The effect of nuclear radiation on the structure of zircon

Holland, Heinrich; Gottfried, David

doi:10.1107/s0365110x55000947

Cited by 397 publications

(228 citation statements)

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“…A very slight suggestion of asymmetry toward lower 20 values is the only indication of peak broadening. The multiple solutions for cell dimensions agreed within the indicated limits of error in Holland and Gottfried (1955) or Fairbairn and Hurley (1957), the c 0 value indicates a modest radiation dosage of about 1.0 X 10 15 a-particles/ mg.…”

Section: Physical Properties Of the Zircon Concentratesmentioning

confidence: 99%

“…Surprisingly, the X-ray and index of refraction measurements have shown that the L-312 zircons now display the radiation damage to be expected in a young rock perhaps 100 million years old (Holland and Gottfried, 1955;Fairbairn and Hurley, 1957). Apparently, annealing of the zircon structure accompanied or followed the disturbance of the contained lead-uranium systems.…”

Section: Evidence On the Nature Of The Disturbance Mechanismsmentioning

confidence: 99%

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Uranium-Lead Isotopic Variations in Zircons: A Case Study

Silver¹,

Deutsch²

1963

The Journal of Geology

256

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Zircons in a single 250-pound block of Precambrian Johnny Lyon granodiorite from the Dragoon Quadrangle in Cochise County, Arizona, have been concentrated with special attention to yield and nature of impurities. Morphology, zoning, color, inclusions, size distribution, radioactivity, refractive indexes, cell dimensions, and other properties have been compared with the isotopic properties in the U-Pb system (and to a less precise degree in the Th-Pb system). It has been observed: (1) Uranothorite impurities, while less than 1 per cent in abundance, contribute much more than 50 per cent of the activity in conventionally prepared concentrates. The presence of uranothorite drastically affects the apparent ages in the zirons. (2) The uranothorite can be satisfactorily removed by an appropriate acid-washing procedure. (3) The uranothoritefree zircon concentrates are not homogeneous and show systematic variations in radioactivity and various isotopic properties as a function of average crystal size. (4) Individual zircons show internal variation in radioactivity and may differ in specific activity from other individuals by as much as an order of magnitude. (5) It is possible to strip outer layers experimentally from an aggregate of zircons to determine variations in composite internal isotopic properties. (6) The family of uranium-lead systems distinguished in the inhomogeneous zircon suite may be utilized to establish patterns of isotopic ratio variations that yield much more useful geochronological information than any single system. (7) All systems in this rock appear to have formed 1,655 million years ago and to have been profoundly disturbed by an event 90 million years ago. There is no evidence of any type of disturbance other than this simple episodic pattern. (8) While the mechanism of disturbance is not directly established, it is evident that radioactivity and radiation damage strongly influence susceptibility of the systems to disturbance. (9) It is possible to offer reasonable explanations for some of the puzzling discrepancies between uranium-lead and thorium-lead ages determined on a single mineral concentrate. (10) Recognition of the existence of families of uranium-lead systems among the variable members of a single mineral species, or in associated mineral species, in a single typical granitic rock provides a powerful tool for investigation of the processes and conditions that have influenced the age-dating systems. (11) The systematic variations in U and Th provide interesting information on the role of some trace elements and accessory minerals in the crystallization history of the rock. (12) The Johnny Lyon granodiorite is the oldest igneous rock dated in Arizona thus far and places a minimum age of 1,655 ± 20 million years on the orogeny called Mazatzal Revolution.

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Section: Physical Properties Of the Zircon Concentratesmentioning

confidence: 99%

Section: Evidence On the Nature Of The Disturbance Mechanismsmentioning

confidence: 99%

Uranium-Lead Isotopic Variations in Zircons: A Case Study

Silver¹,

Deutsch²

1963

The Journal of Geology

256

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“…. ) are known to undergo amorphization as a consequence of the α-decay of radionuclide impurities (typically 238 U, 235 U and 232 Th and their decay products) (Holland and Gottfried 1955, Lumpkin and Ewing 1988, Ewing 1994, Weber et al 1994. Due to the properties (mainly chemical durability) that some of these materials offer as waste forms for the immobilization of high-level waste and plutonium (Weber et al 1998, Ewing 1999, natural materials and their synthetic equivalents have been extensively studied.…”

