Journal articles: 'Hafnium isotope analysis'

1

Shamanin, I. V., and M. A. Kazaryan. "Conditions for Population of Energy Levels Inversion when Active Medium Based on Gadolinium Isotopes Gd155 and Gd156 Couple Neutron Pumping." Alternative Energy and Ecology (ISJAEE), no. 16-18 (September 11, 2018): 55–62. http://dx.doi.org/10.15518/isjaee.2018.16-18.055-062.

Full text

Abstract:

The paper theoretically studies the possibility of energy transformation of fast and epithermal neutrons to energy of coherent photon radiation at the expense of a neutron pumping of the active medium formed by nucleus with longliving isomerous states. The channel of the nucleus formation in isomeric state as a daughter nucleus resulting from the nuclear reaction of neutron capture by a lighter nucleus is taken into consideration for the first time. Assessment of neutron flux spectrum parameters providing transition from the main state into one of the excited ones for the nuclei of isotopes54Xe130,10Ne22is made. It was shown that to transit the isotope nuclei into the excited state by forward neutron scattering on the nuclei it is necessary to “select” the isotopes not only with great specific energy of nucleons coupling but also with a small value of the neutron absorption cross section. Moreover, the paper performs the analysis of cross sections dependence of radiative neutron capture by the nuclei of gadolinium isotopes Gd155and Gd156. As a result, the speed of Gd156nuclei formation is stated to exceed the speed of their “burnup” in the neutron flux. It is provided by a unique combination of absorbing properties of two isotopes of gadolinium Gd155 and Gd156 in both thermal and resonance regions of neutron energy. We have formulated the conditions required for making isotope nuclei excited by forward neutron scattering on nuclei and for storing nuclei in excited states. The relation which allows estimating processes parameters of neutron capture by nuclei, formation and decay of nuclei isomeric states is obtained as a result of analytical solution of differential equations system of nuclide kinetics taking into account the decay of nuclei isomeric states. The paper makes the possibility analysis of neutron pumping of the participating medium created by the hafnium isotope nuclei. The properties of hafnium isotopes nuclei is found to do not allow providing conditions for population inversion of energy levels due to the formation of hafnium nuclei in isomeric state Hf178m2in the neutron flux. The paper shows the possibility of excess energy accumulation in the participating medium created by the nuclei of the pair of gadolinium isotopes Gd155and Gd156due to formation and storage of nuclei in isomeric state at radiative neutron capture by the nuclei of the stable isotope with a smaller mass. It is concluded that when the active medium created by gadolinium nuclei is pumped by neutrons with the flux density of the order of 1013cm-2·s-1, the condition of levels population inversion can be achieved in a few tens of seconds. The wave length of the radiation generated by the medium is 0.0006 nm. Sintered ceramics Gd2O3based on enriched in the 155-th isotope of gadolinium can be considered a possible active medium. Thus, there is a possibility of creation of the laser techniques of new generation with the parameters providing its application in pulse power engineering of the future.

APA, Harvard, Vancouver, ISO, and other styles

2

Fisher, Christopher M., John M. Hanchar, Scott D. Samson, Bruno Dhuime, Janne Blichert-Toft, Jeffery D. Vervoort, and Rebecca Lam. "Synthetic zircon doped with hafnium and rare earth elements: A reference material for in situ hafnium isotope analysis." Chemical Geology 286, no. 1-2 (June 2011): 32–47. http://dx.doi.org/10.1016/j.chemgeo.2011.04.013.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Thirlwall, Matthew F., and Andrew J. Walder. "In situ hafnium isotope ratio analysis of zircon by inductively coupled plasma multiple collector mass spectrometry." Chemical Geology 122, no. 1-4 (May 1995): 241–47. http://dx.doi.org/10.1016/0009-2541(95)00003-5.

Full text

APA, Harvard, Vancouver, ISO, and other styles

4

Aufmuth, P., R. Kirsch, A. Steudel, and E. W�bker. "Isotope shift in hafnium I: Parametric analysis,ab initio calculation, and changes in nuclear charge radii." Zeitschrift f�r Physik D Atoms, Molecules and Clusters 7, no. 2 (June 1987): 153–59. http://dx.doi.org/10.1007/bf01384581.

Full text

APA, Harvard, Vancouver, ISO, and other styles

5

Trešl, Ivan, Oto Mestek, and Miloslav Suchánek. "The Isotope-Dilution Determination of Platinum in Soil by Inductively Coupled Plasma Mass Spectrometry." Collection of Czechoslovak Chemical Communications 65, no. 12 (2000): 1875–87. http://dx.doi.org/10.1135/cccc20001875.

