²³⁸U, ²²⁶Ra and ²¹⁰Pb in some vent waters of the Galapagos Spreading Center

Abstract

The concentrations of ²²⁶Ra, ²³⁸U and ²¹⁰Pb have been measured in waters from the Mussel Bed and the Rose Garden thermal fields at the Galapagos spreading center over a temperature range of ~2.5-16°C. The ²²⁶Ra-T plots yield slopes of 0.112 and 0.036 dpm/kg°C for the Mussel Bed and the Rose Garden respectively yielding a global hydrothermal ²²⁶Ra flux less than 5% of that required to sustain the oceanic inventory. ²³⁸U concentration in waters <9°C is the same as that in ambient sea water whereas water hotter than ~9°C shows a decreasing trend with temperature to zero ²³⁸U at ~29°C. ²¹⁰Pb concentration in Mussel Bed increases with temperature, and extrapolated to ~350°C yields a ²¹⁰Pb concentration considerably less than that expected from ²²²Rn decay and basalt alteration.