ABSTRACT
The highest concentrations of naturally occurring aqueous arsenic (As) are found in certain types of geothermal waters, generally those related to major subduction zones (Webster & Nordstrom, 2003; Nordstrom & Zheng, 2009). This paper outlines natural As enrichment through the diagenetichydrothermal-tectonic cycle, provides examples of high As thermal waters, and outlines some of the main processes affecting As geochemistry in hydrothermal systems.
