Melt inclusions in Ca-pyroxenes from pyroclasts of several Vesuvius eruptions show that pyroxenes (Wo -En 46–48 -En ) formed in shallow reservoirs from K-basalt 20–25 to Wo and/or K-tephrite to K-phonolite magmas over a wide temperature range (800–1200 °C). The 45–50 50–52 data set reflects the general modalities of magma evolution at Vesuvius, where the highly evolved compositions are generally reached under closed-conduit conditions, forcing magmatic crystallization under increasing activity of dissolved volatiles. These data allow the establish- ment of two empirical geothermometric laws that link temperature either to the equilibrium constant of melt-pyroxene pairs or to a compositional parameter of the melt (e.g., CaO). They are used to reconstruct the thermal and compositional evolution of Vesuvius magmas. This evo- lution is often affected by syneruptive mixing processes in the magma storage zone that alter preeruptive conditions. The method can have general applicability for the definition of empir- ical thermometric laws.
Temperature of Vesuvius magmas / Cioni R.; Marianelli P.; Santacroce R.. - In: GEOLOGY. - ISSN 0091-7613. - STAMPA. - 27:(1999), pp. 443-446. [10.1130/0091-7613(1999)027<0443:TOVM>2.3.CO;2]
Temperature of Vesuvius magmas
Cioni R.
;
1999
Abstract
Melt inclusions in Ca-pyroxenes from pyroclasts of several Vesuvius eruptions show that pyroxenes (Wo -En 46–48 -En ) formed in shallow reservoirs from K-basalt 20–25 to Wo and/or K-tephrite to K-phonolite magmas over a wide temperature range (800–1200 °C). The 45–50 50–52 data set reflects the general modalities of magma evolution at Vesuvius, where the highly evolved compositions are generally reached under closed-conduit conditions, forcing magmatic crystallization under increasing activity of dissolved volatiles. These data allow the establish- ment of two empirical geothermometric laws that link temperature either to the equilibrium constant of melt-pyroxene pairs or to a compositional parameter of the melt (e.g., CaO). They are used to reconstruct the thermal and compositional evolution of Vesuvius magmas. This evo- lution is often affected by syneruptive mixing processes in the magma storage zone that alter preeruptive conditions. The method can have general applicability for the definition of empir- ical thermometric laws.File | Dimensione | Formato | |
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