scholarly journals Post-Ore Processes of Uranium Migration in the Sandstone-Hosted Type Deposits: 234U/238U, 238U/235U and U–Pb Systematics of Ores of the Namaru Deposit, Vitim District, Northern Transbaikalia

2021 ◽  
Vol 63 (4) ◽  
pp. 287-299
Author(s):  
V. N. Golubev ◽  
N. N. Tarasov ◽  
I. V. Chernyshev ◽  
A. V. Chugaev ◽  
G. V. Ochirova ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Cross Sections ◽  
Isotopic Age ◽  
Pb Isotope ◽  
Quaternary Period ◽  
Ore Body ◽  
Catchment Areas ◽  
Uranium Migration ◽  
Ore Deposition ◽  
Ore Zones

Abstract To assess the nature of the post-ore behaviour of uranium in the Namaru deposit (Khiagda ore field), U–Pb isotope systems and the isotopic composition of uranium (234U/238U and 238U/235U) were studied. The studied samples represent different ore zones of the deposit and were collected along cross-sections both vertically and horizontally. Wide variations in the isotopic composition of uranium and U–Pb isotopic age have been established. Deviations of the 234U/238U ratio from equilibrium values, which for some samples exceed 50%, along with significant variations in the isotopic age, indicate that permafrost layer, which covered the catchment areas of paleovalleys with meteoric oxygen-containing waters ca. 2.5 Ma ago, did not lead to preserving uranium ores at the deposit. Uranium migration took place during the Quaternary period. The effective combining the U–Pb dating and 234U/238U data in assessing the post-ore redistribution of uranium made it possible to recognize: removal of uranium from some zones of the ore body and its accompanying redeposition in others. Wide variations in the 238U/235U (137.484–137.851) ratios throughout the entire studied cross-sections can be explained by the different locations of samples relatively to the ore deposition front and change in redox conditions as this front advanced. Depletion of the light isotope 235U in the lower zone of the ore body may be associated with the influence of ascending carbonic waters established in the regional basement. The effect of such waters on uranium-bearing rocks causes predominant leaching of light 235U.

Constraints of C–O–S–Pb isotope compositions and Rb–Sr isotopic age on the origin of the Tianqiao carbonate-hosted Pb–Zn deposit, SW China

2013 ◽  
Vol 53 ◽  
pp. 77-92 ◽  
Author(s):  
Jiaxi Zhou ◽  
Zhilong Huang ◽  
Meifu Zhou ◽  
Xiaobiao Li ◽  
Zhongguo Jin
Keyword(s):  
Isotopic Age ◽  
Pb Isotope ◽  
Sw China

scholarly journals Isotopic age dating in Liverpool Land, East Greenland

1987 ◽  
Vol 134 ◽  
pp. 25-37
Author(s):  
B.T Hansen ◽  
J.D Friderichsen
Keyword(s):  
Age Dating ◽  
Isotopic Age ◽  
Pb Isotope ◽  
East Greenland ◽  
Isotope Age ◽  
Caledonian Orogeny ◽  
Plutonic Rocks ◽  
Age Determinations ◽  
Late Part

In Liverpool Land in the eastern part of the Scoresby Sund region gneisses and migmatites were intruded by a number of intermediate plutonites and by younger granites. A number of K-Ar, Rb-Sr and U-Pb isotope age determinations indicate that: 1) the gneisses have a pre-CaIedonian as well as a CaIedonian history, 2) the migmatites were thoroughly reworked during the late part of the Caledonian orogeny, while 3) the plutonic rocks all seem to have been intruded during the Caledonian orogeny.

scholarly journals Uncertainty Analysis of WWER-1000 Core Macroscopic Cross Sections due to Spectral Effects

2020 ◽  
pp. 39-46
Author(s):  
О. Kukhotska ◽  
I. Ovdiienko ◽  
M. Ieremenko
Keyword(s):  
Energy Spectrum ◽  
Isotopic Composition ◽  
Uncertainty Analysis ◽  
Neutron Flux ◽  
Flux Density ◽  
Cross Section ◽  
Cross Sections ◽  
Fuel Burnup ◽  
Thermophysical Parameters ◽  
Neutron Flux Density

