The Taupo Volcanic Zone in New Zealand and the Philippine Mobile Belt in the Philippines are characterized by active
subduction, active volcanism and high seismicity. The main factors affecting characteristics of geothermal systems in both
countries are: tectonic setting, source magmas, maturity of the systems, and depth to the degassing magma body. Within
New Zealand, geothermal systems are grouped into arc- and rift-type. Fluids in arc-type systems contain high amounts of
volatiles (<20%), with high c02 cl, co2 he, and n2 ar ratios. mantle-type volatiles predominate in rift-type systems.>
Philippine geothermal systems are largely arc-type, the topography is rugged, leading to the separation of water and vapor
upflows, as opposed to the overlap found in New Zealand. The relatively shallow depths of degassing magma bodies in
the Philippines results in steeper geochemical gradients, leading to higher proportions of arc-type magmatic water (>40%)
and higher Cl contents (3,000-10,000 mg/kg). Maximum temperatures are also higher, reaching up to >400C. Arc-type
alteration assemblages in New Zealand and the Philippines are similar. Because Philippine geothermal systems are less
mature, have higher temperatures and steeper geochemical gradients than New Zealand ones, advanced argillization is more
widespread occurring down to depths of 2000 m. Mineral phases are more varied due to the active input of magmatic
waters and the formation of vapor conditions at depth, forming P04-, B-, Li-, Ce-, F-, and Cl-bearing minerals at high
temperatures. In the Philippines, high temperature magmatic-hydrothermal to contact metamorphic assemblages containing
biotite, amphiboles and pyroxenes are relatively common, but rare in New Zealand.