【作者】 陈志；

【导师】 陈顒； 杜建国；

【作者基本信息】 中国科学技术大学 ， 固体地球物理学， 2014， 博士

【摘要】 于2008年6月、2008年10月、2009年6月和2010年4月在川西地区的32个温泉点采集了4次水样。测量了120个温泉水样的水化学组分(K+、Na+、 Ca2+、Mg2+、Cl-、SO42-、HCO3和C032-)的含量和氢氧同位素的组成(δD和δ18O)。测量结果表明120个温泉水样的水温和总溶解固体(TDS)分别为8.8℃～83.0℃和151.69mg/1～2159.43mg/1.根据C.A.舒卡列夫的分类方法,将温泉水划分为9种化学类型：Na(Ca)-HCO3(SO4), Na(Mg)-HCO3(SO4) Ca(Na)-HCO3(SO4), Mg(Ca)-SO4, Ca(Mg)-SO4, Ca(Mg)-HCO3, Mg(Ca)-HCO3, Na-Cl (HCO3)和Ca(Na)-SO4(HCO3)。温泉水样的δD、δ18O值均沿当地大气降水线分布,表明该区的温泉水主要接受大气降水的补给。受控于温泉水深循环过程中的水岩反应及深部来源水体的混入,川西地区温泉水样的地球化学特征及热储温度存在明显的空间分布特征。鲜水河断裂带的10-25号温泉水的δD、δ18O值低于其他断裂带温泉的δD、δ18O值,但是其温泉水温、TDS及C1-均较高,这表明该断裂带的温泉水受到深部高温凝结蒸汽的影响。汶川地震前,康定地区的灌顶温泉、龙头沟温泉及二道桥温泉水样的K+浓度升高,增幅为19.3%～54.4%；灌顶温泉和二道桥温泉水样的S042-浓度分别上升了32.0%和59.6%,地震后均降至上升前水平。这可能是震前区域构造挤压应力增强,高K+及SO42-浓度的深部地下水供给量的增加所致。汶川地震后,龙门山断裂带温泉水的化学组分的变化较为明显,其2008年10月采集水样的水化学组分的下降幅度为23%～95%,氢氧同位素组成也回归至大气降水线附近。其他断裂带的温泉水样的水化学组分的变化幅度大多在10%以内,δD、δ18O值的也无明显变化。该断裂带温泉距震中的距离较近,为50-110km。另外,该断裂带为余震的集中发生区。该区温泉水样的水化学组分及氢氧同位素组成的显著变化可能是该区的地壳应力调整造成的。此外,80%以上的余震发生在第一批水样采集的前后两个月(2008年8月21～2009年1月1),因此,2008年10月在龙门山断裂带采集水样的水化学组分的大幅下降,氢氧同位素的与大气降水线同位素趋于一致,可能是地壳应力调整过程中,随余震的衰减,深部流体补给量的减少所致。另外,鲜水河断裂带的八美温泉水样的Na+、HCO3-浓度和TDS在2010年4月17日明显上升,幅度分别为53%、38%和38%,可能与2010年4月28日在距离其15km处发生的5.4级地震有关。更多还原

【Abstract】 Hydrogeochemistry of120water samples from32hot springs in the western Sichuan Province after the Wenchuan Ms8.0earthquake was investigated by analyzing the concentrations of cation(K+, Na+, Ca2+and Mg2+), anion(Cl-, SO42-, HCO3-and CO32-) and the isotopic compositions of hydrogen and oxygen (δD and δ18O). The water samples of the hot springs were collected four times in June2008, October2008, June2009and April2010. Hydrogeochemical data indicated the spring waters can be classified into9chemical types:Na(Ca)-HCO3(SO4), Na(Mg)-HCO3(SO4), Ca(Na)-HCO3(SO4), Mg(Ca)-SO4, Ca(Mg)-SO4, Ca(Mg)-HCO3, Mg (Ca)-HCO3, Na-Cl (HCO3) and Ca(Na)-SO4(HCO3). The values of δD and δ18O of the120water samples were plotted along the local meteoric water line with different extent shifts in the diagram of δD vs δ18O, which indicated that the spring waters were mainly originated from meteoric water and with different extent alteration. Attributed to water-rock interaction and mixture of deep fluids, the geochemical characteristics and the temperatures of the geothermal reservoir showed spatial differences. The values of δD and δ18O for the water samples of the springs nos.10-25from the higher mountain area were more negative, but the temperatures, TDS and Cl-of the springs were higher, which may result from the contribution of condensated water of deep vapor. Concentrations of K+and SO42-of the water samples of the Guanding Spring, Longtougou Spring and Erdaoqiao Spring in the Kangding district exhibited evident increases before the mainshock, with the amplitude ranging from19.3%to59.6%, indicating more supplement of deep fluids enriched in K+and SO42-under the increase of tectonic stress during the before the Wenchuan earthquake. Most of the aftershocks occurred in the Longmenshan fault zone, and more than80%occurred two months before and after the first sampling. The chemical and isotopic variations of the water samples nos.1-5from the Longmenshan fault zone closer to the epicenter area more obviously decreased after the mainshock, with the chemical parameters of the water samples collected in October2008by some23%to95%, and the δD-δ18O plots approached the local meteoric water line after sizeable shift in June2008, indicating less supplement of deep fluids under the stress adjustment. For the water samples from other fault zones, the amplitudes of the chemical variations were less than10%, and no marked changes for the δD and δ18O were observed. Na+, HCO3-and TDS of the water sample from Bamei Spring in the Xianshuihe fault zone increased obviously, with the amplitudes of53%,38%and38%respectively on17April,2010, which may be related to the Ms5.4event of28April,2010with an epicenter distance of15km.更多还原