Geochemical evidence of magma intrusion inferred from diffuse CO2 emissions and fumarole plume chemistry: the 2010–2011 volcanic unrest at Taal Volcano, Philippines

Abstract

We report herein significant increases in the diffuse CO2 emission through the lake and soils of the Taal Volcano Main Crater (Philippines), during a volcano-seismic unrest period in April 2010–June 2011. Monitoring of CO2 emissions from the Taal Main Crater Lake and soils in the fumarole areas started in 2008 with a collaborative project between ITER and PHIVOLCS. In August 2010, the total diffuse CO2 emission from the Taal Main Crater Lake increased almost three times from a previously measured baseline emission value ∼1,000 t day−1 to 2,716 ± 54 t day−1. This increase occurred during anomalous seismic activity which started in April 2010. The highest CO2 emission value in the crater lake was measured in March 2011 at 4,670 ± 159 t day−1 when the volcano was still showing signs of unrest. Significant changes in the CO2/SO2, CO2/H2O, and SO2/H2S ratios in the fumarole gases suggest the occurrence of a magmatic injection several weeks before the onset of the volcano-seismic unrest period. These observed changes in the CO2 emission rate and the fumarole gas composition as the result of magmatic activity were likely caused by magma moving from a deep reservoir to a shallow reservoir.