Search results for "peralkaline magmatism"
showing 2 items of 2 documents
Phase equilibrium constraints on pre-eruptive conditions of recent felsic explosive volcanism at Pantelleria Island, Italy.
2010
International audience; We present experimental phase equilibria carried out on a pantelleritic bulk-rock composition with a peralkalinity index [PI = molar (Na2O + K2O)/Al2O3] = 1*4, which is representative of the most energetic pumice fall eruption of the resurgent post-caldera volcanism on Pantelleria island. For the explored conditions (P = 25-150 MPa; T = 680-800°C; H2Omelt up to 6 wt %; fO2 ≤ NNO, where NNO is nickel-nickel oxide buffer) clinopyroxene is the liquidus phase followed by alkali feldspar and then quartz. The crystallization of amphibole is limited to temperatures below 700°C. Aenigmatite crystallizes near the liquidus for P ≥ 100 MPa. When clinopyroxene is the sole liquid…
Geology and petrochemistry of recent (25 ka) silicic volcanism at Pantelleria Island
2007
built a complex sequence of interfingered deposits emitted by closely spaced eruptive vents which are frequently associated with dome-building phases and pantelleritic lavas flows. Field relationships allowed us to recognize eight eruptive units, all lying above the Montagna Grande trachytes. As a whole, petrochemical characteristics of the erupted products indicate an evolutionary trend in which Na-clinopyroxene was the liquidus phase, followed by alkali feldspar. Amphibole and quartz are late-crystallizing, whereas aenigmatite is both early- and late-crystallizing as well. Aenigmatite and Na-clinopyroxene crystallization buffers efficiently the increase of agpaicity, induced by feldspar c…