Details

Autor(en) / Beteiligte

• Hövelmann, Jörn
• Putnis, Andrew
• Geisler, Thorsten
• Schmidt, Burkhard C.
• Golla-Schindler, Ute

Titel

The replacement of plagioclase feldspars by albite: observations from hydrothermal experiments

Ist Teil von

• Contributions to mineralogy and petrology, 2010, Vol.159 (1), p.43-59

Ort / Verlag

Berlin/Heidelberg: Springer-Verlag

Erscheinungsjahr

2010

Link zum Volltext

Quelle

SpringerLink

Beschreibungen/Notizen

• Oligoclase and labradorite crystals have been experimentally replaced by albite in an aqueous sodium silicate solution at 600°C and 2 kbars. The replacement is pseudomorphic and is characterised by a sharp chemical interface which progresses through the feldspar while preserving the crystallographic orientation. Reaction rims of albite, up to 50 μm thick, can be readily achieved within 14 days. Re-equilibration of plagioclase in an 18 O-enriched sodium- and silica-bearing solution results in oxygen isotope redistribution within the feldspar framework structure. The observed characteristics of the reaction products are similar to naturally albitised plagioclase and are indicative of an interface-coupled dissolution–reprecipitation mechanism. Chemical analyses demonstrate that the albitisation is accompanied by the mobilisation of major, minor and trace elements also including elements such as Al and Ti which are commonly regarded as immobile during hydrothermal alteration. The results contribute to developing our understanding of the close association between large-scale albitisation and secondary ore mineralisation which is common in nature.