CSEDI: Integrated Study of Water (H2O) in the Mantle: Processes and Signature

CSEDI科学计划确定了HB2BO在其中发挥关键作用的两个广泛主题。首先，CSEDI的目标是了解水在地球深处的循环--S。其次，它的目标是了解深部地幔中的熔融和其他相变。近年来，为了确定HB2BO对地幔性质和过程的影响，深部地球学界付出了巨大的努力，然而，CSEDI科学计划提出的关键问题仍然没有得到回答。Hb2BO在地球深部不同层次的赋存仍然没有很强的制约，Hb2BO在这些层之间的通量或Hb2BO在深部地幔中诱导熔融的轨迹也是未知的。在这里，一位理论矿物物理学家(Wentzcovitch)、一位实验岩石学家(Hirschmann)、一位实验岩石物理学家(Kohlstedt)和一位地震学家(Revenaugh)提出了一项多学科的努力，以解决关于HB2BO在地球上的作用的一些中心悬而未决的问题--S地幔。将从地震方面寻找有关上地幔底部低速层的厚度和结构，以及这些层的出现与构造环境之间的联系的证据。这些结果将与在这些深度诱导熔化所需的HB2BO浓度的实验研究相结合，以了解这些特征对地幔中HB2BO储存和运输的意义。实验和从头计算相结合，将考察微量元素对OH取代、化学扩散系数以及橄榄石和辉石蠕变速率的影响。从头算将用于确定HB2BO对上地幔和过渡带弹性的影响，这些结果将用于寻找HB2BO的地震学证据。这项拟议的研究代表了明尼苏达大学一项重要的跨部门多学科倡议，涉及四名教师、两名博士后研究人员、两名研究生和一名本科生。这是将最先进的材料理论结合到与地幔中水的存在有关的深层次地球物理问题上的重要一步。将通过定期小组会议促进这一努力，以确保我们的重点仍然是多学科方法，并促进所有参与者的跨学科学习。对于地质和地球物理系的三个PI，建议的研究与REU的地质和地球物理本科实习生站点(？地球中的流体，从表面到核心？)很好地吻合。其中赫希曼是PI，Revenaugh和Kohlstedt是定期参与者。在过去3年，这些督导曾指导13名实习生。由Wentzcovitch领导的地球和行星材料虚拟实验室VLAB通过研讨会和教程向更广泛的科学界交流结果和方法，通过暑期实习计划培训本科生，以及也将接触到这项研究的研究生和博士后的培训。本项目将通过VLAB-S组织进行推广和成果发布。

The CSEDI Science Plan identifies two broad themes in which HB2BO plays a critical role. First, CSEDI aims to understand cycling of water through the Earth?s deep interior. Second, it aims to understand melting and other phase transitions in the deep mantle. In recent years, the deep Earth community has concentrated a tremendous effort in order to determine the influence of HB2BO on mantle properties and processes, yet, key questions raised by the CSEDI Science Plan remain unanswered. There are still no strong constraints on the inventory of HB2BO in different layers of the deep Earth, nor are the fluxes of HB2BO between these layers or the locus of melting induced by HB2BO in the deep mantle known. Here a multidisciplinary effort is proposed between a theoretical mineral physicist (Wentzcovitch), an experimental petrologist (Hirschmann), an experimental rock physicist (Kohlstedt), and a seismologist (Revenaugh) to address some of the central outstanding issues regarding the role of HB2BO in the Earth?s mantle. Evidence regarding the thickness and structure of low velocity layers at the bottom of the upper mantle, as well as for links between the occurrence of such layers and tectonic environment will be searched for seismically. These results will be combined with experimental studies of the concentrations of HB2BO necessary to induce melting at these depths to understand the significance of these features for HB2BO storage and transport in the mantle. Experiments and ab initio calculations will be combined to examine the influence of minor element on OH substitution, on chemical diffusivity, and on creep rates of olivine and pyroxenes. Ab initio calculations will be use to determine the influence of HB2BO on the elasticity of the upper mantle and transition zone, and those results will be applied to search for seismological evidence of HB2BO. The proposed research represents a significant inter-departmental multi-disciplinary initiative at the University of Minnesota involving four faculty, two post-doctoral researchers, two graduate students, and one undergraduate. It is a major step in incorporating state-of-the-art materials theory to deeply seated geophysical problems related to the presence of water in the mantle. This effort will be facilitated by regular group meetings to ensure that our focus remains on multidisciplinary approaches and to promote interdisciplinary learning of all of the participants. For the three PIs in the Department of Geology and Geophysics, the proposed research dovetails well with the Geology and Geophysics REU undergraduate intern site (?Fluids in the Earth, from the Surface to the Core?) for which Hirschmann is the PI and Revenaugh and Kohlstedt are regular participants. In the past three years, these PIs have supervised thirteen interns. The Virtual Laboratory for Earth and Planetary Materials, VLab, directed by Wentzcovitch is deeply involved in communicating results and methods to the broader scientific community through workshops and tutorials, in the training of undergraduates through the summer internship program, and in the training of graduate students and post-docs which will also be exposed to this research. VLab?s organization will be used to promote and divulge outcomes of this project.