重庆市北温泉与四川康定温泉水之地球化学特征对比

对重庆北温泉从2005年6月至12月进行每月采样监测,结果表明: 北温泉的水化学类型为SO4 - Ca 型, SO2-4 和Ca2+ 分别占阴阳离子总量的86. 8%和79. 7% , pH值接近于中性,属低温热泉。与之相对比的青藏高原东北缘的康定温泉(除二道桥温泉之外)明显富集Na+ ( 67. 6% ) ,阴离子以HCO-3 为主( 86. 4% ) ,水化学类型为HCO3— Na 型,属高温热泉,水源深度较北温泉深1km以上;而康定的二道桥温泉则明显富集Ca2+ ( 53. 3% ) ,阴离子以HCO-3 ( 90% )为主,水化学类型为HCO3— Ca型,属于低温热泉。根据矿物饱和指数和CO2 分压的计算结果,虽然北温泉的泉水均对方解石和白云石达到饱和状态,但只在部分泉点形成少量钙华沉积。康定温泉对方解石为过饱和,而对白云石为不饱和,因此,在康定温泉有较多的方解石钙华沉积。两个地点对石膏均为不饱和。此外,康定温泉的二氧化碳分压远远高于北温泉。北温泉3号泉点的各主要离子浓度均低于北温泉的其它泉点,是由于地表水的混入所造成。根据所测得的硫酸根浓度进行估算,在北温泉3号泉泉水中雨季时地表水的混入约为40% ,旱季时约为20%。 

COMPARISON OF GEOCHEMICAL FEATURES OF WARM SPRINGS BETWEEN CHONGQING AND KANGDING

In this study,we have compared the geochemical characteristics of warm springs in North Springs of Chongqing with that of warm springs in Kangding.North Springs,a famous state park in Chongqing,China,contains eight warm springs for public use.A 70m long travertine cave whose formation remains unclear is estimated 90 ka old.In order to understand the formation of the travertine cave as well as the source and quality of the warm springs,we investigated the physical and chemical features of the spring water between June and December of 2005.Measurements of temperature,pH,conductivity,K~ ,Na~ ,Ca~(2 ),Mg~(2 ),SO~(2-)_4,HCO~-_3 and Cl~-of the eight springs have been conducted monthly since June 2005.The water chemistry of North Springs belongs to low temperature and SO_4-Ca type which shows that SO~(2-)_4is 86.8% in total anions and Ca~(2 ) is 79.7% in total cations.The pH of warm springs is close to neutral.In contrast,warm springs in Kangding located in northeastern edge of Tibetan Plateau belong to high temperature HCO_3-Na type that mainly contain Na~ (67.6%) and HCO~-_3(86.4%).Based on the measured chemical parameters we have calculated the saturation indexes of calcite,dolomite and gypsum as well as P_(co_2) for these warm springs.The calculation shows that calcite and dolomite reaches saturation in the spring water of North Springs. In both locations of Chongqing and Kangding,gypsum is undersaturated in the spring waters.The P_(co_2) of Kangding spring is about 10 times higher than that of North Springs,indicating abundant CO_2 comes from deep source in Kangding.According to the chemical features of the warm springs,the source of North Springs may come from recharge of meteoritic water into deep earth where dissolution of limestone rocks(Jialingjiang and Leikoupo formations,and the latter formation is younger and contains gypsum layers) would occur.Further investigation on how deep of recharge water penetration is needed.The low ion contents of spring No.3 in Chongqing are attributed to mixing of surface water.The SO~(2-)_4 and Ca~(2 ) concentrations in spring No.3 show two end-member mixing between the original spring water and the surface river water.It seems that the amount of the river water contribution to the spring water is related to rainfall.Based on a simple mass balance model of SO_4 concentration and current measurements,the contribution of the surface river water to spring No.3 is about 40% in rainy season and about 20% in dry season.