Melt inclusions were studied in olivine, plagioclase, and orthopyroxen
e from nine basaltic andesite samples collected on young cones of the
Medvezh'ya caldera on Iturup Island, southern Kuril Archipelago. Melts
of the inclusions were classified into three types: (I) magnesian bas
alt (47-49% SiO2, 10.4-5.0% MgO, 0.3% K2O) was detected in inclusions
in olivine and anorthite; (II) highly potassic dacite (64-69% SiO2, 0.
7-1.4% MgO, 5.4-6.8% K2O), in inclusions in plagioclase (An 83-71) fro
m the youngest lava flows of the Kudryavyi cone; and (III) the most ab
undant inclusions, which occur in medium-potassic dacite melt (67-42%
SiO2, 0.7-1.4% MgO, 1.2-2.0% K2O), in plagioclase (An 72-58) in all of
the examined samples and in orthopyroxene. The melt of type I is much
higher in S (0.12 wt %) than the other melts (0.03-0.04 wt %). The ba
salt melt is also rich in Cl (0.12 wt %), whereas the dacite melts var
y broadly in Cl contents: from 0.02 wt % in type II to 0.16 wt % in ty
pe III. The melts are similar in low water contents (<1 wt %). The hom
ogenization temperatures of the melts are as follows: 1200-1300 degree
s C for type I, 1160-1170 degrees C for type II, and 1070-1170 degrees
C for type III.