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Статті в журналах з теми "Th dating"

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Автор: Grafiati

Опубліковано: 1 квітня 2023

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1

Wendt, Kathleen A., Xianglei Li, and R. Lawrence Edwards. "Uranium–Thorium Dating of Speleothems." Elements 17, no. 2 (April 1, 2021): 87–92. http://dx.doi.org/10.2138/gselements.17.2.87.

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Speleothems are important timekeepers of Earth’s climate history. A key advantage of speleothems is that they can be dated using U–Th techniques. Mass spectrometric methods for measuring U and Th isotopes has led to vast improvements in measurement precision and a dramatic reduction in sample size. As a result, the timing of past climate, environment, and Earth system changes can be investigated at exceptional temporal precision. In this review, we summarize the principles and history of U–Th dating of speleothems. Finally, we highlight three studies that use U–Th dated speleothems to investigate past changes to the Asian monsoon, constrain the timing of sociopolitical change in ancient civilizations, and develop a speleothem-based calibration of the 14C timescale.

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2

Min, Kyoung-Won. "(U-Th)/He Dating: Principles and Applications." Journal of the Petrological Society of Korea 23, no. 3 (September 30, 2014): 239–47. http://dx.doi.org/10.7854/jpsk.2014.23.3.239.

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3

Frebel, Anna, and Karl-Ludwig Kratz. "Stellar age dating with thorium, uranium and lead." Proceedings of the International Astronomical Union 4, S258 (October 2008): 449–56. http://dx.doi.org/10.1017/s1743921309032104.

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AbstractWe present HE 1523-0901, a metal-poor star in which the radioactive elements Th and U could be detected. Only three stars have measured U abundances, of which HE 1523-0901 has the most confidently determined value. From comparing the stable Eu, Os, and Ir abundances with measurements of Th and U, stellar ages can be derived. Based on seven such chronometer abundance ratios, the age of HE 1523-0901 was found to be ~13 Gyr. Only an upper limit for Pb could be measured so far. Knowing all three abundances of Th, U, and Pb would provide a self-consistent test for r-process calculations. Pb is the beta- plus alpha-decay end-product of all decay chains in the mass region between Pb and the onset of dominant spontaneous fission above Th and U. Hence, in addition to Th/U also Th, U/Pb should be used to obtain a consistent picture for actinide chronometry. From recent r-process calculations within the classical “waiting-point” model, for a 13 Gyr old star we predict the respective abundance ratios of logϵ(Th/U) = 0.84, logϵ(Th/Pb) = −1.32 and logϵ(U/Pb) = −2.16. We compare these values with the measured abundance ratios in HE 1523-0901 of logϵ(Th/U) = 0.86, logϵ(Th/Pb) > −1.0 and logϵ(U/Pb) > −1.9. With this good level of agreement, HE 1523-0901 is already a vital probe for observational “near-field” cosmology by providing an independent lower limit for the age of the Universe.

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4

Yakubovich, Olga, Mary Podolskaya, Ilya Vikentyev, Elena Fokina, and Alexander Kotov. "U-Th-He Geochronology of Pyrite from the Uzelga VMS Deposit (South Urals)—New Perspectives for Direct Dating of the Ore-Forming Processes." Minerals 10, no. 7 (July 16, 2020): 629. http://dx.doi.org/10.3390/min10070629.

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We report on the application of the U-Th-He method for the direct dating of pyrite and provide an original methodological approach for measurement of U, Th and He in single grains without loss of parent nuclides during thermal extraction of He. The U-Th-He age of ten samples of high-crystalline stoichiometric pyrite from unoxidized massive ores of the Uzelga volcanogenic massive sulfide (VMS) deposit, South Urals, is 382 ± 12 Ma (2σ) (U concentrations ~1–5 ppm; 4He ~10−4 cm3 STP g−1). This age is consistent with independent (biostratigraphic) estimations of the age of ore formation (ca, 389–380 Ma) and is remarkably older than the probable age of the regional prehnite-pumpellyite facies metamorphism (~340–345 Ma). Our results indicate that the U-Th-He dating of ~1 mg weight pyrite sample is possible and open new perspectives for the dating of ore deposits. The relative simplicity of U-Th-He dating in comparison with other geochronological methods makes this approach interesting for further application.

