甘肃东南地区温泉流体地球化学特征

Geochemical Characteristics of Hot Spring Fluid in the Southeastern Gansu Province

根据氢、氧、氦同位素与水化学组分资料,讨论了甘肃东南地区温泉水的来源、地球化学变化及其与2008年汶川MS8.0地震的关系。测定结果表明:样品的溶解性固体总量(TDS)范围为241.7~2 372.1mg/L。采集的7处温泉(通渭汤池河温泉、清水地震台、天水地震台、武山地震台、武山22号井、成县地震台、武都地震台)水样可归为四种化学类型:Na·CaSO_4、Ca·Mg-SO_4、Na-HCO_3·SO_4、Ca·Mg-SO_4·HCO_3。地下热水的化学类型与裂隙深度和围岩的岩性有关,离子浓度和断裂深度基本成正相关。通渭汤池河温泉和武都地震台的δ18O和δD值分别在-11.4‰^-7.6‰和-85.7‰^-57.1‰的范围内,通渭汤池河温泉和武都地震台中3 He/4 He的值分别为0.4×10^(-7)和12.7×10^(-7)。氢、氧、氦同位素组成特征表明温泉水源于大气降水,在循环过程中经历了水岩反应,且可能有地表水的混入。2008年汶川MS8.0地震发生后,研究区域内温泉水中K^+、Ca^(2+)含量总体上升,SO_4^(2-)、Cl^-含量总体下降,Na^+含量变化不明显;热水循环深度受地震影响发生变化。本文确定了甘肃东南地区温泉来源、水化学类型成因及其与汶川MS8.0地震的关系。

Origins of spring waters in southeastern Gansu province and the relationship between the geochemical variation and the 2008 Wenchuan Ms8.0 earthquake were discussed based on the hydrochemical and isotopic data. The total dissolved solids （TDS） of water samples of seven springs（Tongwei Tangchihe spring, Qingshui station, Tianshui station, Wushan station, Wushan 22th well, Chengxian station, Wudu station） ranged from 241.7 mg/L to 2372.1 mg/L. The spring water can be classified into four chemical types （Na· Ca-SO4 ,Ca· Mg-SO4 ,Na-HCO3 · SO4 ,Ca·Mg·SO4·HCO3 ）. Chemical types of the waters were related to fault depths and the [ithology of surrounding rocks. The TDS was in positive correlation with fault depths in general. Values of δ18O and 8D for Ton Tangchihe spring and Wudu station were in the range of - 11. 4‰ - 7. 6‰--85.7‰ --57. 1‰ respectively, and the aHe/4He values of water samples gwel and were 0.4X10 7 and 12. 7 ×10^-7, respectively. The isotope characteristics indicate that those spring waters were originated from atmospheric precipitation followed by interaction between water and rock during circulation with a probable mix of earth＇s surface water. The concentration of K＋ , Ca2＋ increased and concentration of SO4^2- , Cl^- decreased in general while the amount of Na＋ changed unremarkably after the break of 2008 Wenchuan Ms8.0 earthquake, and the depths of hot water circulation were altered because of the earthquake. In this article, the sources of springs in southeast of Gansu province, origins of water chemistry types and its relationship with Ms8.0 earthquake in Wenchuan are determined.