A Modelling Study on the Fractionation of Uranium Among Minerals During Rock Weathering

1992 ◽  
Vol 294 ◽  
Author(s):  
Toshihiko Ohnuki ◽  
Takashi Murakami ◽  
Nobuyuki Yanase
Keyword(s):  
Sequential Extraction ◽  
Rock Weathering ◽  
Ore Deposit ◽  
Secondary Minerals ◽  
Iron Minerals ◽  
Irreversible Sorption ◽  
Rock Alteration ◽  
Weathering Process ◽  
Good Agreement ◽  
Modelling Study

ABSTRACTA modelling study has been carried out to understand the effect of rock alteration on the fractionation of uranium among coexisting minerals (chlorite, vermiculite, kaolinite, amorphous and crystalline iron minerals) at the Koongarra ore deposit, Australia. The model considers the chlorite weathering process, its mechanism and rate, and assumes the presence of reversible and irreversible sorption sites in the secondary minerals. The calculated uranium concentrations at the two different sites in the minerals were compared with the results of sequential extraction experiments. Good agreement between the calculated and observed uranium concentrations was obtained only when an appropriate fraction of uranium is fixed to the irreversible sorption sites of the altered clay minerals. However, a conventional Kd model gave inconsistent uranium concentrations. The calculated results show that the crystalline iron minerals sorb uranium during all stages of weathering, and that the uranium fractionation among the minerals varies with time until the end of the weathering.

Modelling Study on Uranium Migration in Rocks Under Weathering Condition

1994 ◽  
Vol 353 ◽  
Author(s):  
Toshihiko Ohnuki ◽  
Takashi Murakami ◽  
Hiroshi Isobe ◽  
Tsutomu Sato ◽  
Nobuyuki Yanase
Keyword(s):  
Uranium Concentration ◽  
The Other ◽  
Two Dimensional ◽  
Ore Deposit ◽  
Uranium Migration ◽  
Irreversible Sorption ◽  
Rock Alteration ◽  
Weathering Process ◽  
Good Agreement ◽  
Modelling Study

AbstractA modelling study has been completed to understand the effect of rock alteration on uranium migration at the Koongarra ore deposit, Australia. The model considers the weathering process, the mechanism and rate of chlorite alteration, a major mineral of the host rock, and assumes the presence of reversible sorption sites of chlorite and the presence of reversible and irreversible sorption sites of the weathering products. One- and two-dimensional, calculated uranium concentrations were compared with those observed. Good agreement between the calculated and observed uranium concentration profiles was obtained only when an appropriate fraction of uranium is fixed to the irreversible sorption sites of Fe-minerals produced during weathering of chlorite. On the other hand, the conventional Kd model failed to estimate an adequate uranium concentration profile. The results suggest that the fixation of uranium to Fe-minerals has dominated the migration of uranium in the vicinity of the Koongarra ore deposit.

A Modelling Study of the Effect of Rock Alteration on the Redistribution of Uranium

1992 ◽  
Vol 294 ◽  
Author(s):  
Takashi Murakami ◽  
Hideo Kimura
Keyword(s):  
Distribution Coefficients ◽  
Darcy Velocity ◽  
Advection Dispersion ◽  
Rock Porosity ◽  
Uranium Migration ◽  
The One ◽  
Rock Alteration ◽  
Uranium Radionuclide ◽  
Good Agreement ◽  
Modelling Study

ABSTRACTA modelling study was carried out to understand the effect of rock alteration on uranium radionuclide concentrations in rocks, in the vicinity of the Koongarra ore deposit, Australia. The one-dimensional, advection-dispersion-sorption model considers two important factors resulting from the process, mechanism and rate of chlorite weathering, one type of rock alteration that has occurred over a million-year period; (a) the changes in the distribution coefficients of uranium and thorium over time, and (b) that in rock porosity. The distribution coefficient and rock porosity at a given time, are expressed as average values of those of the coexisting minerals. By assuming a Darcy velocity of 0.9 m/y and an initial uranium concentration in the groundwater of 0.5 ppm, similar to present-day values, we were able to derive, from the finite-element modelling, uranium concentrations in the rock which are in good agreement with observed values. The calculated values of 230Th/234U activity ratios show a similar trend to those observed, although more experimental data are necessary to confirm the similarity. However, in the absence of the rock alteration, the calculated results did not agree with those observed. The present study suggests that rock alteration should be included in models used to predict uranium migration over long, geologic timescales.

