Phase relations in the transition zone

Gasparik, Tibor

doi:10.1029/jb095ib10p15751

Cited by 240 publications

(128 citation statements)

References 51 publications

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“…The maximum shock pressure and temperature, as constrained by the former perovskite, are 25-40 GPa and c2,000 1C, respectively [14][15][16][17] . Other occurrences of high-P minerals indicate shock pressures of 13-25 GPa and temperatures of 1,700-2,600 1C in melt pockets [17][18][19][20][21][22][23][24][25] .…”

Section: Discussionmentioning

confidence: 99%

The Tissint Martian meteorite as evidence for the largest impact excavation

et al. 2013

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Section: Discussionmentioning

confidence: 99%

The Tissint Martian meteorite as evidence for the largest impact excavation

et al. 2013

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“…15). Gasparik (1990) suggested that an as yet unanalyzed hydrous magnesium silicate synthesized at 18.6 GPa and 1873 K possesses this structure and further studies on that material are in progress.…”

Section: Tv~]si Silicate Isomorphs Of Transition-metal Oxidesmentioning

confidence: 99%

Crystal chemistry of six-coordinated silicon: a key to understanding the earth's deep interior

Finger¹,

Hazen²

1991

Acta Crystallogr Sect B

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A survey of high-pressure silicates reveals 12 distinct high-density structural topologies with octahedral Si. Seven of these structure types -stishovite, perovskite, ilmenite, hollandite, calcium ferrite, pyrochlore and K2NiF4 type -contain only six-coordinated silicon. Other high-pressure silicates, including those with the garnet, pyroxene, wadeite, anhydrous phase B and phase B structures, contain both tetrahedral and octahedral Si. Five systematic trends among these dozen structures suggest the existence of other, as yet unobserved, possible mantle Si phases. The criteria are: (1) structures like rutile, hollandite and calcium ferrite formed from edge-sharing chains of silicon octahedra; (2) germanates synthesized at room pressure with octahedral Ge; (3) isomorphs of roompressure oxides with 3+ or 4+ transition-metal cations; (4) high-pressure magnesium silicates related to room-pressure aluminates by the substitution 2AI Mg+ Si; and (5) the homologous structures in system Mg-Si-O-H that includes phase B and anhydrous phase B. Each of these criteria can be used to predict other potential octahedral Si phases. Of special interest are predicted structure types that fulfill more than one criterion: diaspore-type (MgSi)O2(OH)2, aerugite-type Mgl0Si3Oi6 , sphene-type CaSi2Os, benitoite-type BaSi409, gibbsite-type MgSi(OH)6 and pseudobrookite-type Fe2SiOs.

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“…MgSiO3 ilmenite is a high pressure polymorph of enstatite that is stable to temperatures as high as 2100 K in the Mg-metasilicate system [Gasparik, 1990]. In the mantle, the stability field of this phase is restricted to lower temperatures by the presence of A1 which tends to stabilize garnet at the expense of ilmenite.…”

Section: Introductionmentioning

confidence: 99%