The current state of the hidden magmatic process beneath the western Eger Rift after the 2011 earthquake swarm traced by isotope studies

通过同位素研究追踪 2011 年群震后埃格尔裂谷西部隐藏岩浆过程的现状

• 批准号: 252970106
• 负责人: Dr. Karin Bräuer
• 金额: --
• 依托单位: Department Hydrogeologie
• 依托单位国家: 德国
• 项目类别: Infrastructure Priority Programmes
• 财政年份: 2014
• 资助国家: 德国
• 起止时间: 2013-12-31 至 2017-12-31
• 项目状态: 已结题
• 来源: https://gepris.dfg.de/gepris/projekt/252970106?language=en
• 关键词: current; state; hidden; magmatic; process

As a result of the detailed isotope-geochemical studies of the mantle-derived fluids related to the 2000 and 2008 earthquake swarms the temporal seismically induced release of crustal derived components could be identified at degassing locations along the Pocatky Plesna Fault Zone (PPZ) and at degassing sites along the Marianske Lazne Fault (MLF), but was also observed in the Vogtland area. Both, after the swarms 2000 and 2008, the admixture of crustal derived components to the steady mantle-derived fluid flow were repeatedly detected for about two years. Besides that a clear increase of mantle-derived helium (up to 6 Ra) was observed at locations in the Cheb basin at least since 2000. This increase indicates the existence of an active magmatic reservoir in the upper mantle beneath the Cheb basin. Superimposed to the progressive increase of mantle-derived helium further temporal increased portions of mantle-derived helium (to 6.3 Ra) were observed before the 2000 and 2008 earthquake swarms at locations close to the Novy Kostel focal zone (NKFZ). The recorded anomalies indicate that both, the 2000 and the 2008 swarm, seems to be linked with supply of fresh magma from a less degassed reservoir in the upper mantle. That means from the view of fluids both swarms seems to be triggered by hidden magma intrusions within the lithosphere. No fluid data could be recorded accompanying the earthquake swarm 2011. Thus, it is yet unknown whether the portion of mantle-derived gas has increased or decreased in the western Eger Rift area in relation to the latest earthquake swarm, and whether indications exist for a further spatial expansion of the area with increased portions of mantle-derived gas in the western Eger Rift, respectively?Therefore, the proposal is mainly focussed on two aims: (1) to evaluate and compare the geodynamic situation within the three degassing centres Cheb Basin (CB), Marianske Lazne and surroundings (ML) and Karlovy Vary (KV) after the earthquake swarm 2011, and (2) to evaluate the fluid signatures at the degassing locations close to the piece of the planned seismic and geoelectric profile together. As a result of the planned fluid studies an update of the distribution pattern of mantle-derived gas is to expect in comparison to situation about 20 years ago. The new fluid data, regional and close of the profiles of geophysical research, allow the evaluation the permeability of fluid migration paths supplying the respective sites by their gas characteristic at the surface and provide information on the current state of the magmatic reservoir. The final discussion of all data will assist the interpretation of spatial anomalies and indications of ascending fluid paths, respectively identified in geophysical studies and will supply essential information for a future ICDP drilling in the western Eger Rift.

通过对与2000年和2008年地震群相关的地幔衍生流体进行详细的同位素地球化学研究，可以在Pocatky Plesna断裂带（PPZ）和Marianske Lazne断裂带（MLF）的脱气位置识别出地壳衍生组分的地震诱发释放，但在Vogtland地区也观察到。在2000年和2008年的群之后，地壳衍生成分与稳定的地幔衍生流体流动的混合物在大约两年的时间里被反复检测到。此外，至少自2000年以来，在契布盆地的一些地方观测到地幔源氦的明显增加（高达6 Ra）。这表明在切布盆地下的上地幔存在活跃的岩浆储层。在2000年和2008年靠近Novy Kostel震源带（NKFZ）的地方，在地幔源氦逐渐增加的基础上，观测到地幔源氦在时间上进一步增加（达到6.3 Ra）。记录的异常表明，2000年和2008年的岩浆群似乎与上地幔中一个脱气较少的储层提供的新鲜岩浆有关。这意味着从流体的角度来看，这两个群体似乎都是由岩石圈内隐藏的岩浆侵入引发的。2011年的地震群没有记录到流体数据。因此，相对于最近的地震群，西埃格尔裂谷地区幔源气体的比例是增加了还是减少了，以及西埃格尔裂谷地区幔源气体的比例增加是否有进一步空间扩张的迹象，目前还不清楚。因此，本研究主要集中在两个方面：1)评价和比较2011年地震后Cheb盆地（CB）、Marianske Lazne及其周边地区（ML）和Karlovy Vary （KV）三个脱气中心的地球动力学情况；2)评价靠近规划地震和地电剖面段的脱气位置的流体特征。由于计划进行的流体研究，预计与大约20年前的情况相比，幔源气体的分布格局将有所更新。新的流体数据，区域和接近的地球物理研究剖面，允许评估流体运移路径的渗透率，通过它们在地面的气体特征，提供有关岩浆储层现状的信息。对所有数据的最后讨论将有助于解释在地球物理研究中分别确定的空间异常和上升流体路径的指示，并将为未来在Eger裂谷西部进行ICDP钻井提供重要信息。