ABR: A Deeper Investigation of Oceanic Spreading Center Magmatic Processes

GSTDTAP

项目编号	1634460
	ABR: A Deeper Investigation of Oceanic Spreading Center Magmatic Processes
	Robert Dunn
主持机构	University of Hawaii
项目开始年	2016
	2016-09-01
项目结束日期	2020-08-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	411270(USD)
国家	美国
语种	英语
英文摘要	Oceanic crust comprises two-thirds of our planet?s surface and, in contrast to the much older continental crust, is being continually created at mid-ocean ridges and then recycled back into the deep earth at ocean trenches at what are called subduction zones. This formation and recycling system of Earth?s oceanic crust continually replenishes life-sustaining heat and elements to the biosphere. Documenting these processes and fluxes is central to our understanding of the Earth?s physical and chemical evolution, with profound impacts on ocean and atmospheric composition, and the sustainability of ecosystems. Of significant importance is the composition and construction of the oceanic crust itself, which is uniquely difficult to study given its location under the oceans. The project will use marine geophysical tools, in particular modern seismic methods that image Earth?s interior, to investigate ocean crust formation and structure of a high quality seismic dataset collected during prior oceanographic expeditions, to reveal the properties of both the plate-boundary magmatic system where ocean crust forms and the seafloor hydrothermal systems that cool the magmatic systems. The project will support a junior female researcher and train and mentor a female Ph.D. student in seismic imaging and interpretation techniques as well as professional development. University of Hawaii undergraduate students will work with the PI to learn the basics of geophysical data collection and how to make their own tomographic images of the Earth?s interior. Outreach will take advantage of the School of Ocean and Earth Science and Technology open house. One of the least understood and most controversial topics of oceanic spreading center science is the formation of lower oceanic crust. While the upper crust is typically emplaced via diking and eruption, there is no general agreement how the lower crust forms. For over two decades there have been many attempts to reconcile geophysical observations from active spreading centers with petrologic and structural observations from tectonic windows into the lower crust. This work has led to a variety of competing models on lower crustal formation. Central to this debate are the amount and distribution of melt in the lower crust and uppermost mantle, the temperature structure of those areas, and the extent of off-axis cooling that could assist the in situ crystallization of the lower crust. The relative lack of modern seismic measurements impedes progress. Most previous seismic studies of the lower crust at active spreading centers were largely performed many years ago with data and methods that are now outdated. Recent high-resolution active-source and co-located broadband seismic experiments along the Eastern Lau Spreading Center present an excellent opportunity to re-examine melt supply and lower crustal formation. Using a large dataset of over 500,000 observations of P and S waveforms, we will perform seismic tomography and full waveform analyses, including full three-dimensional anisotropic imaging of the magmatic system and surrounding crust and mantle. The proposed research will image the lower crust and upper mantle, and provide much-needed constraints on melt distribution and thermal structure within the sub-axial magmatic system. This project will address fundamental questions of melt supply to, and storage within, the crustal magmatic system, as well as inform our understanding of the cooling of the ridge axis and the extraction of heat from the lower crust. The high resolution imaging will allow us to place quantitative constraints on melt fraction, melt distribution, and the thermal structure of the lower crust and mantle. With the new results we will test predictions of specific hypotheses related to crustal genesis along spreading centers.
来源学科分类	Geosciences - Ocean Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/70279
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Robert Dunn.ABR: A Deeper Investigation of Oceanic Spreading Center Magmatic Processes.2016.