Full text

Abstract:

A method of the determination of trace amounts of platinum in soils has been developed and validated. Samples were ignited, spiked by 198Pt and decomposed by acid digestion (HF-HClO4, HCl-HNO3). Platinum was separated from the matrix by tellurium coprecipitation (recovery 55-87%) and its content was calculated by the (194Pt + 195Pt + 196Pt)/198Pt ratio measurement. In spite of the separation step (hafnium and tungsten recovery below 1%), residual spectral interference caused by HfO+ ions was observed. This interference as well as that of 198Hg were removed by mathematical correction. Accuracy of the method was confirmed by analysis of certified reference material and by the standard addition method. Detection limit of the method was 0.08 ng g-1 Pt. It was found out that the main component of the standard uncertainty of results was sampling uncertainty. Analysis of soil samples taken in the neighbourhood of Hřensko (Northern Bohemia) showed high platinum contents near the road with heavy traffic.

APA, Harvard, Vancouver, ISO, and other styles

6

Sialini, P., P. Sajdl, V. Havránek, and V. Vrtílková. "Study of diffusion processes in the oxide layer of zirconium alloys." Koroze a ochrana materialu 60, no. 1 (March 1, 2016): 1–5. http://dx.doi.org/10.1515/kom-2016-0004.

Full text

Abstract:

Abstract In the active zone of a nuclear reactor where zirconium alloys are used as a coating material, this material is subject to various harmful impacts. During water decomposition reactions, hydrogen and oxygen are evolved that may diffuse through the oxidic layer either through zirconium dioxide (ZrO2) crystals or along ZrO2 grains. The diffusion mechanism can be studied using the Ion Beam Analysis (IBA) method where nuclear reaction 18O(p,α)15N is used. A tube made of zirconium alloy E110 (with 1 wt. % of Nb) was used for making samples that were pre-exposed in UJP PRAHA a.s. and subsequently exposed to isotopically cleansed environment of H2 18O medium in an autoclave. The samples were analysed with gravimetric methods and IBA methods performed at the electrostatic particle accelerator Tandetron 4130 MC in the Nucler Physics Institute of the CAS, Řež. With IBA methods, the overall thicknesses of corrosion layers on the samples, element composition of the alloy and distribution of oxygen isotope 18O in the corrosion layer and its penetration in the alloy were identified. The retrieved data shows at the oxygen diffusion along ZrO2 grains because there are two peaks of 18O isotope concentrations in the corrosion layer. These peaks occur at the environment-oxide and oxide-metal interface. The element analysis identified the presence of undesirable hafnium.

APA, Harvard, Vancouver, ISO, and other styles

7

Nasdala, Lutz, Fernando Corfu, John W. Valley, Michael J. Spicuzza, Fu-Yuan Wu, Qiu-Li Li, Yue-Heng Yang, et al. "Zircon M127 - A Homogeneous Reference Material for SIMS U-Pb Geochronology Combined with Hafnium, Oxygen and, Potentially, Lithium Isotope Analysis." Geostandards and Geoanalytical Research 40, no. 4 (July 16, 2016): 457–75. http://dx.doi.org/10.1111/ggr.12123.

Full text

APA, Harvard, Vancouver, ISO, and other styles

8

Choi, Min Seok, Chang-Sik Cheong, Jeongmin Kim, and Hyung Seon Shin. "Hafnium isotope analysis of mixed standard solutions by multi-collector inductively coupled plasma mass spectrometry: an evaluation of isobaric interference corrections." Journal of Analytical Science and Technology 4, no. 1 (2013): 1. http://dx.doi.org/10.1186/2093-3371-4-1.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Brown, M., C. L. Kirkland, and T. E. Johnson. "Evolution of geodynamics since the Archean: Significant change at the dawn of the Phanerozoic." Geology 48, no. 5 (February 27, 2020): 488–92. http://dx.doi.org/10.1130/g47417.1.

