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(1)Hanoi University of Mining and Geology. AGH University of Science & Technology - Kraków - Poland. Faculty of Geology, Geophysics and Environmental Protection. DOCTORAL STUDENT DUONG VAN HAO. Tilte:. “RARE EARTH, NATURAL RADIONUCLIDES AND SELECTED PRECIOUS METALS IN THE IRON OXIDES, COPPER AND GOLD (IOCG) SIN QUYEN DEPOSIT, LAOCAI, NORTH VIETNAM”. Suppervisor: dr. hab. eng. Nguyen Dinh Chau prof AGH Co-Supervisor: dr. eng. Jakub Nowak. Krakow 2018. i.

(2) CONTENTS 1.. Introduction ............................................................................................................ 1. 1.1.. Scope of research ................................................................................................... 1. 1.2.. Background ............................................................................................................ 2. 2.. The investigated region.......................................................................................... 5. 2.1.. Regional tectonic ................................................................................................... 5. 2.2.. Stratigraphy ............................................................................................................ 6. 2.3.. Intrusives ................................................................................................................ 9. 2.4.. Metamorphic formations ..................................................................................... 10. 2.5.. Resource and exploitation ................................................................................... 10. 3.. Prospecting surveys for copper deposit ............................................................... 11. 4.. Applied methods .................................................................................................. 11. 4.1.. Field work ............................................................................................................ 13. 4.1.1. Field geological survey and sampling ................................................................. 13 4.1.2. Field measurements of natural radionuclides ...................................................... 15 4.1.3.. 222Rn. and 220Rn measurement by track detectors CR-39 .................................... 16. 4.2.. Laboratory work .................................................................................................. 20. 4.2.1. Measurement of natural radionuclides in the solid samples using the gamma spectrometer with HPGe detector ........................................................................ 20 4.2.2. Radiochemical analysis for radium and uranium isotopes in water samples ..... 23 4.2.3. Determination of radium isotopes concentrations in water samples ................. .28 4.2.4. Determination of uranium isotopes concentrations in water samples ................ 35 4.2.5. Neutron activation analysis ................................................................................. 36 4.2.6. Analysis of chemical composition of water samples .......................................... 37 4.2.7. Microscope analysis ............................................................................................. 38 4.2.8. Electron dispersion spectrometry analysis .......................................................... 39 4.2.9. Wavlength dispersive spectrometry .................................................................... 40 4.2.10. ICP MS method .................................................................................................. 42 4.2.11. Measurement of δ34S for solid samples ............................................................. 43 5.. Results and discussion ......................................................................................... 45. 5.1.. Field gamma ray surveys ..................................................................................... 45. 5.2.. 40K, 226Ra, 238U. and 232Th in solid samples ......................................................... 48. i.

(3) 5.3.. Radioactive equilibrium in uranium series at the deposit ................................... 53. 5.4.. Chemical composition and radioactivity of the water samples .......................... 54. 5.5.. Radon, thoron concentration in the dwelling air ................................................. 56. 5.6.. Chemical compositions ........................................................................................ 60. 5.7.. Characteristics of ore mineral compositions ....................................................... 67. 5.8.. Mineralization of IOCG Sin Quyen deposit ........................................................ 78. 5.9.. A simplified geological model of regional evolution and mineralization .......... 81. 5.10. Correlations between the investigated elements ................................................. 86 6.. 3D block model .................................................................................................... 94. 6.1.. Data used for model ............................................................................................. 94. 6.2.. Description of the 3D modelling methodology ................................................... 96. 6.3.. Interpolation algorithms..................................................................................... 102. 6.3.1. Kriging algorithm .............................................................................................. 102 6.3.2. Discrete smooth interpolation ............................................................................ 102 6.3.3. Delaunay Triangulation ..................................................................................... 102 6.4.. 3D surface modeling .......................................................................................... 103. 6.5.. 3D geometric model of all ore-bodies ............................................................... 104. 6.6.. 3D model of the ore bodies of different grades and different elements ........... 108. 6.7.. Resources ........................................................................................................... 120. 7.. Conclusions ........................................................................................................ 121. 8.. References .......................................................................................................... 124. LIST OF APPENDICES............................................................................................... 133 APPENDIX A: List of Publications, Poster and Conference papers........................... 133 APPENDIX B: List of Awards and Complementary Achievements .......................... 136. ii.

(4) LIST OF FINGLERS Fig. 1.1. Dynamic global copper price ............................................................................. 3 Fig. 1.2. Growth of global copper mining capacity from 1999 to 2019 .......................... 3 Fig. 1.3. 2015 World Copper Reserves & Mine Production ............................................ 4 Fig. 2.1. Map of main tectonic structures of the region ................................................... 6 Fig. 2.2. Geological map of the Sin Quyen deposit ......................................................... 8 Fig. 4. The workflow performed in this thesis ............................................................... 12 Fig. 4.1a. Satellite picture show the sampling points ..................................................... 14 Fig. 4.1b. Water sampling points on the satellite picture ............................................... 14 Fig. 4.2. View of portable gamma spectrometer GF-5 .................................................. 15 Fig. 4.3a. Radon-Thoron detector CR-39 ....................................................................... 17 Fig. 4.3b. View of the radon-thoron detectors CR-39 ................................................... 18 Fig. 4.4a. The calibration curve for radon chamber ....................................................... 19 Fig. 4.4b. The calibration curve for thoron chamber ..................................................... 19 Fig. 4.5. Diagram of the gamma detector GX4020 ........................................................ 21 Fig. 4.6. Background gamma spectrum measured through 100h by HPGe detector .... 21 Fig. 4.7. The shape of the beakers and samples of the used geometries ....................... 22 Fig. 4.8. Diagram of the Wallac Guardian LSC spectrometer ....................................... 25 Fig. 4.9. The curve showing the method for determination of optimum PSA value based on the sample prepared from 226Ra standard solution ................................. 26 Fig. 4.10. A typical spectrum of α/β measured by alpha/beta Wallac liquid scintillation spectrometer for the. 226Ra. standard sample, where. 226Ra. is in radioactive. equilibrium with its progeny .................................................................................. 27 Fig. 4.11. Block diagram of alpha spectrometer ............................................................ 28 Fig. 4.12. Typical alpha spectrum of a prepared water sample to determine the uranium isotopes measured by alpha spectrometer Canberra 7401 .................................... 28 Fig. 4.13. Dependences of the alpha and beta count rates measured using LSC for the 226Ra. standard sample in the time elapsed from the moment of precipitation...... 29. Fig. 4.14a. Decay diagram of uranium series ................................................................. 32 Fig. 4.14b. Decay diagram of thorium series ................................................................. 33 Fig. 4.15a. Calibration curve for 226Ra determination ................................................... 34 Fig. 4.15b. Calibration curve for 228Ra determination ................................................... 34 Fig. 4.16. Calibration curve for Cu determination using the NAA method .................. 37 iii.

(5) Fig. 4.17. Typical configuration of ICP-AES spectrometer .......................................... 38 Fig. 4.18. Diagram of a modern digital energy dispersive spectroscopy system .......... 39 Fig. 4.19. Configuration of sample, analytical crystal and detector on the Rowland circle ....................................................................................................................... 40 Fig. 4.20. Diagram of the wavelength dispersive spectrometer ..................................... 41 Fig. 4.21. Basic components of an ICP MS ................................................................... 42 Fig. 4.22. Schematic diagram of a continuous flow isotope-ratio mass spectrometer .. 44 Fig. 5.1a. Measured total gamma dose rates and dose rates calculated only from measured 232Th concentration ................................................................................ 47 Fig. 5.1b. Measured total gamma dose rates and dose rates calculated only from measured 40K concentration ................................................................................... 47 Fig. 5.1c. Measured total gamma dose rates and dose rates calculated only from measured 238U concentration ................................................................................. 48 Fig. 5.2a. Calculated total gamma dose rate from. 238U, 232Th. and. 40K. and calculated. only from 232Th concentration ............................................................................... 52 Fig. 5.2b. Calculated total gamma dose rate from. 238U, 232Th. and. 40K. and calculated. only from 40K concentration .................................................................................. 52 Fig. 5.2c. Calculated total gamma dose rate from. 238U, 232Th. and. 40K. and calculated. only from 238U concentration ................................................................................. 53 Fig. 5.3. Distribution of concentrations of 222Rn (a) and 220Rn (b) measured in dwelling air ............................................................................................................................ 57 Fig. 5.4a. Relation between estimated annual committed doses and contribute from 222Rn ....................................................................................................................... 57. Fig. 5.4b. Relation between estimated annual committed doses and contribute from 220Rn ....................................................................................................................... 58. Fig. 5.5. Chondrite-normalized REE patterns for samples in Sin Quyen deposit ......... 61 Fig. 5.6. Oxidation is clearly visible macroscopically in the tailing ............................ 61 Fig. 5.7. Fe-thiosulphate rims developed on pyrrhotite grains ...................................... 61 Fig. 5.8. Position of gold in pyrite .................................................................................. 69 Fig. 5.9. Gold in chalcopyrite, and pyrrhotite. ............................................................... 69 Fig. 5.10. BSE image of the gold mineralization within massive sulphide ore ............ 69 Fig. 5.11a. Intergrowth of uraninite with magnetite and chalcopyrite. ......................... 69 Fig. 5.11b. Intergrowth of uraninite with magnetite, chalcopyrite, allanite .................. 69. iv.