Section: Introductionmentioning

confidence: 99%

“…At this first stage, sharp Bragg maxima are observed that decrease in intensity with increasing radiation dose. The crystalline matrix is expanded (as shown by the unit-cell swelling (Holland andGottfried 1955, Murakami et al 1991)) as a consequence of the shear deformation produced by the localized defects created by α-particles (Ríos and Salje 1999). At intermediate doses the decrease of the intensity of diffraction maxima and their broadening is accompanied by the appearance of two diffuse rings, as observed from electron diffraction images: in natural (Murakami et al 1991, Capitani et al 2000 and irradiated zircon Ewing 1992b, Weber et al 1994) samples, pyrochlores (Lumpkin and Ewing 1988) and Cm-doped Ca 2 Nd 8 (SiO 4 )O 2 (Weber 1993), for example.…”

Section: Introductionmentioning

confidence: 99%

“…Kr + , Xe + ) Ewing 1992a, Meldrum et al 1996) or by actinide doping ( 238 Pu, 244 Cm) (Weber 1990, Weber et al 1994, 1997b. During the amorphization process in natural zircon three different stages may be observed with increasing dose, depending on the age of the sample and/or the content of radioactive impurities (Holland and Gottfried 1955, Murakami et al 1986. At low degrees of damage the material is essentially crystalline, α-particles produce isolated defects and α-recoil nuclei produce a few isolated amorphous regions.…”

Section: Introductionmentioning

confidence: 99%

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Amorphization in zircon: evidence for direct impact damage

Rı́os¹,

Salje²,

Zhang³

et al. 2000

J. Phys.: Condens. Matter

125

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Abstract. X-ray diffraction has been used to characterize the amorphous phase present in a series of radiation-damaged natural zircons with radiation doses ranging from 0.06 to 16 × 10 18 α-decay events g −1 . The fraction of amorphous material present in each of the samples studied has been determined, and its dependence on the radiation dose has been calibrated. Direct determination of the amorphous fraction confirms that amorphization in natural zircon occurs as a consequence of the direct impact within cascades caused by α-recoil nuclei. These results are not consistent with the commonly accepted double-overlap model of damage accumulation.The volume swelling of amorphous regions changes as a function of dose. Thus, the density of amorphous regions depends on the degree of damage up to a certain point (i.e. 8 × 10 18 α-decay events g −1 ), unlike in previous models for which a constant value independent of the radiation dose was assumed.

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Isotope dilution analysis of Ca and Zr in apatite and zircon (U-Th)/He chronometry

Guenthner

Reiners

Chowdhury

2016

Geochem. Geophys. Geosyst.

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Because radiation damage influences He diffusivity, correlations between (U-Th)/He ages and effective uranium (eU, eU 5 U 1 0.235 3 Th) concentrations of single apatite and zircon grains are important for understanding thermal histories. Here we describe a method for quantifying eU concentrations in apatite and zircon grains using isotope dilution ICP-MS measurements of Zr and Ca and stoichiometry of zircon (ZrSiO 4 ) and apatite (Ca 5 (PO 4 ) 3 F) to obtain grain masses. Combined with independent U and Th measurements, these yield eU concentrations not based on the traditional morphologic measurements and assumptions. Additional benefits of this method include correct identification of an apatite or zircon and volume estimates for crystal shards. In some cases, this method gives eU concentrations consistent with those calculated with the morphologic approach, but often significant differences are observed between concentrations calculated from the two methods. Differences in eU concentrations for our apatite grains are greater and less than morphology estimates, and the majority are between 0.7 and 31%. With the exception of two grains, all of our zircon grains have differences between 3 and 34% less than morphology estimates. These differences could result from incorrect grain width measurements, mischaracterized grain shape, or incorrect volume calculations of the pure mineral phase due to inclusions. These morphologic errors-combined with evidence for the accuracy of our isotope dilution method from analyses of reference materialssuggest that eU concentrations calculated from morphology may often be significantly inaccurate. Finally, we demonstrate that differences between the two measurements of eU cause age-eU correlation variations for representative thermal histories.

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The effect of nuclear radiation on the structure of zircon

Cited by 397 publications

References 1 publication

Uranium-Lead Isotopic Variations in Zircons: A Case Study

Uranium-Lead Isotopic Variations in Zircons: A Case Study

Amorphization in zircon: evidence for direct impact damage

Isotope dilution analysis of Ca and Zr in apatite and zircon (U-Th)/He chronometry

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