

406

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“…The Hugoniot of serpentine has been determined for lizardite (Tyburczy et al, 1991) and antigorite (Sekine et al, 2012;Zhang et al, 2014a), indicating a high stability at least up to a shock pressure of 40 GPa. In planetary accretion process, the initial parental body may have some porosity to influence the stability against impact.…”

Section: Introductionmentioning

confidence: 99%

Dynamic water loss of antigorite by impact process

Sekine

Kimura

Kobayashi

et al. 2015

Icarus

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“…Results at still higher pressures were obtained by shock-wave ex periments and Tyburczy et al (1991)). The same effects on the phase behavior of the pyrope composition have been experimen tally investigated for at least two decades.…”

Section: Introductionmentioning

confidence: 89%

Effect of H2O on the phase behavior of pyrope at high pressures and temperatures.

Liu

1993

Geochem. J.

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In comparison to the MgO-Si02-H20 (MSH) system, the addition of A1203 (as required in the pyrope composition) makes the effects of H20 on the high-pressure phase behavior of pyrope extremely complicated. This is because the MgO-A1203-Si02-H20 (MASH) system involves more than twice as many crystalline hydrous phases as the MSH system. Experimental investigations of the effect of H20 on the phase behavior of pyrope have so far revealed only three phase assemblages plus various uniden tified assemblages in the pressure range 1.5-3.5 GPa and in the presence of excess H20. Thus, a theoretical study based on the ambient densities of various phase assemblages which are relevant to the pyrope-H20 composition at various H20 content and at high pressures and temperatures is undertaken in the present work. The results of the present study not only shed light on the unidentified phase assemblages revealed in the experimental studies involving excess H20, but also predict many possible phase assemblages at any given amounts of H20 up to pressures of a few tens of GPa. The high-pressure ilmenite form of pyrope is predicted not to exist when more than 1.1 wt% H20 is present. For a model mantle which is rich in pyrope and contains less than 1 wt% H20, the three polymorphs of Mg3A12Si3 012 (pyrope, ilmenite and perovskite) would diversify into more than ten phase assemblages which con tain various hydrous phases at various pressure and temperature conditions. The effect of H20 on the phase behavior of an aluminous enstatite, which is a more likely candidate than both enstatite and pyrope in the Earth's mantle, is closer to pyrope than to enstatite at high pressures and temperatures.

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Shock wave equation of state of serpentine to 150 GPa: Implications for the occurrence of water in the Earth's lower mantle

Cited by 55 publications

References 49 publications

Seismic Evidence for Partial Melt at the Base of Earth's Mantle

Seismic Evidence for Partial Melt at the Base of Earth's Mantle

Dynamic water loss of antigorite by impact process

Effect of H2O on the phase behavior of pyrope at high pressures and temperatures.

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