(6) Fig. 5.11c. Intergrowth of uraninite with magnetite, pyrite and chalcopyrite ............... 69 Fig. 5.11d. Intergrowth of uraninite with magnetite and younger chalcopyrite II ........ 70 Fig. 5.11e. Intergrowth of uraninite with chalcopyrite. ................................................. 70 Fig. 5.11f. A small crystal of uraninite in silica matrix. ................................................ 70 Fig. 5.11g. Intergrowth of uraninite with magnetite and chalcopyrite .......................... 70 Fig. 5.12a. Ilmenite crystals in amphibolite ................................................................... 70 Fig. 5.12b. Younger generation of sphalerite in intergrowth with pyrrhotite and chalcopyrite .......................................................................................................... 70 Fig. 5.12c. Te-Bismuthinite with chalcopyrite ............................................................... 71 Fig. 5.12d. Pyrite after pyrrhotite in intergrowth with magnetite and chalcopyrite ...... 71 Fig. 5.12e. Sphalerite inclusion in chalcopyrite ............................................................. 71 Fig. 5.13. BSE picture of two different allanite, pale grey is allanite with high concentration of REE ............................................................................................. 71 Fig. 5.14a. WDS-BSE image of uraninite ...................................................................... 71 Fig. 5.14b. WDS-BSE image of uraninite, 1-5 no of analytical points, and black spots are silicates and sulphides. ..................................................................................... 71 Fig. 5.15. Geological and tectonic map of North Vietnam ............................................ 82 Fig. 5.16. Geological cross – section AB on the fig. 5.15 ............................................. 83 Fig. 5.17. Simplified geological model of the regional evolution and mineralization .. 84 Fig. 5.18. The correlation between Cu and Ag concentration ....................................... 89 Fig. 5.19. The correlation between Cu and Au concentration ....................................... 89 Fig. 5.20. The correlation between Cu and Te concentration ........................................ 89 Fig. 5.21. The correlation between Cu and Bi concentration ........................................ 89 Fig. 5.22. The correlation between Cu and Pb concentration ........................................ 90 Fig. 5.23. The correlation between Cu and U concentration ......................................... 90 Fig. 5.24a. The correlation between Cu and Fe concentration ...................................... 90 Fig. 5.24b. The correlation between Fe and Cu concentration ...................................... 90 Fig. 5.25. The correlation between Fe and Co concentration ........................................ 91 Fig. 5.26. The correlation between Ni and Co concentration ........................................ 91 Fig. 5.27. The correlation between U and Pb concentration .......................................... 91 Fig. 5.28. The correlation between U and Au concentration ......................................... 91 Fig. 5.29. The correlation between U and Ag concentration ......................................... 92 Fig. 5.30. The correlation between U and Bi concentration .......................................... 92. v.

(7) Fig. 5.31. The correlation between U and Te concentration .......................................... 92 Fig. 5.32. The correlation between U and Zn concentration ......................................... 92 Fig. 5.33. The correlation between U and Cd concentration ......................................... 93 Fig. 5.34. The correlation between Th and REE concentration ..................................... 93 Fig. 6.1. Schema of the geological survey profiles on the iso-lines of the deposit region ...................................................................................................................... 95 Fig. 6.2. The main steps of the modeling procedure. ..................................................... 97 Fig. 6.3a. Block diagram of 3D modeling process ......................................................... 98 Fig. 6.3b. Schematic diagram of the dip angle and azimuth of the ore bodies in 3D space. ...................................................................................................................... 99 Fig. 6.4. Studied block (S block) for modeling ............................................................ 100 Fig. 6.5. View of the surface model ............................................................................. 103 Fig. 6.6. Projection of all orebodies on the horizontal surface .................................... 105 Fig. 6.7. View of some ore bodies based on cross-sections in 3D .............................. 106 Fig. 6.8. Ore bodies in the cross section (I) and (II) perpendicular to the projection of the ore trending line on the horizontal surface .................................................... 107 Fig. 6.9. Ore bodies with different Cu grades .............................................................. 109 Fig. 6.10. View of slice of the 3D block model of some ore bodies showing different Cu grades. ............................................................................................................. 110 Fig. 6.11. 3D model of the ore bodies with Cu concentration higher than 0.5%. ....... 111 Fig. 6.12. 3D model of the ore bodies with Cu concentration higher than 0.9%. ....... 112 Fig. 6.13. Slice view of the ore bodies in 3D with different copper concentrations ... 113 Fig. 6.14. 3D model of the ore bodies with uranium concentration higher than 50ppm. .. .............................................................................................................................. 114. Fig. 6.15. 3D model of the ore bodies with uranium concentration higher than 100ppm . .. .............................................................................................................................. 115. Fig. 6.16. Slice view of the ore bodies in 3D with different uranium concentrations 116 Fig. 6.17. 3D model of the ore bodies with silver concentration above 500ppb ......... 117 Fig. 6.18. 3D model of the ore bodies with silver concentration above 1000ppb ....... 118 Fig. 6.19. Slice. view. of the. ore. bodies in. 3D. with different silver. concentrations……………………………………………………………………......119. vi.

(8) LIST OF TABLE Table. 5.1. Potassium, uranium, thorium concentrations and gamma absorbed dose rates measured at the IOCG Sin Quyen deposit by potable gamma spectrometer GF-5........................................................................................................................ 46 Table. 5.2. 40K, 226Ra, 238U, 232Th activity concentrations of the solid samples measured by gamma spectrometer couple with HPGe detector and estimated gamma absorbed dose rates ................................................................................................ 50 Table. 5.3. Measured concentrations of some selected chemical composition and 234U, 226Ra. Table. 5.4.. 238U,. and 228Ra in water samples .................................................................. 55. 222Rn. and. 220Rn. concentrations in the air [Bq/m3] and annual dose rate. [mSv/a] inside and outside of the houses located close to the IOCG Sin Quyen deposit .................................................................................................................... 59 Table. 5.5a. Bulk chemical compositions of solid rocks samples and wastes............... 62 Table. 5.5b. REE bulk chemical analyses of solid rocks samples and wastes .............. 65 Table. 5.6. Coefficients of the correlation between the elements in rocks and ore at the Sin Quyen deposit .................................................................................................. 66 Table. 5.7. Timing and mineral paragenesis .................................................................. 72 Table. 5.8. Statistic values of the oxide concentrations (%) in the different allanites measured by WDS method .................................................................................... 73 Table. 5.9. Concentration of REE in older uraninites (wt.%) measured by WDS ........ 74 Table. 5.10. Concentration of REE in younger uraninites (wt.%) measured by WDS . 76 Table. 5.11. Absolute ages of uraninites calculated from each individual data point. .. 77 Table. 5.12. Sulfur stable isotope composition in sulfides from the Sin Quyen deposit ores ......................................................................................................................... 85 Table. 6.1. Ore bodies numbers and their IDs at different vertical cross-sections ...... 101 Table. 6.2. Resources of some ore elements calculated for different grade concentrations ...................................................................................................... 120. vii.

