INGEOSUR   20376
INSTITUTO GEOLOGICO DEL SUR
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Zeolite assemblages in Paleogene basalts of Mallín Ahogado, Northern Patagonian Andes, Neuquén, Argentina.
Autor/es:
MARÍA FLORENCIA GARGIULO Y MARÍA ELENA VATTUONE
Lugar:
París, Francia.
Reunión:
Conferencia; 4th International Federation of European Zeolite Associations (FEZA) Conference; 2008
Institución organizadora:
The French Zeolite Group; Université Pierre et Marie Curie; Federation of European Zeolite Associations (FEZA).
Resumen:
Alkaline zeolite assemblage of mordenite, chabazite, heulandita, natrolite and analcime was found in amygdales and veins of basaltic rocks and as the cement in their breccias at the top level of Ventana Formation. The outcrops are located in the surroundings of Nahuel Huapi lake, Northern Patagonian Andes, Neuquén, Argentina (41°02’14” L.S.; 71°12’55” W.L. and 41°02’42” S.L.;  71°13’56” W.L.). The age of Ventana Formation is Paleocene-Oligocene. Other secondary minerals as hematite, pumpellyite, chlorite/smectite mixed-layer, white mica and chalcedony have also crystallized in amygdales and veins. The primary and relictic minerals in these rocks are: fresh clinopyroxene and lamprobolita, altered plagioclase, scarce and altered olivine and magnetite. The microphenocrystals of plagioclase and olivine are partially or totally replaced by other secondary minerals as pumpellyite, laumontite, albite, chlorite/smectite mixer-layer, hematite and iddingsite. The zeolites were recognized by their morphology and optical properties and by XRD, SEM and EDS methods. The assemblage of laumontite + pumpellyite + albite + C/S mixed-layer is typical of the zeolites facies and indicates that the highest temperature reached was between 200° and 260ºC. In amygdales and cement of the breccias, mordenite, chabazite, heulandite, natrolite, and analcime (+ white mica ± smectite) crystallized, suggesting that the temperature was lower than 200ºC. The aCO2 of the system was variable and became more important at the final stage of the crystallization sequence when has only crystallized massive calcite. The presence of hematite indicates a system with high ƒO2 condition.