Full text

Abstract:

Abstract A time-series analysis of thermobaric ratios (temperature/pressure [T/P]) for Paleoarchean to Cenozoic metamorphic rocks identified significant shifts in mean T/P that may be related to secular change in the geodynamics on Earth. Thermobaric ratios showed significant (>95% confidence) change points at 1910, 902, 540, and 515 Ma, recording drops in mean T/P, and at 1830, 604, and 525 Ma, recording rises in mean T/P. Highest mean T/P occurred during the Mesoproterozoic, and lowest mean T/P occurred from the Cambrian to the Oligocene. Correlated changes were seen between T/P and global data sets of time-constrained hafnium (Hf) and oxygen (O) isotope compositions in zircon. The range of correlated variation in T/P, Hf, and O was larger during the formation of Rodinia than Columbia. Large changes and a wide range for these variables continued through the Phanerozoic, during which a statistically significant 83 m.y. frequency of T/P excursions recorded the high tempo of orogenic activity associated with the separation, migration, and accretion of continental terranes during the formation of Pangea. Since the early Tonian, the decreasing mean T/P of metamorphism, widespread appearance of blueschist and ultrahigh-pressure metamorphism, and wide fluctuations in Hf and O isotope compositions document a change to the modern plate-tectonic regime, characterized by widespread continental subduction and deeper slab breakoff than in the Proterozoic.

APA, Harvard, Vancouver, ISO, and other styles

10

Rodríguez-Castrillón, José Ángel, Mariella Moldovan, and J. Ignacio García Alonso. "Internal correction of hafnium oxide spectral interferences and mass bias in the determination of platinum in environmental samples using isotope dilution analysis." Analytical and Bioanalytical Chemistry 394, no. 1 (March 14, 2009): 351–62. http://dx.doi.org/10.1007/s00216-009-2681-4.

Full text

APA, Harvard, Vancouver, ISO, and other styles

11

Winkler, Wilfried, Denise Bussien, Munktsengel Baatar, Chimedtseren Anaad, and Albrecht von Quadt. "Detrital Zircon Provenance Analysis in the Central Asian Orogenic Belt of Central and Southeastern Mongolia—A Palaeotectonic Model for the Mongolian Collage." Minerals 10, no. 10 (October 2, 2020): 880. http://dx.doi.org/10.3390/min10100880.

Full text

Abstract:

Our study is aimed at reconstructing the Palaeozoic–early Mesozoic plate tectonic development of the Central Asian Orogenic Belt in central and southeast Mongolia (Gobi). We use sandstone provenance signatures including laser ablation U-Pb ages of detrital zircons, their epsilon hafnium isotope signatures, and detrital framework grain analyses. We adopt a well-established terran subdivision of central and southeastern Mongolia. However, according to their affinity and tectonic assemblage we group them into three larger units consisting of continental basement, rift-passive continental margin and arc elements, respectively. These are in today’s coordinates: (i) in the north the late Cambrian collage from which the later Mongol-Okhotsk and the Central Mongolia-Erguna mountain ranges resulted, (ii) in the south a heterogeneous block from which the South Mongolia-Xin’gan and Inner Mongolia-Xilin belts developed, and (iii) in between we still distinguish the intra-oceanic volcanic arc of the Gurvansayhan terrane. We present a model for paleotectonic development for the period from Cambrian to Jurassic, which also integrates findings from the Central Asian Orogenic Belt in China and Russia. This mobilistic model implies an interplay of rift and drift processes, ocean formation, oceanic subduction, basin inversion, collision and suture formation in space and time. The final assemblage of the Central Asian Orogenic Belt occurred in Early Jurassic.

APA, Harvard, Vancouver, ISO, and other styles

12

Liu, Dunyi, Simon A. Wilde, Yusheng Wan, Shiyan Wang, John W. Valley, Noriko Kita, Chunyan Dong, et al. "Combined U–Pb, hafnium and oxygen isotope analysis of zircons from meta-igneous rocks in the southern North China Craton reveal multiple events in the Late Mesoarchean–Early Neoarchean." Chemical Geology 261, no. 1-2 (April 2009): 140–54. http://dx.doi.org/10.1016/j.chemgeo.2008.10.041.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Gao, Peng, Chris Yakymchuk, Jian Zhang, Changqing Yin, Jiahui Qian, and Yanguang Li. "Preferential dissolution of uranium-rich zircon can bias the hafnium isotope compositions of granites." Geology 50, no. 3 (December 1, 2021): 336–40. http://dx.doi.org/10.1130/g49656.1.

