Phlogopite synthesis and stability range

摘要: Abstract A hydroxyl-bearing phlogopite has been synthesized and its upper stability limit determined up to 75,000 psi water vapour pressure. Above the stable phases are forsterite + leucite orthorhombic KAlSiO4 vapour. At lowest temperatures investigated mica grows quickly as randomly stacked one-layer monoclinic (1Md). higher or with longer runs orders either a (1M) three-layer trigonal (3T) polymorph. It is not possible distinguish 1M 3T polymorphs by means of powder X-ray diffraction patterns; however, two-layer (2M) easily identified. The small size synthetic crystals prohibited identification their polymorphic form optical methods single-crystal studies. range two natural phlogopites in accord that phlogopite. transformation 2M was accomplished; ranges could be fixed because sluggish nature transformations character recrystallization. behaviour igneous rocks high low silica accounted for relation curve minimum melting curves “granite” “basalt.” trioctahedral clay micas identified structurally IMd micas. completely disordered produced synthetically subsequent ordering well illustrate observed stages authigenic growth or, conversely, weathering