Layer silicates from a rodingite and its blackwall from Przemi?ów (Lower Silesia, Poland): mineralogical record of metasomatic processes during serpentinization and serpentinite recrystallization

摘要

Minute inclusions of phlogopite and a chlorite-vermiculite intergrade mineral occur in the vesuvianite fromrodingite at Przemi?ów (Lower Silesia). The same inclusions werefound in its blackwall, i.e. outer metasomatic zone formed at theexpense of adjacent ultrabasic rock. These findings demonstratethat potassium was released from the rodingite protolith during theCa-metasomatism that accompanied low-temperatureserpentinization and was consumed by phlogopite formed in therodingite blackwall. Fresh phlogopite persists as small inclusionsin vesuvianite. The abundant phlogopite-derived intergradechlorite-vermiculite in the blackwall documents the potassium-rich composition of the protolith of the rodingite, though itsprimary chemistry is highly modified during metasomaticprocesses. The rodingite blackwall ca be useful as tracer of themetamorphic and tectonic episodes obscured during complexgeological evolution of the ophiolite.