Gem-quality zircon megacrysts from placer deposits in the central highlands, Vietnam - potential source and links to cenozoic alkali basalts

Vuong Bui Thi Sinh, Yasuhito Osanai, Christoph Lenz, Nobuhiko Nakano, Tatsuro Adachi, Elena Belousova, Ippei Kitano

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Gem-quality zircon megacrysts occur in placer deposits in the Central Highlands, Vietnam, and have euhedral to anhedral crystal shapes with dimensions of ~3 cm in length. These zircons have primary inclusions of calcite, olivine, and corundum. Secondary quartz, baddeleyite, hematite, and CO2 fluid inclusions were found in close proximity to cracks and tubular channels. LA-ICP-MS U-Pb ages of analyzed zircon samples yielded two age populations of ca. 1.0 Ma and ca. 6.5 Ma, that were consistent with the ages of alkali basalt eruptions in the Central Highlands at Buon Ma Thuot (5.80–1.67 Ma), Pleiku (4.30–0.80 Ma), and Xuan Loc (0.83–0.44 Ma). The zircon geochemical signatures and primary inclusions suggested a genesis from carbonatite-dominant melts as a result of partial melting of a metasomatized lithospheric mantle source, but not from the host alkali basalt. Chondrite-normalized rare earth element patterns showed a pronounced positive Ce, but negligible Eu anomalies. Detailed hyperspectral Dy3+ photoluminescence images of zircon megacrysts revealed resorption and re-growth processes.

LanguageEnglish
Article number89
Pages1-18
Number of pages18
JournalMinerals
Volume9
Issue number2
DOIs
Publication statusPublished - Feb 2019

Fingerprint

Placers
Gems
placer deposit
Zircon
Basalt
alkali basalt
zircon
Deposits
baddeleyite
Olivine
Corundum
corundum
resorption
carbonatite
Hematite
Calcite
regrowth
Rare earth elements
chondrite
mantle source

Bibliographical note

Copyright the Author(s) 2019. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

Keywords

  • zircon megacrysts
  • placer deposits
  • rare earth elements (REE)
  • carbonatite-dominant melts
  • Central Highlands
  • Vietnam
  • hyperspectral photoluminescence imaging
  • LA-ICP-MS

Cite this

Sinh, Vuong Bui Thi ; Osanai, Yasuhito ; Lenz, Christoph ; Nakano, Nobuhiko ; Adachi, Tatsuro ; Belousova, Elena ; Kitano, Ippei. / Gem-quality zircon megacrysts from placer deposits in the central highlands, Vietnam - potential source and links to cenozoic alkali basalts. In: Minerals. 2019 ; Vol. 9, No. 2. pp. 1-18.
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Gem-quality zircon megacrysts from placer deposits in the central highlands, Vietnam - potential source and links to cenozoic alkali basalts. / Sinh, Vuong Bui Thi; Osanai, Yasuhito; Lenz, Christoph; Nakano, Nobuhiko; Adachi, Tatsuro; Belousova, Elena; Kitano, Ippei.

In: Minerals, Vol. 9, No. 2, 89, 02.2019, p. 1-18.

Research output: Contribution to journalArticleResearchpeer-review

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AU - Sinh, Vuong Bui Thi

AU - Osanai, Yasuhito

AU - Lenz, Christoph

AU - Nakano, Nobuhiko

AU - Adachi, Tatsuro

AU - Belousova, Elena

AU - Kitano, Ippei

N1 - Copyright the Author(s) 2019. Version archived for private and non-commercial use with the permission of the author/s and according to publisher conditions. For further rights please contact the publisher.

PY - 2019/2

Y1 - 2019/2

N2 - Gem-quality zircon megacrysts occur in placer deposits in the Central Highlands, Vietnam, and have euhedral to anhedral crystal shapes with dimensions of ~3 cm in length. These zircons have primary inclusions of calcite, olivine, and corundum. Secondary quartz, baddeleyite, hematite, and CO2 fluid inclusions were found in close proximity to cracks and tubular channels. LA-ICP-MS U-Pb ages of analyzed zircon samples yielded two age populations of ca. 1.0 Ma and ca. 6.5 Ma, that were consistent with the ages of alkali basalt eruptions in the Central Highlands at Buon Ma Thuot (5.80–1.67 Ma), Pleiku (4.30–0.80 Ma), and Xuan Loc (0.83–0.44 Ma). The zircon geochemical signatures and primary inclusions suggested a genesis from carbonatite-dominant melts as a result of partial melting of a metasomatized lithospheric mantle source, but not from the host alkali basalt. Chondrite-normalized rare earth element patterns showed a pronounced positive Ce, but negligible Eu anomalies. Detailed hyperspectral Dy3+ photoluminescence images of zircon megacrysts revealed resorption and re-growth processes.

AB - Gem-quality zircon megacrysts occur in placer deposits in the Central Highlands, Vietnam, and have euhedral to anhedral crystal shapes with dimensions of ~3 cm in length. These zircons have primary inclusions of calcite, olivine, and corundum. Secondary quartz, baddeleyite, hematite, and CO2 fluid inclusions were found in close proximity to cracks and tubular channels. LA-ICP-MS U-Pb ages of analyzed zircon samples yielded two age populations of ca. 1.0 Ma and ca. 6.5 Ma, that were consistent with the ages of alkali basalt eruptions in the Central Highlands at Buon Ma Thuot (5.80–1.67 Ma), Pleiku (4.30–0.80 Ma), and Xuan Loc (0.83–0.44 Ma). The zircon geochemical signatures and primary inclusions suggested a genesis from carbonatite-dominant melts as a result of partial melting of a metasomatized lithospheric mantle source, but not from the host alkali basalt. Chondrite-normalized rare earth element patterns showed a pronounced positive Ce, but negligible Eu anomalies. Detailed hyperspectral Dy3+ photoluminescence images of zircon megacrysts revealed resorption and re-growth processes.

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