Melt Network Geometry in Stressed, Partially Molten Mantle Rocks: Implications for Seismic Anisotropy

GSTDTAP

项目编号	1753482
	Melt Network Geometry in Stressed, Partially Molten Mantle Rocks: Implications for Seismic Anisotropy
	[unavailable]
项目开始年	2018
	2018-07-01
项目结束日期	2021-06-30
资助机构	US-NSF
项目类别	Continuing grant
项目经费	123634(USD)
国家	美国
语种	英语
英文摘要	Melting and deformation are intimately coupled in nature and work in concert to accommodate plate tectonic movements. These movements are associated with earthquakes and volcanic eruptions which are one of the primary natural hazards to human settlements. It is therefore important that we understand how melt and deformation interact deep in our planet. Since we are unable to directly observe this interaction, we rely on the interpretation of various remote sensing surveys. One powerful means of interrogating our planet's interior is to study the sound waves propagating through the Earth after an earthquake. The speed at which waves propagate as well as their damping depends on the details of how melt and crystallized minerals are aligned. This information can therefore be used to detect the spatial extent of partially molten domains as well as their flow direction deep in Earth's interior. The investigator's research aims at constraining the basic physical principles that govern melt and mineral alignment in deforming partially molten rocks through a series of laboratory experiments. The research funded by this proposal will form the basis of a doctoral dissertation of a graduate student in the PI's laboratory and will introduce the student to the scientific method and thinking. Additionally, an analogue experiment will be developed to illustrate the influence of partial melting on sound wave propagation. This experiment will be used in undergraduate and graduate classes taught by the PI as well as for outreach to general public during events like the Cambridge Science Festival. Melting occurs in actively deforming regions of the Earth such as subduction zones and mid-oceanic ridges and affects much of the chemical exchange between mantle, crust and atmosphere. The presence of melt strongly influences the mechanical and transport properties of partially molten rocks and can produce a signature detectable by remote sensing. Remote sensing of plate boundaries gives us a wealth of information about the fundamental forces that drive plate tectonics and forms the basis for testing geodynamic hypotheses. The primary goal of this research is to elucidate the (i) influence of deformation on grain-scale melt network topology and (ii) the influence of deformation with melt present on the evolution of crystallographic preferred orientation (CPO) in olivine, the most abundant mineral in the lithospheric mantle. Both stress-driven melt preferred orientation (MPO) as well as CPO evolve on different length- and time-scales and contribute to the integrated seismic signature of deforming partially molten rocks in nature. The team will synthesize fine-grained olivine rocks with approximately 3 vol% of mid ocean ridge basalt added as a melt phase and deform these rocks in general shear under pressure and temperature conditions typical for the upper mantle (T = 900 - 1200 degrees C, P = 0.3 - 2 GPa). Constant load experiments at load levels covering at least one order of magnitude will be performed to study the effect of stress on the grain-scale melt network topology. Several experiments at a constant stress level will be taken to different finite strains to elucidate the influence of strain on MPO and CPO. Conducting such a comprehensive series of well-controlled experiments will constrain the influence of stress and strain on both MPO as well as CPO development in partially molten mantle rocks. The derived quantitative microstructural data will be used to calculate the seismic signature of the rocks based on several theoretical models. Establishing correlations between measured microstructural quantities and external forces in experiments will provide tight constraints for theoretical models of deforming solid-liquid composites and will facilitate extrapolation of laboratory data to natural conditions. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/72789
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	[unavailable].Melt Network Geometry in Stressed, Partially Molten Mantle Rocks: Implications for Seismic Anisotropy.2018.