The paper presents the results of uncertainty analysis of WWER‑1000 core macroscopic cross sections due to spectral effects during WWER‑1000 fuel burnup and the analysis of cross section sensitivity from thermophysical parameters of the calculated cell, which affect energy spectrum of neutron flux density. The calculation of changes in the isotopic composition during burnup and the preparation of macroscopic cross sections used the developed HELIOS computer model [1] for TVSA, which is currently operated at most Ukrainian WWER‑1000 units. The GRS approach applying Software for Uncertainty and Sensitivity Analyses (SUSA) [2] was chosen to assess the uncertainty of the macroscopic cross sections due to spectral effects and analysis of cross section sensitivity from thermophysical parameters. The spectral effect on macroscopic cross sections was taken into account by calculating the fuel burnup for variational sets of thermophysical parameters (fuel temperature, coolant temperature and density, boric acid concentration) prepared in advance by the SUSA program, as a result of which fuel isotopic composition vectors were obtained. After that, neutronic constants for the reference state were developed for each of the sets of isotopic composition, which corresponded to a certain set of thermophysical parameters. At the next stage, the uncertainty of macroscopic cross sections of the interaction due to the spectral effects on the isotopic composition of the fuel was analyzed using SUSA 4, followed by the analysis of cross section sensitivity from thermophysical parameters of the calculated cell affecting energy spectrum of neutron flux density. In the future, the uncertainty of two-group macroscopic diffusion constants can be used to estimate the overall uncertainty of neutronic characteristics in large-grid core calculations, in particular, in the safety analysis.

scholarly journals Supplemental Material: Interplay of Cretaceous transpressional deformation and continental arc magmatism in a long-lived crustal boundary, central Fiordland, New Zealand

2020 ◽  
Author(s):  
H.J. Blatchford ◽  
et al.
Keyword(s):  
New Zealand ◽  
Cross Sections ◽  
Geochemical Data ◽  
Arc Magmatism ◽  
Sample Collection ◽  
Pb Isotope ◽  
Continental Arc ◽  
Geologic Map ◽  
Backscattered Electron ◽  
Continental Arc Magmatism

Analytical methods used are described in Supplemental Text. Sample collection locations shown in Figure 3 are detailed in Table S1. Isotopic and geochemical data are presented in Tables S2–S4. U-Pb isotope data and geochemistry data for the sample are presented in Tables S5 and S6, respectively. A series of cross sections and a geologic map of the study area including field stations and associated structural measurements are presented in Figure S1. Cathodoluminescence images of zircon grains are shown in Figures S2 and S3. Backscattered electron images of analyzed titanite grains are presented in Figure S4.<br>

THE CYLINDRICAL ORE BODY IN THE PRESENCE OF A CABLE CARRYING AN OSCILLATING CURRENT

Geophysics ◽  
1952 ◽  
Vol 17 (2) ◽  
pp. 378-386 ◽  
Author(s):  
James R. Wait
Keyword(s):  
Electrical Properties ◽  
Massive Sulphide ◽  
Conducting Medium ◽  
Geophysical Prospecting ◽  
Conducting Cylinder ◽  
Sulphide Ore ◽  
Ore Body ◽  
The Media ◽  
Special Case ◽  
Ore Zones

The problem of an infinite cable carrying an oscillating current parallel to a conducting cylinder is solved. The homogeneous electrical properties of the media inside and outside the cylinder can be arbitrary. The special case is considered in detail where the exterior medium is a relatively poor conducting medium. The application to geophysical prospecting for massive sulphide ore zones is discussed.

Alteration of Trace Lead Isotopic Ratios by Postore Metamorphic and Hydrothermal Activity

1973 ◽  
Vol 10 (12) ◽  
pp. 1782-1789 ◽  
Author(s):  
G. L. Cumming ◽  
P. J. Gudjurgis
Keyword(s):  
Isotopic Composition ◽  
Lead Isotope ◽  
Regional Metamorphism ◽  
Hydrothermal Activity ◽  
Isotopic Ratios ◽  
Iron Sulfides ◽  
Ore Body ◽  
Wide Range ◽  
Lead Isotopic Ratios ◽  
Isotope Analyses

Isotope analyses on leads in iron sulfides and trace galenas from two deposits (Big Ledge, British Columbia and Quemont Mine, Quebec) suggest that variations in the isotopic composition may be influenced by postmineralization alteration of ore. It is postulated that when the ore has been subject to regional metamorphism after emplacement, the metamorphism has homogenized the lead isotope ratios throughout the ore body as appears to have happened at Big Ledge, whereas, if postore activity is limited to minor hydrothermal alteration, as at Quemont, then the lead may be left with a wide range of isotopic composition.

scholarly journals Climate in the Great Lakes Region Between 14,000 and 4000 Years Ago from Isotopic Composition of Conifer Wood