(9) LIST OF ABBREVIATIONS 3D: Three dimensions BGO: Bi2Ge4O12 CDF: Cam Duong Formation CMF: Coc My Formations cps: Counts per second CR-39: Trace detector DT: Delaunay triangulation algorithm DSI: Digital smooth interpolation EDTA: Ethylendiamin Tetraacetic Acid ESCAP: Economic and Social Commission for Asia and the Pacific GPS: Global positioning system HPGe: High-purity Germanium HUMG: Hanoi University of Mining and Geology IAEA: International Atomic Energy Agency ICRP: International Commission on Radiological Protection ICSG: The International Copper Study Group ID: Identification INST: Institute for Nuclear Science and Technology IOCG: Iron oxide copper gold ore deposits Ma: Million years: MeV: Million electronvolts ns: nanosecond PAC: Pulse amplitude comparator PSA: Pulse Shape Analysis Q: Quaternary RRF: Red River Fault SPS: Sa Pa Suite Sq1: Lower Sin Quyen Suite Sq2: upper Sin Quyen Suite SqF: Sin Quyen formation TENORM: Technologically enhanced normally occurring radioactive materials UNSCEAR: United Nations Scientific Committee on the Effects of Atomic Radiation WHO: World Health Organization viii.

(10) ACKNOWLEDGEMENT I would like to begin by expressing my gratitude to the UNESCO/AGH UST Chair prof. Janusz Szpytko for awarding me fellowship within the framework of UNESCO/POLAND Co-Sponsored Fellowship in Engineering, and Dean of Faculty of Physics and Applied Computer Science who allocated to me a research grant. Special thanks go to my supervisors prof. Nguyen Dinh Chau and dr Jakub Nowak for their kind support, understanding, and compassion. I also would like to send my thanks to prof. Adam Piestrzyński, prof. Jadwiga Pieczonka, prof. Le Khanh Phon, prof. Niewodniczański, Prof. Marek Wendorff, dr Paweł Jodłowski, dr Andrzej Bolewski, mgr Władysław Zygo, mgr Tomasz Ćwiertnia and other members and colleagues from AGH – University of Science and Technology and Hanoi University of Mining and Geology for their support and their valuable help. I would like to express my thanks to Hanoi University of Mining and Geoglogy, Faculty of Oil and Gas, Department of Geophysics for giving me the permission to study in AGH, and also many thanks to General Department of Geology and Minerals of Vietnam for granting a permission to refer to the database of the archival geology, geophysics. Many thanks to all of my friends from Poland and Vietnam for helping me during my work, among them Sankar Ram from Indian State US for the very useful grammatical corrections. Finally, I express my thanks to my wife, son and family for support, patience and a lot of sacrifice, which helped me and motivated me to finish the work.. ix.

(11) Abstract The IOCG Sin Quyen deposit is the biggest copper mine in Vietnam, it locates in province Lao Cai, 300 km in the North from Hanoi Capital. The deposit was discovered in the 70th years of Last Century by geological and geophysical surveys. The area of Sin Quyen deposit amounts above 100 ha. Since 2006 IOCG Sin Quyen deposit has been exploited as an open pit mine with annual production of 12 000 tons of copper metal. The yearly excavated ore and spoil rocks amount to more than one million ton and seven millions cubic meters respectively. As well known accompanying with copper metal there are many useful elements such as Au, Ag, REE, U and Th. The two lasted elements are radioactive and their concentrations could be enhanced especially in the dumps and reservoirs. So the contamination of the elements can effect radiological on the environment. Though the deposit in question has been investigated by several scientists from Vietnam, Russia, Australia and Japan (Ta Viet Dung 1975, McLean 2001, Ishihara et al., 2011, Gaskov et al., 2012) but some problems such as mineral compositions, ore origin, contents of REE and precious elements and so on still require to be investigated. In order to resolve the above mentioned questions the doctoral thesis of title “Rare earth, natural radionuclides and selected precious metals in the IOCG Sin Quyen deposit, Lao Cai, North Vietnam” had been proposed. The aims of the thesis were: i) study of the impact of the natural radionuclides in the environment; ii) to analyze the concentrations and study of the distribution of the copper and the other elements: Au, Ag, REE, U, Th in the ore bodies and host rocks; iii) to find the correlation between the analyzed different chemical compositions; iv) to attempt study the crystallization period happened at the deposit region. To realize the exercises, on November 2014, author of this thesis together with the groups from AGH UST and Hanoi UMG performed the necessary geological and radioactive surveys on the field and collected above 50 ore, spoil rocks, semi products and 15 water samples from the deposit and its surround. All the collected samples were transported to AGH-UST and analyzed in the adequate laboratories of this University.. x.

(12) Based on the obtained data author of this thesis states that the main radioactive source is the uranium series, it average concentration in the ores is near 17 times higher than the U average concentration in earth crust and equal to 690 Bqkg -1. The. 222Rn. in. dwelling air is near 170 Bqm-3. The average absorbed and the effective dose rate resulted from the gamma radiation and radon in dwelling air are equal to near 200 nGy/h and 7 mSv/year respectively. The surface water is contaminated mostly with U isotopes and other chemical elements. The concentration of. 238U. isotope from Red. river water amounts to 50 mBql-1, while in dig well water at the waste dump amounts to 13.1 Bql-1. There are positive correlations between Cu-U (R=0.78), U-Pb (R=0.97), Cu-Ag (R=0.94), Cu-Au (R=0.73), Cu-Pb (R=0.82), Cu-Bi (R=0.90), Cu-Te (R=0.94). Using the data of U and Pb in uraninite minerals, the ore crystallization periods of the deposit were estimated, and turned out there was one more deposit crystallization in period from 82-42 Ma. In the deposit there are of two allanites’ groups. First is older characterized with richer in REE, the second young one is poorer in REE. The measured 34S of sulfur minerals ranged from -2.78 to +8,65 ‰, the results confirm that the Cu minerals formed during the activities of deep magma fluid. The geological data also enabled author described the dynamic geological evolution of the studied region by simplified model. Apart from the mentioned results author collected above 8000 archival data obtained by boreholes well logging, radiometric measurements in tunnels and outcrops and ore samples analyzed in the Vietnam Geological Institute in Hanoi. Using both the archival and the data of the collected samples and the computer program “MineScape 5.12” from the Department of Deposit and Mining Geology Faculty of Geology, Geophysics and Environmental Protection the 3D model of the studied deposit was built up. The reserves of Cu, Fe, U, Ag and Au were estimated using the 3D model and amount to 539 000; 3 030 000; 188; 24.9 and 19.6 tons, respectively. The Cu reserve calculated by this work is in agreement with that in the Ta Viet Dung report.. xi.

(13) 1. Introduction 1.1. Scope of research In this thesis, the Sin Quyen IOCG deposit located in Lao Cai province - North Vietnam is presented. Generally, the deposit is characterized by uncommon composition of the ore with mineralization of chalcopyrite, gold, allanite, magnetite and uraninite. The Sin Quyen deposit was discovered by geophysical surveys (radioactive and magnetic method). The deposit contains a significant uranium content so the radioactive pollution of the environment maybe happen. Mining usually leads to enhancement of natural radioactive elements concentrations in the mined material, which may cause a significant increase of radiation in the environment. The phenomenon has been named as Technologically Enhanced Normally Occurring Radioactive Materials (TENORM). Therefore, it may be hazardous to miners and people living nearby the mine area and its surroundings. Next problem, are there any correlations between radionuclides and other elements in this deposit? If yes, the data together with the geometric parameters can be used to build 3D model of ore bodies and assessment reserves. On the other hand, the genesis and timing of mineralization of the ore deposit are the subjects of this investigation. The theses of this work were: i) Field radioactive measurements and geological survey; ii) Geological study that would enable to recognise the structure and deposit zones; iii) Determination of the rare earth elements, analysis of selected rare elements and the natural radionuclides in collected solid samples; iv) Studying the relationships between natural radionuclides and selected elements such as chalcophile elements Cu, Au, Ag, Pb, Bi, Te, Zn, Cd; siderophile elements Fe, Co, Ni; lithophile elements Th, U, REE; v) Measurements of the radioactive and heavy elements in air, water and solid samples permit to assess the radiological risk for miners and people living in the region; Apart from the mentioned theses, in this work the problems studied additionally are:. 1.

