The Pizzo-Sopra-la-Fossa tuff cone of Stromboli volcano has been investigated by stratigraphic, petrographic, mineralogical, geochemical and isotopic studies. Its deposits are presently the remnant of a collapsed tuff cone formed by a thick pyroclastic sequence of bomb, lapilli and ash fallout and surge levels. The main outcrop is located above the active craters where acid fumarolic gases strongly altered the juvenile clasts. For this reason, the Pizzo-Sopra-la-Fossa sequence was poorly studied, although it represents a key point for recognising the recent evolution of Stromboli. We mainly focused our studies on Le-Croci outcrops characterized by a 6 meters thick sequence of mainly unaltered fall deposits. Two groups of feeding magmas have been identified, a group constituted by high-K basalts to high-K basaltic- andesites (Pizzo-HKCA) and another formed by shoshonitic basalts (Pizzo-SHO). The two groups can be distinguished on the bases of petrographic, mineralogical and geochemical data. Pizzo-HKCA products have lower phenocryst contents, incompatible trace element abundances and Sr isotopic ratios, with higher 143Nd/144Nd values than Pizzo-SHO. They also show differences in mineral phase composition and zoning. There are also clear evidences that the two magmas were erupted contemporaneously, suggesting the presence of two distinct magma reservoirs, possibly located at different depth. Based on crucial stratigraphic correlations (S.Bartolo- lavas, Lower-Sequence and Post-Pizzo-series), it has been recognised that this dual explosive activity on top of Stromboli, forming the Pizzo-Sopra-la-Fossa tuff cone, occurred only 2 ka ago (during Roman-age), possibly along the activation of NE-trending eruptive fractures.
Dual explosive activity revealed by petrochemical and mineralogical data on tephra: peculiar Roman-age eruptions of Stromboli volcano / L. FRANCALANCI; E. BRASCHI; S. DI SALVO; F. LUCCHI; C.M. PETRONE. - In: MINERALOGICAL MAGAZINE. - ISSN 0026-461X. - STAMPA. - 77:(2013), pp. 1102-1102. (Intervento presentato al convegno Goldschmidt 2013 Conference tenutosi a Firenze (Italia) nel 25-30 Agosto 2013).
Dual explosive activity revealed by petrochemical and mineralogical data on tephra: peculiar Roman-age eruptions of Stromboli volcano
FRANCALANCI, LORELLA;BRASCHI, ELEONORA;
2013
Abstract
The Pizzo-Sopra-la-Fossa tuff cone of Stromboli volcano has been investigated by stratigraphic, petrographic, mineralogical, geochemical and isotopic studies. Its deposits are presently the remnant of a collapsed tuff cone formed by a thick pyroclastic sequence of bomb, lapilli and ash fallout and surge levels. The main outcrop is located above the active craters where acid fumarolic gases strongly altered the juvenile clasts. For this reason, the Pizzo-Sopra-la-Fossa sequence was poorly studied, although it represents a key point for recognising the recent evolution of Stromboli. We mainly focused our studies on Le-Croci outcrops characterized by a 6 meters thick sequence of mainly unaltered fall deposits. Two groups of feeding magmas have been identified, a group constituted by high-K basalts to high-K basaltic- andesites (Pizzo-HKCA) and another formed by shoshonitic basalts (Pizzo-SHO). The two groups can be distinguished on the bases of petrographic, mineralogical and geochemical data. Pizzo-HKCA products have lower phenocryst contents, incompatible trace element abundances and Sr isotopic ratios, with higher 143Nd/144Nd values than Pizzo-SHO. They also show differences in mineral phase composition and zoning. There are also clear evidences that the two magmas were erupted contemporaneously, suggesting the presence of two distinct magma reservoirs, possibly located at different depth. Based on crucial stratigraphic correlations (S.Bartolo- lavas, Lower-Sequence and Post-Pizzo-series), it has been recognised that this dual explosive activity on top of Stromboli, forming the Pizzo-Sopra-la-Fossa tuff cone, occurred only 2 ka ago (during Roman-age), possibly along the activation of NE-trending eruptive fractures.I documenti in FLORE sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.