Details

Autor(en) / Beteiligte

• Giorgetti, G.
• Monecke, T.
• Kleeberg, R.
• Herzig, P. M.

Titel

Intermediate sodium?potassium mica in hydrothermally altered rocks of the Waterloo deposit, Australia: a combined SEM-EMP-XRD-TEM study

Ist Teil von

• Contributions to mineralogy and petrology, 2003-11, Vol.146 (2), p.159-173

Ort / Verlag

Heidelberg: Springer Nature B.V

Erscheinungsjahr

2003

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Metastable intermediate Na-K mica represents a product of hydrothermal alteration in volcanic rocks from the alteration halo of the Waterloo massive sulfide deposit, Australia. The XRD pattern of this solid solution between paragonite and muscovite is characterized by a rational series of basal reflections with d values intermediate between the end members. Transmission electron microscopy revealed that the intermediate Na-K mica forms thick stacks that belong to a two-layer polytype. Na-rich intermediate Na-K mica typically occurs together with paragonite whereas K-rich intermediate Na-K mica is intergrown with muscovite. The intermediate Na-K mica is interpreted to have formed as a result of the incomplete transformation of K-rich mica to Na-rich mica through dissolution and recrystallization processes driven by compositional changes of the hydrothermal fluids interacting with the volcanic rocks. Alteration must have proceeded under non-equilibrium conditions because the composition of the solid solution falls into the miscibility gap separating paragonite and muscovite. [PUBLICATION ABSTRACT]