西藏高温地热显示区氟分布及富集特征

通过对西藏高温地热显示区内12个主要地热田采集的地热、地表水样共30组测试和分析可知,研究区氟含量0.34~19.2mg/L,地下热水中氟含量均高于2.0mg/L,研究区南部氟含量较北区偏高.氟含量高区,地热显示较明显.氟离子在水化学类型为Cl-Na或Cl?SO4-Na等Na型水中富集程度高于HCO3-Na?Ca或HCO3-Ca等Ca型水.研究区高氟地热水的富集机制主要有:深部地热流体的升流混合作用,补给水向下渗流过程中含氟硅酸盐矿物、萤石的溶滤作用.两种机制相比,深部热流的混合作用对地下水形成高浓度F-的贡献更大,但矿物的溶滤作用相对而言更为普遍些.研究区砷的富集机制与氟相似,这也使得二者在空间分布上具有共生性.应加强高氟高砷区地热水的管理与防护,防止其污染地表水环境.

The distribution and enrichment characteristics of fluoride in geothermal active area in Tibet

Thirty geothermal and surface water samples were collected from the twelve main geothermal fields in Tibet to analyze the occurrence and distribution of fluoride in Tibet. The results showed that concentration of fluoride varied between 0.34and 19.2mg/L, fluoride concentrations of all the geothermal water samples exceed 2.0mg/L. The fluoride's concentrations in the south were slightly higher than those in the north in the research area. The more abundant of fluoride, the hotter of the surface temperature. Generally, fluoride was more enriched in Na types' water (e.g. Cl-Na and Cl×SO4-Na types) than in Ca types' water (e.g. HCO3-Na×Ca and HCO3-Ca types). The main mechanisms of fluoride's enrichment in geothermal water may included: the mixture of deep geothermal fluid; the leaching of fluorite and silicate minerals containing fluoride. Comparison these two main mechanisms showed that 1st one was more important for forming extremely high fluoride’s concentration, the 2st one was more common in the research area. The enrichment mechanism of arsenic was similar as fluorine in the study area, and that was why the two elements had similar patterns in the spatial distributions. Strict environment regulations should be placed to manage arsenic and fluoride-contamination.