A top-down origin for martian mantle plumes

Thienen, P. van; Rivoldini, A.; Hoolst, Tim Van; Lognonné, Philippe

doi:10.1016/j.icarus.2006.06.008

Cited by 37 publications

(27 citation statements)

References 62 publications

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“…Polycrystalline olivine (50-100 nm in one dimension) assemblages and the abundance of olivine fragments are increasing with increasing distance from the shock melt vein. Their compositions (Fa [39][40][41][42][43] ) are identical to the original olivine. Very fine-grained (less than approximately 10 nm) granular Mw and ðMg;FeÞSiO 3 Pv were also observed around the polycrystalline olivine assemblages.…”

Section: Resultsmentioning

confidence: 84%

Natural dissociation of olivine to (Mg,Fe)SiO ₃ perovskite and magnesiowüstite in a shocked Martian meteorite

Miyahara

Ohtani

Ozawa

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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We report evidence for the natural dissociation of olivine in a shergottite at high-pressure and high-temperature conditions induced by a dynamic event on Mars. Olivine ) adjacent to or entrained in the shock melt vein and melt pockets of Martian meteorite olivine-phyric shergottite Dar al Gani 735 dissociated into (Mg,Fe)SiO 3 perovskite (Pv)þmagnesiowüstite (Mw), whereby perovskite partially vitrified during decompression. Transmission electron microscopy observations reveal that microtexture of olivine dissociation products evolves from lamellar to equigranular with increasing temperature at the same pressure condition. This is in accord with the observations of synthetic samples recovered from high-pressure and high-temperature experiments. Equigranular O livine is one of the major constituent minerals of terrestrial planets. High-pressure and high-temperature experiments indicate that olivine converts in solid state to its high-pressure polymorphs, ringwoodite subsequent to wadsleyite, with increasing pressure and temperature and finally dissociates at higher pressures to ðMg;FeÞSiO 3 perovskite ðPvÞ þ magnesiowüstite ðMwÞ. It is expected that the dissociation takes place around and below the transition zone of the Earth (1). Seismic observations suggest that ðMg;FeÞSiO 3 Pv and Mw are likely the dominant constituent minerals in the lower mantle. Accordingly, its dissociation mechanism is important to understand the dynamics of the Earth's interior because it affects the physical and chemical properties such as densities and elastic velocities of mantle materials. Since the experimental discovery of the dissociation reaction, many scholars have been searching for evidence for the decomposition reactions in natural samples such as inclusions in diamonds from kimberlites. However, the dissociation of olivine at high-pressure and high-temperature conditions has never been reported from any natural samples so far. Therefore, the dissociation mechanism of olivine in natural samples is still unclear.Planetesimal collision phenomena are recorded in many chondritic, lunar, and Martian meteorites as shock melt veins or melt pockets. Olivine in and around the shock melt veins or melt pockets was converted by the dynamic events in solid-state reactions to its high-pressure polymorphs or its shock-induced monomineralic melt fractionally crystallized to Mg-rich wadsleyite and Fe-rich ringwoodite at high-pressure and high-temperature conditions induced by the dynamic events (2-7). The high-pressure and high-temperature conditions of the dynamic event recorded in Martian meteorites have been estimated by several previous works (8)(9)(10)(11)(12)(13)(14)(15), and the estimated conditions given in some reports are considerably beyond the stability filed of ringwoodite (8, 11). It is likely that olivine dissociated to ðMg;FeÞSiO 3 Pv þ Mw but was overlooked. Accordingly, we carefully scanned olivine grains in the Martian meteorite Dar al Gani (DaG) 735 with a field emission (FE) SEM and laser micro-Raman spectroscopy. Here ...

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Section: Resultsmentioning

confidence: 84%

Natural dissociation of olivine to (Mg,Fe)SiO ₃ perovskite and magnesiowüstite in a shocked Martian meteorite

Miyahara

Ohtani

Ozawa

et al. 2011

Proc. Natl. Acad. Sci. U.S.A.

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show abstract

“…In the latter case, an enhancement of the water content by a factor of 10 at a depth of 10 bars (about 80 km below the 1 bar level) (e.g., Rivoldini et al, 2011). This kind of endothermic phase transition from spinel to perovskite has been suggested as a requirement of mantle convective models for the early formation of Tharsis (Harder and Christensen, 1996;van Thienen et al, 2006). The size and state of the core, and the existence and size of a solid inner core, are also critical to understanding the cessation of an early martian dynamo (Acuna et al, 1999, Breuer andStevenson, 2001).…”

Section: Giant Planets Seismologymentioning

confidence: 95%

Planetary Seismology

Lognonné

Johnson

2015

Treatise on Geophysics

102

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“…The stability range of such a putative perovskite lower mantle and its consequences for mantle plume dynamics were studied by van Thienen et al (2006), comparing the model mantle mineralogy from Bertka and Fei (1997) to the model EH45 from Sanloup et al (1999). Furthermore, uncertainties of a few 100 K in the experimental determinations of the pressure-temperature relation of the perovskite phase transformation and poor knowledge of the planet's thermal state (Breuer and Spohn, 2003) are taken into account.…”

Section: Compositionmentioning

confidence: 99%

“…Furthermore, uncertainties of a few 100 K in the experimental determinations of the pressure-temperature relation of the perovskite phase transformation and poor knowledge of the planet's thermal state (Breuer and Spohn, 2003) are taken into account. For a nominal core sulfur content of 14 wt.%, van Thienen et al (2006) found that a perovskite layer sufficiently thick to affect mantle dynamics can be kept for both hot and cold end-member-type mantle temperature profiles (Breuer and Spohn, 2003). Thus, it is feasible that at least in the early evolution of the planet, when mantle temperatures were much higher, a thin perovskite layer hovered above the core-mantle boundary.…”

Section: Compositionmentioning

confidence: 99%

Interior Structure, Composition, and Mineralogy of the Terrestrial Planets

Sohl

Schubert²

2015

Treatise on Geophysics

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A top-down origin for martian mantle plumes

Cited by 37 publications

References 62 publications

Natural dissociation of olivine to (Mg,Fe)SiO ₃ perovskite and magnesiowüstite in a shocked Martian meteorite

Natural dissociation of olivine to (Mg,Fe)SiO ₃ perovskite and magnesiowüstite in a shocked Martian meteorite

Planetary Seismology

Interior Structure, Composition, and Mineralogy of the Terrestrial Planets

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A top-down origin for martian mantle plumes

Cited by 37 publications

References 62 publications

Natural dissociation of olivine to (Mg,Fe)SiO 3 perovskite and magnesiowüstite in a shocked Martian meteorite

Natural dissociation of olivine to (Mg,Fe)SiO 3 perovskite and magnesiowüstite in a shocked Martian meteorite

Planetary Seismology

Interior Structure, Composition, and Mineralogy of the Terrestrial Planets

Contact Info

Product

Resources

About

Natural dissociation of olivine to (Mg,Fe)SiO ₃ perovskite and magnesiowüstite in a shocked Martian meteorite

Natural dissociation of olivine to (Mg,Fe)SiO ₃ perovskite and magnesiowüstite in a shocked Martian meteorite