Abstract:

The Songshan hot spring is located in the Songshan Forest Park in Yanqing County of Beijing. Granite occurs near the hot spring and fissures are developed in the rock. There are two wells flowing hot water closing to the hot spring. Temperatures of the hot spring and the flowing wells range from 32 ℃ to 42 ℃. The major cations of the hot water are Na⁺, K⁺ and Ca²⁺，and the major anions of the hot water are SO₄^2-, HCO^-3 and Cl-. The hot water is of SO₄-Na type. The hot water has TDS of 0.548-0.566 g/L, pH of 9.14-9.21, H2SiO3 of 87.1-97.1 mg/L and F- of 19.0-20.8 mg/L. Isotopic data of hydrogen and oxygen indicate that the hot water in the study area is of meteoric origin. The recharge altitude of the hot spring is estimated as 1,256-1,351 m, the temperature of the recharge area, 4.4-8.8 ℃, the age of the hot water, 14.19-48.95 a, the temperature of the geothermal reservoir, 114-119 ℃, and the circulation depth of the hot water, 2,236-2,274 m. The Songshan hot spring emerges on the mountain slope after the groundwater in the granite receives recharge from precipitation in the mountain area and undergoes deep circulation and obtains heat flow from beneath.

Key words: hot spring, hydrochemistry, isotope, formation, Beijing