CSEDI Collaborative Research: Optical investigations of a mantle plume laboratory model

地幔柱的概念在联系深部地幔对流与火山活动、地形隆起和地球化学特征的地表表现方面发挥了核心作用。 然而，这一概念仍然不完整。两个问题仍有待解决，以完成我们的地幔柱及其在地球动力学和地球化学演化的作用的理解。第一个，也是激烈争论的主题，是地幔柱在内部加热的对流地幔中的存在和生存，地幔由与板块运动相关的大规模流动所控制。第二个涉及到的程度的地球化学变化所揭示的同位素签名的洋岛玄武岩，我们确定为地幔plume.In的表面表达，以解决这两个问题，PI Lithgow-Bertelloni，Cotel，Whitehead和哈特正在进行实验室实验中的单一的热和成分的地幔柱在均匀和分层的流体。本实验的主要目标是第一，准确地测量和表征整个不断发展的羽流的浮力通量作为初始热通量的函数，和流体成分，第二，分析剪切引起的大规模环流羽流破裂和搅拌内的导管的影响。重点在于使用新的非侵入式光学技术（粒子图像测速法，激光诱导荧光，光偏转和热致变色液晶数字粒子图像测温）。 这些仪器除了可以同时测量组分和温度外，还可以直接测量三维流动结构。 在接下来的三年里，PI打算提供严格的比例关系来阐明-导致稳定羽流和稳态管道或上升时羽流破裂的条件-羽流结构的空间和时间变化，因为它与地震成像有关-夹带物质在热和热化学羽流中存活和相互作用的尺度-与大洋岛屿玄武岩的同位素地球化学变异性的联系：受资助的项目涉及四个专业研究人员之间的密切合作，他们具有从地球物理流体动力学到地球化学等广泛不同的科学和技术专长。因此，这些实验的结果可能会引起地球科学界不同部门的兴趣。所有四个PI都参与实验设计和结果解释。

The concept of plumes within the mantle of the earth has played a central role in linking deep mantle convection to surface expressions of volcanism, topographic uplift, and geochemical signatures. However, the concept continues to remain incomplete. Two issues remain to be resolved to complete our understanding of mantle plumes and their role in the dynamical and geochemical evolution of the planet. The first, and the subject of vigorous controversy, is the very existence and survival of plumes in an internally heated, convecting mantle dominated by the large-scale flow associated with plate motions. The second relates to the degree of geochemical variation revealed by the isotopic signatures of ocean island basalts, which we identify as the surface expression of mantle plumes.In order to address both issues, PIs Lithgow-Bertelloni, Cotel, Whitehead and Hart are conducting laboratory experiments on single thermal and compositional plumes in homogeneous and stratified fluids. The primary goals of the present experiments are first, to accurately measure and characterize the buoyancy flux throughout an evolving plume as a function of the initial heat flux, and fluid composition, and second, to analyze the effects of shearing induced by the large-scale circulation on plume breakup and on stirring within the conduit. The emphasis lies in the use of new non-intrusive optical techniques (Particle Image Velocimetry, Laser-Induced Fluorescence, light deflection, and thermochromic liquid crystals for Digital Particle Image Thermometry). These can directly measure the three-dimensional flow structure in addition to giving the simultaneous measurements of composition and temperature. Over the next three years the PIs intend to provide rigorous scaling relationships to illuminate - The conditions that lead to steady plumes and steady-state conduits or plume breakup upon ascent- Spatial and temporal variations in plume structure as it relates to seismic imaging- The scales at which entrained material survives and interacts in thermal and thermochemical plumes- The link with the isotopic geochemical variability of ocean island basalt.The funded project involves close collaboration between four PIs with widely varying scientific and technical expertise ranging from geophysical fluid dynamics to geochemistry. Hence, the results of these experiments are likely to be of interest to diverse segments of the Earth Sciences community. All four PIs are involved in the experimental design and interpretation of the results.