Seismic-Geochemistry Of Fluid In The Anshan-Haicheng Area,Liaoning Province

The Anshan-Haicheng area in Liaoning province,in which earthquakes occurred frequently,is one of the key regions for monitoring earthquake in China,but systematically monitoring data of groundwater for earthquake prediction are rare in the area.Therefore,this paper aims at studying the temporal and spatial variations of hydrochemistry in the Anshan-Haicheng area in order to identify the chemical types of the groundwater and their genesis and correlate the chemical changes of the waters with seismic activity,and provide the new data for tracing earthquake activity,inspecting hydrochemial anomaly and predicting earthquake.Seventy eight water samples were systematically collected in the Anshan-Haicheng area.Ion concentrations of the water samples were analyzed with a Dionex ICS-900 Ion Chromatography and titration method.The isotopic compositions of hudrogen and oxygen were determined with a Picarro L1102-i Isotopic Water Analyzer?The measurements showed that the water temperatures ranged from 11.0°C to 97.0°C,and the total dissolved solids?TDS?of the water samples ranged from 197.89 mg/L to 829.99mg/L.The water samples can be divided into 6 chemical types.Statistical analysis of water chemical parameters indicated that ion concentrations of the well water showed a tendency of Ca²⁺>Na⁺>Mg²⁺>K⁺,HCO₃^->SO₄^2->Cl^->NO₃^->F^-,those of the lower temperature spring waters showed a similar one of Ca²⁺>Na⁺>Mg²⁺>K⁺,HCO₃^->NO₃^->SO₄^2->Cl^->F^-.The hot spring waters,however,showed a different tendency of Na⁺>K⁺>Ca²⁺>Mg²⁺,SO₄^2->HCO₃^->Cl^->F^->NO₃^-.The?D and?¹⁸O values of the most water samples were distributed along the atmospheric precipitation line in the eastern China in a plot of?D vs?¹⁸O,indicating that the well waters in the study area were mainly recharged with atmospheric precipitation,but the hot spring waters mixed with small amount of deep fluids.The Ca-HCO₃ and Ca?Mg-HCO₃ waters resulted mainly from rock weathering dissolution and cation exchange;Ca-HCO₃?SO₄ and Ca-HCO₃?SO₄?Cl waters from rock weathering dissolution and deep fluid mixing;Ca?Na-SO₄?Cl?HCO₃ waters from rock weathering dissolution with deep brine mixing or likely sewage pollution;Na-SO₄?HCO₃waters from atmospheric precipitation with the mixing of deep source fluids.The obvious hydrochemical anomalies were well correspond to 2 earthquakes of M_L?3.0 occurred in the study area during the sampling duration.The Na⁺,Mg²⁺,Ca²⁺,Cl^-and SO₄^2-can be considered as the sensitive indicators to local seismic activity.The ion concentrations of the samples Nos.HC1,MYS-1 and XAS,especially HC4,increased obviously before the earthquakes,indicating the chemical variation of the water at HC4station was more sensitive to earthquake.The water quality of the study area was comprehensively evaluated by the single factor evaluation method and Nemero index method.The qualification results indicated that the quality of the well and spring waters were up to the standard of drinking water.The quality grade of the waters at the MYS-1 site was IV and that of the 3 hot spring waters were V because of higher F^-concentration.