Noble Gases From Honduras Geothermal Sites

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Journal Article: Noble Gases From Honduras Geothermal Sites

The elemental and isotopic composition of noble gases in hot springs and geothermal test wells were determined as part of a collaborative project to evaluate the potential for geothermal development in Honduras, Central America. The relative abundances of the noble gases in samples from the test wells indicate recharge temperatures for the geothermal systems equivalent to mean annual temperatures. A common ratio of radiogenic 40Ar to 4He of 0.35 corresponding to a K/U ratio of 2 _ 104 was found in samples from three of the studied areas: Platanares, Azacualpa, and San Ignacio. A constant ratio may imply a common reservoir rock, possibly the Valle de Angeles Group of Cretaceous to Eocene age. 3He/4He ratios are correlated in a positive sense with SO4 concentration and in a negative sense with geothermal reservoir temperatures determined from chemical geothermometers. These correlations are best explained by dilution of primary geothermal fluids with cooler sulfate-rich waters. The cooler waters inhibit deep boiling, preserving high 3He/4He ratios in the surface springs. In the El Olivar region, either the cool diluting fluid is sulfate-poor, or there is additional excess 3He provided by nearby Quaternary trachytic to basaltic volcanism of the southern Yojoa Graben.

B. M. Kennedy, H. Hiyagon and J. H. Reynolds

Published Journal 
Journal of Volcanology and Geothermal Research, 1991

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B. M. Kennedy,H. Hiyagon,J. H. Reynolds. 1991. Noble Gases From Honduras Geothermal Sites. Journal of Volcanology and Geothermal Research. (!) .