Klyuchevskoy Volcano, Kamchatka, Russia: The Role of High-Flux Recharged, Tapped, and Fractionated Magma Chamber(s) in the Genesis of High-Al2O3 from High-MgO Basalt   总被引：1，自引：0，他引：1  

KERSTING  ANNIE B.; ARCULUS  RICHARD J. 《Journal of Petrology》1994,35(1):1-41

Mineral Chemistry, and major and trace element variations ofthe basalts from Klyuchevskoy, the world's most active islandare volcano, are most consistently explained by the persistenceof a non-steady state, erupting, recharging, and fractionatingmagma chamber in which fractionation of a parental high-MgObasalt melt produces high-Al₂O₃ basalt. Although fractionalcrystallization is the dominant controlling mechanism, periodicrecharge with a more primitive high-MgO basalt is also an importantprocess contributing to the chemical evolution of the magmas.Hybrid basalts are the mixed product of high-Al₂O₃ basalt rechargedwith high-MgO basalt. The lavas range in composition from high-MgO, low-Al₂O₃ ( 12wt. % MgO, 14 wt. % Al₂O₃) to high-Al₂O₃, low-MgO ( 18 wt. %Al₂O₃, 4 wt. % MgO). The high-MgO lavas are characterized byphenocrysts of olivine (cores FO_90–80 and rims FO_85–75)with chromite inclusions [Cr/(Cr + Al)0.7], clinopyroxene (Wo_46–42En_48–42Fs_15–7),and the rare occurrence of orthopyroxene (En_72–70). Allthe phenocrysts are normally zoned and set in a groundmass ofplagioclase, pigeonite, clinopyroxene, magnetite, orthopyroxene.The high-Al₂O₃ basalts contain plagioclase (An_85–55),olivine (Fo_80–65), clinopyroxene (Wo_45–30En_50–38Fs_23–11), orthopyroxene (En_72–70) phenocrysts, that preserve bothnormal and reverse zoning in a groundmass of plagioclase, pigeonite,olivine, clinopyroxene, magnetite, orthopyroxene. Hybrid basaltshave characteristics of both high-MgO basalts and high-Al₂O₃basalts and preserve complicated normal-to-reverse, reverse-to-normal,and normally zoned phenocrysts. No hydrous minerals are presentin any of the lavas. The varied basaltic magmas erupted from Klyuchevskoy are derivedfrom a magma chamber(s) located near the base of the Kamchatkacrust (pressures 0.5–0.9 GPa) and characterized by relativelyhigh crystallization temperatures, some in excess of 1150C.Under these conditions, the fractionation of a parental high-MgOmagma, produced principally from the melting of a fluid-fluxed,peridotitic mantle wedge, results in the production of a chemicallydiverse spectrum of basalts ranging from high-MgO, low-Al₂O₃to high-Al₂O₃, low-MgO basalt, traversing the relatively primitiveend of both the calc-alkalic and tholeiitic differentiationtrends.  相似文献