POLLUCITE IN SWEDEN - OCCURRENCES, CRYSTAL-CHEMISTRY, PETROLOGY AND SUBSOLIDUS HISTORY

Pollucite is known from three highly fractionated peraluminous pegmati tes in the Swedish Svecokarelides at Varutrask, Uto, and Akerberg. At all three localities, it was penetrated by several generations of feld spar-, mica- and quartz-bearing veins, replaced by (K,Rb)-feldspar, an d subsequently argillized. The primary homogeneous pollucite has a uni form composition close to Poll(80)Anal(20) with Si/Al from 2.4 to 2.5. The pollucite underwent breakdown into Cs,Al- and Na,Si-enriched bleb s, crosscut by several generations of Cs,Al-rich pollucite veinlets (/- quartz), locally flanked by diffuse Na,Si-enrichment. Late-stage hy drothermal fluids generated (K,Rb)-feldspar and forced analcimization by cation exchange along fractures and vein surfaces.