Continental crust composition constrained by measurements of crustal Poisson's ratio

George Zandt, Charles James Ammon

Research output: Contribution to journalArticle

395 Citations (Scopus)

Abstract

DECIPHERING the geological evolution of the Earth's continental crust requires knowledge of its bulk composition and global variability. The main uncertainties are associated with the composition of the lower crust. Seismic measurements probe the elastic properties of the crust at depth, from which composition can be inferred. Of particular note is Poisson's ratio, Σ; this elastic parameter can be determined uniquely from the ratio of P- to S-wave seismic velocity, and provides a better diagnostic of crustal composition than either P- or S-wave velocity alone1. Previous attempts to measure Σ have been limited by difficulties in obtaining coincident P- and S-wave data sampling the entire crust2. Here we report 76 new estimates of crustal Σ spanning all of the continents except Antarctica. We find that, on average, Σ increases with the age of the crust. Our results strongly support the presence of a mafic lower crust beneath cratons, and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions, followed by magmatic underplating, or a model in which crust formation processes have changed since the Precambrian era.

Original languageEnglish (US)
Pages (from-to)152-154
Number of pages3
JournalNature
Volume374
Issue number6518
DOIs
StatePublished - Jan 1 1995

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Poisson ratio
lower crust
continental crust
S-wave
crust
P-wave
wave velocity
craton
underplating
continental collision
delamination
elastic property
seismic velocity
Precambrian
probe
sampling

All Science Journal Classification (ASJC) codes

  • General

Cite this

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Continental crust composition constrained by measurements of crustal Poisson's ratio. / Zandt, George; Ammon, Charles James.

In: Nature, Vol. 374, No. 6518, 01.01.1995, p. 152-154.

Research output: Contribution to journalArticle

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AU - Ammon, Charles James

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Y1 - 1995/1/1

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AB - DECIPHERING the geological evolution of the Earth's continental crust requires knowledge of its bulk composition and global variability. The main uncertainties are associated with the composition of the lower crust. Seismic measurements probe the elastic properties of the crust at depth, from which composition can be inferred. Of particular note is Poisson's ratio, Σ; this elastic parameter can be determined uniquely from the ratio of P- to S-wave seismic velocity, and provides a better diagnostic of crustal composition than either P- or S-wave velocity alone1. Previous attempts to measure Σ have been limited by difficulties in obtaining coincident P- and S-wave data sampling the entire crust2. Here we report 76 new estimates of crustal Σ spanning all of the continents except Antarctica. We find that, on average, Σ increases with the age of the crust. Our results strongly support the presence of a mafic lower crust beneath cratons, and suggest either a uniformitarian craton formation process involving delamination of the lower crust during continental collisions, followed by magmatic underplating, or a model in which crust formation processes have changed since the Precambrian era.

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