Age measurements on radioactive minerals from Sweden

Welin, Eric; Blomqvist, Göran

doi:10.1080/11035897.1964.9626366

Cited by 66 publications

(5 citation statements)

References 15 publications

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“…Tables Table 1 Location, age, wt% ThO2 (from EMPA measurements, see Table 2) and dose (calculated after equation 1) for the investigated allanite-(Ce) samples. * Hetherington et al (2008), ** Welin & Blomqvist (1964), *** Gavryushkina et al (2017) and Vladimirov et al (1997 Table 3 Change of amounts Fe 2+ and Fe 3+ with annealing temperature for samples S74 20414, LB-1, and R1 from Mössbauer spectroscopic analysis (see also Fig. 3 126.3 ± 1.6 149.6 ± 9.5 134.2 ± 4.7 130.9 ± 3.6 1000 126.0 ± 3.9 163.0 ± 12.0 137.2 ± 5.8 133.6 ± 4.9 The Inset shows the rocking curves before and after annealing at temperatures 573 K and 673 K. Fig.…”

Section: Discussionmentioning

confidence: 99%

“…The total REE content is about wt%, however, only 7.06 wt% of this is Ce2O3. The ThO2 content is also slightly lower than in sample R1, 1.18 wt% (see Table 2), but with an age of 1520 Ma as determined using U-Pb-Th isotopes by Welin & Blomqvist (1964). Sample R1 came from the collection of the Fersman Mineralogical Museum of the Russian Academy of Science in Moscow, Russian Federation.…”

Section: Allanite-(ce) Samplesmentioning

confidence: 91%

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Mechanical and structural properties of radiation-damaged allanite-(Ce) and the effects of thermal annealing

et al. 2019

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The onset of thermally induced, heterogeneous structural reorganization of highly radiation-damaged allanite-(Ce) begins at temperatures below 700 K. Three strongly disordered allanite samples (S74 20414: ~0.55 wt% ThO2, 22.1 wt% REE oxides, and maximum radiation dose 3.5 × 10 18 α-decay/g; LB-1: 1.18 wt% ThO2, 19.4 wt% REE oxides, and maximum radiation dose 2.0 × 10 19 α-decay/g; R1: ~1.6 wt% ThO2, 19.7 wt% REE oxides, and maximum radiation dose 2.6 × 10 18 α-decay/g) were step-wise annealed to 1000 K in air. Using orientationdependent nanoindentation, synchrotron single-crystal X-ray diffraction (synchrotron XRD), X-ray powder diffraction (powder XRD), differential scanning calorimetry and thermogravimetric analysis (DSC/TG), mass spectrometry (MS), 57 Fe Mössbauer spectroscopy and high-resolution transmission electron microscopy (HRTEM), a comprehensive understanding of the structural processes involved in the annealing was obtained. As a result of the overall increasing structural order, a general increase of hardness (pristine samples: 8.2-9.3 GPa, after annealing at 1000 K: 10.2-12 GPa) and elastic modulus (pristine samples: 115-127 GPa, after annealing at 1000 K: 126-137 GPa) occurred. The initially heterogeneous recrystallization process is accompanied by oxidation of iron, the related loss of hydrogen and induced stress fields in the bulk material, which cause internal and surface cracking after step-wise annealing from 800-1000 K. HRTEM imaging of the pristine material shows preserved nanometer-sized crystalline domains embedded in the amorphous matrix, despite the high degree of structural 2 damage. The results show that hardness and elastic modulus are sensitive indicators for the structural reorganization process.

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Section: Discussionmentioning

confidence: 99%

Section: Allanite-(ce) Samplesmentioning

confidence: 91%

Mechanical and structural properties of radiation-damaged allanite-(Ce) and the effects of thermal annealing

et al. 2019

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“…The pegmatite carrying the investigated biotite was formed according to U-Pb dating 935 m.y. ago (Welin and Blomqvist, 1964). The K-Ar age of the biotite, 975 m.y., agrees fairly well with this age and virtually all argon produced by radioactive decay is retained.…”

Section: Discussionmentioning

confidence: 99%

Fission track studies on hornblende, biotite and phlogopite from Sweden

Welin¹,

Lundström²,

Åberg³

1972

Bull Geol Soc Finland

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Fission track studies and K-Ar dating on three silicate minerals from Sweden have given the following results: Fission track age K-Ar age RM 07249 hornblende, Malmberget, Fragment 1 1255 m.y. 1875 m.y. » 2 450 » RM 620569 biotite, Ingelsbo Fragment 1 305 » 975 » » 2 520 » » 3 355 » » 4 410 » RM 640448-640451 phlogopite,Ainön,Fragment 1 230 » 555 » » 2 240 » It is concluded from this investigation that due to inhomogeneous uranium distribution, recent uranium movement and sensitivity for annealing, the fission track dating technique is suitable only for the study of the last thermal event in areas which have undergone a complex geological evolution.

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“…2000-1750 Ma (K-Ar and U-Pb determinations, Magnusson 1960; Welin & Blomqvist 1964). The termination of this episode is defined by the late to post-orogenic Revsund granite (Rb-Sr age of 1748f40 Ma, Welin et al 1971) and the postorogenic Varmland granite group ( R b S r age 1654f 30 Ma, Welin 1970) Shortly afterwards extensive (sub-Jotnian) igneous activity took place.…”

Section: Geology and Agementioning

confidence: 96%