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@article{1410920,
author = {Nasdala, Lutz and Corfu, Fernando and Blaimauer, Doris and Chanmuang, Chutimun and Ruschel, Katja and Škoda, Radek and Wildner, Manfred and Wirth, Richard and Zeug, Manuela and Zoysa, E. Gamini},
article_location = {BOULDER},
article_number = {10},
doi = {http://dx.doi.org/10.1130/G39334.1},
keywords = {PB ZIRCON AGES; RADIATION-DAMAGE; ALTERED ZIRCON; GEOCHRONOLOGY; DISSOLUTION; METAMORPHISM; MICROPROBE; ACCURACY; URANIUM; SYSTEMS},
language = {eng},
issn = {0091-7613},
journal = {Geology},
title = {Neoproterozoic amorphous "ekanite" (Ca2Th0.9U0.1Si8O20) from Okkampitiya, Sri Lanka: A metamict gemstone with excellent lead-retention performance},
volume = {45},
year = {2017}
}
TY - JOUR
ID - 1410920
AU - Nasdala, Lutz - Corfu, Fernando - Blaimauer, Doris - Chanmuang, Chutimun - Ruschel, Katja - Škoda, Radek - Wildner, Manfred - Wirth, Richard - Zeug, Manuela - Zoysa, E. Gamini
PY - 2017
TI - Neoproterozoic amorphous "ekanite" (Ca2Th0.9U0.1Si8O20) from Okkampitiya, Sri Lanka: A metamict gemstone with excellent lead-retention performance
JF - Geology
VL - 45
IS - 10
SP - 919-922
EP - 919-922
PB - Geological Society of America
SN - 00917613
KW - PB ZIRCON AGES
KW - RADIATION-DAMAGE
KW - ALTERED ZIRCON
KW - GEOCHRONOLOGY
KW - DISSOLUTION
KW - METAMORPHISM
KW - MICROPROBE
KW - ACCURACY
KW - URANIUM
KW - SYSTEMS
N2 - A rare gemstone form of "ekanite" from Okkampitiya, eastern Sri Lanka, has a chemical composition of Ca2Th0.9U0.1Si8O20, corresponding to that of the tetragonal mineral ekanite. The Okkampitiya material, however, has undergone amorphization and is found in a fully metamict state, which is ascribed to the long-term accumulation of high levels of self-irradiation damage (1.38 x 10(20) alpha decay events per gram). The "ekanite" nevertheless does not show any post-growth chemical alteration, and the radiogenic Pb has been retained. The Okkampitiya "ekanite" yielded a Neoproterozoic Pb-207/Pb-206 age of 562.1 +/- 0.8 Ma (uncertainty quoted at the 95% confidence level) that is concordant within the uncertainties of decay constants. The remarkable Pb-retention performance of "ekanite" contradicts the common hypothesis that metamictization in minerals results in U-Pb discordance. The exceptional chemical durability of the heavily radiation-damaged geological material described here has also implications for materials-science research. High radiation resistance, a key criterion in the search for advanced nuclear waste forms, may not be a prerequisite for high aqueous durability of a solid.
ER -
NASDALA, Lutz, Fernando CORFU, Doris BLAIMAUER, Chutimun CHANMUANG, Katja RUSCHEL, Radek ŠKODA, Manfred WILDNER, Richard WIRTH, Manuela ZEUG a E. Gamini ZOYSA. Neoproterozoic amorphous ''ekanite'' (Ca2Th0.9U0.1Si8O20) from Okkampitiya, Sri Lanka: A metamict gemstone with excellent lead-retention performance. \textit{Geology}. BOULDER: Geological Society of America, 2017, roč.~45, č.~10, s.~919-922. ISSN~0091-7613. Dostupné z: https://dx.doi.org/10.1130/G39334.1.
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