Abstract
In the Mt. Franks area of the Willyama Complex, microfabric evidence suggests that the alteration of andalusite to sillimanite has taken place by a process similar to that suggested by Carmichael (1969). Andalusite is pre- to syn-S2 in age. Alteration to "sericite" has resulted in the formation of "sericite" laths, some of which are crenulated about S2, and some which are syn- and post-S2. "Fibrolite" occurs in these andalusite-"sericite" aggregates within the sillimanite zone and is wholly embedded in "sericite". "Fibrolite" is pre- to syn-S2 in age. This evidence is interpreted as suggesting that the formation of sillimanite from andalusite took place via a "sericite" phase. Further microfabric observations are interpreted to imply constant volume for the reaction aluminosilicate → "sericite". This suggests a situation in which Al3+ is relatively mobile but Al4+ is relatively immobile. This suggestion differs from Carmichael's (1969) idea of Al3+ immobility.
Original language | English |
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Pages (from-to) | 97-112 |
Number of pages | 16 |
Journal | Tectonophysics |
Volume | 58 |
Issue number | 1-2 |
DOIs | |
Publication status | Published - 10 Sept 1979 |
Externally published | Yes |