Impact of geogenic CO2 on the depth distribution of and feedstock provision for deep microbial communities in the Hartousov mofette system in NW Bohemia

位于捷克共和国波希米亚西北部北方切布盆地的Hartoušov mofette系统代表了一个以CO2为主的幔源气体扩散脱气结构，具有较重的d13 C特征（-2 ‰）。从地球化学和微生物的角度来看，这些CO2渗漏形成了微生物群落的有趣和独特的生活栖息地，强烈的地质CO2通量形成了土著微生物群落的特定碳和能源。因此，目前的研究的目的是调查脱气CO2对浅和深的微生物群落在mofette系统和他们的碳和能源的影响，使用有机地球化学，同位素地球化学和地球化学方法。2016年春季，GFZ在Hartoušov mofette油田钻了一个108.5米深的钻孔，恢复了整个沉积层，一直到风化基底。在78.5 m深处，从陆相渐新世到湖相中新世粘土岩的过渡处发生了CO2井喷，表明在该深度段存在一种“CO2储层”，而湖相粘土岩可能起着一种封盖作用。对这个“封印”下面的矿物基质的研究表明，它与上升的CO2相互作用。在更深的陆地渐新世沉积物中，地质CO2似乎刺激了带状钙镁菱铁矿的沉淀，而在“CO2储层”部分，由于孔隙水中的高CO2浓度，碳酸盐溶解。的d13 C信号的散装有机质和化合物特定的d13 C信号的第一次调查过去的微生物生物标志物揭示了显着较重的d13 C信号的沉积物下的湖相中新世粘土岩，表明上升的地质CO2的影响，也对有机基质在更深的核心间隔。虽然我们的第一个结果提供了指示地质CO2和矿物和有机基质之间的相互作用，在深地下，进一步的调查是必要的，以验证这些相互作用，并了解所涉及的过程。

The Hartoušov mofette system located in the northern Cheb Basin (NW Bohemia, Czech Republic) represents a diffuse degassing structure of exhaling mantle derived gases dominated by CO2 with a relative heavy d13C signature (-2 ‰). From a biogeochemical and microbiological point of view these CO2 seeps form an interesting and unique life habitat for microbial communities with intense geogenic CO2 fluxes forming a particular carbon and energy source for the indigenous microbial community. Thus, the aim of the current study is the investigation of the impact of degassing CO2 on the shallow and deep microbial communities in the mofette system and their carbon and energy sources using organic-geochemical, isotope geochemical and biogeochemical approaches. In spring 2016 the GFZ drilled a 108.5 m deep borehole into the Hartoušov mofette field recovering the entire sedimentary successions down to the weathered basement. In 78.5 m depth at the transition from terrestrial Oligocene to lacustrine Miocene claystones a CO2 blow out occurred suggesting a kind of “CO2 reservoir” at this depth interval, whereas the lacustrine claystones might act as a kind of seal. Investigations on the mineral matrix below this “seal” suggest an interaction with the ascending CO2. In the deeper terrestrial Oligocene deposits the geogenic CO2 appears to stimulate the precipitation of zoned calcium-magnesium siderites, while in the “CO2 reservoir” section carbonates are dissolved due to the high CO2 concentrations in the pore water. The d13C signal of the bulk organic matter and the compound specific d13C signal of the first investigated past microbial biomarkers reveal significantly heavier d13C signals for the deposits below the lacustrine Miocene claystones, indicating an influence of the ascending geogenic CO2 also on the organic matrix in the deeper core interval. Although our first results provide indications on the interaction between the geogenic CO2 and the mineral and organic matrix in the deep subsurface, further investigations are necessary to verify these interactions and to understand the involved processes.