(14) 1) Study of the genesis of deposit; 2) timing of mineralization; 3) regional evolution structure model; 4) 3D models of ore-bodies; and 5) estimation of resources available for extraction. 1.2. Background Copper occurs in the Earth’s crust in different varieties of natural forms. It can be found in sulfide minerals (chalcopyrite, chalcocite, bornite, covellite), in silicate minerals (dioptase and chrysycolla), in carbonate forms (malachite and azurite) and as pure "native" copper. Copper always plays an important role in economy. Mining and processing of copper ore and transformation of copper metal into a multitude of products can create jobs and generate wealth for society. The global demand for copper has been continuously growing and is expected to grow in the future, which has consequently resulted in the copper price growth in the past ten years (Fig. 1.1). Based on the information of the International Copper Study Group (ICSG, 2016), the global growth of copper mining capacity has been increasing from 1999 (Fig. 1.2). According to the United States Geological Survey (USGS) (The World Copper Factbook, 2016), copper reserves amount to around 720 million tones (Mt), while identified and undiscovered copper resources are estimated near 2,100 Mt and 3,500 Mt respectively (Fig. 1.3) (ICSG, 2016). The estimated undiscovered copper resources are much higher than identified resources, thus there is still space for further progress in the copper deposits industry. Iron oxide, copper and gold deposits (IOCG) are one of common deposit type containing copper metal, which are known to have a wide spectrum of mineralization styles, and exist in hydrothermal state with low-Ti magnetite and/or hematite, and with Cu-sulfides as major compositions (Hitzman et al, 1992; Hitzman, 2000; Sillitoe, 2003; Williams et al, 2005; Xin et al, 2011). In addition significant amounts of rare earth elements, uranium and some other precious metals (Ag, Au) are accompanying copper. One of the greatest IOCG deposit is the Olympic Dam in South Australia. It is known to be the second biggest uranium producer and the third largest deposit of copper in the world, there is also a significant concentration of gold in this deposit (Kerrich et al, 2000; Hitzman and Valenta, 2005; Porter, 2010; Skirrow, 2011; Sillitoe, 2012). 2.

(15) Fig. 1.1. Dynamic global copper price (ICSG, 2016). Fig. 1.2. Growth of global copper mining capacity from 1999 to 2019 (ICSG, 2016). 3.

(16) Fig. 1.3. 2015 World Copper Reserves & Mine Production (ICSG, 2016). 4.

(17) 2. The investigated region 2.1. Regional tectonic The Sin Quyen deposit is located in northeastern part of Fanxipan belt, within the Red River zone, North Vietnam (Fig. 2.1). The structure of the Red River zone was formed by a variety of tectonic processes, which occurred in many periods from Protezoic to Cenozoic (Leloup et al, 1995; Tran, 2003; Anczkiewicz et al, 2000, 2007; Bui et al, 2004; Lepvrier et al, 2008; Xin et al, 2011, 2015; Trinh et al, 2012; Nguyen et al, 2013; Zelaźniewicz et al, 2013; Junlai et al, 2015). The Fanxipan belt is stretching up to 300 km long in the NW direction and principally consists of Proterozoic rocks. The Fanxipan zone is the boundary between South China Plate and Indochina Plate (McLean, 2001; Hsin et al, 2013; Halpin et al, 2016). In this zone, there are few major NW–SE trending faults including Chay River fault, Red River fault, Da River fault and Ma River fault (Fig. 2.1) (Gilley et al, 2003; Kazuhiro et al, 2005; Faure, 2014). The southwest part of Red River fault consists of five NW-SE oriented main structural units: 1- the Fanxipan uplifted crystalline massif; 2- the Tu Le continental rift system of terrigenous–volcanic formations; 3- Da River rift zone with a wide variety of marine volcanic and associated marine sedimentary formations; 4- the Ma River Unit composed of greenschist facies, oceanic sediments and volcanic formations characterized by ophiolites along the Ma River Fault, and 5the Truong Son fold belt (Fig. 2.1) (Tran, 1979; Metcalfe, 1995; Le and Ngo, 1995; McLean, 2001; Pham et al, 2008; Balykin, 2010; Tong and Vu, 2011; Pham et al, 2013; Zhang et al. 2013; Usuki et al, 2015).. 5.

(18) Fig. 2.1. Map of main tectonic structures of the region (Halpin el al, 2016, modified) 2.2. Stratigraphy In the study region there are sedimentary and metamorphic formations of Proterozoic, Paleozoic and also Cenozoic era. Proterozoic The Sin Quyen deposit occurs in Proterozoic Sin Quyen formation (SqF) (Fig. 2.2). The SqF includes sedimentary rocks and metamorphosed sediments hosting copper bodies. The formation is composed of highly crushed amphibolites, migmatised gneiss, granite-gneiss, schist and altered rocks extending in NW–SE direction between 280 and 320, 50 to 85 of dip, and 400-800m of thickness. The SqF underlies comformable with the Thung Sang formation (TSF) and Cambrian Sa Pa Suite (SPS), and uncomformable with Cam Duong formation (CDF), and Cenozoic Quaternary formations (Q). The structure of the mentioned formations were strongly controlled by Sin Quyen reverse fault and also were penetrated by number of regional dislocations, including Sin Quyen, Pin Ngan Chai and Thung Sang faults, all of them are parallel. 6.

(19) and visible as splays of the major Red River Fault (RRF) (Ta et al, 1975; Bui, 1978; McLean, 2001; Ishihara et al, 2011; Gaskov et al, 2012). From the mineral composition point of view, the SqF can be divided into lower (Sq1) and upper (Sq2) sub-formations. The Sq1 contain 50% of quartz, 15% of graphite, 10% of biotite, and 12% of muscovite as a major minerals and plagioclase, tourmaline, garnet, sillimanite as a minor minerals. While the Sq2 is chiefly consist 61% of plagioclase, 21% of quartz, and 15% of biotite as major minerals and apatite, sphene, calcite and garnet as accessory minerals (Ta et al, 1975; McLean, 2001). Paleozoic The CDF is composed of Paleozoic Cambrian sediments composed of quartz, sericite, schist containing graphite, carbonate, schist, quartz, biotite, chlorite schist. The formation is extending in NW-SE strikes from 280 to 320 and dipping under 20 to 70 (Ta et al, 1975). Cenozoic Cenozoic Quaternary sedimentary formations (Q) in the region are very thin and uncommon, and consist of pebble, sand, clay and sandstone (Ta et al, 1975).. 7.

(20) Fig. 2.2. Geological map of the Sin Quyen deposit. 8.

(21) 2.3. Intrusives The magmatic intrusives are divided into two main formations: Proterozoic Coc My formations (CMF) and Permian suites. The CMF covers up to 30% of the deposit area and consists of amphibolite and granite-gneiss. Permian intrusives are the youngest in the region, and are represented by gabbro–dolerite and plagio-granite intrusions. Amphibolites are the earliest intrusive rocks penetrating into the SqF with thickness from 5 to 50 m and 10 to 100 m in length, extending in NW–SE direction. The intrusive rocks comprise 66% of hornblende, 19% of plagioclase, 6% of biotite as major minerals and other minor minerals such as orthite, epidote, apatite, ores, chlorite and calcite. In the zone close to the copper ore bodies there usually occur other minerals such as allanite, calcite, and quartz (Ta et al, 1975; McLean, 2001; Ishihara et al, 2011). Granite-gneiss occupies up to 25% of the deposit and is highly crushed and migmatized. Those rocks occur as dykes and lenses 2-200 m in thickness, 10-3000 m in length and extend in NW–SE direction. The granite-gneiss comprises 66% of plagioclase, 26% of quartz, and 7% of biotite as major minerals and zircon and apatite as minor minerals (Ta et al, 1975). The gabbro–dolerite occurs in the zone of contact between the SqF and the SPS and extends in NW–SE direction. The gabbro–dolerite comprises of amphibole [64%], plagioclase [18%], biotite [7%], chlorite [5%] and other: calcite and disseminated pyrite, pyrrhotite, chalcopyrite (Ta et al, 1975; McLean, 2001; Ishihara et al, 2011). The plagio-granites occur in fracture zones of the deposit and penetrate through the SqF into SPS rocks and the CMF with 0.5-20 m thickness and 10-300 m length. The plagio-granites consist of plagioclase (63%), quartz (26%) and biotite (6%) as major minerals and microline, muscovite, apatite, chlorite, and sometimes traces of zircon and albite as minor minerals. In the zone close to the plagio-granite there is plagiopegmatite composed of quartz, plagioclase, biotite, allanite and epidote (Ta et al, 1975).. 9.

