Ion micro-probe U-Pb zircon geochronology of peak and retrograde stages of ultrahigh-pressure metamorphic rocks from the Kokchetav massif, northern Kazakhstan

Ikuo Katayama, Shigenori Maruyama, Christopher D. Parkinson, Kentaro Terada, Yuji Sano

Research output: Contribution to journalArticle

149 Citations (Scopus)

Abstract

Sensitive high resolution ion micro-probe (SHRIMP) U-Pb analyses of zoned zircons were performed to constrain the age and geodynamic significance of the Kokchetav ultrahigh-pressure (UHP) metamorphic rocks, which recrystallized at P > 60 kbar and T> 1000°C. Cathodoluminescence images were correlated with micro-assemblages of mineral inclusions in zircons from diamond-bearing gneisses. These revealed UHP mineral-bearing cores and low-pressure mineral-bearing rims, some zircons also retain inherited cores. Our SHRIMP data identified four discrete stages: Middle Proterozoic protolith age, 537 ± 9 Ma for UHP metamorphic conditions, 507 ± 8 Ma for the late-stage amphibolite facies overprint, and 456-461 Ma for post-orogenic thermal events. Thus, we conclude that Middle Proterozoic supracrustal protoliths of the Kokchetav UHP-HP rocks were subducted to mantle depths in the Middle Cambrian, and exhumed to mid-crustal levels in the Late Cambrian. The exhumation rate calculated from the SHRIMP data and relative P-T conditions is approximately 5 km/Ma. The rapid exhumation rate for the massif is in the same range as other UHP metamorphic terranes, and suggests that slab decoupling may be a driving force for exhumation of UHP metamorphic rocks from mantle depths.

Original languageEnglish
Pages (from-to)185-198
Number of pages14
JournalEarth and Planetary Science Letters
Volume188
Issue number1-2
DOIs
Publication statusPublished - 2001
Externally publishedYes

Fingerprint

Geochronology
Metamorphic rocks
Kazakhstan
geochronology
metamorphic rocks
ion microprobe
metamorphic rock
zircon
Bearings (structural)
Ions
probes
exhumation
Minerals
ions
minerals
protolith
Proterozoic
high resolution
Earth mantle
mineral

Keywords

  • Kokchetav Kazakhstan
  • Mineral inclusion
  • Polym metamorphism
  • Probe
  • SHRIMP data
  • U/Pb
  • Zircon

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Ion micro-probe U-Pb zircon geochronology of peak and retrograde stages of ultrahigh-pressure metamorphic rocks from the Kokchetav massif, northern Kazakhstan. / Katayama, Ikuo; Maruyama, Shigenori; Parkinson, Christopher D.; Terada, Kentaro; Sano, Yuji.

In: Earth and Planetary Science Letters, Vol. 188, No. 1-2, 2001, p. 185-198.

Research output: Contribution to journalArticle

Katayama, Ikuo ; Maruyama, Shigenori ; Parkinson, Christopher D. ; Terada, Kentaro ; Sano, Yuji. / Ion micro-probe U-Pb zircon geochronology of peak and retrograde stages of ultrahigh-pressure metamorphic rocks from the Kokchetav massif, northern Kazakhstan. In: Earth and Planetary Science Letters. 2001 ; Vol. 188, No. 1-2. pp. 185-198.
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