Conditions of formation of the iron-containing minerals, Hällefors silver mines, Bergslagen, Sweden

1986 ◽  
Vol 50 (355) ◽  
pp. 101-110 ◽  
Author(s):  
A. W. Jasiński
Keyword(s):  
Aqueous Solutions ◽  
Iron Oxides ◽  
Iron Ore ◽  
Silver Deposit ◽  
Ore Deposit ◽  
Iron Minerals ◽  
Sulphide Precipitation ◽  
Iron Ore Deposit ◽  
Two Stages

AbstractThe Hällefors silver deposit is regarded as a volcanogenic-exhalative iron ore deposit with dispersed amounts of Ag-Pb-Zn (±Cu) which has undergone secondary remobilization leading to the concentration of sulphides and sulphosalts. Based on data from the iron oxides and sulphides, the sulphide-sulphosalt mineralization is believed to have been formed in two stages. The first is characterized by the ranges 573-473 K and 2.25–1.5 kbar, higher gradient of changes of log aS2 with temperature and mostly sulphide precipitation; the second by the ranges 473–443 K, lower gradient of changes of log aS2 and mainly sulphosalt deposition. Assuming the precipitation was from fluids and aqueous solutions, possible conditions of formation of some of the iron minerals have been determined.

scholarly journals Analysis of Soil Categories on Seismograf Sensor in Java Island Based on Ground Predominant Period and Vs30

2015 ◽  
Vol 5 (02) ◽  
pp. 34
Author(s):  
Nugroho Budi Wibowo ◽  
Dian Susri Nurhaci
Keyword(s):  
Hard Rock ◽  
Soft Rock ◽  
Processing Method ◽  
Soil Conditions ◽  
Rock Weathering ◽  
European Research ◽  
Predominant Period ◽  
Data Processing Method ◽  
Weathering Process ◽  
Stiff Soil

<p>The aim of this research is to analyze the categorization of soil at sensor site locations based on predominant period of the ground and Vs30. This study was conducted at nine sites seismograph sensors in Java and Madura. Data processing method is using HVSR (Horizontal to Vertical Ratio) based on the SESAME European research project. The Java and Madura Vs30’s data were obtained from the USGS. This study utilizes the criteria of JRA 1990 and BSSC 2000 were used to determine the soil categories. It is found that the criteria of JRA 1900 and BSSC 2000 satisfies some sites namely LEM, KMMI, UGM and WOJI. The site of LEM and UGM have a soil that can be categorized in C type (dense soil / sand to soft rock) with dense soil conditions to the rock weathering process. Site KMMI can be categorized in D type (stiff soil) with dense soil conditions. Whereas the site WOJI can be categorized in A + B type (Hard rock and firm to hard rock) with hard rock conditions.</p>

scholarly journals Characterizing a vine terroir by combining a pedological field model and a survey of the vine growers in the Anjou Region (France)

OENO One ◽  
2003 ◽  
Vol 37 (4) ◽  
pp. 199
Author(s):  
Fabrice Bodin ◽  
René Morlat
Keyword(s):  
Field Model ◽  
Parent Rock ◽  
Operational Method ◽  
Natural Factors ◽  
Rock Alteration ◽  
Experimental Plots ◽  
Plant Behaviour ◽  
Good Agreement ◽  
Made In

<p style="text-align: justify;">The aim of this research was to develop an operational method of characterization of «terroirs» in response to the request from wine professionals. A study based on both a survey of vine growers and a characterization of the natural factors of «terroir» (geological, pedological and mesoclimatic components) using the concept of Basic Terroir Unit (B.T.U) was made in 18 communes of the Anjou region. The natural factors of “terroir” were characterized by (1) a geological component (stage and nature of the parent rock) and (2) an agro-pedological component studied according to a field model allowing to distinguish three kinds of soil environments named : Rock, Alteration and Altérite. Each of them represent a functioning unit in wich an homogenous response in terms of vine behaviour can be expected. The approach based on the survey of vine growers was developed in order to replace the network of experimental plots of land formerly used to integrate the plant behaviour in its environment. These networks required considerable investment in time and money. Our study showed that vine growers perceived correctly the behaviour of the vine through different variables relative to the soil, the climate and the plant. They distinguished particularly well between two of the environments (Rock and Alterite) generated by the model. There was good agreement between the results obtained with the two approaches (survey and characterization of natural factors of «terroirs»).</p>

Uranium Fixation During Uranium Migration Under an Oxidizing Condition

1994 ◽  
Vol 353 ◽  
Author(s):  
Takashi Murakami ◽  
Katsuyuki Tsuzuki ◽  
Tsutomu Sato ◽  
Hiroshi Isobe ◽  
Toshihiko Ohnuki
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Rock Specimen ◽  
Uranium Mineral ◽  
Ore Deposit ◽  
Iron Minerals ◽  
Transmission Electron ◽  
Uranium Migration ◽  
20 Nm

AbstractA rock specimen, collected downstream of the Koongarra uranium ore deposit, Australia, was examined mainly by high resolution transmission electron microscopy in order to understand the uranium fixation mechanism. Uranium was found to exist as saleeite (Mg(UO2)2(PO4)2.10H2O) microcrystals of 1 – 20 nm scattered between iron minerals (mainly goethite and hematite) of 2 – 50 nm. The microtextural relationship between saléeite and the iron minerals revealed that the iron minerals function as catalyst for the formation of saléeite. The intermediate metamict microstructures of the saléeite microcrystals are consistent with the estimated formation age of saléeite, 1 to 3 × 106 years. Uranium has been, thus, fixed as saléeite downstream as well as in the secondary ore deposit. Saléeite in the secondary ore deposit showed completely periodic to fully metamict microstructures, suggesting that saléeite, a major uranium mineral in the secondary ore deposit, probably began to form a few million years ago and continued to form for the next million years.