(22) 2.4.. Metamorphic formations. The metamorphic formations were briefly described by Ta et al, (1975). They occur at the center of deposit in various forms such as lenses, chambers or vein bunches with 0.5 – 100 m thick, 1 - 1000 m long and trend from 2800 to 3200 and are dipping from 650 to 900. The metamorphic formations contain pyroxene, garnet, hastingsite, quartz, albite, orthite, apatite, biotite, plagioclase, vezuvian, chlorite, epidote, calcite and allanite. The metamorphic rocks can be divided into two groups: 1) skarn-pyroxenegarnet rocks and 2) skarn-hastingsite-biotite-quartz rocks groups. The skarn-pyroxenegarnet rocks group composed of pyrrhotite ores, rare chalcopyrite and the skarnhastingsite-biotite-quartz group including magnetite ore, uraninite, sulfide ore (mainly chalcopyrite-pyrrhotite). 2.5. Resource and exploitation The Sin Quyen deposit is the largest IOCG deposit in North Vietnam, with a total area above 100 ha and includes seventeen ore-bodies. The reserves of Cu, REE, S, Au and Ag amount to 550 000; 334 000; 843 000; 34.7 and 25.3 tons, respectively (ESCAP, 1990). Since 2006, the Sin Quyen deposit has been exploited as an open pit mine with an annual average production of 12,000 tons of copper metal. Every year, more than million tons of ore and seven million cubic meters of rocks are excavated (Le et al, 2015). According to the VINACOMIN Company project from 2006, the Sin Quyen mine can be actived for 19-years as an open pit mine and after this period will be transformed to the underground mine for 21 years. Initially, the project assumed the reserves amounting at least 53 million tons of copper ore, but according to the recent reports from the same company the copper reserves increased up to 100 million tons (http://dongsinquyen.vn, 2013).. 10.

(23) 3. Prospecting surveys for copper deposit Based on the previous geological cartographic surveys and geological map informations, the geologists decided to perform the necessary geophysical and geological surveys for more detailed prospecting of the ore deposits (Reedman, 1979a). In order to do the prospecting of the copper ore, the geologists often use the electrical, magnetic and radiometric methods. The magnetic surveys are to locate of the magnetic anomaly zones established by magnetic minerals (magnetite, pyrite…) accompaning to copper minerals. The magnetic measurements are often performed using proton precession magnetometer. The copper minerals also often occur with the minerals bearing uranium and thorium, therefore geologists perform radiometric serveys. In combination of the mentioned methods, the zones rich in minerals bearing Cu, Fe and radioactive elements (U, Th) can be localized (McLean, 2011). Additionally, hydrogeochemical survey using water from streams and springs is commonly used in areas related with copper deposits (Miller et al, 1982). Since the main copper minerals are chalcopyrite, chalkozine, bornite and so on, the minerals are rich in sulphur, are easily dissolved in water forming sulfuric acid and decreasing pH of water. For analyzing the chemical composition of copper and other accompanying elements, the ore and rock samples are collected and analysed using laboratory methods. The main tasks of the laboratory analysis are to: (i) determine the quantity of the elements and interesting isotopes; (ii) document the spatial distribution of the minerals in the studied deposit (Reedman, 1979b). 4. Applied methods The applied methods include field and laboratory works. Geological and geophysical surveys involve sampling, gamma spectrometer and radon and thoron measurements in field. The laboratory works consist of chemical track of CR-39 detectors; determining natural radionuclides and chemical compositions in water samples by ICP-AES, LSC and alpha spectrometer; determining minerals, natural radionuclides, chemical and δ34S sulfur isotopic compositions in solid samples by gamma spectrometer, NAA, ICPMS, EDS, WDS and Elemental Analysis – Isotope Ratio Mass spectrometry. All the methods performed in the framework of this thesis are presented on Fig. 4.. 11.

(24) Fig. 4. The workflow performed in this thesis 12.

(25) 4.1. Field work 4.1. 1. Field geological survey and sampling The field geological survey in the Sin Quyen deposit was described in details in Ta’s report (1975). The report principally consists of the geological and geophysical data obtained by well logging and chemical analyses. The data was concerned with the distribution and characteristics of the copper ore bodies and other useful metals of this deposit, but so far information about radioactive elements, timing, genesis and the interrelation between different elements and radionuclides require further studies. The thesis was based on the data collected during the field geological survey and analyses of the samples collected during two field campaigns. The first one was made by the groups of Geologists and Geophysicists from AGH University of Science and Technology (AGH UST) and Hanoi University of Mining and Geology (HUMG) in November 2014. During this first campaign, the geological and geophysical surveys were carried out simultaneously with sampling and gamma spectrometric measurements at 44 points of the profile crossing formations and perpendicular to the strike line of ore-bodies. Additionally the samples were taken from the floatation plant, from tailing ponds and solid waste dumps. To estimate the radioactive hazard on environment, radon concentrations in the air were measured in 22 selected inhabited houses using trace detectors (CR-39) and water samples were collected from household taps, retention reservoir, surface runoff (Red river), and from dip wells at the private houses. During the first campaign, 49 rock, ore, sediment samples (signed as W01 to W49) and 15 water samples (signed as SQ01-SQ15) were collected. During the second campaign in June 2015, the author of this thesis collected 29 rocks and ore samples from the main ore-bodies. The coordinates of all the sampling and gamma measurement points were measured by Garmin GPS, version 60CSx with ±3 m of uncertainty (Fig. 4.1a, b). All water and solid samples were sent to AGH UST and Canadian Labs (ACME Lab) for analysis.. 13.

(26) Fig. 4.1a. Satellite picture show the sampling points. Fig. 4.1b. Water sampling points on the satellite picture. 14.

(27) 4.1.2. Field measurements of natural radionuclides The field gamma-ray spectroscopy is the quantitative measurement of the gamma emitters occurring in the formations outcrop on or near surface area. The field gammaray spectrometric measurements were performed using portable gamma spectrometer GF-5-Channel manufactured by GF Instrument Company(TM) (from the Czech Republic) (Fig. 4.2). The instrument consists of the NaI(Tl) detector 0.35 dm3 of volume and analyser with 512 channels. The GF spectrometer measures the gamma rays of the energies from 100 to 3000 keV, the maximum intensity amounts to 250000 cps,. and. it. can. work. at. temperature. ranging. from. -10. to. +50°C. (http://www.gfinstruments.cz). At every measured point the detector was placed one meter above the earth surface, and the automatic measuring lasted for 3 minutes. The outcomes of the field spectrometric measurements are the concentrations of natural radioactive elements K(%), eU(ppm), eTh(ppm) and gamma absorbed dose rate D(nGy/h). The obtained data, in cooperation with the Geological Survey, were used for sampling.. Fig. 4.2. View of portable gamma spectrometer GF-5. 15.

(28) 4.1.3.. 222Rn. and 220Rn measurement by track detectors CR-39. The concentration of. 222Rn. and. 220Rn. in the dwelling air was measured using track. detectors, product of Radiosys – Hungarian company. The Radiosys detector consists of two CR-39 track detectors placed in two special diffusion chambers (Fig. 4.3a, b); one chamber is “shallow” and the second is “deep”. The shallow detector is used for simultaneous detection of. 222Rn. and. 220Rn. and the second detector is used for. 222Rn. detection (Tokonami et al., 2005). Each chamber is made of plastic formed as cylindrical in shape with an inner volume of about 30 cm3. The CR-39 films are placed at the bottom of each chamber. Radon (222Rn) in the air can penetrate into the deep chamber by diffusion through an air gap between its lid and bottom. Since this air gap functions as a high diffusion barrier,. 220Rn. flow slows down and cannot reach the. chamber through such a narrow slit due to its very short half-life (55.4 s) compared to that of. 222Rn. (3.82 days). So most of the. 220Rn. can not reach the CR-39 films in the. deep chamber. The shallow chamber is used to detect. 220Rn. more effectively, because. in the “shallow” chamber there are six opened holes, each 6 mm in diameter, which are exposited directly to the air in the dwelling. In each surveyed house the radon isotopes’ concentrations were measured at two points, one at the inside and the other one at the outside. The exposition on the radon air usually lasts nearly 3 months. At every house the CR-39 detector was hung at the height of 1.5 to 1.8 m above the floor’s surface and 2 m horizontally offset from the doors and walls. After exposition, the track detectors were collected and transported to the Institute for Nuclear Science and Technology of Vietnam (INST), where the CR39 detectors were chemically etched with a NaOH 6.25M solution at 80 °C. The etching processes lasted over 6 hours, then the trace density was counted under OLIMPUS CX21 Microscope. The. 222Rn. and. 220Rn. concentrations in Bq/m3 were. determined using the calibration curves for adequate chambers and densities tracks. The calibration curves for. 222Rn. and for. 220Rn. are presented on Fig. 4.4a, b. respectively (INST, 2013). The annual committed dose rate resulting from the inhalation of 222Rn and 220Rn inside and outside the dwellings were calculated using the formulae (4.1) and (4.2) respectively (UNSCEAR, 2000):. 16.

