Evaluating the Role of Fluid and Melts in Mediating Element Recycling and Exhumation During Retrograde Metamorphism Following UHP Metamorphism

GSTDTAP

项目编号	1624546
	Evaluating the Role of Fluid and Melts in Mediating Element Recycling and Exhumation During Retrograde Metamorphism Following UHP Metamorphism
	Stacia Gordon
主持机构	Board of Regents, NSHE, obo University of Nevada, Reno
项目开始年	2016
	2016-09-01
项目结束日期	2019-08-31
资助机构	US-NSF
项目类别	Continuing grant
项目经费	47275(USD)
国家	美国
语种	英语
英文摘要	Nontechnical Abstract Plate tectonics introduces a feedback loop in which subduction of crustal material at convergent plate margins continually injects less dense rocks formed at the surface back into Earth's dense mantle. As this crustal material is subducted, it interacts with the mantle, exchanges elements, and continuously drives the geochemical evolution of Earth. In order to determine the effect of element recycling during the exhumation of subducted rocks, it is necessary to investigate the chemical reactions that occur during the exhumation of crustal rocks back to Earth's surface. Ultrahigh-pressure (UHP) terranes contain rocks that were carried down to mantle depths via subduction and then returned to the surface. Some of the rocks within UHP terranes preserve "pristine" mineral assemblages that equilibrated at mantle depths. Typically the outermost rind of these rocks contain new or "retrogressed" mineral assemblages that formed as the rocks were being exhumed to the surface. By comparing the chemistry of the "fresh" to the "retrogressed" UHP rocks, the chemical changes that are triggered by exhumation will be examined and their impact upon the geochemical evolution of Earth will be assessed. Technical Abstract Mass transfer within subduction zones remains poorly understood. In particular, there is limited knowledge of the P-T conditions at which elemental recycling occurs and of what transporting agents drive the elemental-recycling processes. Many field-based studies have focused upon exhumed high-pressure and ultrahigh-pressure (UHP) terranes to better understand the devolatilization reactions and products that occur along the prograde path as crustal rocks are subducted deep within Earth. In contrast, the retrograde reactions that transpire during the exhumation of these deeply subducted rocks have largely been ignored despite the fact that peak temperatures generally occur along the retrograde path and devolatilization and melting reactions are common. Retrograde metamorphic reactions and associated mass transfer may thus have a great influence on elemental-recycling processes in subduction zones and may also dictate the nature of the exhumation processes that bring crustal material from UHP depths to the surface. This integrated field and laboratory study of the Western Gneiss Region will reveal whether large-scale elemental recycling occurs during retrogression of UHP crustal rocks and whether these processes influence the rates and mechanisms by which UHP terranes are exhumed back to Earth's surface.
来源学科分类	Geosciences - Earth Sciences
文献类型	项目
条目标识符	http://119.78.100.173/C666/handle/2XK7JSWQ/70172
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Stacia Gordon.Evaluating the Role of Fluid and Melts in Mediating Element Recycling and Exhumation During Retrograde Metamorphism Following UHP Metamorphism.2016.