DOI: 10.1038/ngeo2462
论文题名: Mechanisms and geologic significance of the mid-lithosphere discontinuity in the continents
作者: Karato S.-I. ; Olugboji T. ; Park J.
刊名: Nature Geoscience
ISSN: 17520894
出版年: 2015
卷: 8, 期: 7 起始页码: 509
结束页码: 514
语种: 英语
英文摘要: The stable continents have a puzzling structure. Recent seismological studies have revealed a marked drop in seismic velocity at middle-lithosphere depths, but a generally small velocity drop at the lithosphere-asthenosphere boundary. The mid-lithosphere discontinuity has previously been attributed to changes in composition and/or crystal alignment (anisotropy) caused by metasomatic alteration, as well as to partial melting and/or accretion of intruded materials that occurred after the formation of the continents. We show that these models cannot easily explain the global presence of a large seismic velocity drop in the middle lithosphere and a small velocity change at the lithosphere-asthenosphere boundary. These models are also difficult to reconcile with long-term continental stability and, in particular, observations of nearly depth-invariant ages of rocks in the continental lithosphere that do not support the notion of late alteration events. Instead, we propose an elastically accommodated grain-boundary sliding model that predicts a substantial velocity drop at the mid-lithosphere discontinuity and a weak seismic signal at the lithosphere-asthenosphere boundary, as observed, without invoking late-stage modifications to the lithosphere. In this model, the mid-lithosphere discontinuity is a general feature of the stable continents, the precise depth of which depends primarily on temperature and water content. Consequently, the depth of the mid-lithosphere discontinuity may provide clues to the evolution of continents. © 2015 Macmillan Publishers Limited. All rights reserved. Citation statistics:
资源类型: 期刊论文
标识符: http://119.78.100.158/handle/2HF3EXSE/106320
Appears in Collections: 气候减缓与适应 科学计划与规划
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作者单位: Department of Geology AndGeophysics, Yale University, New Haven, CT, United States; Department of Geology, University of Maryland, College Park, MD, United States
Recommended Citation:
Karato S.-I.,Olugboji T.,Park J.. Mechanisms and geologic significance of the mid-lithosphere discontinuity in the continents[J]. Nature Geoscience,2015-01-01,8(7)