Incomplete retention of radiation damage in zircon from Sri Lanka

Lutz Nasdala, Peter W Reiners, John I. Garver, Allen K. Kennedy, Richard A. Stern, Etienne Balan, Richard Wirth

Research output: Contribution to journalArticle

135 Citations (Scopus)

Abstract

A suite of 18 zircon gemstones from placers in the Highland/Southwestern Complex, Sri Lanka, were subjected to a comprehensive study of their radiation damages and ages. The investigation included X-ray diffraction, Raman and PL spectroscopy, electron microprobe, PIXE and HRTEM analysis, as well as (U-Th)/He and SHRIMP U-Th-Pb age determinations. Zircon samples described in this study are virtually homogeneous. They cover the range from slightly metamict to nearly amorphous. Generally concordant U-Th-Pb ages averaging 555 ± 11 Ma were obtained. Late Ordovician zircon (U-Th)/He ages scattering around 443 ± 9 Ma correspond reasonably well with previously determined biotite Rb-Sr ages for rocks from the HSWC. Slightly to moderately metamict zircon has retained the radiogenic He whereas only strongly radiation-damaged zircon (calculated total fluences exceeding ∼3.5 × 1018 α-events/g) has experienced significant He loss. When compared to unannealed zircon from other localities, Sri Lanka zircon is about half as metamict as would correspond to complete damage accumulation over a ∼555 m.y. lasting self-irradiation period, suggesting significant annealing of the structural radiation damage. Insufficient consideration of this has often resulted in significant underestimation of radiation effects in zircon. We suggest to estimate "effective α-doses" for Sri Lanka zircon by multiplying total α-fluences, which were calculated using the zircon U-Th-Pb age, by a correction factor of 0.55. This conversion may be applied to literature data as well, because all gem-zircon samples from Sri Lanka (this work and previous studies) seem to reveal the same general trends of property changes depending on the radiation damage. The use of "effective α-doses" for Sri Lanka zircon contributes to more reliable quantitative estimates of radiation effects and makes possible direct comparison between natural and synthetic radiation-damaged zircon.

Original languageEnglish (US)
Pages (from-to)219-231
Number of pages13
JournalAmerican Mineralogist
Volume89
Issue number1
StatePublished - Jan 2004
Externally publishedYes

Fingerprint

Sri Lanka
radiation damage
Radiation damage
zircon
radiation effects
fluence
dosage
highlands
chronology
biotite
radiation
estimates
Radiation effects
electron spectroscopy
Raman spectroscopy
rocks
damage
trends
irradiation
annealing

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Nasdala, L., Reiners, P. W., Garver, J. I., Kennedy, A. K., Stern, R. A., Balan, E., & Wirth, R. (2004). Incomplete retention of radiation damage in zircon from Sri Lanka. American Mineralogist, 89(1), 219-231.

Incomplete retention of radiation damage in zircon from Sri Lanka. / Nasdala, Lutz; Reiners, Peter W; Garver, John I.; Kennedy, Allen K.; Stern, Richard A.; Balan, Etienne; Wirth, Richard.

In: American Mineralogist, Vol. 89, No. 1, 01.2004, p. 219-231.

Research output: Contribution to journalArticle

Nasdala, L, Reiners, PW, Garver, JI, Kennedy, AK, Stern, RA, Balan, E & Wirth, R 2004, 'Incomplete retention of radiation damage in zircon from Sri Lanka', American Mineralogist, vol. 89, no. 1, pp. 219-231.
Nasdala L, Reiners PW, Garver JI, Kennedy AK, Stern RA, Balan E et al. Incomplete retention of radiation damage in zircon from Sri Lanka. American Mineralogist. 2004 Jan;89(1):219-231.
Nasdala, Lutz ; Reiners, Peter W ; Garver, John I. ; Kennedy, Allen K. ; Stern, Richard A. ; Balan, Etienne ; Wirth, Richard. / Incomplete retention of radiation damage in zircon from Sri Lanka. In: American Mineralogist. 2004 ; Vol. 89, No. 1. pp. 219-231.
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