Radiocarbon ◽  
2006 ◽  
Vol 48 (2) ◽  
pp. 205-217 ◽  
Author(s):  
Steven W Leavitt ◽  
Irina P Panyushkina ◽  
Todd Lange ◽  
Alex Wiedenhoeft ◽  
Li Cheng ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Great Lakes ◽  
Cross Sections ◽  
Lake Michigan ◽  
Laurentide Ice Sheet ◽  
Great Lakes Region ◽  
Floristic Similarity ◽  
Ancient Wood ◽  
Conifer Trees ◽  
Conifer Wood

The isotopic composition of ancient wood has the potential to provide information about past environments. We analyzed the δ13C, δ18O, and δ2H of cellulose of conifer trees from several cross-sections at each of 9 sites around the Great Lakes region ranging from ∼4000 to 14,000 cal BP. Isotopic values of Picea, Pinus, and Thuja species seem interchangeable for δ18O and δ2H comparisons, but Thuja appears distinctly different from the other 2 in its δ13C composition. Isotopic results suggest that the 2 sites of near-Younger Dryas age experienced the coldest conditions, although the Gribben Basin site near the Laurentide ice sheet was relatively dry, whereas the Liverpool site 500 km south was moister. The spatial isotopic variability of 3 of the 4 sites of Two Creeks age shows evidence of an elevation effect, perhaps related to sites farther inland from the Lake Michigan shoreline experiencing warmer daytime growing season temperatures. Thus, despite floristic similarity across sites (wood samples at 7 of the sites being Picea), the isotopes appear to reflect environmental differences that might not be readily evident from a purely floristic interpretation of macrofossil or pollen identification.

scholarly journals Lead isotopes and selected metals in ice from Law Dome, Antarctica

1998 ◽  
Vol 27 ◽  
pp. 349-354 ◽  
Author(s):  
K.J. R. Rosman ◽  
W. Chisiiolm ◽  
C. F. Boutron ◽  
S. Hong ◽  
R. Edwards ◽  
...  
Keyword(s):  
Isotopic Composition ◽  
Lead Isotopes ◽  
Ice Core ◽  
Sample Selection ◽  
Technical Skills ◽  
East Antarctica ◽  
Pb Isotope ◽  
Core Samples ◽  
Naturally Occurring ◽  
Stable Lead Isotopes

The isotopic composition of Pb and the concentrations of Pb, Ba and Bi wert- measured in selected ice-core samples from Law Dome, East Antarctica, to a depth of 1196 m. The range of concentrat ions found in decontaminated ice was 0.03-1.5 pgg−1 for Pb, 0.9-6.1 pgg−1 for Ba and 0.4 17 fgg −1 for Bi, excluding the deepest sample which contained ~1 pjpm of rock dust. The abundances of all four stable lead isotopes were measured and gave 206Pb/207Pb ratios up to ~1.23. Avalue of 208Pb/207Pb= 2.78 was measured in the deepest sample and is consistent with reported Pb isotope ratios of Antarctic gran-ulites. Although the element concentrations in some samples were lower than have been reported elsewhere, geochemkal and isotopic evidence indicated that a number of samples were contaminated with Pb not present in the original ice. However, it appears that the technical skills now available are approaching the level where careful sample selection, decontamination and analysis can yield accurate results for the concentration and isotopic composition of Pb in Earth's purest naturally occurring ice.

scholarly journals Supplemental Material: Interplay of Cretaceous transpressional deformation and continental arc magmatism in a long-lived crustal boundary, central Fiordland, New Zealand

2020 ◽  
Author(s):  
H.J. Blatchford ◽  
et al.
Keyword(s):  
New Zealand ◽  
Cross Sections ◽  
Geochemical Data ◽  
Arc Magmatism ◽  
Sample Collection ◽  
Pb Isotope ◽  
Continental Arc ◽  
Geologic Map ◽  
Backscattered Electron ◽  
Continental Arc Magmatism

Analytical methods used are described in Supplemental Text. Sample collection locations shown in Figure 3 are detailed in Table S1. Isotopic and geochemical data are presented in Tables S2–S4. U-Pb isotope data and geochemistry data for the sample are presented in Tables S5 and S6, respectively. A series of cross sections and a geologic map of the study area including field stations and associated structural measurements are presented in Figure S1. Cathodoluminescence images of zircon grains are shown in Figures S2 and S3. Backscattered electron images of analyzed titanite grains are presented in Figure S4.<br>

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