Full text

Abstract:

Abstract Hafnium (Hf) isotopes in zircon are important tracers of granite petrogenesis and continental crust evolution. However, zircon in granites generally shows large Hf isotope variations, and the reasons for this are debated. We applied U-Pb geochronology, trace-element, and Hf isotope analyses of zircon from the Miocene Himalayan granites to address this issue. Autocrystic zircon had εHf values (at 20 Ma) of–12.0 to–4.3 (median =–9). Inherited zircon yielded εHf values (at 20 Ma) of–34.8 to +0.3 (median =–13); the majority of εHf values were lower than those of autocrystic zircon. The εHf values of inherited zircon with high U concentrations resembled those of autocrystic zircon. Geochemical data indicates that the granites were generated during relatively low-temperature (<800 °C) partial melting of metasedimentary rocks, which, coupled with kinetic hindrance, may have led to the preferential dissolution of high-U zircon that could dissolve more efficiently into anatectic melt due to higher amounts of radiation damage. Consequently, Hf values of autocrystic zircon can be biased toward the values of U-rich zircon in the source. By contrast, literature data indicate that granites generated at high temperatures (>820–850 °C) generally contain autocrystic and inherited zircons with comparable Hf isotope values. During higher-temperature melting, indiscriminate dissolution of source zircon until saturation is reached will result in near-complete inheritance of Hf isotope ratios from the source. Our results impose an extra layer of complexity to interpretation of the zircon Hf isotope archive that is not currently considered.

APA, Harvard, Vancouver, ISO, and other styles

14

STEPANYUK, L. M., L. V. SHUMLYANSKYY, S. I. KURYLO, V. O. SYOMKA, S. M. BONDARENKO, S. A. WILDE, and A. A. NEMCHIN. "The U-Pb Zircon Geochronology (LA-ICP-MS) of Geological Processes in Granulites of Middle Bouh Area. Article 3. Rock association in the lower reaches of the Yatran river." Mineralogical Journal 43, no. 1 (2021): 34–50. http://dx.doi.org/10.15407/mineraljournal.43.01.034.

Full text

Abstract:

LA-ICP-MS method was applied to investigate U-Pb and Lu-Hf isotope systematics of zircon crystals from charnockitic gneiss and biotite-garnet-hypersthene enderbite that occur in the lower reaches of the Yatran river (Yatran block of the Bouh river area). According to the obtained isotope data, charnockitic gneiss hosts three zircon populations. The oldest one is represented by three crystals that have isotope age between 3125 and 3300 Ma, and εHf values between –2.3 and –7.5. The next population is well-defined, it has an age of 2038±25 Ma and large variations of Hf isotope composition: 176Hf/177Hf — from 0.28122 to 0.28261, εHf — from –9.3 до 4.6. However, the ages of most of the analyzed zircons spread along the concordia between 2300 and 2800 Ma. All zircons in this population have a similar Hf isotope composition 176Hf/177Hf = 0.28072 to 0.28092, which does not depend on the age. It is characteristic that the oldest (with preserved U-Pb isotope systematics) crystals have positive or slightly negative εHf values. Most of the U-Pb isotope analyses of zircons from enderbite fall on the discordia line that has an upper interception age of 2029 ± 18 Ma. A small number of discordant grains have 207Pb/206Pb ages up to 2500 Ma. Hafnium isotope composition in zircons from enderbite varies widely: 176Hf/177Hf = 0.28131 to 0.28151, and εHf from –6.2 to 1.8.

APA, Harvard, Vancouver, ISO, and other styles

15

Malitch, Kreshimir N., Elena A. Belousova, William L. Griffin, Laure Martin, Inna Yu Badanina, and Sergey F. Sluzhenikin. "Oxygen-Hafnium-Neodymium Isotope Constraints on the Origin of the Talnakh Ultramafic-Mafic Intrusion (Norilsk Province, Russia)." Economic Geology 115, no. 6 (September 1, 2020): 1195–212. http://dx.doi.org/10.5382/econgeo.4743.

Full text

Abstract:

