Geochemical implication of 87Sr/86Sr ratio of high-temperature deep groundwater in a fractured granite aquifer

Abstract

The Dongrae thermal water area located at the southeast margin of the Korean Peninsula is one of the oldest hot springs in Korea and has been used in spas since the 9th Century. In this paper, a geochemical significance of 87 Sr/ 86 Sr ratios from deep thermal water, groundwater, surface water and rainwater in the Dongrae area is discussed. The bedrock of this thermal water-bearing aquifer is composed of Mesozoic granitoids. For temperatures up to 71°C, the thermal water is Na-Cl type, whereas shallow cold groundwater is Ca(-Na)-HCO 3 type. 87 Sr/ 86 Sr ratios of the thermal water are in the 0.705651 ± 11-0.705696 ± 12 range and have remained nearly unchanged over the past 4 years (2004)(2005)(2006)(2007).87 Sr/ 86 Sr ratios of the shallow cold groundwater, surface water and rainwater range from 0.705781 ± 26 to 0.705789 ± 12, 0.706700 ± 14 and 0.707375 ± 11 respectively.87 Sr/ 86 Sr ratios of the thermal water in the Dongrae area are lower than those of groundwater, surface water, rain water as well as aquifer bearing granite. These Sr isotopic signatures indicate that the circulation rate between thermal water and current meteoric water, including groundwater, surface water and rain water in the Dongrae area should be very slow. Therefore, the thermal water might be derived from a high temperature paleogroundwater reservoir rather than from circulation of young meteoric water heated by current heat sources. Our data show that 87 Sr/ 86 Sr ratios may become an important time lag indicator for the groundwater cycle between deep and shallow groundwater in a fractured granite aquifer system.

Fault “Corrosion” by Fluid Injection: A Potential Cause of the November 2017 MW 5.5 Korean Earthquake

“…2-/Clratios, potentially explicable as consequences of increased Ca 2+ from dissolution of plagioclase or from ion exchange associated with precipitation of Mg 2+ during hydrolysis of other igneous minerals to clay minerals and chlorite, and increased SO 4 2from oxidation of pyrite, FeS 2 . Such complexity, indicating interactions between the rock and water that originated as meteoric water or palaeoseawater, has been recognized previously in hot spring waters from SE Korea (e.g., [67,73]).…”

Hydrogeochemical Characteristics and Geothermometry Applications of Thermal Waters in Coastal Xinzhou and Shenzao Geothermal Fields, Guangdong, China

“…It is clear that Li, Rb, and Cs are concentrated in biotite, which contains an order of magnitude more Li than the whole rock. Sr has a similar property to K and Ca and thus can be found in K-and Ca-rich minerals such as sulfate, carbonate, and feldspar [45]. These minerals provide the primary source of Li, Rb, Cs, and Sr for the geothermal waters.…”

Landside tritium leakage over through years from Fukushima Dai-ichi nuclear plant and relationship between countermeasures and contaminated water

“…A key aspect of this study is that the water examined was groundwater, not surface water. To reveal the hydrogeological origin of the groundwater sources, Sr isotope ratio ( 87 Sr/ 86 Sr) was also measured as a natural tracer of water-rock interaction and ground water mixing patterns [15][16][17][18] .…”