Results 171 to 180 of about 157,575 (214)

U‐Pb age of the Yxsjöberg Tungsten‐Skarn deposit, Sweden

GFF, 1994
Abstract The Yxsjoberg scheelite‐skam deposit of western Bergslagen (south‐central Sweden) formed in Palaeoproterozoic time when aqueous fluids migrating along lithologic discontinuities replaced limestones in acid volcanic rocks. The age of the mineralization and, thus, the source of the fluids are controversial.
Romer, R., Öhlander, B.
openaire   +3 more sources

U-Pb age of the Baltoro granite, northwest Himalaya, and implications for monazite U-Pb systematics

Geology, 1989
The 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
openaire   +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

Zircon U-Pb ages for the Early Cambrian time-scale

Journal of the Geological Society, 1992
Single zircons from two Early Cambrian volcanic horizons have been analysed using the SHRIMP ion microprobe. Full details of the analytical procedures and data reduction are given. Zircons from tuff within the Lie de Vin Formation, near Tiout, Morocco, show little spread in U-Pb age and have a mean value of 521 ± 7 Ma (2σ).
Compston, W., Williams, I. S., Kirschvink, J. L., Zichao, Zhang, Guogan, Ma   +4 more
openaire   +2 more sources

A minimum UPb age for Siberian flood-basalt volcanism

Geochimica et Cosmochimica Acta, 1996
Abstract Establishing an accurate and precise age for Siberian flood-basalt volcanism is of great importance in evaluating causes for the unequaled mass extinction of flora and fauna at the Permian-Triassic boundary. We report a new, minimum UPb age obtained from zircon and baddeleyite from the mineralized Noril'sk I intrusion that cuts the lower ...
S.L. Kamo, G.K. Czamanske, T.E. Krogh
openaire   +1 more source

U–Pb age of titanite in the Mylonite Zone, southwestern Sweden

Geologiska Föreningen i Stockholm Förhandlingar, 1993
Abstract U–Pb dating of titanite from a mafic lens in the Mylonite Zone in southwestern Sweden yields an almost concordant age of c. 920 Ma. The titanite formed during retrogression of granulite-to amphibolite-facies rocks. Sources for Ti and Ca in titanite were Fe-Ti oxides and relatively grossular-rich garnets, respectively.
Leif Johansson, Åke Johansson
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Zircon UPb ages of Guyana greenstone-gneiss terrane

Precambrian Research, 1982
Abstract Isotopic UPb 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
openaire   +1 more source

U-Pb age of autochthonous paleoproterozoic charnockite in the Aldan Shield

Doklady Earth Sciences, 2012
Autochthonous and parautochthonous charnockites in granulite facies of the Aldan Shield (the Aldan River upper flow) were dated. According to the geological observation data, the autochthonous and parautochthonous granite formation included successive development of nebulite (Lc1), its melting product such as early diatectite (Lc3), later “layer-by ...
V. A. Glebovitskii, I. S. Sedova, N. G. Berezhnaya, A. N. Larionov, N. G. Rizvanova, L. M. Samorukova   +5 more
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U–Pb ages for magmatism and deformation in the New Quebec Orogen

Canadian Journal of Earth Sciences, 1997
The New Quebec Orogen is a Paleoproterozoic fold and thrust belt, active from 2.17 to 1.77 Ga, bordering the eastern margin of the Archean Superior Province. The orogen developed on a long-lived, passive continental margin and comprises two volcanic – sedimentary sequences.
N. Machado, T. Clark, J. David, N. Goulet   +3 more
openaire   +1 more source

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   +1 more source