Search results for "Alkaline magmas"
showing 3 items of 3 documents
Water solubility in trachytic and pantelleritic melts: an experimental study
2021
International audience; Solubility experiments were performed on a trachyte and a pantellerite from Pantelleria. The trachyte has SiO 2 = 65.2 wt%, Al 2 O 3 = 15.2 wt% and a peralkaline index (P.I. = molar[(Na 2 O + K 2 O)/Al 2 O 3 ]) ∼ 1 while the pantellerite has SiO 2 = 72.2 wt%, Al 2 O 3 = 11 wt% and a P.I. = 1.3. Solubility experiments were performed in the pressure range of 50-300 MPa at T = 950°C for the trachyte and 50-200 MPa at T = 850°C for the pantellerite. The water content of experimental glasses was determined by Karl Fischer titration, elemental analyser and FT-IR spectroscopy. Water content appears similar in both compositions for analogous pressure conditions, varying from…
Experimental and thermodynamic constraints on mineral equilibrium inpantelleritic magmas
2020
Abstract Crystallization experiments on two pantellerites from Pantelleria, Italy, provide new evidence for the relationships between mineral phases in pantelleritic rocks as well as the influence of temperature and redox conditions on mineral assemblages. Experiments were performed at 1 kbar with temperature ranging between 750–900°C, and fluid saturation conditions with XH2O (=H2O/H2O+CO2) between 0 and 1. Redox conditions were fixed at, or slightly below, the FMQ buffer. Results show that at temperature of 900 °C pantelleritic magmas are well above the liquidus regardless their water content; we also observed a decrease in liquidus temperature (800°C) with increasingly reducing condition…
A revision of the structure and stratigraphy of pre-Green Tuff ignimbrites at Pantelleria (Strait of Sicily)
2013
International audience; At Pantelleria, peralkaline silicic magmas were erupted across a range of eruptive typologies and magnitudes: pyroclastic flows, Plinian to strombolian pumice fallout and lava flows. In this paper we focus on the intermediate cycle of eruptive activity which is bracketed by ignimbrite units slightly older than the two caldera collapses which marked the volcanological activity of the island. This age interval (180-85 ka) was punctuated by six ignimbrite-forming eruptions (silicic and variably peralkaline) for a cumulative erupted magma volume of approximately 6 km3 dense rock equivalent. Based on new 40Ar/39Ar (Na,K)-feldspar ages and petrographic data, we propose an …