Hot, concentrated, saline solution that has circulated through crustal rocks in an area of anomalously high heat flow and become enriched in substances leached from those rocks (e.g. chlorides of Na, K, and Ca); it often contains dissolved metals, in which case it forms an important intermediary in the deposition of ore deposits. One of the best-documented examples is the brine from boreholes in the Salton Sea geothermal field in southern California, discovered in the early 1960s, with temperatures between 300 and 325 °C, density 1021 kg/m3, and containing appreciable concentrations of Cu, Pb, Zn, and Ag. Hot brine solutions may also form through sea water–rock reactions in hydrothermal systems at oceanic ridges, e.g. in the median valley of the Red Sea.