小江断裂带及邻近地区温泉地球化学特征与地震活动关系研究*

(云南省地震局,云南 昆明 650224)

小江断裂带; 温泉; 地球化学特征; 中强地震

Research on Relationship between Geochemical Characteristics of Thermal Springs and Seismic Activity in Xiaojiang Fault Zone and its Adjacent Area
WANG Yun,ZHAO Ci-ping,LIU Feng,CHEN Kun-hua,RAN Hua

(Earthquake Administration of Yunnan Province,Kunming 650224,Yunnan,China)

Xiaojiang Fault zone; thermal spring; geochemical characteristics; moderate-strong earthquake

备注

小江断裂带属现今仍在活动的断裂,同时也是一条破坏性地震多发带。为探究特定地区的地球化学场与地震的耦合关系,寻找特定的前兆观测组分,笔者选取并计算了小江断裂带及邻近地区的95处温泉的热储温度。利用温泉的水化学数据(K+、Na+、Ca2+、Mg2+、SO2-4、Cl-、HCO-3),结合该区域的构造特征及地震活动规律,对温泉的水化学、水温、热储温度、稳定同位素(δ13C,3He/4He)等地球化学特征进行了研究。结果 表明温泉中主要离子含量、TDS含量、水温及热储温度的高值区域在空间上主要沿小江断裂带展布,且呈北高南低的分布特征。水温和热储温度高值区内中强地震(M≥4.7)分布少; 相反,低值区内中强震活动频繁,且强度相对较大。碳、氦同位素特征显示,CO2气体的碳同位素(δ13C)组成具有明显的生物成因特征; 幔源氦(百分含量)同素所占比例相对较低,表明小江断裂带中南段壳幔连通程度低,脱气作用几乎都发生在地壳范围。

The Xiaojiang Fault is not only a still-active fault nowadays but also a destructive earthquake-prone zone.In order to explore the coupling relationship between geochemical field and earthquake in specific areas and look for the specific precursor observational component,the geothermal reservoir temperatures of 95 thermal springs was selected and calculated in Xiaojiang fault zone and its adjacent areas.Using the hydrochemistry data(K+,Na+,Ca2+,Mg2+,SO2-4,Cl-,HCO-3)in the thermal springs,integrated with the regional tectonic features and regular pattern of seismic activity,the geochemical characteristics of hydrochemistry,water temperature,geothermal reservoir temperature and stable isotopes(δ13C,3He/4He)was studied. The results show that the high values area of main ion content,TDS,water temperature and geothermal reservoir temperatures mainly spatially distributed along the Xiaojiang Fault,and had the distribution characteristic of decreasing from north to south gradually. The moderate-strong earthquakes(M≥4.7)occurred less in high-value region of water temperature and geothermal reservoir temperature,however the activity of the moderate-strong earthquakes was frequent and the intensity of it was relatively high in the low-value region. Stable isotope characteristics of carbon and helium showed that carbon isotope composition(δ13C)of CO2 gas had obvious biogenic features,and the proportion of mantle-derived helium(percentage of mantle-derived He)was relatively low,which indicated that connectivity between crust and mantle was not well in the middle and south segment of Xiaojiang Fault,so the degasification almost occurred in the crust.