TY - JOUR
T1 - Gem-quality zircon megacrysts from placer deposits in the central highlands, Vietnam—potential source and links to cenozoic alkali basalts
AU - Sinh, Vuong Bui Thi
AU - Osanai, Yasuhito
AU - Lenz, Christoph
AU - Nakano, Nobuhiko
AU - Adachi, Tatsuro
AU - Belousova, Elena
AU - Kitano, Ippei
N1 - Funding Information:
Funding: This study was funded by the Monbukagakusho/Ministry of Education, Culture, Sports, Science and a Technology-Japan (MEXT) scholarship at Kyushu University. Y.O. is funded by JSPS KAKENHI grants No. 16H02743, 22244063, and 21253008. C.L. and E.B. gratefully acknowledge the use of instrumentation funded through an honorary-associate agreement with the ARC CFSS/GEMOC at Macquarie University, Sydney. Financial support to C.L. was provided by the Austrian Science Fund (FWF), through project J3662-N19. N.N. is funded by JSPS KAKENHI grants No. 15K05345 and 18H01316.
Funding Information:
This study was funded by the Monbukagakusho/Ministry of Education, Culture, Sports, Science and a Technology-Japan (MEXT) scholarship at Kyushu University. Y.O. is funded by JSPS KAKENHI grants No. 16H02743, 22244063, and 21253008. C.L. and E.B. gratefully acknowledge the use of instrumentation funded through an honorary-associate agreement with the ARC CFSS/GEMOC at Macquarie University, Sydney. Financial support to C.L. was provided by the Austrian Science Fund (FWF), through project J3662-N19. N.N. is funded by JSPS KAKENHI grants No. 15K05345 and 18H01316. Acknowledgments: The authors thank Le Thi Thu Huong from Senckenberg museum in Frankfurt, Germany, and Nguyen Thi Minh Thuyet from Hanoi University of Science, Vietnam for their help during fieldwork and sample collection in Vietnam. Special thanks to the local zircon miners in Central Highlands, Vietnam for providing insights into their mining operations. We are indebted to three anonymous reviewers for their critical comments on the manuscript.
Publisher Copyright:
© 2019 by the authors. Licensee MDPI, Basel, Switzerland.
PY - 2019
Y1 - 2019
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 CO 2 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 Dy 3+ 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 CO 2 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 Dy 3+ photoluminescence images of zircon megacrysts revealed resorption and re-growth processes.
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U2 - 10.3390/min9020089
DO - 10.3390/min9020089
M3 - Article
AN - SCOPUS:85062345443
VL - 9
JO - Minerals
JF - Minerals
SN - 2075-163X
IS - 2
M1 - 89
ER -