| 项目编号: | 1361487
|
| 项目名称: | CSEDI: Layering within cratonic lithosphere: Integrated constraints from xenoliths, seismic structure and geodynamical modeling |
| 作者: | Karen Fischer
|
| 承担单位: | Brown University
|
| 批准年: | 2013
|
| 开始日期: | 2014-06-01
|
| 结束日期: | 2018-05-31
|
| 资助金额: | USD519493
|
| 资助来源: | US-NSF
|
| 项目类别: | Continuing grant
|
| 国家: | US
|
| 语种: | 英语
|
| 特色学科分类: | Geosciences - Earth Sciences
|
| 英文关键词: | cratonic mantle
; layering
; internal structure
; craton
; different type
; grain size
; constraint
; continent
; seismic structure
; viscosity structure
; year
; xenolith constraint
; range
; xenolith-based geochemical
; mantle lithosphere
; geodynamical numerical modeling
; model
; thick mantle lithosphere
; seismic velocity structure
; integrated program
; geodynamical modeling
; seismological layering
; xenolith microstructural analysis
; seismological constraint
; internal layering
; excellent xenolith suite
; cratonic layering
|
| 英文摘要: | Cratons are the old, stable cores of continents. They are regions that have not experienced significant deformation for the last 2.5 billion years. A variety of geochemical and geophysical data indicate that they are underlain by thick mantle lithosphere that is unusually cold relative to the surrounding mantle. The internal structure of the cratonic mantle also includes layering in both physical and chemical properties. However, much remains to be learned about the origin of this internal structure. The researchers plan to use the velocities at which seismic waves propagate through the cratonic mantle to provide bounds on the temperature of the mantle rocks, their chemical composition, and their grain size and rock fabric. The multidisciplinary research team plans to directly measure the geochemistry and rock fabric of samples of the cratonic mantle that have been erupted to the surface to provide complementary information on their chemical evolution and deformation history. The goals of the proposed work are to: 1) better constrain layering in geochemical and seismic velocity structure internal to cratonic mantle lithosphere, 2) explore the relationships among different types of layering, and 3) shed new light on the processes that formed the cratons and the mechanisms that permit them to remain stable over billions of years. Understanding the stable cores of continents will help us understand the evolution of the Earth and its continents through time. This project will contribute to the education and career development of two or more graduate students and several undergraduates, and the interdisciplinary nature of the project will serve to broaden their research expertise. Our faculty team will also teach a semester-long seminar at Brown on the topic of cratons for upper-level undergraduates and graduate students.
The team proposes an integrated program of seismological and xenolith-based geochemical and microstructural analyses and geodynamical modeling focused on three mantle lithospheres that have experienced varying degrees of disruption in the last 2 billion years: the Slave craton, the Wyoming craton and the Colorado Plateau. Each region provides excellent xenolith suites that sample the deep cratonic mantle and broadband stations that will allow progress on resolving seismic velocity structure. They plan to investigate the relationships between different types of layering in the cratonic mantle (mid-lithospheric seismic discontinuities, layering in azimuthal anisotropy, depletion, refertilization, grain size, olivine fabrics) with a variety of new techniques. Joint inversions of scattered wave, surface wave, ambient noise and SKS splitting data will provide better constraints on seismic structure. In xenoliths from a range of mantle depths we will use well-established analytical techniques to determine bulk and trace element compositions and major, trace and water contents in their constituent minerals to establish: the pressure-temperature conditions of the last tectonomagmatic event, the degree of hydration of the mantle, and the source of the metasomatic fluids/melts that affected the lithospheric mantle (subduction-related versus subduction-unrelated). Xenolith microstructural analyses will yield constraints on grain size, water content, and lattice preferred orientation. Thermobarometry, modal analyses, volatile content and grain size will be used to predict seismic velocities via a combination of elastic models (which include the effects of composition) and anelastic effects; these predictions will be compared to the observed seismological layering. Based on these comparisons, a range of models will be defined that reflect the best fits to geochemical, microstructural and seismological constraints. To explore the implications of these models for the stability of the cratonic mantle, we will use the xenolith constraints to calculate effective viscosity using experimental flow laws for olivine, as well as density. The range of possible density and viscosity structures for each study region will be incorporated in geodynamical numerical modeling of lithospheric stability, including their vulnerability to subduction processes at their margins. This work will provide new insight on several questions. 1) What is the internal layering (physical and chemical) of the cratonic mantle lithosphere? How do different types of layering correlate with each other? 2) How has their internal structure permitted stable cratons to remain largely intact over billion-year time-scales? How does subduction at the edges of a craton affect the stability of the cratonic mantle lithosphere? 3) How do the different types and scales of cratonic layering 'test' models of cratonic formation? |
| 资源类型: | 项目
|
| 标识符: | http://119.78.100.158/handle/2HF3EXSE/96727
|
| Appears in Collections: | 影响、适应和脆弱性
气候减缓与适应
|
|
There are no files associated with this item.
|
| Recommended Citation: | |
Karen Fischer. CSEDI: Layering within cratonic lithosphere: Integrated constraints from xenoliths, seismic structure and geodynamical modeling. 2013-01-01.
|
|
|