A thermochemical study of glasses and crystals along the joins silica-calcium aluminate and silica-sodium aluminate

Navrotsky, Alexandra; Péraudeau, G.; McMillan, Paul F.; Coutures, Jean-Pierre

doi:10.1016/0016-7037(82)90183-1

Cited by 156 publications

(79 citation statements)

References 18 publications

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“…11), perhaps because recondensation onto interchondrule matrix occurred at lower temperatures. However, the alkalis prefer to be incorporated into glasses via the coupled substitution (Na,K)(Al,Fe 3+ )O 2 = SiO 2 (e.g., Taylor and Brown 1979;Navrotsky et al 1982;Roy and Navrotsky 1984), which may explain why the individual Bishunpur rim analyses scatter about the atomic Na/Al = 1 line in Fig. 11.…”

Section: Evaporation Condensation and The Formation Of Chondrule Rimsmentioning

confidence: 99%

Re-examining the role of chondrules in producing the elemental fractionations in chondrites

Alexander¹

2005

Meteoritics &Amp; Planetary Science

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Abstract-The matrices of all primitive chondrites contain presolar materials (circumstellar grains and interstellar organics) in roughly CI abundances, suggesting that all chondrites accreted matrix that is dominated by a CI-like component. The matrix-normalized abundances of the more volatile elements (condensation temperatures <750-800 K) in carbonaceous and ordinary chondrites are also at or slightly above CI levels. The modest excesses may be due to low levels of these elements in chondrules and associated metal. Subtraction of a CI-like matrix component from a bulk ordinary chondrite composition closely matches the average composition of chondrules determined by instrumental neutron activation analysis (INAA) if some Fe-metal is added to the chondrule composition. Measured matrix compositions are not CI-like. Sampling bias and secondary redistribution of elements may have played a role, but the best explanation is that ∼10-30% of refractory-rich, volatile depleted material was added to matrix.If most of the more volatile elements are in a CI-dominated matrix, the major and volatile element fractionations must be largely carried by chondrules. There is both direct and indirect evidence for evaporation during chondrule formation. Type IIA and type B chondrules could have formed from a mixture of CI material and material evaporated from type IA chondrules. The Mg-SiFe fractionations in the ordinary chondrites can be reproduced with the loss of type IA chondrule material and associated metal. The loss of evaporated material from the chondrules could explain the volatile element fractionations. Mechanisms for how these fractionations occurred are necessarily speculative, but two possibilities are briefly explored.

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Section: Evaporation Condensation and The Formation Of Chondrule Rimsmentioning

confidence: 99%

Re-examining the role of chondrules in producing the elemental fractionations in chondrites

Alexander¹

2005

Meteoritics &Amp; Planetary Science

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“…The volatilization of fluorine from silicate melts has been investigated by several workers using weight loss and/or bulk chemical analysis techniques [6][7][8][9] and the present study uses the relatively high volatility of fluorine in melts in the Na20-AI203-SiO 2 system to investigate fluorine diffusion in these silicate melts. This system was chosen because the structure and physical properties of melts in the base system has been investigated by various workers [10][11][12][13][14] and the normative compositions of many fluorine-rich igneous melts containing greater than 50 mole % of feldspars + feldspathoids are well-represented by this system.…”

Section: Introductionmentioning

confidence: 99%

Chemical diffusion of fluorine in melts in the system Na2OAl2O3SiO2

Dingwell

Scarfe

1985

Earth and Planetary Science Letters

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The volatilization of fluorine from three melts in the system Na20-A1203-SiO 2 has been investigated at 1 atm pressure and 1200-1400°C. The melts chosen have base compositions corresponding to albite, jadeite and a peraluminous melt with 75 mole % SiO 2. Melt spheres were suspended from platinum loops in a vertical tube furnace in a flow of oxygen gas, then quenched, sectioned and analysed by electron microprobe. The microprobe scans indicate that transport of fluorine to the melt-vapor interface is by binary, concentration-independent interdiffusion of fluorine and oxygen. F-O interdiffusivity increases in the order albite < peraluminous

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“…Calcium in peraluminous melts will be involved in a similar substitution, Ca 0.5 AlO 2 = SiO 2 . Energetically, the alkali aluminate substitution is favored over the Ca aluminate (Navrotsky et al 1982;Roy and Navrotsky 1984). Thus, as the alkalis recondense they are likely to displace the Ca on the Al bonded sites, perhaps promoting the crystallization of CPX and, therefore, explaining the rough inverse correlation between Ca/Al and Na/Al ratios in the chondrule mesostases (Fig.…”

Section: The Elemental Compositions Of Chondrule Mesostasesmentioning

confidence: 99%

Alkali elemental and potassium isotopic compositions of Semarkona chondrules

Alexander

Grossman

2005

Meteoritics &Amp; Planetary Science

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Nevertheless, based on Na CPX-mesostasis distribution coefficients, the alkali contents of the cores of most chondrules in Semarkona were probably established at the time of final crystallization. However, Na CPX-mesostasis distribution coefficients also show that alkali zonation in type I Semarkona chondrules was produced by entry of alkalis after solidification, probably during parent body alteration. This alkali metasomatism may have gone to completion in some chondrules. Our preferred explanation for the lack of systematic isotopic enrichments, even in alkali depleted type I chondrule cores, is that they exchanged with the ambient gas as they cooled.

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A thermochemical study of glasses and crystals along the joins silica-calcium aluminate and silica-sodium aluminate

Cited by 156 publications

References 18 publications

Re-examining the role of chondrules in producing the elemental fractionations in chondrites

Re-examining the role of chondrules in producing the elemental fractionations in chondrites

Chemical diffusion of fluorine in melts in the system Na2OAl2O3SiO2

Alkali elemental and potassium isotopic compositions of Semarkona chondrules

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