Results 231 to 240 of about 4,877,471 (257)

U-Pb ?????????????????? ?????? ???? ?????????????????? ?????????? ???????????? ???????????????? ?????????????????????????? ?????????? ???????????????????? ?????????? ?????????? ????????????

2015
?????????????????? ???????????????????? ???????????????????????? ???????????????? ???? ?????????????????????????? ???????????????????????? ?????????? ??? ?????????? ???????????? ?? ?????????????? ?????????????????? ?????????? ??????????. ???????????????????????? ?????????????????????? ?????????????? ICP-MS ?? ???????????????? ????????????????. ?????? ??
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

Air abrasion experiments in U-Pb dating of zircon

Chemical Geology, 1986
Abstract Air abrasion of zircon grains can remove metamict material that has lost radiogenic Pb and zircon overgrowths that were added during younger events and thereby improve the precision of the age measurements and permit closer estimates of the original age.
S.S. Goldich, Lynn B. Fischer
openaire   +1 more source

A new method integrating high-precision U–Pb geochronology with zircon trace element analysis (U–Pb TIMS-TEA)

Geochimica et Cosmochimica Acta, 2010
Increased precision in isotope-dilution thermal ionization mass spectrometry (ID-TIMS) U–Pb geochronology has revealed age complexities in zircon populations that require new tools for understanding how the growth of zircon is related to geologic processes.
Schoene, B., Latkoczy, C., Schaltegger, Urs, Günther, D.   +3 more
openaire   +2 more sources

The three-dimensional UPb method: Generalized models and implications for UPb two-stage systematics

Chemical Geology, 1992
Four forms of the three-dimensional UPb method established so far are physically generalized within the framework of a UPb two-stage evolution. Such a generalization provides an explicit insight into the principle of conventional UPb discordia dating. Its implications for both UPb geochronology and Pb isotopic geology are illustrated for whole-rock
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Partial resetting of the UPb isotope system in monazite through hydrothermal experiments: An SEM and UPb isotope study

Chemical Geology, 1997
Abstract Natural monazites of different grain sizes were treated experimentally under hydrothermal conditions and their UPb isotope systematics measured before and after the runs. Runs were carried out with monazite grain size fractions ranging from 40 to 125 μm in diameter, and on 207 Pb 206 Pb ages close to 380 Ma.
Stephan Teufel, Wilhelm Heinrich
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Zircon recrystallisation microstructures andthe implications for U-Pb dating

2021
<p>Uranium-lead dating of zircon has been used extensively in geochronological studies based on the widespread occurrence of zircon and its resistance to chemical and physical weathering. Previous research has shown that despite their apparent robustness, many zircons contain evidence for recrystallisation, such as the replacement of the ...
Jasper Huijsmans, Maartje Hamers, Martyn Drury, Jim Lee   +3 more
openaire   +2 more sources

Synthesis and purification of 205Pb for UPb geochronology

Chemical Geology: Isotope Geoscience section, 1987
Abstract 205Pb is a synthetic isotope of great utility in UPb geochronology, but it has never been widely available in a purified, useable form. We have successfully completed two production runs with a total yield of ∼100μg 205Pb. The isotope was produced by 24–27-MeV proton irradiation using cyclotron facilities of Atomic Energy of Canada Limited
Randall R. Parrish, Tom E. Krogh
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UPb geochronology of the Sri Lankan basement

Precambrian Research, 1994
Abstract UPb ages of zircons and monazites from ortho- and paragneisses representing the major crystalline basement units of Sri Lanka establish a new geochronological framework, which is consistent with previously published work on SmNd model ages, RbSr whole-rock ages, and UPb mineral ages.
S. Hölzl, A.W. Hofmann, W. Todt, H. Köhler   +3 more
openaire   +1 more source

Rb–Sr and U–Pb dating of bentonites

Canadian Journal of Earth Sciences, 1983
A 6 in. (15 cm) bentonite in the Z coal (Cretaceous–Tertiary boundary) in eastern Montana was sampled at four different places, and biotite, sanidine, and zircon were separated from the clay. U–Pb analyses of purified zircons yielded small systematic variations from concordant U–Pb dates.
H. Baadsgaard, J. F. Lerbekmo
openaire   +1 more source