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The effect of salinity on the maximum thermal gradient of a hydrothermal system at hydrostatic pressure

October 1, 1971

The effect of salinity on the temperature-depth relations of a brine of constant composition, enclosed in a vein system, but freely connected to the surface, and everywhere at the boiling point for the hydrostatic head, was calculated by using a mathematical model. The Na-Ca-K-Cl brines which are found in thermal springs and in fluid inclusions in ore minerals were approximated by the available data for vapor-saturated NaCl-H2O solutions. In general, the results are similar to those calculated by D. E. White in 1968 for H 2 O, except that the gradients are steeper because of the increase in density and the decrease in vapor pressure caused by the dissolved salt. As a practical rule, the depth to an isotherm in a 5, 10, 15, 20, and 25 wt percent NaCl brine system is, respectively, 92, 84, 77, 70, and 63 percent (+ or -2 percent) of the depth to the same isotherm in an H2O system. From the data presented, the minimum depth to the growth site of crystals containing fluid inclusions which indicate boiling of the brine can be estimated. Among other applications, these results are useful toward the understanding of the behavior of brines in geothermal areas which may or may not contain compositional stratification.

Citation Information

Publication Year 1971
Title The effect of salinity on the maximum thermal gradient of a hydrothermal system at hydrostatic pressure
DOI 10.2113/gsecongeo.66.6.940
Authors John L. Haas
Publication Type Article
Publication Subtype Journal Article
Series Title Economic Geology
Series Number
Index ID 70227135
Record Source USGS Publications Warehouse
USGS Organization