3 TYPES OF BASALT OF THE BASALTIC ANDESIT E MEDVEZHYA CALDERA, ITURUP, SOUTHERN KURIL ISLANDS

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.