. Bulletin of the British Museum (Natural History), Mineralogy. PETROLOGICAL STUDIES IN GLEN URQUHART, INVERNESS-SHIRE 135 six plus quartz instead of four plus quartz (cf. parageneses of Table II). The relationships between plagioclase and " epidote " and between diopside and actino- lite have been considered above.^ Muscovite and biotite are also, of course, pro- jections into the ACFK plot from a system containing water, but they have no corresponding anhydrous minerals to pair with as have " epidote " (anorthite) and actinolite (diopside). microcline. muscovite calc
. Bulletin of the British Museum (Natural History), Mineralogy. PETROLOGICAL STUDIES IN GLEN URQUHART, INVERNESS-SHIRE 135 six plus quartz instead of four plus quartz (cf. parageneses of Table II). The relationships between plagioclase and " epidote " and between diopside and actino- lite have been considered above.^ Muscovite and biotite are also, of course, pro- jections into the ACFK plot from a system containing water, but they have no corresponding anhydrous minerals to pair with as have " epidote " (anorthite) and actinolite (diopside). microcline. muscovite calclte Fig. 5. The ACFK tetrahedron for rocks with excess siUca in the lower part of the amphibohte facies. The field of limestones and skarns in the ACF diagram involves the three phases : ct-" an "-" di ". The same field in the ACK diagram (Text-fig. 3) and the FCK diagram (Text-fig 4) is in each case a quadrilateral, which can, for phase rule purposes, be split into two triangular fields. Moreover, in each plot there are two possible ways of dividing the appropriate quadrilateral, indicating that the alternative parageneses are in crossed relationship. Thus, in the ACK diagram the quadrilateral is: ct-" an "-mu-mic, which can be divided according to Stability A into [ct- " an "-mu] and [ct-mic-mu] by the two-phase join ct-mu, or according to Stability B into [ct-" an "-mic] and [" an"-mu-mic] by the join " an "-mic. Similarly, for the FCK diagram the quadrilateral is ct-" di "-phlog-mic, which can be divided ^ For the purpose of representing theoretical assemblages in this discussion " an " is used to represent plagioclase or " epidote " or both, " di " is used to represent diopside or a calciferous amphibole or both. The remaining minerals are represented by the abbreviations of Table Please note that these images are extracted from scanned page images that may ha
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