Hydrogeochemistry and Origin of Thermal Groundwater in Bedrock Aquifers in Tianjin, China

Thermal groundwater resources were found to have occurred in deep-seated bedrock aquifers in the northeastern North China plain near Tianjin, China. Meso- to Neo-Proterozoic and Paleozoic carbonate rocks on the Cangxian uplift are capable of yielding 960-4 200 m 3/d of 60 to 96 ℃ water from the wells ranging in depth between 1 000 and 4 000 m. Conductive heat flow of 0.063 to 0.144 2 W/m 2 from the deep crust is responsible for this anomalous geothermal field. The water in the Ordovician aquifer is characterized by relatively high TDS, high concentrations of SO 4 and SO 4·Cl-Na·Ca type, but the waters from the Meso- to Neo-Proterozoic and Cambrian aquifers, by relatively low TDS, low concentrations of SO 4 and predominantly Cl·SO 4-Na type. It is noted that when the temperature of the waters increases at a rate of 10 ℃ in the range of 30-100 ℃, the content of SiO 2 increases at a rate of 12 to 15 mg/L, and fluoride concentration increases at a rate of 2.3 to 2.5 mg/L. Hydrochemical and isotopic data suggest that the thermal water in the bedrock aquifers is of meteoric origin and recharged in the northern mountain area to the north of the Baodi-Ninghe fault, and then flows laterally for a long distance from the north to the south to the city of Tianjin. Temperature of the waters increases because of heat exchange with the rocks and recharge by conductive heat flow from beneath.

Genesis of Coal Metamorphism of Late PalaeozoicCoals in the South of North China——A Further Approach to the Effects of ThermalGroundwater on Coal Metamorphism

The close relationship between the genesis of coal metamorphism and the evolution of the regional tectonic framework is expounded on the basis of an analysis of the geological factors causing the metamorphic zonation of the Late Palaeozoic coals in southern North China; in terms of the mechanism for the formation of palaeogeothermal anomalies, the effects of thermal groundwater on coal metamorphism is highlighted and a geological model for thermal groundwater metamorphism of coal established; with the concept of the palaeogeotherm-coal metamorphism system, the genesis of coal metamorphism is analysed according to the distribution pattern of three geological factors: heat source, heat-carrier and channel, and heat-collector.

Hydrochemical and Isotopic Evidence of Origin of Thermal Karst Water at Taiyuan,Northern China

Thermal karst groundwaters with temperatures ranging from 32.8 to 62.5 ℃ were found at Taiyuan（太原） City,the capital of Shanxi（山西） Province.To identify the origin of the thermal groundwater,the following tracers were used in this study：δD,δ18O,4He,3He/4He,and major chemical constituents in water.Hydrochemical and isotopic data indicate that the thermal groundwaters in the basin area are a mixture of thermal waters from the West Mountain and those from the East Mountain.Furthermore,the 4He and 4Heexc concentrations of the thermal groundwater samples are usually lower than those of the cold groundwater samples,and there is an evidently negative correlation between the temperature and the 4He concentration in thermal groundwaters from the West Mountain and the ba-sin,which means that with the increase in temperature,the He concentration increases in the vapor phase and decreases in the aqueous phase.In the plot of 3He/4He vs.4He/20Ne of all water samples：air,crust,and mantle,all thermal groundwater samples are distributed near the line between the point of air and that of crust,suggesting that atmospheric and crustal helium is the main source for that in thermal groundwaters.In other words,there are no mantle-derived fluids mixed in the thermal groundwaters.