Abstract The ultramafic-mafic Talnakh intrusion in the Norilsk province (Russia) hosts one of the world’s major platinum group element (PGE)-Cu-Ni sulfide deposits. This study employed a multitechnique approach, including in situ Hf-O isotope analyses of zircon combined with whole-rock Nd isotope data, in order to gain new insights into genesis of the Talnakh economic intrusion. Zircons from gabbrodiorite, gabbroic rocks of the layered series, and ultramafic rocks have similar mantle-like mean δ18O values (5.39 ± 0.49‰, n = 27; 5.64 ± 0.48‰, n = 34; and 5.28 ± 0.34‰, n = 7, respectively), consistent with a mantle-derived origin for the primary magma(s) parental to the Talnakh intrusion. In contrast, a sulfide-bearing taxitic-textured troctolite from the basal part of intrusion has high δ18O (mean of 6.50‰, n = 3), indicating the possible involvement of a crustal component during the formation of sulfide-bearing taxitic-textured rocks. The Hf isotope compositions of zircon from different rocks of the Talnakh intrusion show significant variations, with ɛHf(t) values ranging from –3.2 to 9.8 for gabbrodiorite, from –4.3 to 11.6 for unmineralized layered-sequence gabbroic rocks, from 2.3 to 12 for mineralized ultramafic rocks, and from –3.5 to 8.8 for mineralized taxitic-textured rocks at the base of the intrusion. The significant range in the initial 176Hf/177Hf values is ascribed to interaction of distinct magma sources during formation of the Talnakh intrusion. These include (1) a juvenile source equivalent to the depleted mantle, (2) a subcontinental lithospheric source, and (3) a minor crustal component. Initial whole-rock Nd isotope compositions of the mineralized taxitic-textured rocks from the base of the intrusion (mean ɛNd(t) = –1.5 ± 1.8) differ from the other rocks, which have relatively restricted ranges in initial ɛNd (mean ɛNd = 0.9 ± 0.2). The major set of ɛNd values around 1.0 at Talnakh is attributed to limited crustal contamination, presumably in deep magma chambers, whereas the smaller set of negative ɛNd values in taxitic-textured rocks is consistent with greater involvement of a crustal component and reflects an interaction with the wall rocks during emplacement.

APA, Harvard, Vancouver, ISO, and other styles

16

Matteini, Massimo, Elton L. Dantas, Marcio M. Pimentel, and Bernhard Bühn. "Combined U-Pb and Lu-Hf isotope analyses by laser ablation MC-ICP-MS: methodology and applications." Anais da Academia Brasileira de Ciências 82, no. 2 (June 2010): 479–91. http://dx.doi.org/10.1590/s0001-37652010000200023.

Full text

Abstract:

The Lutetium-Hafnium isotopic system represents one of the most innovative and powerful tools for geochronology and isotopic studies. Combined U-Pb and Lu-Hf in situ analyses on zircon by LA-MC-ICP-MS permit to characterize isotopically the host magma from which it crystallized furnishing significant information for sediment provenance and crustal evolution studies. In this paper e describe the Lu-Hf systematic by LA-MC-ICP-MS developed in the laboratory of Geochronology of the University of Brasilia and report the results obtained by repeated analyses of 176Hf/177Hf isotopic ratio of three zircon standards: GJ-1 = 0.282022 ± 11 (n=56), Temora 2 = 0.282693 ± 14 (n=25) and UQZ = 0.282127 ± 33 (n=11). The 176Hf/177Hf ratio (0.282352 ± 22, n=14) of gem quality zircon used as in-house standard have been also characterized. As a geological application, we analyzed two complex zircons selected from a migmatitic rocks from the Borborema Province, NE Brazil. On the basis of U-Pb and Lu-Hf data, two main crystallization events have been identified in both studied zircons. An older event at ca. 2.05 Ga recognized in the inherited cores represents a well-characterized paleoproterozoic magmatic event that affected the whole Borborema Province. A second crystallization event at ~ 575 Ma, recognized at the rims, represents a Neoproterozoic (Brazilian) high grade metamorphic-magmatic event.

APA, Harvard, Vancouver, ISO, and other styles

17

Mitchell, Ross N., Christopher J. Spencer, Uwe Kirscher, Xiao-Fang He, J. Brendan Murphy, Zheng-Xiang Li, and William J. Collins. "Harmonic hierarchy of mantle and lithospheric convective cycles: Time series analysis of hafnium isotopes of zircon." Gondwana Research 75 (November 2019): 239–48. http://dx.doi.org/10.1016/j.gr.2019.06.003.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Knudsen, T. L., W. Griffin, E. Hartz, A. Andresen, and S. Jackson. "In-situ hafnium and lead isotope analyses of detrital zircons from the Devonian sedimentary basin of NE Greenland: a record of repeated crustal reworking." Contributions to Mineralogy and Petrology 141, no. 1 (April 2001): 83–94. http://dx.doi.org/10.1007/s004100000220.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Ellis, Laura-Jayne A., Anastasios G. Papadiamantis, Stefan Weigel, and Eugenia Valsami-Jones. "Synthesis and characterization of Zr- and Hf-doped nano-TiO 2 as internal standards for analytical quantification of nanomaterials in complex matrices." Royal Society Open Science 5, no. 6 (June 2018): 171884. http://dx.doi.org/10.1098/rsos.171884.

