Hydrothermal synthesis and mineralogy of the alkali amphiboles
The mineralogy of the alkali amphiboles is reviewed., Various suggestions are put forward to rationalise the nomenclature of these minerals. Several alkali amphibole compositions have been successfully synthesized for the first tine using hydrothermal synthesis techniques. The compositions of these...
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| Format: | Thesis |
| Language: | unknown |
| Published: |
1973
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| Online Access: | http://etheses.dur.ac.uk/8199/ http://etheses.dur.ac.uk/8199/1/8199_5199.PDF |
| Summary: | The mineralogy of the alkali amphiboles is reviewed., Various suggestions are put forward to rationalise the nomenclature of these minerals. Several alkali amphibole compositions have been successfully synthesized for the first tine using hydrothermal synthesis techniques. The compositions of these minerals correspond to richterite-K, eckermannite-K and sundiusite-K". In addition five amphiboles of intermediate composition have been synthesized. Two of these minerals have compositions between richterite and tremolite indicating only partial 'A' site occupation. Attempts to synthesize- amphiboles of miyashiroite-K composition have failed to yield amphibole and the condensed product is a phyllosilicate. A survey of all the available alkali amphibole analyses has revealed only two possible miscibility gaps in the alkali amphiboles, one in the area of the miyashiroite composition and the other in the ferroeckerraannite field. Many of the analyses in the literature are of a suspect quality and various suggestions have been made to decide on the quality of an analysis. A method of representing alkali amphiboles of intermediate composition has been found by using the substitutions in the Y sites which are balanced by substitutions in the 2 and X sites. This method has revealed that there is complete solid solution between riebeckite and arfvedsonite, magnesioarfvedsonite and magnesioriebeckite, and richterite and eckermannite. A suggested nomenclature fbr these compositions has also been proposed. Alkali amphiboles from the celebrated nepheline syenite ofXIlimaussaq, S.W. Greenland have been analysed and these analyses reveal a compositional trend from close to katophorite to arfvedsonite. Electron microprobe analyses of alkali amphiboles from the saturated rocks of Tugtutoq, S.W. Greenland show a trend in compositions from ferrorichterite to riebeckite-arfvedsonite. XArfvedsonites from the late-stage lujavrites of Ilimaussaq contain high concentrations of potassium. This element has been shown to be exchanged between ... |
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