The stability of phlogopite + enstatite at high pressures; a model for micas in the interior of the Earth

Modreski, Peter J.; Boettcher, A. L.

doi:10.2475/ajs.272.9.852

Cited by 100 publications

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“…Temperature (t) Fig. 3 Comparison of the dehydrous curves of amphibole and phlogopite in the different compositional systems Curves 1 and 2 are the dehydrous ones of amphibole in pyrolite (Green, 1973) and basalt (Lambert and Wylli, 1972), and curves 3, 4, and 5 are the dehydrous curves of phiogopite in the system: 50% phlogopite+50% diopsite (Modreski and Boettcher, 1973), 60% phlogopite+40% corundum (Modreski and Boettcher, 1973) and 50% phlogopite+50% enstatite (Modreski and Boettcher, 1972) respectively. Ringwood (1975) has suggested that 0.1% water in the mantle is sufficient to bring about partial melting of garnet pyrolite, thus forming a lowvelocity zone in the mantle.…”

Section: Discussionmentioning

confidence: 99%

“…Relative to eclogite used in the present experiments, the potassic basalt shows high dehydration temperatures of amphibole and low Si02, Al203 and CaO and high MgO, which is consistent with the difference between pyrolite and basalt mentioned in the literature. The total compositions of the systems corresponding to curves 3, 4 and 5 are as follows: (1) 50% phlogopite+50% diopside (Modreski and Boettcher, 1973), (2) 60% phlogopite+40% corundum (Modreski and Boettcher, 1973); (3) 50% phlogopite+50 enstatite (Modreski and Boettcher, 1972). It is clear that system (1) has higher CaO and Si02, lower Al203 and higher dehydration temperatures of phiogopite than (2) and that system (3) has higher MgO and no CaO, and a larger slope of temperature to pressure in the dehydration curve of phlogopite than system (1).…”

Section: Discussionmentioning

confidence: 99%

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Experimental Study of the Influence of Hydrous Minerals on the Melting Behaviour of Rocks at High Temperatures and Pressures

Haifei¹,

Xie²,

Yousheng³

et al. 1996

Acta Geologica Sinica (Eng)

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The experimental study on the melting of potassic basalt and eclogite with about 2% water at 800-1300CC and 1.0-3.5 GPa shows that the solidi of both rocks are significantly lower than those obtained from the previous experiments of the same type of rocks under dry conditions, and the former which is enriched in potassium hai a lower melting point than the latter. It is consistent with the previous study. The melting temperature of eclogite increases with pressure, whereas potassic basalt has similar properties only at 1.5-2.5 GPa and >3.0 GPa, and at 2.5-3.0 GPa the melting temperature decreases with pressure. This can be explained as follows: (1) eclogite only has one hydrous mineral amphibole and the dehydous temperature is lower than the wet solidus of the rock. (2) Amphibole exists in potassic basalt at the pressures lower than 2.5 GPa and phlogopite exists at pressures higher than 2.5 GPa, and the special compositions of both minerals determine that amphibole has a dehydration temperature higher than or close to that of the wet solidus of the rocks, while phlogopite has a dehydration temperature lower than that of the wet solidus. On the other hand the features of the continuous solidus in the experiment of hydrous eclogite were produced by the fact that the dehydration temperature of its amphibole lower than or close to the melting temperature of the hydrous conditions. So the melting tempera. ture lowers at higher pressures. Therefore, the composition of the rocks in the lithosphere and the types of hydrous minerals and their stable PT conditions are the important factors controlling the solidi of rocks. It can quite well explain the partial melting of rocks and the origin of the low velocity zone in the deep lithosphere.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Experimental Study of the Influence of Hydrous Minerals on the Melting Behaviour of Rocks at High Temperatures and Pressures

Haifei¹,

Xie²,

Yousheng³

et al. 1996

Acta Geologica Sinica (Eng)

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“…Aluminiumrich hornblendes from peridotitic rocks are stable to even higher temperatures, and the dashed curve marks the approximate limit based on many experimental syntheses (Mysen and Boettcher,i975). For micas the maximum temperature stability is for Fefree phlogopite, which breaks down to forsterite + liquid in the presence of enstatite (Modreski and Boettcher, 1972 ). Fe-bearing phlogopite found in xenoliths from the Earth's mantle is stable to a slightly lower temperature.…”

Section: ~ Cmentioning

confidence: 99%

Mineralogy of the planets: a voyage in space and time

Smith

1979

Mineral. mag.