Full text

Abstract:

The reliable quantification of nanomaterials (NMs) in complex matrices such as food, cosmetics and biological and environmental compartments can be challenging due to interactions with matrix components and analytical equipment (vials and tubing). The resulting losses along the analytical process (sampling, extraction, clean-up, separation and detection) hamper the quantification of the target NMs in these matrices as well as the compatibility of results and meaningful interpretations in safety assessments. These issues can be overcome by the addition of known amounts of internal/recovery standards to the sample prior to analysis. These standards need to replicate the behaviour of target analytes in the analytical process, which is mainly defined by the surface properties. Moreover, they need to carry a tag that can be quantified independently of the target analyte. As inductively coupled plasma mass spectrometry is used for the identification and quantification of NMs, doping with isotopes, target analytes or with chemically related rare elements is a promising approach. We present the synthesis of a library of TiO 2 NMs doped with hafnium (Hf) and zirconium (Zr) (both low in environmental abundance). Zirconia NMs doped with Hf were also synthesized to complement the library. NMs were synthesized with morphological and size properties similar to commercially available TiO 2 . Characterization included: transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy, X-ray diffraction spectroscopy, Brunauer–Emmett–Teller total specific surface area analysis, cryofixation scanning electron microscopy, inductively coupled plasma optical emission spectroscopy and UV–visible spectrometry. The Ti : Hf and Ti : Zr ratios were verified and calculated using Rietveld refinement. The labelled NMs can serve as internal standards to track the extraction efficiency from complex matrices, and increase method robustness and traceability of characterization/quantification.

APA, Harvard, Vancouver, ISO, and other styles

20

Lei, Huan‐Ling, Tao Yang, Shao‐Yong Jiang, and Wei Pu. "A simple two‐stage column chromatographic separation scheme for strontium, lead, neodymium and hafnium isotope analyses in geological samples by thermal ionization mass spectrometry or multi‐collector inductively coupled plasma mass spectrometry." Journal of Separation Science 42, no. 20 (September 9, 2019): 3261–75. http://dx.doi.org/10.1002/jssc.201900579.

Full text

APA, Harvard, Vancouver, ISO, and other styles

21

Yan, Quanshu, Susanne Straub, Paterno Castillo, Haitao Zhang, Liyan Tian, and Xuefa Shi. "Hafnium isotope constraints on the nature of the mantle beneath the Southern Lau basin (SW Pacific)." Scientific Reports 10, no. 1 (October 15, 2020). http://dx.doi.org/10.1038/s41598-020-74565-0.

Full text

Abstract:

Abstract New Hf isotope data provide new insights into the nature of the mantle beneath the southern Lau basin, adding new constraints on the displacement process of the Pacific mid-ocean ridge basalt (MORB)-type mantle by the Indian MORB-type mantle. The Hf isotopic ratios (176Hf/177Hf) of submarine lavas from the eastern Lau spreading center (ELSC) range from 0.283194 (εHf = 14.92) to 0.283212 (εHf = 15.54), with an average value of 0.283199 (εHf = 15.11) whereas those from the Valu Fa ridge (VFR) vary from 0.283221 (εHf = 15.88) to 0.283200 (εHf = 15.14), with an average of 0.283214 (15.61), indicating that ELSC lavas have a slightly more radiogenic Hf isotopic composition than VFR lavas. In contrast to the results from previous studies, the new Hf analyses combined with previous Nd isotope data clearly show that both VFR and ELSC have the distinct Hf–Nd isotope composition of the so-called DUPAL isotopic anomaly in the Indian MORB-type mantle. The DUPAL isotopic signature at VFR demonstrates for the first time that the inflow of the Indian MORB-type mantle has reached the southern tip of tectonic propagation in the southern Lau basin.

APA, Harvard, Vancouver, ISO, and other styles

22

Любимков, Л. С., Д. Б. Поклад, and С. А. Коротин. "Девять близких К-гигантов с планетами: детальный анализ химического состава." Astrophysics, December 2, 2022, 515–35. http://dx.doi.org/10.54503/0571-7132-2022.65.4-515.