(29) D(mSv / a)  0.025 Rn  0.0084 Tn. (4.1). D(mSv / a)  0.0095 Rn  0.0007 Tn. (4.2). Where Rn and Tn are the concentrations expressed in Bq/m3 of the. 222Rn. and. 220Rn. respectively; coefficients are defined equal “dose conversion factor” multiply “equilibrium factors” multiply “annual time (h)” for Rn and equal “dose conversion factor” multiply “equilibrium equivalent concentrations (EEC)” multiply “annual time (h)” for Tn respectively.. Fig. 4.3a. Radon-Thoron detector CR-39. 17.

(30) Fig. 4.3b. View of the radon-thoron detectors CR-39 (RADOSYS User Manual, 2013). 18.

(31) 14000. 12000. (n.cm-2)=2,19.222Rn+197. trace density (n/cm2). u(a)=2,52%, u(b)=100% 10000. 8000. 6000. 4000. 2000. 0 0. 1000. 2000. 3000. 4000. 5000. 6000. 222. Rn [kBq.h.m3]. Fig. 4.4a. The calibration curve for radon chamber. 8000. (n.cm-2) =1.84.220Rn - 73 trace density (n/cm2). u(a)=3.6%, u(b)=216% 6000. 4000. 2000. 0 0. 1000. 2000. 3000. 4000. 220. Rn[kBq.h.m3]. Fig. 4.4b. The calibration curve for thoron chamber. 19. 5000.

(32) 4.2. Laboratory work 4.2.1. Measurement of natural radionuclides in the solid samples using the gamma spectrometer with HPGe detector The gamma spectrometer coupled with a semiconductor HPGe detector (Canberra GX4020) is characterized by the following parameters: 1- relative efficiency of 42% and resolution of 1.9 keV at 1332 keV line; 2- the range of measured energy from 3 keV to 10 MeV. The detector is connected by a Desktop Inspector, and processing Genie 2000 software (Canberra). During measurements, to decrease the gamma-rays from cosmic and surrounding instrument, the detector is placed in a house build by lead bricks 10 cm in thickness, and cadmium and copper sheets inner lining 1 mm thick, and with the bottom paved by a lead layer 15 cm thick (Fig. 4.5). The detector is covered by 5 cm thick lead shield. The cover can be moved to change and replace samples. The background measurements were made for an empty beaker and lasted to obtain the time ensuring the relative uncertainty of the count rate at the peak 1764 keV (214Bi) lower than 2% (Fig. 4.6). The gamma spectrometer was calibrated using the IAEA reference materials RGU, RGTH, RGK as standard for the respectively (Jodlowski & Kalita, 2010).. 20. 226Ra, 232Th. and 40K.

(33) Fig. 4.5. Diagram of the gamma detector GX4020: (1) semiconductor HPGe detector, (2) the protective cap detector, (3) lining room, (4) lead upper movable cover, (5) protective lead, (6) the Dewar vessel with liquid nitrogen (LN2), (7) pre-amplifier. Fig. 4.6. Background gamma spectrum measured through 100h by HPGe detector (Jodlowski & Kalita, 2010) Depending on the sample volume, three geometries were used: 48.4 cm3 and 121.2 cm3 cylindrical geometries and the Marinelli beaker of 710 cm3. The shapes of the sample beakers are shown in Fig. 4.7.. 21.

(34) Fig. 4.7. The shape of the beakers and samples of the used geometries. (a) low geometry (48.4 cm3); (b) small geometry (121.2 cm3); (c) large geometry (710 cm3) The preparation and measuring procedures for samples are shortly described as follow Jodlowski & Kalita, 2010. The samples were ground and dried in an oven at 120C for 24 hours to ensure that moisture is completely removed, then weighed and packed in radon-impermeable aluminum beaker 121.2 ml capacity and sealed to prevent escape of radon gas. The weighed and tightly sealed samples were left for at least 22 days to reach secular equilibrium between 222Rn and 226Ra in the samples. Gamma lines of 1000.8 keV (0.7%) from (15.0%) and 1764.5 keV (15.9%) from. 234Pa. 214Bi. 22. and 609.3 keV (46.1%), 1120.3 keV. were used to determine the content of.

(35) 238U. and 226Ra, while content of 232Th were determined from the gamma lines of 911.2. keV (29.0%) and 969.0 keV (2.3%) from. 228Ac. and 583.0 keV (30.9%) and 2614.4. keV (35.8%) from 208Tl (ICRP, 1983; IAEA, 1989). 40K was determined from its 1461 keV gamma line. The maximum counting time for each sample was 50 hours, the obtained relative uncertainty was less than 3%. The self-gamma absorption from the different density of the measured and standard samples were introduced following Jodlowski (2006). To avoid influence of the chemical composition of the sample, all energies of the measured gamma ray were higher than 500 keV. Activity concentrations of 40K, 226Ra and 232Th were calculated by formula:. (4.3) where: Nsp, Msp and Nst, Mst are the net measured intensities and masses of the sample and standard respectively, C is the correction factor for the differences between the density of the sample and standard sample. The gamma absorbed dose rate was calculated using the measured activity concentrations of 226Ra, 232Th and 40K (UNSCEAR, 2000): D(nGy / h)  0.041 K  0.462 Ra  0.604 Th. where K, Ra and Th are specific activites of. 40K, 226Ra. (4.4) and. 232Th. of the sample. expressed in [Bq/kg] 4.2.2. Radiochemical analysis for radium and uranium isotopes in water samples 4.2.2.1. Alpha/beta spectrometry with liquid scintillation detector A liquid scintillation spectrometer is used to measure the alpha and beta particles emitted from the prepared sample mixed with a liquid scintillation cocktail. As a consequence of the interacting of the ionization radiation with liquid scintillation cocktail, light photons are produced, the light photons are led to the photomultiplier and transformed into electric signals. Based on the record of the impulse intensities one can determine the content of the studied isotopes in the prepared sample. The Winspectral Wallac 1414 Alpha/Beta Liquid Scintillation Counter is used for measuring isotopes emitting alpha and beta particles in the collected water samples. 23.

(36) The block diagram of the Wallac Guardian 1414 spectrometer is shown in Fig. 4.8. Photons of light formed by liquid cocktail are recorded by two photomultipliers working in coincidental mode. Additionally, Wallac Guardian 1414 is equipped with a background active reduction system, pulse amplitude comparator (PAC) and the system separating the pulses coming from the α particles from the pulses formed by the β particles (PSA- Pulse Shape Analysis). The background active reduction system contains a BGO scintillation crystal (Bi2Ge4O12), working in the anti-coincidental mode with the photomultipliers’ system. Natural background radiation interacting simultaneously with both the BGO probe and liquid cocktail generates pulses. These pulses are rejected by the anti-coincidental system, in consequence the measured natural background is significantly reduced. PAC system is used to compare the amplitude of the pulses generated from the different phenomena. The amplitudes of the pulses generated by the alpha or beta particles emitted from the prepared sample are often significantly higher than those generated by the thermal noise or absorption of the radiation emitted from contaminant on the vessel wall, resulting with PAC system rejecting most of the impulses coming from the unsuitable phenomena. The PSA system is used to distinguish pulses derived from α and β particles. The pulses generated by ionizing radiation in a liquid cocktail consist of two parts: the "fast" and the "delayed". The pulses resulting from β particulates are generally short and mainly composed of the "fast", while the impulses arising from α particles are significantly longer than those from the β particles. Base on the ration of the charges from the short part and the whole pulses, one can separate the pulses from the alpha or beta particles. In the Wallac spectrometer, the values of PSA range from 1 to 255, with increase of PSA value the pulses are classified as the pulses from alpha particles.. 24.

