A METASTABLE DISEQUILIBRIUM ASSEMBLAGE OF HYDROUS HIGH-SANIDINE ADULARIA + LOW ALBITE FROM LA VIQUITA GRANITIC PEGMATITE, SAN LUIS PROVINCE, ARGENTINA

CERNÝ PETR; GALLISKI, M. A., ; TEERSTRA D.K.,; MARTÍNEZ, V. ; CHAPMAN R.; OTTOLINI L. ; MACBRIDE L.; FERREIRA K.

Mendoza

Simposio; 5th International Symposium on Granitic Pegmatites; 2011

Studies of feldspars in granitic pegmatites are mainly devoted to the primary rock-forming phases.Examination of these early feldspar generations substantially contributes to the understanding ofpegmatite geochemistry, regional and internal fractionation, solidifi cation and cooling conditions. The geochemical signature of feldspars also aids in pegmatite classifi cation and in evaluation of economic potential.We describe an occurrence of highly disordered adularia in La Viquita pegmatite, the infl uence oflate fl uids on its structural state, and its coexistence with a virtually completely ordered albite. Thisis, to the best of our knowledge, the fi rst case of a high-sanidine adularia recognized in Argentina, the first documented hydrous adularia, and the second documented case of metastable coexistence of high sanidine with low albite.