Site characterization of the PIER-ICDP drill holes by imaging the subsurface electrical conductivity structure: local and regional structure beneath Mytina and Neualbenreuth Maar (ConeEM)

波希米亚地块，华力西造山带的最东端，是中欧和西欧最大的稳定的前二叠纪岩石的大陆内单位之一。即便如此，西部地区仍包括正在进行的地球动力学活动，如地震活动或增强的CO2通量和脱气，这表明深部岩浆过程、幔源流体及其迁移。中地壳震群的发生、气流量的变化与地幔和泉水同位素组成的变化之间似乎存在着潜在的相关性。此外，在该地区还发现了几座第四纪火山;它们的补给途径和深部岩浆过程之间的相互作用、一般构造框架及其表面表现形式尚未完全了解。解决有关这一复杂地球动力系统的开放性地球科学问题是PIER-ICDP埃格裂谷项目的核心部分。2015/2016年，在可能钻探位置的场地表征框架内，在埃格裂谷进行了大地电磁（MT）实验。MT数据感测地球的电阻率，这是一个对含水流体、部分熔体或金属化合物等低电阻率相的存在特别敏感的物理参数。这一实验揭示了第一个区域地壳传导率模型。最突出的特征是深达通道为地幔流体提供通道。它们位于剖面中部的Bublák和Hartoušov mofettes下方，以及剖面南部的第四纪maars下方。由于这个实验是集中在mofettes和地震群的现场覆盖是不够的，以进一步解释异常下的玛尔斯明确作为一个进料通道或附近的缝合带的印记之间的两个主要构造units.Therefore，我建议MT实验集中在第四纪火山的位置，因为其中两个是计划ICDP钻孔的候选人。主要目标是（i）提供钻探位置的现场表征和基线研究，（ii）对浅层和地壳尺度的电导率进行成像，包括浅层maar结构以及断层和缝合带等构造特征，（iii）对流体通道及其与拟议的深层下地壳岩浆源的关系进行成像，（iv）调查第四纪火山、附近的Tachov断层带以及Saxothurigian和Teplá-Barrandian单元之间的缝合带之间的空间关系，（v）对不同的地球物理、岩石物理、地质和微生物观测得出一致的地质解释。

The Bohemian Massif, the easternmost part of the Variscan orogenic belt, is one of the largest stable intra-continental units of pre-Permian rocks in Central and Western Europe. Even so the western part comprise ongoing geodynamic activity in terms of seismicity or enhanced CO2 flux and degassing suggesting deep magmatic processes, mantle-derived fluids and their migration. It seems to exist an underlying correlation between the occurrence of mid-crustal earthquake swarms, gas flux variations and changes of isotope composition at mofettes and springs. In addition, several Quaternary volcanoes have been discovered in the area; their feeding pathways and the interplay between deep magmatic processes, the general tectonic framework and their surface manifestation is not fully understood. Addressing open geo-scientific questions regarding this complex geodynamic system is central part of the funded PIER-ICDP Eger Rift project. Within the framework of a site characterization for possible drill locations, a Magnetotelluric (MT) experiment in the Eger Rift was conducted in 2015/2016. MT data sense the electrical resistivity of the Earth, a physical parameter that is particularly sensitive to the presence of low-resistivity phases such as aqueous fluids, partial melts or metallic compounds. This experiment revealed the first regional crustal conductivity model. Most prominent features are deep reaching channels providing pathways for mantle derived fluids. They are located beneath the Bublák and Hartoušov mofettes in the central part and beneath the Quaternary maars in the southern part of the profile. Since this experiment was focused on the mofettes and the earthquake swarms the site coverage is not sufficient to further interpret the anomaly beneath the maars unambiguously as a feeding channel or the imprint of the nearby suture zone between two major tectonic units.Therefore I propose a MT experiment centred on the location of the Quaternary volcanoes, since two of them are candidates of planned ICDP boreholes. The major objectives are (i) providing a site characterization and baseline study for drilling locations, (ii) imaging the electrical conductivity on shallow and crustal scale, including shallow maar structure as well as tectonic features such as fault and suture zones, (iii) imaging fluid pathways and their relation to a proposed deep seated lower crustal magmatic sources, (iv) investigate the spatial relation between the Quaternary volcanoes, the nearby Tachov fault zone and the suture zone between the Saxothuringian and Teplá-Barrandian units, (v) derive a consistent geological interpretation of different geophysical, petrophysical, geological and micro-biological observations.