(37) Fig. 4.8. Diagram of the Wallac Guardian LSC spectrometer: SP - measuring vessel with the sample, P1 - photomultiplier, D - probe scintillation crystal BGO, CScoincidental system, ACS – anti-coincidental system, SUM – summation, GAC gateway anti-coincidence, AMP - amplifier, AD - analog-digital (Wallac 1996) In this work, in order to determine the optimum values for PSA, the method is based on the measurement of the the alpha and beta particles emitted from standard samples. The standard sample is prepared from the standard solution of well-known activity 226Ra. isotope concentration, then the sample is prepared by the chemical procedure. (following procedure of Nguyen, 2010). On the basis of the measured intensities of α and β counts (at any given value of the parameter PSA), activity of 226Ra isotope for a sample is calculated by the following formulae:  ARa  226 . . ARa226 .  . ARa226 . I  (t )  I 0 (t ) K (t )     60. (4.5). I  (t )  I 0 (t ). (4.6). K  (t )     60 ( I  (t )  I 0 )  ( I  (t )  I 0 (t )) ( K (t )  K  (t ))  (     )  60.     where ARa 226 , ARa226 , ARa226 - are the. 226Ra. (4.7). isotope activitys in the sample, calculated. on α and β channels (Iα, Iβ) and their sum. Kα(t), Kβ(t) - the ratio of total activity of the adequate α and β decay isotopes in the 226Ra. series, which are created as a consequence of the decay processes, during time (t). 25.

(38) elapsed from the precipitation time of radium chemical procedure to the initial activity of 226Ra. The Kα(t), Kβ(t) can be calculated using the Bateman equation. εα, εβ - efficiency of detection of α and β emitted from the isotopes of the 226Ra series. Based on the activities of. 226Ra. is calculated using the formulas (4.5), (4.6) and (4.7),. the graphs of the dependence of the 226Ra values on the parameter PSA are drown. The point of intersection of three curves (Fig. 4.9.) corresponds to the optimum PSA value (Nguyen et al., 1997; Nguyen 2010).. Fig. 4.9. The curve showing the method for determination of optimum PSA value based on the sample prepared from 226Ra standard solution (PSA optimum value in this case is 105) A typical spectrum of α/β measured by alpha/beta Wallac liquid scintillation spectrometer for the. 226Ra. standard sample, where. with its progeny, is shown in Fig. 4.10.. 26. 226Ra. is in radioactive equilibrium.

(39) Fig. 4.10. A typical spectrum of α/β measured by alpha/beta Wallac liquid scintillation spectrometer for the 226Ra standard sample, where 226Ra is in radioactive equilibrium with its progeny 4.2.2.2. Alpha spectrometer coupled with semiconductor detector Due to very short distance of passages of the  particles (in air approx. 3.5 cm for particle energy of 5 MeV (Dziunikowski, 1995)), it is necessary to prepare very thin sample and a measurement inside a vacuum chamber. In this study a spectrometer Canberra model 7401(TM) was used, with the silicon semiconductor detector with to 300 mm2 of the active surface. The measurement is maintained in the pressure vacuum chamber at 30 µHg of pressure. A schematic diagram of the measurement system is shown in Fig. 4.11. Fig. 4.12 presents an example of α spectrum of water sample prepared for determination of the uranium isotopes.. 27.

(40) Fig. 4.11. Block diagram of alpha spectrometer. S - sample, D - detector, AMP amplifier, AD - analog-to-digital, MAA- multichannel amplitude analysis, VP vacuum pump (Canberra, 2006). Fig. 4.12. Typical alpha spectrum of a prepared water sample to determine the uranium isotopes measured by alpha spectrometer Canberra 7401 4.2.3. Determination of radium isotopes (226Ra and. 228Ra). concentrations in water. samples 226Ra. and. 228Ra. isotopes in water sample are determined using the radiochemical. procedure and the / liquid scintillation spectrometer (Nguyen, 2010). The radiochemical procedure involves the separation of radium isotopes from water sample in sulphate compound together with barium carrier. In order to eliminate the interfering isotopes occurring in the precipitate such as 210Pb and 210Po, the precipitate is dissolved up in the EDTA solution and again precipitation of Ba(Ra)SO 4 through decreasing the pH solution by addition of acetic acid is achieved. Finally the obtained 28.

(41) precipitate is cleaned up by distilled water and centrifuge, and placed in the glass vial and mixed with gel scintillation cocktail “Perkin Elmer” company and measured using the / 1414 Wallac Liquid Scintillation Counter (Tomza 1975; Tomza and Lebecka 1981; Nguyen et al., 1997). To eliminate the background radiation originating from the chemical reagents, cosmic and electronic noise, the background sample from the distilled water is prepared together with a series of the investigated water samples. Standard sample 226Ra is used to determine the efficiency of the applied chemical procedure and to control the value of the PSA parameter (see paragraph 4.2.2.1). Every sample is measured every day for two hours until the expected equilibrium between 226Ra and its short-lived products is established (above 21 days). The contents of the. 226Ra. and. 228Ra. in the measured water sample are estimated on the basis of the. dependence of the net measured intensities in  and  channels on the time elapsed from the precipitation radium in water sample (the net count rate). An example of dependences of the count rates measured in alpha and beta channels for sample prepared from the 226Ra standard solution is presented on Fig. 4.13. Standard solution 226Ra 1000 alfa beta 800. cpm. 600. 400. 200. 0 0. 100. 200. 300. 400. 500. 600. elapsed time (h). Fig. 4.13. Dependences of the alpha and beta count rates measured using LSC for the 226Ra standard sample in the time elapsed from the moment of precipitation.. 29.

(42) Fig. 4.14a, b present the decay diagrams of the radioactive equilibrium, in the 222Rn, 218Po, 214Po) 218Po. 226Ra. 226Ra. and. 228Ra. respectively. At the. group, there are four alpha decay isotopes ( 226Ra,. and two beta decay isotopes (214Pb, 214Bi) (222Rn - T1/2 = 3.825 day,. - T1/2 = 3.05 min, 214Pb – T1/2 = 26.8 min, 214Bi - T1/2 = 19.7 min and 214Po - T1/2. = 1.64 · 10-4s). In the 228Ra group there are only two beta decay isotopes (228Ra, 228Ac). Since the the half-life of. 210Pb. isotope (T1/2) is 22.3 years, this isotope may be. considered as a stable in the laboratory time scale. The half-live (T1/2) of 226Ra is 1620 years, and the longest progeny in this group is 222Rn with T1/2 equal to 91.8 h, so in the group the secular equilibrium is established after approximately 500 h from the completion of preparation. In the 228Ra group, 228Ra (T1/2 = 5.75 years), the secular equilibrium between 228Ac. 228Ra. and. (T1/2 = 6.13 h) is formed after 20 hours of precipitation. Reference to the lab time. (one month), the 228Th can be regarded as a “stable” isotope, due to its T1/2 is 1.9 years. In the. 224Ra. group there are four alpha decay isotopes ( 224Ra,. 220Rn, 216Po, 212Po). and. two beta decay ones (212Pb, 212Bi). The T1/2 of 224Ra amounts to 3.62 d and the longest progeny isotope is 212Pb with T1/2 is 10.6 h, so in the group the transient equilibrium is established after 50 h, and the activity of the. 224Ra. group decreases as the decay low. for 224Ra isotope, and at 500 h of the elapsed time, the total activity of the 224Ra group lowering below 2% in comparison with the activity of this isotope at the precipitation time. So at this elapsed time, the contribution of the. 224Ra. group in the total alpha and. beta count rates can be neglected. 226Ra. concentration in water sample is determined by the formula: 226. I500 Ra  Ra  226 F 500  60    V. (4.8). where I500 - the net count rates (cpm) of the sample is measured in the alpha channel at  226 the 500 h of the elapsed time; FRa500 (K) is the factor which corresponds to relative. -activity of the 226Ra group at the 500 h of elapsed time from the sample preparation; this factor can be calculated using the Bateman equation or empirically using the sample prepared from the. 226Ra. standard solution;  is the detection efficiency of the. liquid scintillation detector for the alpha particle and it can be estimated using the. 30.

