MAJOR ELEMENT, SULFUR AND CHLORINE COMPOSITIONS OF OLIVINE-HOSTED MELT INCLUSIONS FROM MAYON VOLCANO, PHILIPPINES

Mayon Volcano is one of the most active volcanoes in the Philippine archipelago. This stratovolcano has erupted 49 times since its first recorded eruption in 1616. Mayon exhibits a wide range of eruptive styles including powerful volcanic activity and thus presents potentially serious hazards to the almost 900,000 people living around the volcano. We have analyzed olivine-hosted melt inclusions from tephra deposits erupted from Mayon’s central vent and from two of its parasitic cinder cones for major elements, S, and Cl. The melt inclusions contain 900 – 3300 ppm and 500 – 1300 ppm of S and Cl, respectively. These elevated values reflect their subduction zone origin. Melt inclusions from the central vent lavas have consistently higher S and Cl contents than those from cinder cone lavas. The S and Cl contents of melt inclusions from the 1897 eruption are notably high which suggest that elevated volatile contents may be responsible for its unusual explosivity. Although not obvious from whole rock data, combined major and volatile compositions of the olivine-hosted melt inclusions indicate that the more-evolved central vent andesitic lavas could originate from basaltic parents similar to those erupted from the parasitic cinder cones.