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Extracting meaningful U-Pb ages from core–rim mixtures
Gondwana Research, 2021Abstract Zircon crystals frequently comprise discrete growth zones, each of which may preserve temporal information on different geological processes. However, discrete growth domains can be below the spatial resolution of the applied analytical technique, resulting in composite isotopic ratios when mixed during sampling. Here, we develop a technique
Hugo K.H. Olierook +5 more
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U-Pb Ages from the Neoproterozoic Doushantuo Formation, China
Science, 2005U-Pb zircon dates from volcanic ash beds within the Doushantuo Formation (China) indicate that its deposition occurred between 635 and 551 million years ago. The base records termination of the global-scale Marinoan glaciation and is coeval with similar dated rocks from Namibia, indicating synchronous deglaciation.
Daniel, Condon +5 more
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Interpretation of discordant U‐Pb zircon ages: An evaluation
Journal of Metamorphic Geology, 1997The most widely used technique for the determination of high precision mineral growth ages in igneous and metamorphic rocks is dating of zircons with the U‐Pb method. The interpretation of these ages, particularly in metamorphic settings, is hampered by an incomplete understanding of the common phenomenon of partial Pb‐loss in zircon.
Mezger, Klaus, KROGSTAD, E. J.
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U-Pb AGE OF THE CHATTANOOGA SHALE
Geological Society of America Bulletin, 1960An attempt was made to date the upper black unit of the Gassaway member of the Chattanooga shale which carries the maximum U/Pb ratio. Three samples were analyzed by isotopic dilution techniques. The U238-Pb206 ages on all 3 samples agreed within their experimental errors. The average of the two samples with reasonably small errors gave an apparent age
J. C. COBB, J. L. KULP
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U‐Pb
AbstractU‐Pb ages of zircon in four different Apollo 14 breccias (14305, 14306, 14314, and 14321) were obtained by secondary ion mass spectrometry. Some of the analyzed grains occur as cogenetic, poikilitic zircon grains in lithic clasts, revealing magmatic events at ~4286 Ma, ~4200–4220 Ma, and ~4150 Ma.
F. Thiessen +3 more
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U-Pb age of the Baltoro granite, northwest Himalaya, and implications for monazite U-Pb systematics
Geology, 1989The Baltoro granite is a major late- to post-tectonic plutonic phase of the Karakoram batholith of the northwest Himalaya in northern Pakistan. U-Pb zircon analyses indicate both emplacement at 21.0 ±0.5 Ma and significant Precambrian zircon inheritance.
Randall R. Parrish, Rein Tirrul
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Discordant Zircon U–Pb Ages from the Uganda Basement
Nature Physical Science, 1971FOR several years there has been controversy about the ages of the Uganda basement gneisses. Potassium–argon ages of micas from the basement rocks1 range from 600 to 415 m.y. whereas results for the apparently unconformably overlying Karagwe–Ankolean and Buganda–Toro sedimentary systems2,3 to the south (around the north end of Lake Victoria) suggest an
P. J. LEGGO, M. AFTALION, R. T. PIDGEON
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U-Pb dating of a speleothem of Quaternary age
Geochimica et Cosmochimica Acta, 1998We demonstrate that U-Pb dating is a promising method for secondary carbonate materials of Quaternary age and older by obtaining a 206Pb∗/238U age for a speleothem with high U (>10 μg g−1) and very low Pb (
Richards, DA +4 more
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Zircon UPb ages of Guyana greenstone-gneiss terrane
Precambrian Research, 1982Abstract Isotopic UPb studies of zircons collected from weathered metagreywackes of the Barama-Mazaruni Supergroup of northern Guyana, South America, demonstrate an age of origin of ca. 2250 Ma. This is the best estimate for the age of the associated metavolcanic rocks.
Allan K. Gibbs, William J. Olszewski
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