【摘要】 根据水化学组分和氢、氧同位素数据,讨论了首都圈西部盆岭构造区断裂带地下热水的化学类型及其形成过程。结果显示,水样的TDS为225～1449mg/L,δ18 O和δD值分别为-12.42‰～-9.54‰,-90.8‰～-71.88‰。水的循环受盆岭构造区中的断裂和水头压力控制。Na-SO4型水主要出现在片麻岩和花岗岩裂隙中,由深循环过程中长石类矿物水解和硫化物的氧化作用形成。Na.Ca-HCO3型水主要分布在含泥质条带互层的碳酸盐岩储层中,受方解石和白云石溶解、泥质条带中的易溶盐淋滤作用和与粘土矿物的Na-Ca离子交换的控制。第四系砂砾石含水层热水水化学类型较复杂,有Ca.Mg-HCO3,Na.Ca-HCO3,Na-HCO3,Na-HCO3.SO4.Cl,Na-HCO3.Cl,Na-SO4.Cl等,这可归因于含水层深度、断裂性质、沉积物粒度和岩性等因素。δ18 O和δD指示地热水来源于大气降水。δD值随地下水温度升高而降低的特征可能由深层古水和浅层地下水的混合作用或是同位素交换反应导致。镇川堡103℃热水的δ18 O和δD受水岩反应和蒸汽散失的共同作用。本研究对地热水开发和地震监测方面有一定应用价值。更多还原

【Abstract】 Chemical types and origins of geothermal waters in the basin and range province of the west region of Beijing are discussed.Ion compositions were detected by Dionex IC-900 Ion Chromatography and titration.δ18O and δD of the water samples were measured with the Picarro L1102 Isotope Detector.The TDS of the thermal waters are in the range of 225~1449 mg/L.The Na-SO4 type waters are from fractures in gneisses and granites,which may originate from feldspar hydrolysis and sulfide oxidation in the deep circulation of waters which is controlled by faults and head pressure.The Na·Ca-HCO3 type waters are from carbonates with interbedding argillite,resulting from dissolving calcite,dolomite,and cation exchange.However,the geothermal waters from Quaternary aquifers of different depths and locations in the basin are geochemically different(Ca·Mg-HCO3,Na·Ca-HCO3,Na-HCO3,Na-HCO3·SO4·Cl,Na-HCO3·Cl,Na-SO4·Cl),which can be attributed to ion exchanging with different rocks,aquifer depths,or fault features.The values of δ18O and δD range from-12.4 to-9.5‰ and from-90 to-72‰,respectively,indicating an origin of meteoric water.The negative correlation of δD and groundwater temperature probably implies mixing of ancient and modern groundwater or isotope exchange reactions underground.Water-rock interaction and steam loss are deduced to have a profound impact on the values of δ18O and δD in a geothermal well in Tianzhen of 103℃.The results can be applied to geothermal development and earthquake monitoring.更多还原