Full text

Abstract:

Исследован химический состав 9-ти К-гигантов с планетами, расположенных в пределах 100 пк от Солнца. При этом использованы фундаментальные параметры звезд, найденные нами ранее; для гиганта μ Leo по линиям FeI переопределены индекс металличности [Fe/H] = +0.26 и параметр микротурбулентности Vt = 1.3 км/с. Определено содержание 17-ти химических элементов от лития (Z = 3) до гафния (Z = 72). Анализ линий некоторых элементов выполнен при отказе от предположения ЛТР (локальное термодинамическое равновесие). По инфракрасным линиям молекулы CN найдено содержание азота и отношение изотопов углерода 12С/13С. Низкие значения 12С/13С = 8-18 доказывают, что программные гиганты прошли глубокое конвективное перемешивание в фазе FDU (First Dredge-Up). При анализе полученных содержаний добавлены наши недавние данные для магнитных гигантов EK Eri и OU And, полученные по той же методике. Литий не был найден у 7 из 11-ти рассматриваемых гигантов. Отсутствие лития в атмосферах звезд, испытавших глубокое перемешивание в фазе FDU, соответствует предсказаниям теории. Однако у 4-х гигантов литий был нами обнаружен; ранее у 3 из них было найдено магнитное поле. Эти два явления, т.е. присутствие лития в атмосфере и наличие магнитного поля, неожиданные для post- FDU гигантов с точки зрения стандартной теории, находят объяснение в рамках единой гипотезы: захват звездой планеты с массой в несколько масс Юпитера. Для 11-ти рассмотренных гигантов мы нашли ярко выраженную корреляцию между величинами [N/C] и [N/O]. Сравнение наблюдаемой зависимости с теоретической моделью, учитывающей вращение, показало, что теория не может объяснить высокие значения [N/C] = 1.0-1.4, полученные для большинства гигантов. The chemical composition of nine K-giants with planets is studied, which are located within 100 pc from the Sun. The fundamental parameters of the stars obtained by us earlier are used in this regard; for the giant μ Leo the metallicity index [Fe/H] = +0.26 and the microturbulent parameter Vt = 1.3 km/s are redetermined from FeI lines. Abundances of 17 chemical elements from lithium (Z = 3) to hafnium (Z = 72) are found. An analysis of lines of some elements is made without the supposition of LTE (local thermodynamic equilibrium). From the infrared CN molecular lines the nitrogen abundance and the carbon isotope ratio 12Ñ/13Ñ are found. The low values 12Ñ/13Ñ = 8-18 show that the programme giants passed through the deep convecting mixing in the FDU (First Dredge-Up) phase. When analyzing the abundances obtained we added our recent data for the magnetic giants EK Eri and OU And found from the same technique. Lithium was not found for 7 of 11 giants in question. An absence of lithium in atmospheres of stars passed through the deep mixing in the FDU phase corresponds to the theory predictions. However for 4 giants lithium was found by us; earlier for 3 of these 4 stars the magnetic field has been detected. These two phenomena unexpected for post-FDU giants from the viewpoint of standard theory, i.e. the presence of lithium in atmosphere and the existence of magnetic field, can be explained in the framework of one hypothesis: an engulfment by a star of the planet with the mass of several Jupiter masses. For 11 giants considered we found the pronounced correlation between the [N/C] and [N/O] values. A comparison of the observed relation with the theoretical model computed with rotation showed that the theory cannot explain the high values [N/C] = 1.0-1.4 obtained for the most of the giants.

APA, Harvard, Vancouver, ISO, and other styles

23

Mitchell, Ross N., Christopher J. Spencer, Uwe Kirscher, and Simon A. Wilde. "Plate tectonic–like cycles since the Hadean: Initiated or inherited?" Geology, April 26, 2022. http://dx.doi.org/10.1130/g49939.1.

Full text

Abstract:

Interpretation of Earth’s oldest preserved crustal archive, the Jack Hills zircon of Western Australia, has been controversial in terms of the onset of plate tectonics. We conduct time-series analysis on hafnium isotopes of the Jack Hills zircon and reveal an array of statistically significant cycles that are reminiscent of plate-tectonic subduction. At face value, such cycles may suggest early Earth conditions similar to those of today—the uniformitarian hypothesis that plate tectonics was essentially operational since “day one”. On the other hand, in the context of expected secular changes due to planetary evolution and geological observations, the cycles could instead imply that modern plate-tectonic subduction inherited mantle convective harmonics already facilitated by an early phase of stagnant-lid delamination—the “lid-to-plates” hypothesis. Either way, any model for the nature of plate tectonics must incorporate conditions operating during Hadean time, either by initiation of plate tectonics then or by later inheritance of preexisting cycles of mantle convection.

