贵州石阡地区热矿水同位素地球化学研究

ISOTOPIC GEOCHEMICAL STUDTIES OF THERMAL MINERAL WATERS IN THE SHIQIAN AREA,GUIZHOU

根据石阡地区热矿水分布区的水文地质、构造、岩相资料和热矿水的水化学及同位素的研究成果,可将本区热矿水分成Ⅰ、Ⅱ、Ⅲ三个小区:Ⅰ区位于印江至石阡的袍木寨背斜、石阡断裂带北段上,含水围岩为咸化海相白云岩含膏盐建造,为矿化度高,Sr^(2+)、SO_4^(2-)、δD、δ^(18)O较高的SO_4^(2-)型水。Ⅲ区位于红石走滑断裂束,含水围岩为浅海灰岩建造,为矿化度低,Sr^(2+)、SO_4^(2-)、δD、δ^(18)O较低的HCO_3^-型水。Ⅰ、Ⅲ区热矿水年龄较低。Ⅱ区位于上述两构造带的复合部位,其热矿水为Ⅰ、Ⅲ区热矿水混合而成。为年龄较高的水化学和同位素组成介于上述二者之间的SO_4^(2-)·HCO_3^-型水。

On the basis of the information of hydrogeology, tectonic geology and rock faciesin places where thermal mineral waters are distributed in the Shiqian area anddata of isotopic and hydrochemical studies for them, three subareas of thermalmineral waters can be distinguished, i.e.: subareas Ⅰ, Ⅱ and Ⅲ. Subarea Ⅰissituated in the north parts of the Shiqian fault zone and the Paomuzhai anticlinefrom Yinjiang to Shiqian. Their water--bearing host rock is a formation ofgypsum-bearing dolomite of saline marine facies. TDS, Sr^(2+) and SO_4^(2-) contents, δD and δ^(18)O in the thermal mineral waters of subarea Ⅰ are higher than those insubarea Ⅱ. Their hydrochomical typo is SO_4^(2-)-Ca^(2+). Subarea Ⅲ is situated in theHongshi strike-slip fault bundle. Water--bearing host rocks are a formation oflimestone of neritic facies. TDS, Sr^(2+) and SO_4^(2-) contents, δD and δ(18)O in the thermalmineral waters of subarea Ⅲ are lower than those of subarea Ⅱ. Their hydrochem-ical type is HCO_3^--Ca^(2+).Mg^(2+).^(14)C dating ages of thermal mineral waters in subar-eas Ⅰ and Ⅲ are younger than those of subarea Ⅱ. Subarea Ⅱ is situated in acompounding locus of the two above-mentioned tectonic zones. Thermal mineralwaters in subarea Ⅱ are composed of a mixture of those of subareas Ⅰ and Ⅲ andare older than those of subareas Ⅰ and Ⅲ. Their hydrochemical type is SO_4^(2-).HCO^--Ca^(2+).Mg^(2+) type which is hydrochemically and isotopically intermediatte betweensubareas Ⅰ and Ⅲ.