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5

Li, Qiuli, Yu Liu, Guoqiang Tang, Kaiyi Wang, Xiaoxiao Ling, and Jiao Li. "Zircon Th–Pb dating by secondary ion mass spectrometry." Journal of Analytical Atomic Spectrometry 33, no. 9 (2018): 1536–44. http://dx.doi.org/10.1039/c8ja00125a.

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M257 and Qinghu zircons are suggested as more suitable Th–Pb dating standards with higher radiogenic ²⁰⁸Pb. The correlation between the apparent Th–Pb age and the corresponding Th content points out the radiogenic lead loss.

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6

Harrison, T. M., E. J. Catlos, and J. M. Montel. "U-Th-Pb Dating of Phosphate Minerals." Reviews in Mineralogy and Geochemistry 48, no. 1 (January 1, 2002): 524–58. http://dx.doi.org/10.2138/rmg.2002.48.14.

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7

Cheng, Hai, Jess Adkins, R. Lawrence Edwards, and Edward A. Boyle. "U-Th dating of deep-sea corals." Geochimica et Cosmochimica Acta 64, no. 14 (July 2000): 2401–16. http://dx.doi.org/10.1016/s0016-7037(99)00422-6.

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8

Catlos, E. J., Sorena S. Sorensen, and T. Mark Harrison. "Th-Pb ion-microprobe dating of allanite." American Mineralogist 85, no. 5-6 (May 2000): 633–48. http://dx.doi.org/10.2138/am-2000-5-601.

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9

Nuriel, Perach, Gideon Rosenbaum, Jian-Xin Zhao, Yuexing Feng, Suzanne D. Golding, Benoît Villemant, and Ram Weinberger. "U-Th dating of striated fault planes." Geology 40, no. 7 (July 2012): 647–50. http://dx.doi.org/10.1130/g32970.1.

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10

Hillaire-Marcel, C., C. Causse, O. Carro, J. Casanova, B. Ghaleb, and C. Goetz. "Th/U dating of open carbonate systems." Chemical Geology 70, no. 1-2 (August 1988): 127. http://dx.doi.org/10.1016/0009-2541(88)90562-1.

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11

Liao, Xin, Qiu-li Li, M. J. Whitehouse, Yue-heng Yang, and Yu Liu. "Allanite U–Th–Pb geochronology by ion microprobe." Journal of Analytical Atomic Spectrometry 35, no. 3 (2020): 489–97. http://dx.doi.org/10.1039/c9ja00426b.

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12

Campa-Bousoño, Celia, Ángel García-Pérez, Ana Moreno, Miguel Iglesias, Hai Cheng, R. Lawrence Edwards, and Heather Stoll. "Continuous color model as a tool to improve speleothem age model development." International Journal of Speleology 50, no. 3 (October 2021): 313–26. http://dx.doi.org/10.5038/1827-806x.50.3.2389.

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Because they can archive a variety of geochemical proxies and be precisely and accurately dated with the U-Th decay series chronometer, stalagmites are widely used for paleoclimate reconstructions. However, limitations in the use of this chronometer arise because U-Th dating is analytically time consuming, expensive, and requires a relatively large sample size. These limitations restrict the number of absolute dates usually obtained, which can result in significant uncertainties in the age model and inhibit the ability to archive high resolution records of environmental variability, particularly in those stalagmites where there are variations in growth rate not constrained by U-Th dates. Here, we explore the relationship between stalagmite color and growth rate. Consequently, we evaluate the use of a simple, practically non-destructive approach to model the age-depth relationship of stalagmites using the sample color to provide a continuous record of growth rate. The method was developed by comparing high-resolution color images with pre-determined U-Th dates along the growth axes of seven stalagmites. The obtained results suggest that prior to dating, a color-derived, continuous growth rate model may be used to identify important changes in growth rate which may aid in the determination of the most efficacious locations for U-Th dating. Further, continuous color-derived interpolations between U-Th derived dates may be superior to traditional linear interpolation methods. Such an approach has the potential to greatly improve a researcher’s ability to efficiently choose sampling locations for more precise, albeit laborious and costly, U-Th dating.

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13

Bersch, Michael G. "Electron Microprobe Dating of Uraninite from the Mcallister Pegmatite, Alabama." Microscopy and Microanalysis 5, S2 (August 1999): 538–39. http://dx.doi.org/10.1017/s1431927600016019.