APA, Harvard, Vancouver, ISO, and other styles

24

Mitchell, Ross N., Christopher J. Spencer, Uwe Kirscher, and Simon A. Wilde. "Plate tectonic–like cycles since the Hadean: Initiated or inherited?" Geology, April 26, 2022. http://dx.doi.org/10.1130/g49939.1.

Full text

Abstract:

Interpretation of Earth’s oldest preserved crustal archive, the Jack Hills zircon of Western Australia, has been controversial in terms of the onset of plate tectonics. We conduct time-series analysis on hafnium isotopes of the Jack Hills zircon and reveal an array of statistically significant cycles that are reminiscent of plate-tectonic subduction. At face value, such cycles may suggest early Earth conditions similar to those of today—the uniformitarian hypothesis that plate tectonics was essentially operational since “day one”. On the other hand, in the context of expected secular changes due to planetary evolution and geological observations, the cycles could instead imply that modern plate-tectonic subduction inherited mantle convective harmonics already facilitated by an early phase of stagnant-lid delamination—the “lid-to-plates” hypothesis. Either way, any model for the nature of plate tectonics must incorporate conditions operating during Hadean time, either by initiation of plate tectonics then or by later inheritance of preexisting cycles of mantle convection.

APA, Harvard, Vancouver, ISO, and other styles

25

Mitchell, Ross N., Christopher J. Spencer, Uwe Kirscher, and Simon A. Wilde. "Plate tectonic–like cycles since the Hadean: Initiated or inherited?" Geology, April 26, 2022. http://dx.doi.org/10.1130/g49939.1.

Full text

Abstract:

Interpretation of Earth’s oldest preserved crustal archive, the Jack Hills zircon of Western Australia, has been controversial in terms of the onset of plate tectonics. We conduct time-series analysis on hafnium isotopes of the Jack Hills zircon and reveal an array of statistically significant cycles that are reminiscent of plate-tectonic subduction. At face value, such cycles may suggest early Earth conditions similar to those of today—the uniformitarian hypothesis that plate tectonics was essentially operational since “day one”. On the other hand, in the context of expected secular changes due to planetary evolution and geological observations, the cycles could instead imply that modern plate-tectonic subduction inherited mantle convective harmonics already facilitated by an early phase of stagnant-lid delamination—the “lid-to-plates” hypothesis. Either way, any model for the nature of plate tectonics must incorporate conditions operating during Hadean time, either by initiation of plate tectonics then or by later inheritance of preexisting cycles of mantle convection.

APA, Harvard, Vancouver, ISO, and other styles

26

Colón, Dylan P., Ilya N. Bindeman, Jörn-Frederik Wotzlaw, Eric H. Christiansen, and Richard A. Stern. "Origins and evolution of rhyolitic magmas in the central Snake River Plain: insights from coupled high-precision geochronology, oxygen isotope, and hafnium isotope analyses of zircon." Contributions to Mineralogy and Petrology 173, no. 2 (January 13, 2018). http://dx.doi.org/10.1007/s00410-017-1437-y.

Full text

APA, Harvard, Vancouver, ISO, and other styles

27

Gamal El Dien, Hamed, Zheng-Xiang Li, Mohamed Abu Anbar, Luc S. Doucet, J. Brendan Murphy, Noreen J. Evans, Xiao-Ping Xia, and Jiangyu Li. "The largest plagiogranite on Earth formed by re-melting of juvenile proto-continental crust." Communications Earth & Environment 2, no. 1 (July 5, 2021). http://dx.doi.org/10.1038/s43247-021-00205-8.

Full text

Abstract:

AbstractThe growth of continental crust through melt extraction from the mantle is a critical component of the chemical evolution of the Earth and the development of plate tectonics. However, the mechanisms involved remain debated. Here, we conduct petrological and geochemical analyses on a large (up to 5000 km2) granitoid body in the Arabian-Nubian shield near El-Shadli, Egypt. We identify these rocks as the largest known plagiogranitic complex on Earth, which shares characteristics such as low potassium, high sodium and flat rare earth element chondrite-normalized patterns with spatially associated gabbroic rocks. The hafnium isotopic compositions of zircon indicate a juvenile source for the magma. However, low zircon δ18O values suggest interaction with hydrothermal fluids. We propose that the El-Shadli plagiogranites were produced by extensive partial melting of juvenile, previously accreted oceanic crust and that this previously overlooked mechanism for the formation of plagiogranite is also responsible for the transformation of juvenile crust into a chemically stratified continental crust.

APA, Harvard, Vancouver, ISO, and other styles

Journal articles on the topic 'Hafnium isotope analysis'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles