Deep Groundwater Evolution at Outokumpu, Eastern Finland : From Meteoric Water to Saline Gas-Rich Fluid
Deep Groundwater Evolution at Outokumpu, Eastern Finland : From Meteoric Water to Saline Gas-Rich Fluid
复制标题
芬兰东部奥托昆普深层地下水演化：从大气水到富含含盐气体的流体
DOI：
--
复制
发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Riikka Kietäväinen
中科院分区：
文献类型：
--
作者：
Riikka Kietäväinen
在前寒武纪大陆盾内，富含天然气的盐水在世界各地都可以从基岩裂缝和上地壳的孔隙中找到。几个过程，从海水蒸发或冻结，然后渗透到水-岩石相互作用，已被认为是负责这些沃茨的特征。除了水与基岩之间的反应外，栖息在这些沃茨（即深层生物圈）中的活跃微生物群落可能通过生物地球化学反应，特别是通过促进深层碳循环，在塑造其周围环境方面发挥重要作用。利用地球化学和同位素方法研究了芬兰东部2.5 km深的Outokumpu深钻孔中深层地下水的起源和演化。样品材料包括通过管道采样、泵送和加压方法从钻孔中提取的水和气体，以及断裂矿物。使用不同的采样技术对水样进行了类似的分析。然而，由于在管道取样和泵送过程中发生了不受控制的脱气，因此建议应使用加压方法进行气体取样。沿钻孔沿着可识别出五种水类型，反映了岩性的变化，并表明与地表以及Outokumpu基岩内部相互隔离。提出了一个演变模型，其中包括在比目前气候条件温暖的情况下降水和大气降水的渗入，水的稳定同位素组成发生变化，几乎停滞的地下水与基岩之间的水-岩相互作用导致盐度增加，以及碳氢化合物的非生物和生物形成。水的稳定同位素和放射性惰性气体和核惰性气体积累的两条独立证据表明，奥托昆普深钻孔地下水与始新世-中新世时期的大气水循环隔绝，将演化模型置于数百万年至数千万年的时间框架内。研究结果揭示了深层地下水如何在地球化学和微生物过程中随时间和空间而演变。此外，它们强调了这些环境的复杂性，因为它们越来越多地用于地下建筑，并为评估核废物处置的长期安全性提供了背景信息。
Within Precambrian continental shields, saline, gas-rich groundwaters are found in all over the world from bedrock fractures and pore spaces in the upper crust. Several processes, from seawater evaporation or freezing followed by infiltration to water–rock interaction, have been suggested to be responsible for the characteristic features of these waters. In addition to reactions between water and the bedrock, active microbial communities inhabiting these waters, i.e. the deep biosphere, may play a significant role in shaping their surroundings by biogeochemical reactions, especially by contributing to the deep carbon cycle. The origin and evolution of deep groundwater in the 2.5 km deep Outokumpu Deep Drill Hole in eastern Finland was investigated using geochemical and isotopic methods. The sample material included water and gas derived from the drill hole by tube sampling, pumping and pressurised methods, as well as fracture minerals. Similar results were obtained for water samples using different sampling techniques. However, as uncontrolled degassing took place during tube sampling and pumping, it is suggested that pressurised methods should be used for gas sampling. Five water types were discerned along the drill hole, which reflect changes in lithology and indicate isolation from the surface and from each other within the Outokumpu bedrock. An evolutionary model was proposed that includes precipitation and infiltration of meteoric water at warmer than present climatic conditions, a shift in the stable isotopic composition of water and an increase in salinity through water–rock interaction between virtually stagnant groundwater and the bedrock, and both the abiotic and biotic formation of hydrocarbons. Two independent lines of evidence from water stable isotopes and the accumulation of radiogenic and nucleogenic noble gases indicated isolation of the Outokumpu Deep Drill Hole groundwaters from the meteoric water cycle from the EoceneMiocene epochs, placing the evolutionary model in the time frame of millions to tens of millions of years. The results shed light on how deep groundwaters have evolved in geochemical and microbiological processes through time and space. Furthermore, they emphasise the complexity of these environments, as they are being increasingly utilised for underground construction, and provide background information for assessment of the long-term safety of nuclear waste disposal.