Measurement of Uranium Series Radionuclides in Rock and Groundwater at the Koongarra ore Deposit, Australia, by Gamma Spectrometry

1994 ◽  
Vol 353 ◽  
Author(s):  
Nobuyuki Yanase ◽  
Keiichi Sekine
Keyword(s):  
Gamma Rays ◽  
Gamma Spectrometry ◽  
Chemical Separation ◽  
Separation Procedure ◽  
Ore Deposit ◽  
Rock Samples ◽  
Absorption Correction ◽  
Groundwater Samples ◽  
Energy Gamma ◽  
Good Agreement

AbstractGamma spectrometry without any self-absorption correction was developed to measure low energy gamma rays emitted by uranium and actinium series radionuclides in rock samples and groundwater residues collected at the Koongarra ore deposit, Australia. Thin samples were prepared to minimize the self-absorption by uranium in the samples. The present method gave standard deviations of 0.9 to 18% for the measurements of concentrations of uranium and actinium series radionuclides. The concentrations of 238U, 230Th and 235U measured by gamma spectrometry were compared with those by alpha spectrometry that requires a complicated chemical separation procedure. The results obtained by both methods were in fairly good agreement, and it was found that the gamma spectrometry is applicable to rock and groundwater samples having uranium contents up to 8.1% (103 Bq/g) and 3 Bq/1 of 238U, respectively. The detection limits were calculated to be of the order of 10−2 Bq/g for rock samples and 10−2 Bq/1 for groundwater samples. The concentrations of uranium and actinium series radionuclides can be determined precisely in these samples using gamma spectrometry without any self-absorption correction.

Geological Characteristics and Prospecting Criteria of Sanbao Silver Polymetallic Ore Deposit in Malipo Cuntry of Yunnan Province

2013 ◽  
Vol 868 ◽  
pp. 88-91
Author(s):  
Jian She Wang ◽  
Yong Feng Yan ◽  
Dong Wang ◽  
Peng Yu Feng
Keyword(s):  
Low Temperature ◽  
Yunnan Province ◽  
Wall Rock ◽  
Ore Genesis ◽  
Ore Deposit ◽  
Geological Characteristics ◽  
Polymetallic Deposit ◽  
Wall Rock Alteration ◽  
Rock Alteration ◽  
Polymetallic Ore

Sanbao silver polymetallic deposit is overally located in the front of "North convex" in Laojun Mountain granite body, belonging to polymetallic deposit of stratabounded medium-low temperature hydrothermal reformation genesis. It has been found that six mineralized belt, having developed the wall-rock alteration. The prospecting criterion is determined by ore genesis and ore-controlling factor.

Effects of Chlorite Alteration on Uranium Redistribution in Koongarra, Australia

1990 ◽  
Vol 212 ◽  
Author(s):  
Takashi Murakami ◽  
Hiroshi Isobe ◽  
Robert Edis
Keyword(s):  
Diffraction Study ◽  
Host Rock ◽  
Uranium Concentration ◽  
Major Constituent ◽  
X Ray Diffraction ◽  
Ore Deposit ◽  
X Ray ◽  
Uranium Ore ◽  
Iron Minerals ◽  
Uranium Migration

ABSTRACTThe relevance of alteration of chlorite, one of the major constituent minerals of the host rock to uranium ore at Koongarra, to the redistribution of uranium in the vicinity of the ore deposit has been examined. The chlorite alteration is produced by weathering; chlorite is transformed to vermiculite, through regularly interstratified chlorite/vermiculite. The Fe released from chlorite reprecipitates to form iron minerals, possibly ferrihydrite. Vermiculite is then replaced by kaolinite (and possibly smectite), further releasing Fe. On the millimeter scale, an alpha autoradiography study has shown that uranium concentrations are qualitatively proportional to the extent of the alteration; altered chlorite grains having higher uranium concentration. On the meter scale, the X-ray diffraction study has revealed that the abundances of chlorite, vermiculite, and kaolinite correspond well to the low, intermediate, and high uranium concentration zones, respectively. These suggest that the interaction of the uraniferous solution with chlorite causes the alteration of chlorite and the precipitation and sorption of uranium in the alteration products from the solution, and thus, the uranium migration is retarded at Koongarra.

Sign in / Sign up

Export Citation Format

Share Document