Evolution of a Geothermal Brine from a Low-Temperature Radioactive Spring

Abstract

Geochemical and fluid composition provide interesting insight on the diagenesis of a low-temperature geothermal brine and radioactive mineral spring (MKR) that emerges at base of the Carpenter’s Mountain near the Milk River Mineral Hotel and Spa in Clarendon, Jamaica. A drastic shift of δ18O and δD isotopes from the global meteoritic water line (GWML) indicates significant depletion of δ18O and the enrichment δD in the region of influence from seawater. Concentrations of boron (B), lithium (Li), and strontium (Sr) reveal important information on the mixing of these geothermal fluids and seawater. Cationic ratios of Li/B vs. SO42-/Cl- indicate deep circulating fluid signatures derived mainly from ions leached during long water/rock interactions with weathered basement volcanic rocks and evaporites. MRT thermal waters containing dissolved Radon222 are piped into the Milk River Mineral Hotel & Spa and diverted to Roman tiled baths for balneotherapeutic tourism. The heated geothermal brine ascends along fractures of the proposed active E-W trending, left-lateral strike-slip geostructure: the South Coast Fault (SCF). The SCF transects the Clarendon Plains and transfers motion to two of the island’s restraining bends. Hydrogeochemical data suggests a more complicated underlying structure at the site. A hypothetical model of the hydrodynamic saline fluids migrating from the geothermal system along permeable fractures of the South Coast Fault is conceptualized from hydrogeochemical, isotopic, geological, and structural data. Brines are classified based on their high Cl- concentration and are classified as a concentration of more than 10000 mg/L total dissolved solids (Davis, 1964).