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In the early days of geochronology, attempts were made to date U-Th bearing rocks and minerals using the Pb-U-Th chemical method, but fundamental assumptions that all the lead was of radiogenic origin, and the system was closed, often were invalid. With the advent of the U-Th-Pb isotopic and common-lead methods of dating rocks and minerals, the chemical method was deemed clinically dead. However, several workers, for example, Montel et al., Suzuki and Adachi, have recently demonstrated new life for the chemical method. Using, the same theoretical basis as the chemical method, geologically reasonable dates often can be obtained by electron microprobe analysis of U-Th rich monazite (Ca-REE-U-Th phosphate). Other U- or Thrich minerals sometimes can be used to obtain microprobe U-Th-Pb dates, e.g., zircon, xenotime, uraninite.Microprobe U-Th-Pb dates of uraninites from the McAllister Ta-Sn pegmatite, Coosa County, Alabama, are reported here. The McAllister pegmatite is a NW-SE dike-like body in the western part of the Rockford granite pluton. Polished grain mounts were made from screened table runs of heavy mineral separates. Wodginite (Mn, Sn, Nb, Ta-oxide), tantalite-columbite, zircon, cassiterite comprise most of the grains in the samples. Uraninite occurs as inclusions, generally <0.01 mm, in these grains (Figure 1).U, Th, Pb concentrations were measured using a JEOL 8600 Superprobe. Operating conditions were 100 nA, 20 kV, and count times up to 200 seconds for peak plus background. The U Mβ, Th Mα, and Pb Mα peaks were measured. Standards were UO2, ThO2, and PbS.

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14

Geyh, Mebus A., and Christian Schlüchter. "Calibration of the 14C Time Scale Beyond 22,000 BP." Radiocarbon 40, no. 1 (1997): 475–82. http://dx.doi.org/10.1017/s003382220001835x.

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The conventional 14C time scale between 11,500 and 22,000 sidereal years has been calibrated by TIMS U/Th dates for corals. Only a few studies have been made for the time beyond this range. Obtaining samples suitable for numerical dating or estimating the reservoir correction of the 14C dates has been difficult, but we do not have these problems with TIMS U/Th dating of interstadial and interglacial lignite, because reservoir corrections are unnecessary.

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15

Farley, K. A. "(U-Th)/He Dating: Techniques, Calibrations, and Applications." Reviews in Mineralogy and Geochemistry 47, no. 1 (January 1, 2002): 819–44. http://dx.doi.org/10.2138/rmg.2002.47.18.

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16

Williams, M. L., and M. J. Jercinovic. "Application of Electron Microprobe Age Mapping and Dating of Monazite." Microscopy and Microanalysis 6, S2 (August 2000): 406–7. http://dx.doi.org/10.1017/s1431927600034528.

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High resolution X-ray mapping and dating of monazite (Th, REE-phosphate) using the electron microprobe is an exceptionally powerful technique for structural, metamorphic, and tectonic analysis in geology. Age determination of geologic materials has been conventionally accomplished by mass spectrometry-based analysis of radioisotopic ratios in minerals from hand-picked mineral separates, careful sampling of individual grains out of petrographic thin sections, or by detailed ion probe analysis. Recently, use of the electron microprobe for dating purposes has been attempted. In principal, the concentrations of Th, U and Pb uniquely define the age if non-radiogenic Pb is either not initially present or can be subtracted from the total Pb. Monazite contains high concentrations of Th and U and does not appear to incorporate significant non-radiogenic Pb during mineral growth. Furthermore, monazite is a ubiquitous accessory phase in many metamorphic and igneous rocks, making it ideal for microprobe dating.

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17

Yakubovich, Olga, Ilya Vikentyev, Ekaterina Ivanova, Mary Podolskaya, Ivan Sobolev, Eugenia Tyukova, and Alexander Kotov. "U-Th-He Geochronology of Pyrite from Alteration of the Au-Fe-Skarn Novogodnee-Monto Deposit (Polar Urals, Russia)—The Next Step in the Development of a New Approach for Direct Dating of Ore-Forming Processes." Geosciences 11, no. 10 (September 27, 2021): 408. http://dx.doi.org/10.3390/geosciences11100408.

