La terre intérieure. Entretiens avec Victor Malka

Gauthier, Joseph D.; Memmi, Albert

doi:10.2307/40133517

Cited by 5 publications

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“…(b) Coexisting biotites and muscovites from two-mica granites of the French Massif Central. (A) Marche Orientale massif (Gauthier, 1974), (I) St Sylvestre massif, and zinnwaldites (*) of Heinrich (1967). The hatched zone (lower right) shows the position of Li-free or Li-poor primary muscovites from two-mica granites (Monier and Robert, 1986a) have very complex compositions owing to additional substitutions involving principally Ti and Fe 3 + in biotites and Ti,Fe 3 § and [7 xu (interlayer vacancy) in muscovites.…”

Section: Comprehensive View Of Experimental Resultsmentioning

confidence: 99%

“…(a) the 'ferrous lithium micas' of Foster (1960); (b ) the 'lithium-iron micas' of Rieder et al (1970); (c) the 'zinnwaldites' of Heinrich (1967); (d) the analyses, on separated minerals, of two sets of coexisting biotites and primary muscovites from granites from the French Massif Central; the first set comes from the Marche orientale massif (Gauthier, 1974) and the second one comes from the two-mica granite of the St Sylvestre massif (Monier, 1985).…”

Section: Comparison With Natural Lithium Micasmentioning

confidence: 99%

“…These leucogranites exhibit important differentiation phenomena up to extremes highly enriched in Na, F, Li, Rb, ... (Ranchin, 1971;Gauthier, 1974;Friedrich, 1984). The crystalchemical characters of their micas evolve with the differentiation of the host rock and lie in a wide range of compositions.…”

Section: Comparison With Natural Lithium Micasmentioning

confidence: 99%

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Evolution of the Miscibility Gap Between Muscovite and Biotite Solid Solutions with Increasing Lithium Content: An Experimental Study in the System K₂O-Li₂O-MgO-FeO-Al₂O₃-SiO₂-H₂O-HF at 600°C, 2 kbar P_H₂O: Comparison with Natural Lithium Micas

Monier

Robert²

1986

Mineral. mag.

110

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ABSTRACT. This paper presents the results of an experimental study of the miscibility gap between trioctahedral and dioctahedral micas in the system K20 Li20-MgOFeO AI203-SiO2-H20-HF at 600~ under 2 kbar Pu2o. The existence of this miscibility gap is known from previous experimental studies. The gap is large in the lithium-free system; its width reduces progressively with increasing Li content; for sufficient Li contents (Li > 0.6 atom per formula unit, based on 11 oxygens), a single Li-mica phase is obtained, intermediate between trioctahedral and dioctahedral micas. Any bulk composition located inside the miscibility gap gives an assemblage of two micas, one of the biotite-type and one of the muscovite-type. All the compositions located outside the gap, and, in particular, those belonging to the joins phlogopite-trilithionite and muscovite-zinnwaldite (or its magnesian equivalent) give a single mica phase, provided that the fluorine content is sufficient. The ratio Li/F ~ 1 is a convenient suitable value. The types of micas and the evolutions of their compositions are well characterized by their interplanar distance do6 o. These experimental results allow the interpretation of most compositions of naturally occurring lithium micas, in the range 0 ~< Li ~< 1 a./f.u. Natural micas of biotite-type and muscovite-type are located on both sides of the miscibility gap and their compositions get closer with increasing Li content.

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Section: Comprehensive View Of Experimental Resultsmentioning

confidence: 99%

Section: Comparison With Natural Lithium Micasmentioning

confidence: 99%