ABSTRACT: Tholeiitic Hydrothermal Systems of the Aleutian Volcanic Arc
John W. Reeder
Shallow tholeiitic magma bodies because of typical high rates of ascent to shallow depths could serve as significant heat sources for large moderate-temperature shallow hydrothermal reservoirs. A 13 km3 shallow water-dominated reservoir at about a 195°C temperature has been discovered in the Makushin Volcano caldera complex of Unalaska Island of the Eastern Aleutian Islands. The volcano is a tholeiitic volcanic center that consists of basalts, andesites, and only traces of dacites. It has been thought previously that silicic volcanic centers would be required as heat sources for such a hydrothermal system.
The northern part of Atka Island is the largest volcanic center for the central Aleutian Islands, which is dominated by two large tholeiitic Holocene stratovolcanoes, Korovin and Mount Kluichef. Mount Kluichef is situated on the NW rim of a Quaternary Kluichef (Atka) caldera. Fumaroles and hot springs are numerous along active tectonic faults that flank the caldera complex, just as there are at Makushin Volcano. A large water-dominated hydrothermal reservoir similar to the Makushin hydrothermal reservoir is now strongly suspected to exist in the Atka caldera complex.
Other tholeiitic volcanic centers in the Aleutian arc as well as in other Circum-Pacific volcanic arc regions might also contain significant hydrothermal reservoirs.
AAPG Search and Discovery Article #90097©1990 Fifth Circum-Pacific Energy and Mineral Resources Conference, Honolulu, Hawaii, July 29-August 3, 1990