CHEMICAL AND ISOTOPIC VARIATIONS IN HOT AND COLD SPRINGS AND STREAMS ALONG THE LUANGWA RIFT ZAMBIA

The Luangwa Rift, part of the southwest branch of the East African Rift System, exhibits geothermal activity depicted by hot springs. Understanding the chemistry of heat for the springs is an important component of the Project for Rift Initiation and Development and Evolution (PRIDE). We sampled and analyzed the chemistry and stable carbon isotopes of hot and cold springs along the Luangwa Rift in eastern Zambia. The temperature of the hot springs ranged from 35 to 84 ºC, the pH ranged from 5.3 to 8.6, total dissolved solids (TDS) ranged from 0.02 to 1.41 g/L, silica concentrations ranged from 8.7 to 99.9 mg/L, dissolved inorganic carbon concentrations ranged from 68 to 94 mg/L and the carbon isotope ratio ranged from -19 to -4‰ The temperature of the cold springs ranged from 17 to 25 ºC, the pH ranged from 4.4 to 7.9, TDS ranged from 46 to 669 mg/L, silica concentrations ranged from 0.04 to 62.9 mg/L, alkalinity ranged from 68 to 94 mg/L. The temperature of the streams ranged from 12 to 17ºC, the pH ranged from 4.6 to 7.9, TDS ranged from 0.01 to 0.26 g/L, silica concentrations ranged from 3.3 to 10.0 mg/L, alkalinity ranged from 68 to 94 mg /L. The physical and chemical properties of the hot springs are due to the temperature of the thermal source and the extent of rock-water interaction. The more basic pH of hot springs compared to cold springs and surface waters is indicative of weathering of silicate minerals in the metamorphic basement. Our results will be used to integrate geochemical, geophysical, and structural data to better understand incipient rifting mechanisms in the southwest branch of the East African Rift System and serve as a model for analogous rift systems.