Geochemistry of boron in fluids of Los Humeros and Los Azufres hydrothermal systems, Mexico.

Separated water from geothermal wells of high-temperature geothermal fields Los Humeros and Los Azufres in Mexico are unusually rich in boron. According to the isotopic composition, boron in both fields has magmatic origin. Since the Los Humeros fluids, in contrast to Los Azufres, do not show any correlation between B and Cl and have Cl/B ? 1, a mechanism is proposed based on the B and Cl partitioning between a deep acidic brine and the upper steam reservoir.