Results 331 to 340 of about 668,632 (409)

A U–Pb age for mineralized Nipissing diabase, Gowganda, Ontario

Canadian Journal of Earth Sciences, 1986
Concordant baddeleyite and rutile analyses from mineralized Nipissing diabase at Gowganda's Castle mine yield a U–Pb age of [Formula: see text]. Baddeleyite is a primary phase of the diabase; therefore the age dates the magmatic emplacement. The genesis of rutile is less certain: rutile could have formed during an episode of alteration, veining, and ...
F. Corfu, A. J. Andrews
openaire   +2 more sources

Tanz Zircon Megacrysts: A New Zircon Reference Material for the Microbeam Determination of U-Pb Age and Zr-O Isotopes

Journal of Analytical Atomic Spectrometry, 2021
We present a detailed characterization of Tanz zircon megacrysts for the microbeam determination of U-Pb ages, Zr isotopes, Hf isotopes, O isotopes and trace element mass fractions.
Zhaochu Hu, Xian‐Hua Li, Tao Luo, Wen Zhang, J. Crowley, Qiu-li Li, Xiaoxiao Ling, Chuan Yang, Yang Li, Lanping Feng, X. Xia, Shao‐Bing Zhang, Zaicong Wang, Jing‐Liang Guo, Lei Xu, Jie Lin, Xiaoming Liu, Z. Bao, Yongsheng Liu, K. Zong, Wei Chen, S. Hu   +21 more
semanticscholar   +1 more source

Zircon and apatite U-Pb age constraints from the Bundelkhand craton and Proterozoic strata of central India: Insights into craton stabilization and subsequent basin evolution

, 2021
The geologic processes involved in attaining strengthened cratonic lithosphere remain debated despite their importance for stabilization and long-term preservation.
C. Colleps, N. McKenzie, Mukund Sharma, H. Liu, T. Gibson, W. Chen, D. Stockli   +6 more
semanticscholar   +1 more source

Extracting meaningful U-Pb ages from core–rim mixtures

Gondwana Research, 2021
Abstract 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, Christopher L. Kirkland, Milo Barham, Matthew L. Daggitt, Julie Hollis, Michael Hartnady   +5 more
openaire   +1 more source

U-Pb Ages from the Neoproterozoic Doushantuo Formation, China

Science, 2005
U-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, Maoyan, Zhu, Samuel, Bowring, Wei, Wang, Aihua, Yang, Yugan, Jin   +5 more
openaire   +2 more sources

Interpretation of discordant U‐Pb zircon ages: An evaluation

Journal of Metamorphic Geology, 1997
The 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.
openaire   +1 more source

U-Pb AGE OF THE CHATTANOOGA SHALE

Geological Society of America Bulletin, 1960
An 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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SA01 – A Proposed Zircon Reference Material for Microbeam U‐Pb Age and Hf‐O Isotopic Determination

Geostandards and Geoanalytical Research, 2019
A new natural zircon reference material SA01 is introduced for U‐Pb geochronology as well as O and Hf isotope geochemistry by microbeam techniques. The zircon megacryst is homogeneous with respect to U‐Pb, O and Hf isotopes based on a large number of ...
Chao Huang, Hao Wang, Jin-Hui Yang, J. Ramezani, Chuan Yang, Shao‐Bing Zhang, Yueheng Yang, X. Xia, Lianjun Feng, Jie Lin, Tiantian Wang, Q. Ma, Huaiyu He, Liewen Xie, Shitou Wu   +14 more
semanticscholar   +1 more source

U‐Pb SIMS ages of Apollo 14 zircon: Identifying distinct magmatic episodes

Meteoritics & Planetary Science, 2019
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, A. A. Nemchin, J. F. Snape, M. J. Whitehouse   +3 more
openaire   +4 more sources

Discordant Zircon U–Pb Ages from the Uganda Basement

Nature Physical Science, 1971
FOR 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
openaire   +1 more source