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Hafnium isotope evidence for a transition in the dynamics of continental growth 3.2Gyr ago

Naeraa, Tomas LU ; Scherstén, Anders LU ; Rosing, M. T.; Kemp, A. I. S.; Hoffmann, J. E.; Kokfelt, T. F. and Whitehouse, M. J. (2012) In Nature 485(7400). p.627-627
Abstract
Earth's lithosphere probably experienced an evolution towards the modern plate tectonic regime, owing to secular changes in mantle temperature(1,2). Radiogenic isotope variations are interpreted as evidence for the declining rates of continental crustal growth over time(3-5), with some estimates suggesting that over 70% of the present continental crustal reservoir was extracted by the end of the Archaean eon(3,5). Patterns of crustal growth and reworking in rocks younger than three billion years (Gyr) are thought to reflect the assembly and break-up of supercontinents by Wilson cycle processes and mark an important change in lithosphere dynamics(6). In southern West Greenland numerous studies have, however, argued for subduction settings... (More)
Earth's lithosphere probably experienced an evolution towards the modern plate tectonic regime, owing to secular changes in mantle temperature(1,2). Radiogenic isotope variations are interpreted as evidence for the declining rates of continental crustal growth over time(3-5), with some estimates suggesting that over 70% of the present continental crustal reservoir was extracted by the end of the Archaean eon(3,5). Patterns of crustal growth and reworking in rocks younger than three billion years (Gyr) are thought to reflect the assembly and break-up of supercontinents by Wilson cycle processes and mark an important change in lithosphere dynamics(6). In southern West Greenland numerous studies have, however, argued for subduction settings and crust growth by arc accretion back to 3.8 Gyr ago(7-9), suggesting that modern-day tectonic regimes operated during the formation of the earliest crustal rock record. Here we report in situ uranium-lead, hafnium and oxygen isotope data from zircons of basement rocks in southern West Greenland across the critical time period during which modern-like tectonic regimes could have initiated. Our data show pronounced differences in the hafnium isotope-time patterns across this interval, requiring changes in the characteristics of the magmatic protolith. The observations suggest that 3.9-3.5-Gyr-old rocks differentiated from a >3.9-Gyr-old source reservoir with a chondritic to slightly depleted hafnium isotope composition. In contrast, rocks formed after 3.2 Gyr ago register the first additions of juvenile depleted material (that is, new mantle-derived crust) since 3.9 Gyr ago, and are characterized by striking shifts in hafnium isotope ratios similar to those shown by Phanerozoic subduction-related orogens(10-12). These data suggest a transitional period 3.5-3.2 Gyr ago from an ancient (3.9-3.5 Gyr old) crustal evolutionary regime unlike that of modern plate tectonics to a geodynamic setting after 3.2 Gyr ago that involved juvenile crust generation by plate tectonic processes. (Less)
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publication status
published
subject
in
Nature
volume
485
issue
7400
pages
627 - 627
publisher
Nature Publishing Group
external identifiers
  • wos:000304608000045
  • scopus:84867599827
ISSN
0028-0836
DOI
10.1038/nature11140
language
English
LU publication?
yes
id
ba906e1d-cfcc-4ea0-abfc-57bec97c7957 (old id 2799780)
date added to LUP
2012-06-25 12:28:16
date last changed
2017-11-19 03:20:45
@article{ba906e1d-cfcc-4ea0-abfc-57bec97c7957,
  abstract     = {Earth's lithosphere probably experienced an evolution towards the modern plate tectonic regime, owing to secular changes in mantle temperature(1,2). Radiogenic isotope variations are interpreted as evidence for the declining rates of continental crustal growth over time(3-5), with some estimates suggesting that over 70% of the present continental crustal reservoir was extracted by the end of the Archaean eon(3,5). Patterns of crustal growth and reworking in rocks younger than three billion years (Gyr) are thought to reflect the assembly and break-up of supercontinents by Wilson cycle processes and mark an important change in lithosphere dynamics(6). In southern West Greenland numerous studies have, however, argued for subduction settings and crust growth by arc accretion back to 3.8 Gyr ago(7-9), suggesting that modern-day tectonic regimes operated during the formation of the earliest crustal rock record. Here we report in situ uranium-lead, hafnium and oxygen isotope data from zircons of basement rocks in southern West Greenland across the critical time period during which modern-like tectonic regimes could have initiated. Our data show pronounced differences in the hafnium isotope-time patterns across this interval, requiring changes in the characteristics of the magmatic protolith. The observations suggest that 3.9-3.5-Gyr-old rocks differentiated from a >3.9-Gyr-old source reservoir with a chondritic to slightly depleted hafnium isotope composition. In contrast, rocks formed after 3.2 Gyr ago register the first additions of juvenile depleted material (that is, new mantle-derived crust) since 3.9 Gyr ago, and are characterized by striking shifts in hafnium isotope ratios similar to those shown by Phanerozoic subduction-related orogens(10-12). These data suggest a transitional period 3.5-3.2 Gyr ago from an ancient (3.9-3.5 Gyr old) crustal evolutionary regime unlike that of modern plate tectonics to a geodynamic setting after 3.2 Gyr ago that involved juvenile crust generation by plate tectonic processes.},
  author       = {Naeraa, Tomas and Scherstén, Anders and Rosing, M. T. and Kemp, A. I. S. and Hoffmann, J. E. and Kokfelt, T. F. and Whitehouse, M. J.},
  issn         = {0028-0836},
  language     = {eng},
  number       = {7400},
  pages        = {627--627},
  publisher    = {Nature Publishing Group},
  series       = {Nature},
  title        = {Hafnium isotope evidence for a transition in the dynamics of continental growth 3.2Gyr ago},
  url          = {http://dx.doi.org/10.1038/nature11140},
  volume       = {485},
  year         = {2012},
}