气候变化领域集成服务门户(CCPortal): Lower Crustal Composition in the Southwestern United States

CCPortal

DOI	10.1029/2019JB019011
	Lower Crustal Composition in the Southwestern United States
	Sammon L.G.; Gao C.; McDonough W.F.
发表日期	2020
ISSN	21699313
卷号	125 期号:3
英文摘要	The composition of the lower continental crust is well studied but poorly understood because of the difficulty of sampling large portions of it. Petrological and geochemical analyses of this deepest portion of the continental crust are limited to the study of high-grade metamorphic lithologies, such as granulite. In situ lower crustal studies require geophysical experiments to determine regional-scale phenomena. Since geophysical properties, such as shear wave velocity (Vs), are nonunique among different compositions and temperatures, the most informative lower crustal models combine both geochemical and geophysical knowledge. We explored a combined modeling technique by analyzing the Basin and Range and Colorado Plateau of the United States, a region for which plentiful geochemical and geophysical data are available. By comparing seismic velocity predictions based on composition and thermodynamic principles to ambient noise inversions, we identified three compositional trends in the southwestern United States that reflect three different geologic settings. The Colorado Plateau (thick crust), Northern Basin and Range (medium crust), and Southern Basin and Range (thin crust) have intermediate, intermediate-mafic, and mafic deep crustal compositions. Identifying the composition of the lower crust depends heavily on its temperature because of the effect it has on rock mineralogy and physical properties. In this region, we see evidence for a lower crust that overall is intermediate-mafic in composition (53.7 (Formula presented.) 7.2 wt.% SiO (Formula presented.)) and notably displays a gradient of decreasing SiO (Formula presented.) with depth. © 2020. American Geophysical Union. All Rights Reserved.
英文关键词	Basin and Range; Colorado Plateau; deep crust composition; granulite; lower crust
语种	英语
来源期刊	Journal of Geophysical Research: Solid Earth
文献类型	期刊论文
条目标识符	http://gcip.llas.ac.cn/handle/2XKMVOVA/187927
作者单位	Department of Geology, University of Maryland, College Park, MD, United States; Department of Earth Sciences and Research Center for Neutrino Science, Tohoku University, Sendai, Japan
推荐引用方式 GB/T 7714	Sammon L.G.,Gao C.,McDonough W.F.. Lower Crustal Composition in the Southwestern United States[J],2020,125(3).
APA	Sammon L.G.,Gao C.,&McDonough W.F..(2020).Lower Crustal Composition in the Southwestern United States.Journal of Geophysical Research: Solid Earth,125(3).
MLA	Sammon L.G.,et al."Lower Crustal Composition in the Southwestern United States".Journal of Geophysical Research: Solid Earth 125.3(2020).