The deep-rooted serpentinite mud volcanism of the Mariana Forearc

申请人制定了两个主要的研究目标：确定马里亚纳前弧活跃泥火山大厦的时空变化，并将实验室分析产生的数据集与成熟的沉积复合体（地中海，日本）中深层泥火山的类似数据相结合。这种比较将有助于确定泥火山在不同类型的俯冲带中的功能，并将揭示它们作为俯冲板块直接窗口的作用。该提案的第一部分集中在西北太平洋的马里亚纳辐合边缘，作为一个古老，寒冷的俯冲带，拥有地球上最大的泥火山。在IODP 366期间，将在三个泥火山的峰顶和侧翼钻三个断面，它们具有不同的尺寸，深度，并且距离海沟的距离越来越远。不来梅大学（MARUM）的测量特别强调确定泥浆基质流变学与其矿物学之间的关系，通过测试蛇形泥浆的单轴固结，并确定其半定量矿物学组成，特别注意粘土部分，可能是造成流变学差异的原因。申请人还计划通过测量碎屑和泥浆基质的粘度、渗透率和指数性质，探索泥火山产物的供给通道几何形状与来源之间的联系。通过对喷发机制的初步地球物理表征，这些测量将使泥火山大厦与它们的深层起源联系起来。第二部分包括将马里亚纳资料与另外两个对泥火山作用感兴趣的地区——地中海海脊和南开海槽——进行整合。这是一个更大的努力的一部分，通过利用泥火山的发生作为对深层过程的自然洞察，来了解所谓的俯冲工厂。这三个环境代表了泥火山在不同深度的上板块或下板块扎根的区域。马里亚纳前弧的钻探活动与ODP 160相当，当时完成了两个样带，同样多的地中海脊喷发复合体的泥火山。在过去，ODP 160的沉积物已经用不同的技术进行了广泛的分析，并构成了申请人进行比较分析的起点。除此之外，MARUM从地中海海脊和南开的沉积物将通过本提案第一部分中进行的大部分相同测量来分析，以联系这三个关键区域（在几何形状上有很大不同），并研究泥火山产物的流变行为如何影响俯冲带的流体和固体平衡。

The applicant formulates two main research goals: determine the spatial and temporal variability in active mud volcanoes edifices of the Mariana forearc and integrate the datasets produced from the laboratory analyses with similar data from deep-seated mud volcanoes in mature accretionary complexes (Mediterranean, Japan). This comparison will allow to establish the function of mud volcanoes in different types of subduction zones and will shed new light on their role as direct windows into the subducting slab. The first part of this proposal is focusing on the Mariana convergent margin, northwestern Pacific Ocean, as an old, cold subduction zone hosting the largest mud volcanoes on earth. During IODP 366, three transects will be drilled on summits and flanks of three mud volcanoes with different dimensions, depths and located at increasing distances from the trench. Particular emphasis of the measurements at MARUM (University of Bremen) will be on determining the relationship between the mud matrix rheology and its mineralogy, by testing the serpentine mud with for uniaxial consolidation and determining its semi quantitative mineralogical composition with a specific attention on the clay fraction, probable responsible for the rheological differences. The applicant is also planning to explore the connection between feeder channel geometry and source of the mud volcanoes products by measuring viscosity, permeability and index properties of both clasts and mud matrix. These measurements will allow linking the mud volcanoes edifices with their deep origins through a preliminary geophysical characterization of the eruption mechanism. The second part consists in integrating the Mariana data with two other areas interested by mud volcanism, the Mediterranean Ridge and the Nankai trough. This is part of a bigger effort to understand the socalled subduction factory by exploiting the occurrence of mud volcanoes as a natural insight into deep processes. These three settings represent regions where the mud volcanoes are rooting in the upper plate or in the downgoing slab at different depths. The drilling campaign on the Mariana forearc is an effort comparable with the ODP 160, when two transect on just as many mud volcanoes of the Mediterranean Ridge accretionary complex were completed. The sediments from ODP 160 have been extensively analyzed with different techniques in the past and constitute the applicant starting point to base a comparative analysis. In addition to that, sediments from MARUM expeditions from both the Mediterranean Ridge and Nankai will be analyzed through most of the same measurements performed during the first part of this proposal to relate these three key areas (as substantially different in geometry) and examine how the rheological behavior of the mud volcanoes products is affecting the fluid and solid balance in subduction zones.