U-Pb isotope systematics of micro-zircon inclusions: Implications for the age and origin of eclogite xenolith from the Colorado Plateau
Tomohiro Usui, Katsura Kobayashi, Eizo Nakamura
Institute for Planetary Materials
We improved the U-Pb zircon dating method employing HR-SIMS by applying i) preparation of precise and homogeneous zircon standards by ID-TIMS, ii) simultaneous analysis of Pb isotopes by multi-collection system, and iii) use of a highly focused primary ion beam as small as 5 μm in diameter. Using the improved HR-SIMS technique, U-Pb ages of zircons in an eclogite xenolith from the Colorado Plateau were determined. Zircon occurs as small inclusions (< 20 μm) in most constituent minerals. Ten zircons were measured, and the concordant analyses of these zircon data yielded a weighted mean value of 65.2 ± 0.7 Ma for the age of crystallization. Petrographic and geochemical observations suggest that this zircon age represents the age of initial subduction of basaltic oceanic crust. We conclude that the eclogite xenolith was a fragment of basaltic oceanic crust subducted to > 90 km depth along a cold geotherm with a subduction rate of > 2 cm/y in Tertiary.
Proceedings of the Japan Academy Series B: Physical and Biological Sciences
https://doi.org/10.2183/pjab.78.51
Eclogite xenolith
HR-SIMS
ID-TIMS
U-Pb age
Agricultural and Biological Sciences(all)
10.2183/pjab.78.51
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Colorado Plateau (US) Physics & Astronomy 100%
eclogite Physics & Astronomy 82%
zircon Medicine & Life Sciences 80%
Isotopes Medicine & Life Sciences 47%
secondary ion mass spectrometry Physics & Astronomy 44%
isotopes Agriculture & Biology 44%
plateaus Agriculture & Biology 39%
inclusions Physics & Astronomy 34%
Usui, T., Kobayashi, K., & Nakamura, E. (2002). U-Pb isotope systematics of micro-zircon inclusions: Implications for the age and origin of eclogite xenolith from the Colorado Plateau. Proceedings of the Japan Academy Series B: Physical and Biological Sciences, 78(3), 51-56. https://doi.org/10.2183/pjab.78.51
U-Pb isotope systematics of micro-zircon inclusions : Implications for the age and origin of eclogite xenolith from the Colorado Plateau. / Usui, Tomohiro; Kobayashi, Katsura; Nakamura, Eizo.
In: Proceedings of the Japan Academy Series B: Physical and Biological Sciences, Vol. 78, No. 3, 03.2002, p. 51-56.
Usui, T, Kobayashi, K & Nakamura, E 2002, 'U-Pb isotope systematics of micro-zircon inclusions: Implications for the age and origin of eclogite xenolith from the Colorado Plateau', Proceedings of the Japan Academy Series B: Physical and Biological Sciences, vol. 78, no. 3, pp. 51-56. https://doi.org/10.2183/pjab.78.51
Usui T, Kobayashi K, Nakamura E. U-Pb isotope systematics of micro-zircon inclusions: Implications for the age and origin of eclogite xenolith from the Colorado Plateau. Proceedings of the Japan Academy Series B: Physical and Biological Sciences. 2002 Mar;78(3):51-56. https://doi.org/10.2183/pjab.78.51
Usui, Tomohiro ; Kobayashi, Katsura ; Nakamura, Eizo. / U-Pb isotope systematics of micro-zircon inclusions : Implications for the age and origin of eclogite xenolith from the Colorado Plateau. In: Proceedings of the Japan Academy Series B: Physical and Biological Sciences. 2002 ; Vol. 78, No. 3. pp. 51-56.
@article{64ad723a3c5f4bcb9abb7b5267817c11,
title = "U-Pb isotope systematics of micro-zircon inclusions: Implications for the age and origin of eclogite xenolith from the Colorado Plateau",
abstract = "We improved the U-Pb zircon dating method employing HR-SIMS by applying i) preparation of precise and homogeneous zircon standards by ID-TIMS, ii) simultaneous analysis of Pb isotopes by multi-collection system, and iii) use of a highly focused primary ion beam as small as 5 μm in diameter. Using the improved HR-SIMS technique, U-Pb ages of zircons in an eclogite xenolith from the Colorado Plateau were determined. Zircon occurs as small inclusions (< 20 μm) in most constituent minerals. Ten zircons were measured, and the concordant analyses of these zircon data yielded a weighted mean value of 65.2 ± 0.7 Ma for the age of crystallization. Petrographic and geochemical observations suggest that this zircon age represents the age of initial subduction of basaltic oceanic crust. We conclude that the eclogite xenolith was a fragment of basaltic oceanic crust subducted to > 90 km depth along a cold geotherm with a subduction rate of > 2 cm/y in Tertiary.",
keywords = "Colorado Plateau, Eclogite xenolith, HR-SIMS, ID-TIMS, U-Pb age, Zircon",
author = "Tomohiro Usui and Katsura Kobayashi and Eizo Nakamura",
doi = "10.2183/pjab.78.51",
journal = "Proceedings of the Japan Academy Series B: Physical and Biological Sciences",
publisher = "Japan Academy",
T1 - U-Pb isotope systematics of micro-zircon inclusions
T2 - Implications for the age and origin of eclogite xenolith from the Colorado Plateau
AU - Usui, Tomohiro
AU - Kobayashi, Katsura
AU - Nakamura, Eizo
N2 - We improved the U-Pb zircon dating method employing HR-SIMS by applying i) preparation of precise and homogeneous zircon standards by ID-TIMS, ii) simultaneous analysis of Pb isotopes by multi-collection system, and iii) use of a highly focused primary ion beam as small as 5 μm in diameter. Using the improved HR-SIMS technique, U-Pb ages of zircons in an eclogite xenolith from the Colorado Plateau were determined. Zircon occurs as small inclusions (< 20 μm) in most constituent minerals. Ten zircons were measured, and the concordant analyses of these zircon data yielded a weighted mean value of 65.2 ± 0.7 Ma for the age of crystallization. Petrographic and geochemical observations suggest that this zircon age represents the age of initial subduction of basaltic oceanic crust. We conclude that the eclogite xenolith was a fragment of basaltic oceanic crust subducted to > 90 km depth along a cold geotherm with a subduction rate of > 2 cm/y in Tertiary.
AB - We improved the U-Pb zircon dating method employing HR-SIMS by applying i) preparation of precise and homogeneous zircon standards by ID-TIMS, ii) simultaneous analysis of Pb isotopes by multi-collection system, and iii) use of a highly focused primary ion beam as small as 5 μm in diameter. Using the improved HR-SIMS technique, U-Pb ages of zircons in an eclogite xenolith from the Colorado Plateau were determined. Zircon occurs as small inclusions (< 20 μm) in most constituent minerals. Ten zircons were measured, and the concordant analyses of these zircon data yielded a weighted mean value of 65.2 ± 0.7 Ma for the age of crystallization. Petrographic and geochemical observations suggest that this zircon age represents the age of initial subduction of basaltic oceanic crust. We conclude that the eclogite xenolith was a fragment of basaltic oceanic crust subducted to > 90 km depth along a cold geotherm with a subduction rate of > 2 cm/y in Tertiary.
KW - Colorado Plateau
KW - Eclogite xenolith
KW - HR-SIMS
KW - ID-TIMS
KW - U-Pb age
KW - Zircon
U2 - 10.2183/pjab.78.51
DO - 10.2183/pjab.78.51
JO - Proceedings of the Japan Academy Series B: Physical and Biological Sciences
JF - Proceedings of the Japan Academy Series B: Physical and Biological Sciences