Geophysical imaging of the deep seated pluming system feeding and controlling the Logatchev Hydrothermal vent field at the Mid-Atlantic Ridge near 15°N

该项目的总体目标是研究热液喷口位置、地壳结构和深部岩浆管道系统之间的关系。研究区为SPP1144的北部测量区，即15 - 20转换断裂以南的大西洋中脊，包括显著的Logatchev热液喷口田。Logatchev喷口的流体化学表明，海水向下到达地幔深度，导致地幔的蛇纹石化。在Maria S. Merian巡航MSM10/2期间，将使用地球物理技术，以地震P波和s波速度和电导率为关键参数，寻找通口场下存在蛇纹岩化的证据。利用气枪、海底地震仪和深拖曳拖曳的主动地震将在二维空间上研究地壳和最上层地幔的结构。被动地震学（在MSM06/2期间部署，在海底的时间为12个月）将通过探测沿断层排列的局部地震来定位活动断层，从而确定热液流体的路径。电磁测量和柔度测量将解决分布轴下异常低剪切强度和低电阻率的区域。这些区域表明存在部分熔体，但熔体连通性不同。对所有数据的联合分析和解释将使我们能够解决地壳内或地壳/地幔边界包含部分熔融和熔融透镜的区域的二维和三维结构。此外，还将对地壳孔隙结构和断层进行成像。因此，我们的研究将提供关于流体、岩浆和热量在何处以及如何从地幔输送到海底的基本信息，地壳结构模型可以与地表Logatchev火山口的位置相关。

The overall goal of the proposed project is to investigate the relationship between the occurrence of hydrothermal vent sites, the crustal structure, and the deep-seated magmatic plumbing system. The study area is the northern survey area of the SPP1144, i.e., the Mid-Atlantic Ridge to the south of the Fifteen-Tweenty transform fault and includes the prominent Logatchev hydrothermal vent field. The fluid chemistry of the Logatchev vents suggest that seawater reaches down to mantle depth and causes serpentinization of the mantle. Geophysical techniques will be used during Maria S. Merian cruise MSM10/2 to search for evidence indicating the existence of serpentinization under the the vent field using seismic P- and S-wave velocity and electrical conductivity as key parameters. Active seismics using airguns, ocean bottom seismometers, and a deep tow streamer will be used to study the structure of the crust and upper most mantle in two-dimensions. Passive seismology (deployment during MSM06/2; time on the seafloor - 12 month) will locate active faults and hence pathways for hydrothermal fluids by detecting local earthquakes that align along faults. Electromagnetic measurements and measurements of the compliance will resolve regions of anomalously low shear strength and low electrical resistivity beneath the spreading axis. Such regions are indicative for the presence of partial melt with varying melt connectivity. The joint analysis and interpretation of all data will allow us to resolve the two- and three-dimensional structure of regions containing partial melt and melt lenses within the crust or at the crust/mantle boundary. In addition, the crustal porosity structure and faults will be imaged. Our study will thus provide elementary information on where and how fluids, magma and heat is transported from the mantle to the seafloor and crustal structrual models can be related to the location of the Logatchev vent sites on the surface.