(43) sample of. 226Ra. standard solution or arbitrarily can be taken as 100 % (Horrocks,. 1974); V – the volume of water sample. 228Ra. concentration in water sample is determined using the beta count rate. The total. beta count rate at 500 h elapsed time consists of both beta count rates from 226Ra. groups. The count rate of the beta particles emitted. 226Ra. 228Ra. and. group occurring in the. prepared studied sample is calculated by formula as follow:  226  I Ra500  I 500  C . where C. (4.9). I st500  st ; I st500 and Ist500 are the count rates for the I 500. 226Ra. standard sample. measured in beta and alpha channels at 500h elapsed from the sample precipitating time. The count rate from 228Ra group in the studied sample is calculated by formula:  228 Ra  226 I Ra500  I total  500  I   500. (4.10). where I total  500 - the count rate measured in the beta channel for the studied sample. The 228Ra content in the prepared water sample is calculated by the formula: 228. Ra .  228 I Ra500. (4.11).  228 FRa500  60    .V.  228 FRa500 is the factor corresponding to the relative beta activity of the. 228Ra. group at the. 500 h elapsed time from the sample preparation,  - the efficiency of the detection of the beta particles emitted from. 228Ra. group which is determined using the sample. prepared from the 232Th standard solution. In the present study the contents of. 226Ra. and 228Ra in water samples were determined. using the values interpolated on the 500 h from the adequate curves of the dependences of the net count rates Iα-500 and Iβ-500 measured in alpha and beta channels. For the calculation of the concentration of emitter. 226Ra. 228Ra. is the value Iβ-500 less a part of beta. decay products. At the time of 500 hours the activity ratio of β decay. nuclides to α decay nuclides in the 226Ra group is 0.5, regarding the beta efficiency of the gel liquid scintillation cocktail equal to 0.85 (Nguyen 2010), therefore the ratio of. 31.

(44) / for the. 226Ra. group can be arbitrarily regarded equal to 0.425. So the part of beta. intensity originating from the 228Ra group can be calculated: Iβ = Iβ-500 - 0.425 • Iα-500. Calibration curves were prepared based on the values of Iα-500 and Iβ-500 for water samples with known activity of. 226Ra, 228Ra.. These curves are shown in Fig. 4.15a, b. (Nowak, 2013).. Fig. 4.14a. Decay diagram of uranium series. 32.

(45) Fig. 4.14b. Decay diagram of thorium series. 33.

(46) Fig. 4.15a. Calibration curve for 226Ra determination. Fig. 4.15b. Calibration curve for 228Ra determination. 34.

(47) 4.2.4. Determination of uranium isotopes (234U, 238U) concentrations in water samples The determination of the uranium isotopes in water sample requires the radiochemical method. The radiochemical method is used following the modified procedure described by Nguyen (2010). The well known amount of the. 232U. trace is added to. water sample at the very beginning of the chemical procedure then the uranium isotopes are precipitated of (NH4)2U2O7 together with MnO2. The precipitate is washed with distilled water. The obtained precipitate is dissolved in HCl acid and absorbed uranium fractions in chromatographic column with Dowex 1x8, 100-200 mesh. The uranium fractions are removed into plastic cups by HNO3 acid (named Mn fractions) and distilled water (uranium fractions) from column then dried and dissolved in HCl acid. To the obtained liquid sample Neodymium and HF acid are added and then filtered through 0.1 m aperture to acquire uranium compounds. The obtained sample is dryed and measured by alpha spectrometer. The measuring time for every sample is chosen for the uncertainty of the count rate at 232U. peak is below 2%. To eliminate the background derived from the chemical. reagents, electronic noise or alpha particles emitted from the surrounding, the background sample from the distilled water is also prepared and measured. The concentration of. 234U, 238U. isotopes in water sample is calculated using the. formula: sp bg I 234  I 234 ) /V st bg I 232  I 232. (4.12). sp bg I 238  I 238  ( A232  st ) /V bg I 232  I 232. (4.13). C 234  ( A232 . C 238. C234, C238 - the concentration of 234U, 238U isotopes in water sample [mBq/L]; A232 - activity tracer 232U isotope added to the sample water [mBq]; sp bg sp bg sp bg , I 238 I 234 , I 234 , I 238 , and I 232 , I 232 are the count rates (counts/min) in the peak of. 238U. and 232U for the studied and background samples respectively;. V - Volume of water samples [L].. 35. 234U,.

(48) 4.2.5. Neutron activation analysis (NAA) Neutron activation analysis (NAA) is one of the instrumental methods for determining the concentrations of elements in solid materials. The NAA method can be briefly described as follows (Glascock, 2004). The sample is irradiated by neutron flux, and a certain fraction of the neutron flux is absorbed, some elements are formed into radioactive isotopes in consequence. After irradiation, the radiation emitted from the sample is measured. Based on the gamma ray energy and gamma intensity measured by gamma spectrometer one can determine the contents of the elements in the samples In this study, the copper concentrations in selected solid samples were analysed by NAA at the Faculty of Physics and Applied Computer Science of AGH UST. With 10 g of mass per sample, it was powdered to 0.1 mm size, dried at temperature of 120oC for 1 day and irradiated with neutron flux. The neutron source is neutrons/sec of yield. The cross section of the. 63Cu. and. 65Cu. 239Pu-Be. with 5x106. for thermal neutron. absorption are 4.51 and 2.3 barn respectively (Batra & Garg, 1989). In the copper sample there are two nuclear reactions, first is 63Cu (n, γ) 64Cu and the second - 65Cu (n, 2n). 64Cu. with yield of 69.1 and 30.9 % respectively. The product of both above. mentioned reactions is. 64Cu. with T1/2 = 12.7 h. The. 64Cu. undergoes two alternative. decays β- with 38.5% or β+ with 61.5% of efficiency. The gamma ray of 1345.8 keV from the - decay is emitted with 0.475 % of yield. Accompanied by the + decay two the gamma rays of 511 keV (from annihilation) and gamma ray of 1039.2 keV with the yield of 9.23 % are emitted also. The time of neutron irradiation amounts to above 2 days  3T1/2, cooling time is about 15 minutes. Then the sample is measured two times by gamma spectrometer with HPGe detector. The measurement time for every measurement was 1 hour, the first measurement is performed 15 minutes after the irradiation end, and the second is performed at the time, when the gamma intensity of the sample decreased by 7% in comparison with the first measurement. The Cu concentration is calculated using the gamma count rate in the peak 511 keV and calibration curve (Fig. 4.16).. 36.

(49) Fig. 4.16. Calibration curve for Cu determination using the NAA method (netron source Pu-Be 5.106 n/cm2.s; activation time 48 hours; cooling time 15 minutes; measurment time 1 hour; gamma spectrometer with HPGe detector) 4.2.6. Analysis of chemical composition of water samples The chemical composition of water samples was analysed using an ICP-AES PerkinElmer Optima 7300 DV spectrometer. The diagram of the ICP-AES PerkinElmer Optima 7300 DV spectrometer is presented in Fig. 4.17. The ICP-AES instruments include four principal parts: the sample introduction system composed of nebulizer and spray chamber; ICP torch; transfer optics; and spectrometer. An ICP produces excited atoms and ions from the studied water sample. Excited atoms and ions emit characteristic wavelength of light, intensities of which are proportional to the concentration of particular element in the analysed sample. (Henk J van de Wiel, 2004). In this study, the chemical compositions of water samples were analyzed using an ICPAES at the FGGEP, AGH UST and calibrated with a multi-element standard solution of the Merck Company. The induced couple plasma instrument worked with a cooling argon flow of 14 L/min, a reflected RF power of 1350 W, both auxiliary gas 37.

(50) and nebulizer flow rates of 1.0 L/min, a sample intake of 0.8 mL/min. The limit of determination depended on the individual element and ranged from a few to tens ppb with 3% of uncertainty. Fig. 4.17. Typical configuration of ICP-AES spectrometer (Boss and Fredeen, 2004) 4.2.7. Microscope analysis Before the microscope analysis, the polished sections of samples were prepared in the Polishing Laboratory of Faculty of Geology, Geophysics and Environmental Protection of AGH UST (FGGEP AGH-UST). The cross-section of polished section was chosen to observe the maximum possible number of minerals and mineralogical information. Then the samples were observed in reflected light using a Nikon Optihop polarizing microscope. The microscope was equipped with optical lenses with magnification of 10x, 20x, 30x, 40x and 50x. The photographs were made with a digital camera Sony Exwave HAD integrated with the Nikon Optihop polarizing microscope and with the appropriate scale showing magnification.. 38.