Water Chemistry and Mineralogy of Morgan and Growler Hot Springs, Lassen KGRA, California

Abstract

Recent geochemical and isotopic studies have focused much attention on the Lassen hydrothermal system. Here, we report on additional data for the hot spring deposits occurring at Morgan and Growler Hot Springs in the Lassen KGRA. Because these springs contain substantial amounts of dissolved chloride, halite and sylvite are found above the water level as evaporitic deposits, along with gypsum. One spring is depositing pyrite that contain significant amounts of arsenic, antimony, and thallium. A yellow compound, composed o arsenic and sulfur, is being deposited in another spring. Arsenic and antimony concentrations are high in the spring waters; the dissolved thallium concentration is not known. The dissolved arsenic appears to be a conservative species and follows chloride. Antimony appears to be independent of dissolved arsenic and to be linearly related to chloride and measured orifice temperatures at Morgan Hot Springs.