A geochemical study of geothermal water has been carried out in the Tianshui and its northern-southern area. Geothermal water of Wushan and Tianshui is bicarbonate water of low salinity characterized by pH in 7.94-9.06 and low total dissolved solids (TDS) (226-255 mg/L), which were probably formed by water-rock interaction between meteoric rain, biotite plagioclase gneiss rock and carbonate sediment in reservior. While geothermal water of Tongwei and Qingshui is sulfate water with characteristics of pH in 7.1-8.07 and high total dissolved solids (TDS) (915-1 793 mg/L), which may arised from water-rock interaction between meteoric rain, variscan granite and sinian amphogneiss. The isotopic data show that the origin of thermal water is meteoric water and not severely affected by water-rock isotope exchange. Assessments of various chemical geothermometer applied on the geothermal waters suggested the probable existence of a deep geothermal reservoir of middle-low enthalpy (70-111癈) in the Tianshui and its northern- southern area. The sustainable utilization of the thermal water will be maintained if the total withdrawal rate is relatively small, and an alternative pumping and non-pumping pattern is used in Tianshui and its northern-southern area with mean yearly rainfall of near 500 mm.
[1] Gemici Ü,Tarcan G,olak M,et al.Hydrogeochemical and hydrogeological investigations of thermal waters in the Emet area (Kütahya, Turkey)[J].Applied Geochemistry,2004,19:105-117.
[2] Cruz V J,Frana Z.Hydrogeochemistry of thermal and mineral water springs of the Azores archipelago (Portugal)[J].Journal of Volcanology and Geothermal Research,2006,151:382-398.
[3] Ahmad M,Akram W,Hussain D S,et al.Origin and subsurface history of geothermal water of Murtazabad area, Pakistan—an isotopic evidence[J].Applied radiation and isotope,2001,55:731-736.
[4] Papp C D,Niţoi E.Isotopic composition and origin of mineral and geothermal waters from Tuţnad Băi Spa, Harghita Mountains, Romania[J].Journal of Geochemical Exploration,2006,89:314-317.
[5] Ahmad M,Akram W,Ahmad N,et al.Assessment of reservoir temperatures of thermal springs of the northern areas of Pakistan by chemical and isotope geothermometry[J].Geothermics,2002,31:613-631.
[6] 陈彦文,李生永.甘肃省东部地下热水的分布特征与勘查开发前景分析[J].地下水,2007,29(4):43~44.
[7] 张万军.武山温泉地下热水成因浅析[J].甘肃冶金,2009,31(4):48~49.
[8] 张守训,李百祥.天水及其南北地区温泉分布的地质-地球物理特征[J].西北地震学报,2006,28(3):252~257.
[9] Stumm W,Morgan J J.Aquatic chemistry:chemical equilibria and rates in natural waters,3rd ed[M].New York: John Wiley and Sons,1996.
[10] 赵全升,冯 娟,安乐生.德州市深层地下水水质演化研究[J].地理科学,2009,29(5):766~772.
[11] 李丽娟,李海滨,王 娟.澜沧江水文与水环境特征及其时空分异[J].地理科学,2002,22(1):49~56.
[12] Pastorelli S,Marini L,Hunziker J C.Chemistry,isotope values(δD,δ18O,δ34SSO4)and temperatures of the water inflows in two Gotthard tunnels,Swiss Alps[J].Applied Geochemistry,2001,16:633-649.
[13] 王君波,朱立平,鞠建廷,等.西藏纳木错东部湖水及入湖河流水化学特征初步研究[J].地理科学,2009,29(2):288~293.
[14] 王 蔚,张景荣,胡桂兴,等.湘西北地区现代温泉地球化学[J].中国科学(B辑),1995,25(4):427~433.
[15] Craig H.Isotopic variations in meteoric waters[J].Science,1961,l33:1702-1703.
[16] 高志发.西北地区大气降水、地表水及地下水同位素组成特征探讨[J].甘肃地质学报,1993,2(2):94~101.
[17] 章新平,田立德,刘晶淼,等.沿三条水汽输送路径的江水中18O变化特征[J].地理科学,2005,25 (2):190~196.
[18] 上官志冠,都吉夔,臧 伟,等.郯庐断裂及胶辽断块区现代地热流体地球化学[J].中国科学(D辑),1998,(1):23~29.
[19] Motyka R J,Nye G J,Turner D L,et al.The Geyser Bight geothermal area, UmnakIsland, Alaska[J].Geothermics,1993,22(4):301-327.
[20] Marini L,Bonaria V,Guidi M,et al.Fluid geochemistry of the Acqui Terme-Visone geothermal area(Piemonte,Italy) [J].Applied Geochemistry,2000,15:917-935.
[21] Gherardi F,Panichi C,Yock A,et al.Geochemistry of the surface and deep fluids of the Miravalles volcano geothermal system(Costa Rica)[J].Geothermics,2002,31:91-128.
[22] Koh Y,Choi B,Yun S,et al.Origin and evolution of two contrasting thermal groundwaters (CO2-rich and alkaline) in the Jungwon area,South Korea:Hydrochemical and isotopic evidence[J].Journal of Volcanology and Geothermal Research,2008,178:777-786.
[23] 汪集旸,熊亮萍,庞忠和.中低温对流型地热系统[M].北京:科学出版社,1993.
[24] Arnorsson S.Application of the silica geothermometer in low temperature hydrothermal areas in Iceland[J].American Journal of Science,1975,275:763-783.
[25] Giggenbach W F.Geothermal solute equilibria derivation of Na-K-Mg-Ca geoindicators[J].Geochim Cosmochim Acta,1988,52:2749-2765.
[26] Gemici Ü,Filiz Ş.Hydrochemistry of the Çeşme geothermal area in western Turkey[J].Journal of Volcanology and Geothermal Research,2001,110:171-187.
[27] Sepúlveda F,Dorsch K,Lahsen A,et al.Chemical and isotopic composition of geothermal discharges from the Puyehue-Cordon Caulle area (40.5°S),Southern Chile[J].Geothermics,2004,33:655-673.
[28] Chiodini G,Cioni R,Guidi M,et al.Chemical geothermometry and geobarometry in hydrothermal aqueous solutions:a theoretical investigation based on a mineral-solution equilibrium model[J].Geochim. Cosmoch Acta,1991,55:2709-2727.
[29] 王腊春,史运良.西南喀斯特山区三水转化与水资源过程及合理利用[J].地理科学,2006,26(2) :173~178.
[30] 邓 伟,翟金良,闫敏华.水空间管理与水资源的可持续性[J].地理科学,2003,23(4):385~390.
[31] 周 训,周海燕,方 斌,等.浅析开采条件下地下热水资源的演变[J].地质通报,2006,25 (4): 482~486.
