| 腾冲热海地热田高温热泉中的硫代砷化物及其地球化学成因 |
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| 引用本文： | 郭清海,刘明亮,李洁祥.腾冲热海地热田高温热泉中的硫代砷化物及其地球化学成因[J].地球科学,2017,42(2):286-297. |
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| 作者姓名： | 郭清海 刘明亮 李洁祥 |
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| 作者单位： | 1.中国地质大学生物地质与环境地质国家重点实验室，湖北武汉 430074 |
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| 基金项目： | 国家自然科学基金项目41572335生物地质与环境地质国家重点实验室自主研究课题GBL11505 |
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| 摘 要： | 以我国大陆范围内典型的岩浆热源型水热系统——云南腾冲热海为研究区，在国内首次对热泉中硫代砷化物含量及其地球化学成因进行了分析.研究采用的在野外对富硫化物水样进行快速冷冻处理、而后在实验室进行砷的形态分离和测试的方法明显优于当前通用的水样砷含量及其形态分析的预处理和测试方法.主要原因为后者在采样现场对水样的酸化处理可使样品中三硫代砷酸盐以非定形态硫砷化合物的形式沉淀，且用常规阴离子交换柱在野外无法实现硫代砷酸盐的完全回收及其与砷酸盐的分离.受岩浆流体输入和热储内高温条件下强烈流体-岩石相互作用的控制，热海水热系统排泄的中性-偏碱性热泉中富集硫化物和砷，为热泉中硫代砷化物的形成提供了必要条件.热海热泉中检出的硫代砷化物包括一硫代砷酸盐、二硫代砷酸盐和三硫代砷酸盐，在总砷中所占比例最高分别可达26.7%、43.3%和33.7%.热海地热田的2个子区(硫磺塘和澡塘河) 的热泉沿不同断裂带出露，地热水升流过程中经历的冷却方式也不同，使硫磺塘热泉具有相对较高的总硫化物含量和总砷含量，并导致其中各类硫代砷酸盐具有更高的含量范围.
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| 关 键 词： | 热泉 硫代砷化物 地球化学 热海 腾冲 |
| 收稿时间： | 2016-11-07 |
Thioarsenic Species in the High-Temperature Hot Springs from the Rehai Geothermal Field (Tengchong) and Their Geochemical Geneses |
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| Abstract: | Rehai, located in the Tengchong volcanic region of Yunnan Province, is a typical magma-heated hydrothermal system in mainland China. Taking Rehai as the study area, the thioarsenic species in hot springs were quantitatively determined for the first time and their geochemical geneses were identified. The sulfide-rich geothermal water samples were collected and immediately treated via rapid freezing technique in-situ and then detertnine the arsenic species in the lab, which is superior to the traditional methods of pretreatment and measurement of aqueous arsenic. The traditional acidification treatment of arsenic-bearing, sulfide-rich water sample inevitably results in the precipitation of tri-thioarsenate as the form of amorphous S-As compounds. Furthermore, the common use of anion-exchange column is not capable of fully collecting thioarsenic species and separating them from arsenate in-situ. Under the control of magmatic fluid input and intense fluid-rock interactions at high reservoir temperatures, the neutral to slightly alkaline hot springs discharged from the Rehai hydrothermal system are rich in sulfide and arsenic, facilitating the formation of thioarsenic species. Mono-thioarsenate, di-thioarsenate and tri-thioarsenate were detected in the Rehai hot springs with ratios to total arsenic up to 26.7%, 43.3% and 33.7%, respectively. In two sub-hydrothermal areas of Rehai, i.e. the Liuhuangtang area and the Zaotanghe area, the hot springs are distributed along the main N-S stretching faults and the secondary E-W stretching faults, respectively, and therefore the geothermal waters went through different cooling processes (adiabatic cooling and mixing with shallow cold groundwaters, respectively) prior to their discharge to the surface. Thus the hot springs from Liuhuangtang have relatively higher concentrations of sulfide and arsenic as well as various thioarsenic species. |
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