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Equilibrium progressive condensation of the solar nebula is regarded as a useful theoretical boundary, but complex processes involving crystal-liquid differentiation in, and collisions between, planetesimals are used to interpret the properties of meteorites and terrestrial planets. Chemical differentiation in the nebula begins with condensation and aggregation of dust, which can yield oxidized and reduced products depending whether C/O is less or greater than unity. Simple models for direct accretion of condensed materials into planets are reviewed but not adopted. For the Earth, the early history is constrained by Archaean rocks dating from -3.8 x lO 9 yr whose properties indicate a non-reducing atmosphere, and a mantle that yielded volcanic rocks mostly similar to recent ones. Physical interactions involving small bodiesThe upper mantle (above 200 km depth) contains peridotitic rocks attributable to crystal-liquid differentiation and metamorphism. Volatile elements exist in mica and other minerals, but are sparse. Abundances of sider0Phile and chalcophile elements are high enough to require late accretion of material rich in these elements, the presence of a barrier between upper mantle and core, and some extraction by sinking sulphide. The mantle (deeper than 200 kin) and core are inaccessible to direct study but interpretation of seismic data coupled with high-pressure laboratory studies requires inversion to dense phases in the mantle (especially perovskite?) and presence of light elements in the core (mainly S?). The bulk composition is modelled by cosmochemical analogy constrained by geophysical and geochemical parameters. The early condensate may be augmented by 1. 5 +0.5? over (Mg+Si), and metal by 1.2++O.I?, while alkalies are probably depleted six-fold. Radial heterogeneity from a reduced interior to an oxidized exterior is suggested. For the Moon, sections cover observations, petrologic interpretations, and bulk chemical composition. For the origin of the

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“…Green and Ringwood, 1967;Mort and Green, 1978). However, Modreski andBoettcher (1972, 1973) also found that orthopyroxenes crystallized from highly potassic melts with potash:alumina ratios close to unity were Al-poor, whereas those precipitated from potassic, metaluminous melts had high A1 contents. Evidently the alkalis : alumina ratio of melts has a great influence on the A1 content of coexisting orthopyroxene.…”

Section: Electron Microprobe Analyses Of Crystalline Phasesmentioning

confidence: 99%

“…Recasting the chemical composition of orendite into a 'phlogopite-norm' (Carmichael, 1967; see also Beswick, 1976) suggests that the amount of water in the experiments on orendite (1.23 %) was less than the amount required to satisfy all of the potential phlogopite in this rock. (Barton and Hamilton, 1979), the vapour-absent melting of titan-phlogopite (Forbes and Flower, 1974), the vapour-absent melting of pure magnesian-phlogopite (Yoder and Kuslairo, 1969), the vapour-absent melting of phlogopite+enstatite (Modreski and Boettcher, 1972), and the vapour-absent melting of phlogopite + diopside (Modreski and Boettcher, 1973). Yoder and Kushiro (1969), Eggler (1972) and Holloway (1973) indicates that under these conditions phlogopite will break down at lower temperatures than would be the case if sufficient water were present to satisfy all of the potential phlogopite.…”

Section: K-rich Magmas 271mentioning

confidence: 99%

Water-undersaturated melting experiments bearing upon the origin of potassium-rich magmas

Bartoň

Hamilton

1982

Mineral. mag.

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ABSTRACT. The water-undersaturated melting relationships of an orendite (with 1.23 ~o H20 as shown by chemical analysis) from the Leucite Hills, Wyoming, have been determined at pressures up to 30 kbar. The dominant liquidus and near-liquidus phases are leucite, olivine, orthopyroxene, clinopyroxene, and garnet. Leucite is stable only at pressures below 5 kbar, but at 27 kbar, minor olivine, orthopyroxene, clinopyroxene, and garnet crystallize simultaneously at or near the liquidus. The following reaction relationships occur with falling temperature in the orendite magma: (a) a reaction between olivine and melt to yield orthopyroxene at pressures above 12 kbar; (b) a reaction between olivine and melt to yield phlogopite at pressures below 12 kbar; (c) a reaction between olivine, orthopyroxene and melt to yield phlogopite and probably clinopyroxene at pressures above 12 kbar; (d) a reaction between leucite and melt to yield sanidine at pressures below 5 kbar. Electron microprobe analyses demonstrate that the ortho-and clinopyroxenes crystallized from orendite are aluminiumpoor; the clinopyroxenes contain insufficient aluminium to balance sodium and titanium (A1 < Na+2Ti) and these elements must either be partly balanced by (undetermined) chromium or ferric iron or be involved in substitutions which do not require trivalent ions for charge balance. The experimental results indicate that relatively silica-rich potassic magmas such as orendite form under water-undersaturated (essentially carbon dioxide free) conditions at pressures of about 27 kbar by small degrees of melting of phlogopite-garnet-lherzolite or by larger degrees of melting of peridotite which has been enriched in potassium and incompatible elements. The peralkalinity of some potassic magmas (such as orendite and wyomingite) could reflect a primary geochemical characteristic of the source rock, but could also result from the melting of phlogopite in the presence of residual pyroxenes. The association of silica-poor, mafic madupites and relatively silica-rich orendites and wyomingites in the Leucite Hills can be explained in terms of the relative effects of water and carbon dioxide on melting processes within the upper mantle. 9

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The stability of phlogopite + enstatite at high pressures; a model for micas in the interior of the Earth

Cited by 100 publications

References 0 publications

Experimental Study of the Influence of Hydrous Minerals on the Melting Behaviour of Rocks at High Temperatures and Pressures

Experimental Study of the Influence of Hydrous Minerals on the Melting Behaviour of Rocks at High Temperatures and Pressures

Mineralogy of the planets: a voyage in space and time

Water-undersaturated melting experiments bearing upon the origin of potassium-rich magmas

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