Kaipohan: An apparently nonthermal manifestation of hydrothermal systems in the Philippines

Fluid geochemistry and soil gas fluxes (CO2–CH4–H2S) at a promissory Hot Dry Rock Geothermal System: The Acoculco caldera, Mexico

“…1A). Similar characteristics were also reported for some geothermal areas of the Philippines named 'Kaipohans' (Bogie et al 1987). As described later in the Discussion section, they could be a good analog of Los Azufres and Alcaparrosa areas (López-Hernandez et al, 2009).…”

“…As proposed by López-Hernandez et al (2009), Los Azufres and Alcaparrosa locations are similar to some low-temperature geothermal areas in the Philippines, named as 'Kaiophans' by Bogie et al (1987). They consist in areas of advance argillic alteration with nonpermanently flowing cold springs.…”

“…If the gas flux is high enough, the perched aquifer can become saturated in gases. Furthermore, dissolution of H 2 S produces sulfate water with low pH, which lowers the effective solubility of CO 2 and enhances CO 2 migration towards the surface (Bogie et al, 1987). At Los Azufres and Alcaparrosa, the presence of shallow water bodies is evidenced by the chemical and isotopic composition of springs revealing meteoric water recently infiltrated in the subsurface.…”

Hydrothermal activity in the Tulancingo–Acoculco Caldera Complex, central Mexico: Exploratory studies

“…Apparent resistivity distribution in the Acoculco Caldera based on the magnetotelluric (MT) method at 5 s (corresponding to 1200-1500 m depth). Contours in m. referred to as "kaipohans", have occurred in Philippine geothermal fields (Bogie et al, 1987;López-Hernández and Castillo-Hernández, 1997). When well EAC-1 was drilled in this area, many of the workers became disoriented or had trouble breathing because of the release of borehole gases.…”

“…One should note that the gases from New Zealand's kaipohans (Bogie et al, 1987) have a greater magmatic contribution. According Polak et al (1982), the high 3 He/ 4 He ratio (R/R air = 6.3) measured in the gas emissions from the Los Azufres pond suggests a high geothermal potential for this zone.…”