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GEOREF RECORD

Thermal annealing of fission tracks in fluorapatite, chlorapatite, manganoanapatite, and Durango Apatite; experimental results

Casey E. Ravenhurst, Mary K. Roden-Tice and Donald S. Miller
Thermal annealing of fission tracks in fluorapatite, chlorapatite, manganoanapatite, and Durango Apatite; experimental results
Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre (July 2003) 40 (7): 995-1007

Abstract

It is well known that the optically measured lengths of fission tracks in apatite crystals are a function of etching conditions, crystallographic orientation of the track, composition of the crystal, and the state of thermal annealing. In this study we standardize etching conditions and optimize track length measurability by etching until etch pits formed at the surface of each apatite crystal reached widths of about 0.74 mu m. Etching times using 5M HNO (sub 3) at 21 degrees C were 31 s for Otter Lake, Quebec, fluorapatite; 47 s for Durango, Mexico, apatite; 33 s for Portland, Connecticut, manganoanapatite; and 11 s for Bamle, Norway, chlorapatite. An etching experiment using two etchant strengths (5M and 1.6M HNO (sub 3) ) revealed that, despite significant differences in etch pit shape, fission-track length anisotropy with respect to crystallographic orientation of the tracks is not a chemical etching effect. A series of 227 constant-temperature annealing experiments were carried out on nuclear reactor induced tracks in oriented slices of the apatites. After etching, crystallographic orientations of tracks were measured along with their lengths. The 200-300 track lengths measured for each slice were ellipse-fitted to give the major (c crystallographic direction) and minor (a crystallographic direction) semi-axes used to calculate equivalent isotropic lengths. The equivalent isotropic length is more useful than mean length for thermal history analysis because the variation caused by anisotropy has been removed. Using normalized etching procedures and equivalent isotropic length data, we found that the fluorapatite anneals most readily, followed by Durango apatite, manganoanapatite, and lastly chlorapatite.


ISSN: 0008-4077
EISSN: 1480-3313
Coden: CJESAP
Serial Title: Canadian Journal of Earth Sciences = Revue Canadienne des Sciences de la Terre
Serial Volume: 40
Serial Issue: 7
Title: Thermal annealing of fission tracks in fluorapatite, chlorapatite, manganoanapatite, and Durango Apatite; experimental results
Affiliation: Rensselaer Polytechnic Institute, Troy, NY, United States
Pages: 995-1007
Published: 200307
Text Language: English
Summary Language: French
Publisher: National Research Council of Canada, Ottawa, ON, Canada
References: 31
Accession Number: 2003-076412
Categories: GeochronologyMineralogy of non-silicates
Document Type: Serial
Bibliographic Level: Analytic
Illustration Description: illus. incl. 6 tables
Country of Publication: Canada
Secondary Affiliation: GeoRef, Copyright 2018, American Geosciences Institute.
Update Code: 200323
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