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We report on the application of the U-Th-He method for the direct dating of pyrite from the alteration halo of the Novogodnee-Monto Au-Fe-skarn deposit, Polar Urals. The deposit is genetically related to the formation of volcanogenic complexes of the Ural Paleozoic belt. A modification of the original methodology for measuring U, Th and He isotopes in a single grain allowed us to determine a U-Th-He age of 382 ± 8 Ma (2σ) based on six pyrite samples from the altered rocks of the deposit (U mass fraction ~0.2 mg/kg; Th/U ~ 3.5; 4He specific volume ~ 10−5 cm3·STP·g−1). This age is consistent with estimates of the age of ore formation and coeval with the end of the period of island arc magmatic activity. Our results indicate that U-Th-He dating for pyrite samples of ~1 mg in weight from the hydrothermal-metasomatic halo of ore bodies is possible, providing a crucial next step in the development of U-Th-He pyrite geochronology.

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18

Wang, Li-Sheng, Ye-Jian Wang, Jun Ye, Xue-Feng Wang, Ju-Le Xiao, and Zhi-Bang Ma. "Rapid Extraction Chemistry Using a Single Column for 230Th/U Dating of Quaternary Hydrothermal Sulfides." Minerals 11, no. 9 (September 9, 2021): 983. http://dx.doi.org/10.3390/min11090983.

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230Th/U dating can provide high-precision age constraints on Quaternary hydrothermal sulfides. However, low content of U and Th often involves extraction chemistry for the separation and enrichment of U and Th, but these chemical processes are very complex. We developed a simplified procedure consisting of total sample dissolution and single-column extraction chemistry, which can reduce the time and improve the accuracy of the dating. Concentrated HCl-HF followed by HNO3 was added to ensure complete dissolution. A single column filled with 0.4 mL of AG 1-X8 anion resin was used, then 8 M HNO3, 8 M HCl and 0.1 M HNO3 were used to elute most of the matrix metals, Th and U. This process provided more than 95% recoveries for U and Th, and negligible blanks. Meanwhile, Pb and Bi interferences were tested and showed no effect on the U and Th isotope ratio. The 230Th/238U activity of the Geological Survey of Japan geochemical reference material JZn-1 in secular equilibrium was determined and showed a radioactive equilibrium (1.00 ± 0.01, n = 5, all errors 2σ) and an in-house standard QS-1 was consistent to 0.0078 ± 0.0001 (n = 8, ±2σ) with an average age of 705 ± 10 yrs BP (n = 8, ±2σ). The technique greatly shortens the sample preparation time and allows more concise and effective analysis of U-Th isotopes. It is ideally suited for the high-precision 230Th/U dating of Quaternary submarine hydrothermal sulfides and sulfides from other settings.

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19

Huang, Yong-Shu, Qiu-Li Li, Yu Liu, Ping-Ping Liu, Sun-Lin Chung, and Xian-Hua Li. "238U–206Pb dating of U-series disequilibrium zircons by secondary ion mass spectrometry." Journal of Analytical Atomic Spectrometry 36, no. 5 (2021): 999–1006. http://dx.doi.org/10.1039/d0ja00510j.

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Theoretical and analytical methods for ²³⁸U–²⁰⁶Pb dating of U-series disequilibrium zircons by secondary ion mass spectrometry are developed. U–Pb dates improve age precision 3 times better than U–Th dating for zircon >150 ka.

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20

Lyalina, L. M., I. L. Kamensky, and I. N. Tolstikhin. "Origin, sites and mobility of helium and argon isotopes in meliphanite." Доклады Академии наук 488, no. 3 (September 26, 2019): 303–6. http://dx.doi.org/10.31857/s0869-56524883303-306.

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The similarity of U-Th-4He age of meliphanite and the age of regional metamorphism (1800 Ma) seems to indicate a good retention of radiogenic 4He in the mineral, but contradicts with the experience of U-Th-4He dating. To analyze this result 3He concentration was measured, which appeared to be very low, about 2 % of the totally produced 3He. Radiogenic 3,4He isotopes occupier radiation tracks. Intersections of these tracks with cleavage planes provide migration of He atoms from the mineral and 4He, produced due to U and Th decay, should be almost completely lost. Instead, meliphanite contains trapped He occurring in specific cavities of the crystalline structure. Extraction of He isotopes from meliphanite by its step-wise heating in vacuum confirmed this conclusion. Using U-Th-4He system for dating (as it is often done in thermochronology) can lead to incorrect results. Both isotopes, 3He and 4He, should be used to identify the origin of helium in minerals.

