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Global Volcanism Program | Image GVP-07840

The rock around the Almolonga volcano Zunil geothermal field on the SE flank of Cerro Quemado volcano is extensively hydrothermally altered. The geothermal area is located along the Zunil fault zone, which juxtaposes brownish-red weathered to lightly altered andesite to dacite lava flows with white-to-pink heavily altered and brecciated volcanic rock. Hydrothermal alteration minerals include kaolinite, pyrite, gypsum, and alunite. The NE-SW-trending left-lateral fault zone runs parallel to the valley of the Río Samalá. Photo by Bill Rose, 1981 (Michigan Technological University).

The rock around the Almolonga volcano Zunil geothermal field on the SE flank of Cerro Quemado volcano is extensively hydrothermally altered. The geothermal area is located along the Zunil fault zone, which juxtaposes brownish-red weathered to lightly altered andesite to dacite lava flows with white-to-pink heavily altered and brecciated volcanic rock. Hydrothermal alteration minerals include kaolinite, pyrite, gypsum, and alunite. The NE-SW-trending left-lateral fault zone runs parallel to the valley of the Río Samalá.

Photo by Bill Rose, 1981 (Michigan Technological University).

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Keywords: geothermal | hydrothermal alteration | exposure | stratigraphy


Almolonga