Doctoral Dissertations

Muchen Sun

Keywords and Phrases

Crustal structure; East Africa; Mantle transition zone; Northeast Asia; Receiver function

Abstract

"In spite of numerous geophysical studies have been conducted in East Africa and Northeast Asia, the structure and evolution of the crust, upper mantle, and the mantle transition zone (MTZ) are still controversial. The MTZ discontinuities beneath the study area are imaged by stacking an unprecedented volume of receiver functions (RFs). The normal MTZ thickness beneath the Western Branch of the EARS and Tanzania Craton indicates the absence of present-day thermal upwelling from the lower mantle. In contrast, beneath the Eastern Branch, a significant MTZ thinning reveals the existence of thermal upwelling from either the upper MTZ or the lower mantle. A normal MTZ thickness beneath southern Africa and the negligible disparity of the mean MTZ thicknesses between on and off cratonic regions suggest the absence of thermal influence from the African Superswell and cratonic keels on the MTZ beneath southern Africa. The major volcanoes in northeast China are underlain by a thickened MTZ, which can be interpreted by an anomalously high-water concentration in the MTZ released from the stagnated slab. An abnormally thin MTZ beneath the Hangay Dome suggests the possible existence of thermal upwelling from the lower mantle.

Additionally, the crustal structure in the Malawi Rift Zone (MRZ) has been investigated using RFs and gravity modeling. The small crustal stretching factor is consistent with the general absence of volcanism in the MRZ. The high Vp/Vs beneath the southern MRZ may indicate the existence of partial melting. Abnormally low Vp/Vs along the western boundary of the MRZ may be related to the CO2 suffusion of rift boundary faults"--Abstract, page iv.

Advisor(s)

Gao, Stephen S.
Liu, Kelly H.

Committee Member(s)

Locmelis, Marek
Wronkiewicz, David J.
Fu, Xiaofei

Department(s)

Geosciences and Geological and Petroleum Engineering

Degree Name

Ph. D. in Geology and Geophysics

Publisher

Missouri University of Science and Technology

Publication Date

Spring 2019

Journal article titles appearing in thesis/dissertation

  • Receiver function imaging of mantle transition zone discontinuities beneath the Tanzania Craton and adjacent segments of the East African Rift System
  • Absence of thermal influence from the African Superswell and cratonic keels on the mantle transition zone beneath southern Africa: Evidence from receiver function imaging
  • Mantle transition zone structure beneath northeast Asia: Evidence from receiver functions
  • Crustal structure in the Malawi and Luangwa rift zones and adjacent areas

Pagination

xiv, 116 pages

Note about bibliography

Includes bibliographic references.

Geographic Coverage

East Africa
Southern Africa
Northeast Asia

Rights

© 2019 Muchen Sun, All rights reserved.

Document Type

Dissertation - Open Access

File Type

text

Language

English

Thesis Number

T 11554

Electronic OCLC #

1105154956

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