Thermal history and origin of the Tanzanian Craton from Pb isotope thermochronology of feldspars from lower crustal xenoliths

Jeremy J. Bellucci, William F. McDonough, Roberta L. Rudnick

Research output: Contribution to journalArticlepeer-review

25 Citations (Scopus)

Abstract

Common and radiogenic Pb isotopic compositions of plagioclase and anti-perthitic feldspars from granulite-facies lower crustal xenoliths from the Labait Volcano on the eastern margin of the Tanzanian Craton have been measured via laser ablation MC-ICP-MS. Common Pb in plagioclase and a single stage Pb evolution model indicate that the lower crust of the Tanzanian Craton was extracted from mantle having a 238U/204Pb of 8.1±0.3 and a 232Th/238U of 4.3±0.1 at 2.71±0.09Ga (all uncertainties are 2σ). Since 2.4Ga, some orthoclase domains within anti-perthites have evolved with a maximum 238U/204Pb of 6 and 232Th/238U of 4.3. The spread in Pb isotopic composition in the anti-perthitic feldspars yields single crystal Pb-Pb isochrons of ~2.4Ga, within uncertainty of U-Pb zircon ages from the same sample suite. The Pb isotopic heterogeneities imply that these granulites resided at temperatures <600°C in the lower crust of the Tanzanian Craton from ca. 2.4Ga to the present. In concert with the chemistry of surface samples, mantle xenoliths, and lower crustal xenoliths, our data imply that the cratonic lithosphere in Tanzania formed ca. ~2.7Ga, in a convergent margin setting, and has remained undisturbed since 2.7Ga.

Original languageEnglish
Pages (from-to)493-501
Number of pages9
JournalEarth and Planetary Science Letters
Volume301
Issue number3-4
DOIs
Publication statusPublished - 2011 Jan 15
Externally publishedYes

Keywords

  • Anti-perthite
  • Feldspar
  • LA-MC-ICP-MS
  • Lower crust
  • Tanzanian Craton
  • Thermochronology

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology
  • Earth and Planetary Sciences (miscellaneous)
  • Space and Planetary Science

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