Over the last 42 ka, volcanic activity at Lipari Island (Aeolian Arc, Italy) produced lava domes, flows and pyroclastic deposits with rhyolitic composition, showing in many cases evidence of magma mixing such as latitic enclaves and banding. In this same period, on nearby Vulcano Island, similar rhyolitic lava domes, pyroclastic products and lava flows, ranging in composition from shoshonite to rhyolite, were erupted. As a whole, the post-42 ka products of Lipari and Vulcano show geochemical variations with time, which are well correlated between the two islands and may correspond to a modification of the primary magmas. The rhyolitic products are similar to each other in their major elements composition, but differ in their trace element abundances (e.g. La ranging from 40 to 78 ppm for SiO2 close to 75 wt%). Their isotopic composition is variable, too. The 87Sr/86Sr (0.704723–0.705992) and 143Nd/144Nd (0.512575–0.512526) ranges partially overlap those of the more mafic products (latites), having 87Sr/86Sr from 0.7044 to 0.7047 and 143Nd/144Nd from 0.512672 to 0.512615. 206Pb/204Pb is 19.390–19.450 in latites and 19.350–19.380 in rhyolites. Crystal fractionation and crustal assimilation processes of andesitic to latitic melts, showing an increasing content in incompatible elements in time, may explain the genesis of the different rhyolitic magmas. The rocks of the local crustal basement assimilated may correspond to lithotypes present in the Calabrian Arc. Mixing and mingling processes between latitic and rhyolitic magmas that are not genetically related occur during most of the eruptions. The alignment of vents related to the volcanic activity of the last 40 ka corresponds to the NNW–SSE Tindari–Letojanni strike-slip fault and to the correlated N–S extensional fault system. The mafic magmas erupted along these different directions display evidence of an evolution at different PH2O conditions. This suggests that the Tindari–Letojanni fault played a relevant role in the ascent, storage and diversification of magmas during the recent volcanic activity.
Petrology of the post-40 ka products in the Vulcano-Lipari volcanic complex (Aeolian Islands, Italy): an example of volcanism controlled by tectonics
GIONCADA, ANNA;MAZZUOLI, ROBERTO;
2003-01-01
Abstract
Over the last 42 ka, volcanic activity at Lipari Island (Aeolian Arc, Italy) produced lava domes, flows and pyroclastic deposits with rhyolitic composition, showing in many cases evidence of magma mixing such as latitic enclaves and banding. In this same period, on nearby Vulcano Island, similar rhyolitic lava domes, pyroclastic products and lava flows, ranging in composition from shoshonite to rhyolite, were erupted. As a whole, the post-42 ka products of Lipari and Vulcano show geochemical variations with time, which are well correlated between the two islands and may correspond to a modification of the primary magmas. The rhyolitic products are similar to each other in their major elements composition, but differ in their trace element abundances (e.g. La ranging from 40 to 78 ppm for SiO2 close to 75 wt%). Their isotopic composition is variable, too. The 87Sr/86Sr (0.704723–0.705992) and 143Nd/144Nd (0.512575–0.512526) ranges partially overlap those of the more mafic products (latites), having 87Sr/86Sr from 0.7044 to 0.7047 and 143Nd/144Nd from 0.512672 to 0.512615. 206Pb/204Pb is 19.390–19.450 in latites and 19.350–19.380 in rhyolites. Crystal fractionation and crustal assimilation processes of andesitic to latitic melts, showing an increasing content in incompatible elements in time, may explain the genesis of the different rhyolitic magmas. The rocks of the local crustal basement assimilated may correspond to lithotypes present in the Calabrian Arc. Mixing and mingling processes between latitic and rhyolitic magmas that are not genetically related occur during most of the eruptions. The alignment of vents related to the volcanic activity of the last 40 ka corresponds to the NNW–SSE Tindari–Letojanni strike-slip fault and to the correlated N–S extensional fault system. The mafic magmas erupted along these different directions display evidence of an evolution at different PH2O conditions. This suggests that the Tindari–Letojanni fault played a relevant role in the ascent, storage and diversification of magmas during the recent volcanic activity.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
