Synmagmatic crustal thickening and the importance of garnet fractionation in making continental crust

GSTDTAP

项目编号	1850832
	Synmagmatic crustal thickening and the importance of garnet fractionation in making continental crust
	Cin-Ty Lee (Principal Investigator)
主持机构	William Marsh Rice University
项目开始年	2019
	2019-06-15
项目结束日期	2020-05-31
资助机构	US-NSF
项目类别	Standard Grant
项目经费	172684(USD)
国家	美国
语种	英语
英文摘要	Earth has an unusual bimodal hypsometry among the rocky planets in the solar system. Today, about 70% of Earth's surface lies below ~4 km below sea level while the remaining parts of the Earth's surface ride above sea level, manifested as continents. This bimodal hypsometry drives much of the mass cycling on Earth's surface and fuels the evolution of Earth's habitability. Understanding why Earth is the only planet with such a pronounced bimodality rests on the understanding of why Earth has continents - one of the most fundamental questions of geology. In addition to these scientific impacts, this project will support a course taught on scientific illustration and field observation. Undergraduates students will be mentored, and the team will collaborate with instructors in the Houston area high schools to introduce geology and natural history to under-represented minorities, and provide short courses and lectures at Rice's continuing education program and the Houston Museum of Natural Science. The continental crust is felsic, meaning that it is enriched in silica and depleted in Fe and Mg compared with the mafic oceanic crust. But how the continental crust achieved its felsic composition when the building blocks are mafic is unclear. In subduction zones, crustal composition correlates with crustal thickness and arcs built on thick crust tend to be more felsic, like the continental crust. This proposal seeks to understand the fundamental mechanism linking crustal thickening and differentiation, with an emphasis on the role of garnet in the formation of the continental crust. The key to testing the hypothesis is whether garnet fractionation drives oxidation or reduction of the residual magma. Thus, the objective is to quantify how much of the iron in garnet is ferric, and the researchers will study samples from the North American Cordillera and analog localities, such as New Zealand and Tibet. Ferric iron content will be determined using the electron microprobe flank method, calibrated against Mossbauer spectroscopic measurements. Trace element and oxybarometric constraints on volcanic and plutonic rocks from these areas will be conducted to evaluate whether differentiated magmas have experienced oxidation and garnet fractionation. Combined investigation of magmas and cumulates will provide a comprehensive view of continental crust-forming magmatism. The formation of continental crust is the culmination of feedbacks between climate, tectonics, magmatism, and the deep Earth. 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/213182
专题	环境与发展全球科技态势
推荐引用方式 GB/T 7714	Cin-Ty Lee .Synmagmatic crustal thickening and the importance of garnet fractionation in making continental crust.2019.