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21

Reiners, P. W. "(U-Th)/(He-Pb) double dating of detrital zircons." American Journal of Science 305, no. 4 (April 1, 2005): 259–311. http://dx.doi.org/10.2475/ajs.305.4.259.

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22

Pyle, D. M., M. Ivanovich, and R. S. J. Sparks. "Magma–cumulate mixing identified by U–Th disequilibrium dating." Nature 331, no. 6152 (January 1988): 157–59. http://dx.doi.org/10.1038/331157a0.

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23

Burley, David, Marshall I. Weisler, and Jian-xin Zhao. "High Precision U/Th Dating of First Polynesian Settlement." PLoS ONE 7, no. 11 (November 7, 2012): e48769. http://dx.doi.org/10.1371/journal.pone.0048769.

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24

Henderson, Gideon M., Niall C. Slowey, and Marty Q. Fleisher. "U-Th dating of carbonate platform and slope sediments." Geochimica et Cosmochimica Acta 65, no. 16 (August 2001): 2757–70. http://dx.doi.org/10.1016/s0016-7037(01)00621-4.

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25

Cooperdock, Emily H. G., and Daniel F. Stockli. "Dating exhumed peridotite with spinel (U–Th)/He chronometry." Earth and Planetary Science Letters 489 (May 2018): 219–27. http://dx.doi.org/10.1016/j.epsl.2018.02.041.

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26

Shuster, David L., Paulo M. Vasconcelos, Jonathan A. Heim, and Kenneth A. Farley. "Weathering geochronology by (U-Th)/He dating of goethite." Geochimica et Cosmochimica Acta 69, no. 3 (February 2005): 659–73. http://dx.doi.org/10.1016/j.gca.2004.07.028.

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27

Farley, K. A., and M. K. Clark. "Progress and problems with apatite (U–Th)/He dating." Geochimica et Cosmochimica Acta 70, no. 18 (August 2006): A166. http://dx.doi.org/10.1016/j.gca.2006.06.333.

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28

Van Der Wijk, Albert, Farid El-Daoushy, Arend R. Arends, and Willem G. Mook. "Dating peat with U/Th disequilibrium: Some geochemical considerations." Chemical Geology: Isotope Geoscience section 59 (January 1986): 283–92. http://dx.doi.org/10.1016/0168-9622(86)90077-1.

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29

Zeitler, P. K., A. L. Herczeg, I. McDougall, and M. Honda. "U-Th-He dating of apatite: A potential thermochronometer." Geochimica et Cosmochimica Acta 51, no. 10 (October 1987): 2865–68. http://dx.doi.org/10.1016/0016-7037(87)90164-5.

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30

Ito, Hisatoshi. "Zircon U–Th–Pb dating using LA-ICP-MS: Simultaneous U–Pb and U–Th dating on the 0.1Ma Toya Tephra, Japan." Journal of Volcanology and Geothermal Research 289 (December 2014): 210–23. http://dx.doi.org/10.1016/j.jvolgeores.2014.11.002.

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31

Guillong, M., A. von Quadt, S. Sakata, I. Peytcheva, and O. Bachmann. "LA-ICP-MS Pb–U dating of young zircons from the Kos–Nisyros volcanic centre, SE Aegean arc." J. Anal. At. Spectrom. 29, no. 6 (2014): 963–70. http://dx.doi.org/10.1039/c4ja00009a.

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32

Prostředník, Jan, Vítězslav Kuželka, Lenka Kovačiková, and Jan Novák. "Archeological research in graves of the Church of Saint Elisabeth of Jilemnice, in the light of environmental analysis." Journal of the National Museum (Prague), Natural History Series 188, no. 1 (December 1, 2019): 59–80. http://dx.doi.org/10.2478/jnmpnhs-2019-0002.

