Thermal annealing characteristics of spontaneous fission tracks in zircon

Tagami, Takahiro; Ito, Hisatoshi; Nishimura, Susumu

doi:10.1016/0168-9622(90)90024-7

Cited by 67 publications

(39 citation statements)

References 22 publications

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“…The upper thermal limit of the zircon partial-annealing zone thus provides an estimate about the maximum temperature reached during the alpine event. Depending of the zircon type (amount of ␣-damage), the upper limit of the zircon partial-annealing temperature varies from 240 • C (Brandon et al, 1998;Bernet, 2009) to 300 • C (Tagami et al, 1998). The temperatures obtained by Gabalda et al (2009) in the western part of their transect in the Brianç onnais Zone houillère are higher than the experimentally determined zircon annealing temperatures.…”

Section: Introductionmentioning

confidence: 64%

Diachronous evolution of the alpine continental subduction wedge: Evidence from P–T estimates in the Briançonnais Zone houillère (France – Western Alps)

Lanari

Guillot

Schwartz

et al. 2012

Journal of Geodynamics

118

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a b s t r a c tThe study of continental subduction processes requires detailed Pressure Temperature (P-T) paths to understand the kinematic of burial and exhumation of continental units. In the French Western Alps, the Brianç onnais zone is a remnant of the continental subduction wedge. P-T conditions have been estimated in its most internal parts, but there is a lack of data in the western part, known as the "Zone houillère". This Brianç onnais Zone houillère is classically divided into two sub-units: the upper and lower Houiller units. This study focuses on both of these in the Clarée valley, north of Brianç on. In this low-grade metamorphic terrain, estimation of P-T history is complicated because there are few adapted methods and these rocks have a poor metamorphic mineralogical content, including detrital metamorphic minerals inherited from their hercynian history. Therefore, to acquire accurate P-T estimates a multi-method approach is required, involving qualitative and quantitative Raman Study of Carbonaceous Material (RSCM), chemical analysis from quantified X-ray maps and thermodynamic modelling of chlorites and K-white micas. Such multi-approach P-T estimates on a sandstone sample allow distinguishing hercynian peak metamorphic conditions of 371 ± 26 • C and 3.5 ± 1.4 kbar and alpine peak metamorphic conditions of 275 ± 23 • C and 5.9 ± 1.7 kbar. These results are consistent with our RSCM and T max estimates. Raman study conducted on organic-rich schist samples shows an eastward increase of the alpine T max in the upper Houiller unit, from 280 to 300 • C across the Brianç onnais Zone houillère. In contrast, carbonaceous material included in detrital grains of muscovite in the sandstone exhibits higher temperatures. This hercynian T max is estimated using thermodynamic modelling at 376 ± 50 • C. According to these results and previous work in more internal parts of the Brianç onnais zone, a geodynamic reconstruction is proposed, which is characterized by a diachronous evolution of the Brianç onnais zone involved in alpine continental subduction at different times. The geothermal gradient in the Brianç onnais zone changes from 8 • C/km during early continental subduction, to 40 • C/km during the collisional event at about 35-30 Ma. The intermediate gradient of 15 • C/km estimated in the Brianç onnais Zone houillère suggests that this unit was buried later, than the more internal Brianç onnais units, after 40 Ma.

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Section: Introductionmentioning

confidence: 64%

Diachronous evolution of the alpine continental subduction wedge: Evidence from P–T estimates in the Briançonnais Zone houillère (France – Western Alps)

Lanari

Guillot

Schwartz

et al. 2012

Journal of Geodynamics

118

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“…The sample was then polished with ¼ mm diamond paste for 10 min at 60 rpm. Finally, the zircon etching was made with NaOH:KOH (1:1) at 225 AE 2 C (Tagami et al 1990) in periods varying from 4 to 72 h (Garver, 2003). The time of the adequate etching can be different for each sample, and all samples were etched for 16 h.…”

Section: Fission Track Methodsmentioning

confidence: 99%

Fission track and U–Pb in situ dating applied to detrital zircon from the Vale do Rio do Peixe Formation, Bauru Group, Brazil

Dias

Tello

Chemale³

et al. 2011

Journal of South American Earth Sciences

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“…After that the grains were mounted in sheets of Teflon PFA, sanded, and polished. The etching was done by treating with a mixture of KOH/NaOH (1 : 1) and heating eutectically to (225 ± 2) • C [25] during 18 h. For more details see Tagami et al [26] After the standard etching, it was observed that ca 60% of the zircon grain samples presented the etching anisotropy, which meant that all these grains would be discarded by the fission track researchers. The natural 'monocrystal' of the Rio do Peixe was cut at the prismatic surface (Fig.…”

Section: Methodsmentioning

confidence: 99%

Micro‐Raman spectroscopy and SEM/EDX applied to improve the zircon fission track method used for dating geological formations

Dias

Sáenz

Constantino

et al. 2008

J Raman Spectroscopy

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The zircon mineral is widely studied in geochronology. In the case of the fission track method (FTM), the age is determined by the density of fission tracks at the zircon surface, which can be observed with an optical microscope after an appropriate chemical treatment (etching). The etching must be isotropic at the zircon grain surface to be used in the FTM, which leads those zircon grains whose etching is anisotropic to be discarded. The only reason for this discarding is the nonuniform morphology of the surface grain seen by optical microscopy, that is, no further physicochemical analysis is performed. In this work, combining micro-Raman and scanning electron microscopy (SEM) to study the etching anisotropy, it was shown that zircon grains that present at least one area at the surface where the density of fission track is uniform can be used in the FTM. The micro-Raman showed characteristic spectra of the standard zircon sample either from the areas where there are tracks or from where there are not. The only difference found was in the Raman bandwidths, which were broader for the areas with higher density of fission tracks. This suggests simply a decrease in the relative percentage of the crystalline/amorphous phases at these areas. The SEM/energy dispersive spectrometry (EDX) showed that there were no significant differences in the principal chemical composition at the areas with and without fission tracks.

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Thermal annealing characteristics of spontaneous fission tracks in zircon

Cited by 67 publications

References 22 publications

Diachronous evolution of the alpine continental subduction wedge: Evidence from P–T estimates in the Briançonnais Zone houillère (France – Western Alps)

Diachronous evolution of the alpine continental subduction wedge: Evidence from P–T estimates in the Briançonnais Zone houillère (France – Western Alps)

Fission track and U–Pb in situ dating applied to detrital zircon from the Vale do Rio do Peixe Formation, Bauru Group, Brazil

Micro‐Raman spectroscopy and SEM/EDX applied to improve the zircon fission track method used for dating geological formations

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