How Important Were Mid-Ocean Ridge Processes in the Formation of Shatsky Rise?

GSTDTAP

项目编号	1658069
	How Important Were Mid-Ocean Ridge Processes in the Formation of Shatsky Rise?
	Jennifer Georgen
主持机构	Old Dominion University Research Foundation
项目开始年	2017
	2017-03-01
项目结束日期	2020-02-29
资助机构	US-NSF
项目类别	Standard Grant
项目经费	40154(USD)
国家	美国
语种	英语
英文摘要	Volcanic provinces that occur in the submarine environment are not as well studied as those on land, but size and magmatic output of submarine eruptions can be immense. This project focuses on the Shatsky Rise large igneous province (LIP) in the western Pacific Ocean. Shatsky Rise has a volume of 3.2-6.9 million cubic kilometers and an area roughly the same as California. Seafloor magnetic and bathymetric data suggest that this LIP began to form 140-150 million years ago, at or near a setting in the plate tectonic system called a ridge-ridge-ridge triple junction. Ridge-ridge-ridge triple junctions occur when three divergent spreading centers meet in a single area; the triple junction associated with Shatsky Rise marked the intersection of the Pacific, Izanagi, and Farallon plates. The high magmatic fluxes inferred for Shatsky Rise, particularly for Tamu Massif in the southern portion of the plateau, have led previous investigations to suggest that a thermal plume or chemical heterogeneity in the mantle was the source of the magmatism. This project aims to investigate the importance of triple junction plate boundary configuration in the formation of Shatsky Rise. Understanding how the tectonic plates controlled the three-dimensional flow patterns in the upper mantle beneath Shatsky Rise is crucial to unraveling how this voluminous LIP formed. Two undergraduate students will participate in this project. One student will concentrate on the modeling component of the project, while the other will develop STEM education materials on geological processes that generate LIPs, with Shatsky Rise as the example. The project addresses several outstanding questions: (1) What was the nature of plate-driven, three-dimensional mantle flow at the triple junction where Shatsky Rise was emplaced? (2) Did triple junction geometry cause flow along the ridge axes that could have influenced the spatial dispersion of a mantle plume or geochemical heterogeneity? (3) What was the magnitude of upwelling velocity at the triple junction? (4) What was the shape and size of the three-dimensional mantle volume that experienced melting, and did ridge-related upwelling extend over anomalous depths compared to a setting where only two plates diverge? and (5) What was the degree of melting, compared to normal mid-ocean ridge basalt? Unraveling the geological processes that contributed to the emplacement of Shatsky Rise is challenging, particularly since considerable time has elapsed since this LIP began to form and no direct observational method can be used to characterize the mantle plume or geochemical heterogeneity that may have been associated with it. There are, however, relatively abundant marine geophysical and geological data available for the Shatsky Rise region, which enable modeling of plate-boundary-related processes. This project uses a finite element model of the Pacific-Izanagi-Farallon triple junction to constrain how mantle upwelled in response to the divergence of three plates. Models incorporate the geometry of the Pacific-Izanagi-Farallon triple junction from plate reconstructions, realistic relative plate motion vectors, and particle tracking to follow the advection of mantle material. A subset of models also includes treatment of mantle dehydration viscosity and the effect of triple junction plate boundary migration. The model calculations can be compared to existing seafloor data and geochemical analyses to improve inferences about the nature, location, and spatial dispersion of heterogeneous mantle material involved in Shatsky Rise formation.
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/70808
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Jennifer Georgen.How Important Were Mid-Ocean Ridge Processes in the Formation of Shatsky Rise?.2017.