Amphiboles from subvolcanic dacitic-rhyolitic blocks of a Tortonian conglomerate in north-east Sicily have been analyzed by microprobe. Analytical results show that different amphibole types are present either of the ferro-magnesian (cummingtonite) or of the calcic group (hornblende and actinolite). Coexisting cummingtonite and hornblende suggest crystallization with solidus intersecting solvus between the two amphibole groups below T + 725-760°C. Growth of actinolite over hornblende is here interpreted as resulting from low temperature incomplete reaction, and disequilibrium, of hornblende in to actinolite because of the low transformation rate
Relazioni Strutturali e composizionali fra cummingtonite, orneblenda ed attinoto coesistenti in porfiriti K-calc-alcaline della Sicilia nord-orientale
CIRRINCIONE, ROSOLINO
1992-01-01
Abstract
Amphiboles from subvolcanic dacitic-rhyolitic blocks of a Tortonian conglomerate in north-east Sicily have been analyzed by microprobe. Analytical results show that different amphibole types are present either of the ferro-magnesian (cummingtonite) or of the calcic group (hornblende and actinolite). Coexisting cummingtonite and hornblende suggest crystallization with solidus intersecting solvus between the two amphibole groups below T + 725-760°C. Growth of actinolite over hornblende is here interpreted as resulting from low temperature incomplete reaction, and disequilibrium, of hornblende in to actinolite because of the low transformation rateI documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