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Анотація:

Abstract Archaeological research in the area of the chateau park uncovered the relic of the Gothic church of St. Elisabeth, dated to the second half of the 13 th century. It is a single-nave building with a rectangular finish (length 25 m, boat width 13 m, presbytery width 10.5 m). The church probably had an older predecessor - a wooden structure on a stone foundation, dating from the mid-13 th century. At the same time, the church site was a burial place: a grave of a young woman and a 1.5-year-old child, dated 13 th /14 th century were found outside the presbytery wall. In the presbytery, there were 3 graves of men dating back to the 14 th century. It is very likely that these are the Lords of the Wallenstein family. Archaeological research in graves in the Church of St. Elisabeth unearthed a small collection of animal bone remains. The occurrence of bones of young and mature cattle and domestic fowls, which are abundant in the archaeozoological assemblage, indicates the prevailing meat consumption of these animals. The butchering marks on their bones document removal of meat from the carcasses.

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33

Gautheron, Cécile, Mathias Hueck, Sébastien Ternois, Beatrix Heller, Stéphane Schwartz, Philippe Sarda, and Laurent Tassan-Got. "Investigating the Shallow to Mid-Depth (>100–300 °C) Continental Crust Evolution with (U-Th)/He Thermochronology: A Review." Minerals 12, no. 5 (April 29, 2022): 563. http://dx.doi.org/10.3390/min12050563.

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Анотація:

Quantifying geological processes has greatly benefited from the development and use of thermochronometric methods over the last fifty years. Among them is the (U-Th)/He dating method, which is based on the production and retention, within a crystal structure, of radiogenic 4He atoms associated with the alpha decay of U, Th and Sm nuclei. While apatite has been the main target of (U-Th)/He studies focusing on exhumation and burial processes in the upper levels of the continental crust (~50–120 °C), the development of (U-Th)/He methods for typical phases of igneous and metamorphic rocks (e.g., zircon and titanite) or mafic and ultramafic rocks (e.g., magnetite) over the last two decades has opened up a myriad of geological applications at higher temperatures (>100–300 °C). Thanks to the understanding of the role of radiation damage in He diffusion and retention for U-Th-poor and rich mineral phases, the application of (U-Th)/He thermochronometry to exhumation processes and continental evolution through deep time is now mainstream. This contribution reviews the (U-Th)/He thermochronometer principle and the influence of radiation damage in modifying the diffusion behavior. It presents applications of (U-Th)/He dating to problems in tectonic and surface processes at shallow to middle crustal depths (>100–300 °C). New and promising applications using a combination of methods will stimulate a research avenue in the future.

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34

Aciego, S. M., M. P. Lamb, D. J. DePaolo, B. M. Kennedy, and W. E. Dietrich. "Combining U–Th/He eruption age dating and 3He cosmogenic dating to constrain landscape evolution." Geochimica et Cosmochimica Acta 70, no. 18 (August 2006): A2. http://dx.doi.org/10.1016/j.gca.2006.06.018.

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35

Tang, Xu, Qiu-Li Li, Bin Zhang, Peng Wang, Li-Xin Gu, Xiao-Xiao Ling, Chen-Hui Fei, and Jin-Hua Li. "The Chemical State and Occupancy of Radiogenic Pb, and Crystallinity of RW-1 Monazite Revealed by XPS and TEM." Minerals 10, no. 6 (May 31, 2020): 504. http://dx.doi.org/10.3390/min10060504.

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Monazite ((Ce, La, Nd, Th)PO4) is one of the widely used minerals for U–Th–Pb dating in geochronology. To better understand the possible effects of radiogenic Pb on the in situ dating method, a natural monazite U–Th–Pb standard sample (RW-1) was chemically and structurally characterized down to atomic scales by using the combination of Raman spectrum (RM), X-ray photoelectron spectroscopy (XPS), and transmission electron microscopy (TEM). The experimental results revealed that radiogenic Pb exists as Pb2+ and substitutes for the Ce site in the monazite crystal lattice. Moreover, TEM imaging demonstrated that monazite is well crystalline revealed by an atomic structure in most areas except for a few tiny defects, which are likely attributed to alpha self-healing from an electronic energy loss of α particles. The characterization of the chemical state and occupancy of radiogenic Pb, and the distribution of Pb and Th in monazite at the nanoscale and atomic scale could provide insight for us to understand the mechanisms of the nanogeochronology.

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36

Geyh, Mebus A., and G. J. Hennig. "Multiple Dating of a Long Flowstone Profile." Radiocarbon 28, no. 2A (1986): 503–9. http://dx.doi.org/10.1017/s0033822200007645.

