Structure and Dynamics of a Silicic Magmatic System Associated with Caldera-Forming Eruptions at Batur Volcanic Field, Bali, Indonesia   总被引：1，自引：1，他引：1  

REUBI  O.; NICHOLLS  I. A. 《Journal of Petrology》2005,46(7):1367-1391

The Batur volcanic field (BVF), in Bali, Indonesia, underwenttwo successive caldera-forming eruptions that resulted in thedeposition of silicic ignimbrites. The magmas erupted duringand between these eruptions show a broad range of compositionsfrom low-SiO₂ andesite to high-SiO₂ dacite. On the basis oftheir geochemistry and mineralogy these magmas may be assignedto six groups: (1) homogeneous andesites with phenocryst compositionsessentially in equilibrium with the whole-rock composition;(2) remobilized crystal-rich low-SiO₂ andesites with resorbedphenocrysts in equilibrium with the whole-rock composition;(3) mixed low-SiO₂ dacite with a relatively large range of phenocrystcompositions, with most phenocrysts slightly too evolved tobe in equilibrium with the whole-rock; (4) extensively mixedlow-SiO₂ dacites with a very large and discontinuous range ofphenocryst compositions, with most phenocrysts either more Mg-richor more evolved than the equilibrium compositions; (5) remobilizedcrystal-rich low-SiO₂ dacites with resorbed and euhedral phenocrysts;(6) homogeneous high-SiO₂ dacites lacking evidence for magmamixing and showing narrow ranges of phenocryst compositionsin equilibrium with the whole-rock composition. This range ofsilicic magmas is interpreted to reflect a combination of closed-and open-system fractional crystallization, magma mixing andremobilization of cumulate piles by heating. The variety ofmagmas erupted simultaneously during the caldera-forming eruptionssuggests that the magmatic system consisted of several independentreservoirs of variable composition and degree of crystallization.The magmatic evolution of individual reservoirs varied fromclosed-system fractional crystallization to fully open-systemevolution, thereby resulting in simultaneous production of magmaswith contrasted compositions and mineralogy. Extensive emptyingof the magmatic system during the caldera-forming eruptionsled to successive or simultaneous eruption of several reservoirs. KEY WORDS: caldera; ignimbrite; magmatic chambers; magma mixing; petrology; Sunda Arc  相似文献