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Dense speleothem samples are considered as closed systems and are, therefore, possibilities for any dating method. Four dating methods (14C, U/Th, paleomagnetism, and electron spin resonance = ESR) were used for samples up to 1,000,000 yr old and taken along a vertical flowstone profile in the Heggen cave in West Germany. Also δ18O and δ13C analyses were carried out.The reliability of the results of each method is dependent on the diagenetic processes that took place during the complex growth history of the flowstone. Speleothem growth was interrupted during glacial periods. During interglacial periods, at least the stalagmite growth rate was greater by one order of magnitude than during interstadial periods. During the periods of low interstadial growth rate various processes might have changed the 14C, 18O, and 13C concentrations, leaching might have removed uranium, recrystallization might have moved thorium several centimeters, and increased content of radon in the cave might have exaggerated the accumulated dose (AD) at the speleothem surface. As a result, 14C ages may be too small and U/Th as well as ESR data may be too large.

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37

Zhang, H. C., H. F. Fan, F. Q. Chang, W. X. Zhang, G. L. Lei, M. S. Yang, Y. B. Lei, and L. Q. Yang. "AMS Dating on the Shell Bar Section from Qaidam Basin, Ne Tibetan Plateau, China." Radiocarbon 50, no. 2 (2008): 255–65. http://dx.doi.org/10.1017/s0033822200033555.

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Radiocarbon dating by accelerator mass spectrometry (AMS) of the shell bar section of Qaidam Basin, NE Tibetan Plateau, shows that this section was formed between ~39.7 and ~17.5 14C kyr BP and represented the highest paleolake development period since the Late Pleistocene. It was difficult to obtain reliable dates due to the low organic carbon content, which was formed mainly by authochtonous algae-bacteria (Zhang et al. 2007a). In order to improve the dating, 14C ages of both the alkali residual and acid-soluble components of the organic carbon were measured to check the consistency of the dating results. Total organic carbon (TOC) content and stable carbon isotopes (δ13Corg) might also be used as critical references for checking the reliability of dates. For example, in our study of the shell bar section from Qaidam Basin, we found that when the TOC content was higher than 0.15% and/or δ13Corg was lower than −23, the AMS dates were reliable. AMS dating of fossil shells demonstrated that they could provide valuable age information. The ages given by fossil shells are comparable to those of bulk carbonate from a similar sampling site, and are about 15~18 kyr older than the ages given by organic matter. Due to the U/Th dating requirements and open nature of the system, we concluded that U/Th dating results are unreliable and that this technique is unsuitable for dating halite deposits from Qaidam Basin.

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38

Evans, N. J., B. I. A. McInnes, B. McDonald, M. Danišík, T. Becker, P. Vermeesch, M. Shelley, E. Marillo-Sialer, and D. B. Patterson. "An in situ technique for (U–Th–Sm)/He and U–Pb double dating." Journal of Analytical Atomic Spectrometry 30, no. 7 (2015): 1636–45. http://dx.doi.org/10.1039/c5ja00085h.

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39

Yang, Yue-Heng, Fu-Yuan Wu, Yang Li, Jin-Hui Yang, Lie-Wen Xie, Yan Liu, Yan-Bin Zhang, and Chao Huang. "In situ U–Pb dating of bastnaesite by LA-ICP-MS." J. Anal. At. Spectrom. 29, no. 6 (2014): 1017–23. http://dx.doi.org/10.1039/c4ja00001c.

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40

Geyh, Mebus A., and Bernhard Eitel. "Radiometric Dating of Young and Old Calcrete." Radiocarbon 40, no. 2 (1997): 795–802. http://dx.doi.org/10.1017/s0033822200018749.

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To obtain a better understanding of the relationship between calcrete genesis and the results of different absolute dating methods, thermoluminescence (TL), radiocarbon (14C) and uranium/thorium (U/Th) were applied to coeval sample; take from a very young calcrete profile in Namibia. The methodically different ages reflect the characteristics of the applied dating methods, the genetics of calcrete and different events of calcrete genesis. The conventional 14C ages and the TL dates cover the last 50 ka, while the corresponding U/Th dates of coeval samples are many times larger, Uranium-series dates are not related to the deposition of the host material or to its cementation if the ages are smaller than ca. 120 ka. The TL clock is set to zero during eolian transport and the corresponding radiometric ages of the quartz and feldspar grains date the time of their deposition. The 14C ages of the cement correspond, on the other hand, to a time shortly after the onset of the cementation and long before its termination. In the case of very old calcrete, the mixture of young and old cement results in ambiguous ages if they cannot be confirmed by an independent technique.

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41

Lin, Jo C., Wallace S. Broecker, Sidney R. Hemming, Irena Hajdas, Robert F. Anderson, George I. Smith, Maxwell Kelley, and Georges Bonani. "A Reassessment of U-Th and14C Ages for Late-Glacial High-Frequency Hydrological Events at Searles Lake, California." Quaternary Research 49, no. 1 (January 1998): 11–23. http://dx.doi.org/10.1006/qres.1997.1949.

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U-Th isochron ages of tufas formed on shorelines suggest that the last pluvial event in Lake Lahontan and Searles Lake was synchronous at about 16,500 cal yr B.P. (equivalent to a radiocarbon age of between 14,000 and 13,500 yr B.P.), whereas the timing of this pluvial event determined by radiocarbon dating is on the order of 1000 yr younger. The timing of seven distinct periods of near desiccation in Searles Lake during late-glacial time has been reinvestigated for U-Th age determination by mass spectrometry. U-Th dating of evaporite layers in the interbedded mud and salt unit called the Lower Salt in Searles Lake was hampered by the uncertainty in assessing the initial 230Th/232Th of the samples. The resulting ages, corrected by a conservative range of initial 230Th/232Th ratios, suggest close correlation of the abrupt changes recorded in Greenland ice cores (Dansgaard-Oeschger events) and wet–dry conditions in Searles Lake between 35,000 and 24,000 cal yr B.P.

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42

Farley, K. A., and D. F. Stockli. "(U-Th)/He Dating of Phosphates: Apatite, Monazite, and Xenotime." Reviews in Mineralogy and Geochemistry 48, no. 1 (January 1, 2002): 559–77. http://dx.doi.org/10.2138/rmg.2002.48.15.

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43

Ueki, Sami, and Yuji Sano. "In situ ion microprobe Th-Pb dating of Silurian conodonts." GEOCHEMICAL JOURNAL 35, no. 5 (2001): 307–14. http://dx.doi.org/10.2343/geochemj.35.307.

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44

Cross, A., S. Jaireth, R. Rapp, and R. Armstrong. "Reconnaissance-style EPMA chemical U–Th–Pb dating of uraninite." Australian Journal of Earth Sciences 58, no. 6 (August 2011): 675–83. http://dx.doi.org/10.1080/08120099.2011.598190.

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45

Wernicke, Rolf S., and Hans J. Lippolt. "Dating of vein Specularite using internal (U+Th)/4He isochrons." Geophysical Research Letters 21, no. 5 (March 1, 1994): 345–47. http://dx.doi.org/10.1029/94gl00014.

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46

Henderson, G. M. "U-Th Isochron Dating of the Marine Oxygen-Isotope Record." Mineralogical Magazine 62A, no. 1 (1998): 602–3. http://dx.doi.org/10.1180/minmag.1998.62a.1.318.

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47

Latham, A. G., H. P. Schwarcz, and D. C. Ford. "The paleomagnetism and U-Th dating of Mexican stalagmite, DAS2." Earth and Planetary Science Letters 79, no. 1-2 (August 1986): 195–207. http://dx.doi.org/10.1016/0012-821x(86)90053-1.

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48

Martínez-Aguirre, A., and J. M. Alcaraz-Pelegrina. "U/Th dating of carbonate deposits from Chafarinas Islands, Spain." Journal of Radioanalytical and Nuclear Chemistry 298, no. 2 (May 15, 2013): 1005–16. http://dx.doi.org/10.1007/s10967-013-2532-9.

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49

Pickering, Julia, William Matthews, Eva Enkelmann, Bernard Guest, Chris Sykes, and Brett M. Koblinger. "Laser ablation (U-Th-Sm)/He dating of detrital apatite." Chemical Geology 548 (August 2020): 119683. http://dx.doi.org/10.1016/j.chemgeo.2020.119683.

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50

Alcaraz-Pelegrina, J. M., and A. Martínez-Aguirre. "U/Th dating of carbonate deposits from Constantina (Sevilla), Spain." Applied Radiation and Isotopes 65, no. 7 (July 2007): 798–804. http://dx.doi.org/10.1016/j.apradiso.2007.01.006.

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