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Metamict and chemically altered vesuvianite

Eby, Ray K. and Janeczek, Janusz and Ewing, Rodney C. and Ercit, T. Scott and Groat, Lee A. and Chakoumakos, Bryan C. and Hawthorne, Frank C. and Rossman, George R. (1993) Metamict and chemically altered vesuvianite. Canadian Mineralogist, 31 (2). pp. 357-369. ISSN 0008-4476.

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Partly metamict vesuvianite samples from two localities were examined and compared. The unit cell of one is enlarged owing to volume expansion caused by the buildup of radiation damage. The other sample sustained enough damage to exclude accurate determination of unit-cell parameters. BSE imaging shows that both samples have undergone chemical alteration, and electron-microprobe data indicate that the alteration has resulted in a heterogeneous distribution of radionuclides on the micrometer scale. HRTEM and SAED analyses reveal a wide variation in the extent of alpha-recoil damage, which corresponds to the heterogeneous distribution of the radionuclides. The progressive stages of metamictization also are observed in detail with TEM. Partly metamict vesuvianite recrystallizes over the range 600-850°C, which is broader than the range found in other metamict silicates. Combined thermogravimetric analysis and isothermal annealing show that, upon heating (in N_2 or Ar), metamict vesuvianite begins to recrystallize at 600°C, and at 900°C decomposes in to the multiphase assemblage grossular+ gehlenite+wollastonite. Unpolarized IR spectra of both vesuvianite samples are similar and also resemble those of radiation-damaged zircon and titanite, suggesting that the major structural features of the aperiodic state are similar for complex ceramics of different composition.

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Rossman, George R.0000-0002-4571-6884
Additional Information:© 1993 Mineralogical Association of Canada. Received March 23, 1992, revised manuscript accepted September 2, 1992. Sample V73 was collected by a prospector, the late Bob Beal, who then brought the sample to Jack A. Adams, formerly of the U.S. Geological Survey, for identification. By XRD of the as-found and heated sample Adams identified the sample as metamict vesuvianite and later donated it to the Department of Geology, UNM. Roger Aines provided us with assistance in preliminary IR measurements of sample V53. Useful comments and suggestions were provided by Joe Blatz and Fred Shmuck, who reviewed the manuscript. NSERC of Canada provided assistance in the form of fellowships to RKE, operating grants to FCH and LAG, and an infrastructure grant to FCH. This work was also supported by Basic Energy Sciences of DOE, grant #DE-FGO4-84ER45099 to RCE. TEM was done in the Electron Microbeam Analysis Facility of the Department of Geology, UNM, supported in part by NSF, NASA, BES and the state of New Mexico. Research done at ORNL was supported by the Division of Materials Sciences. DOE contract #DE-AC05-84OR21400 with Martin Marietta Energy Systems, and at Caltech by NSF grant #EAR-8916064.
Funding AgencyGrant Number
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Department of Energy (DOE)DE-FG04-84ER45099
state of New MexicoUNSPECIFIED
Department of Energy (DOE)DE-AC05-84OR21400
Martin Marietta Energy SystemsUNSPECIFIED
Subject Keywords:vesuvianite, metamict, radiation damage, alteration, transmission electron microscopy, back-scattered electron imaging, infrared spectroscopy, thermogtavimetric analysis.
Issue or Number:2
Record Number:CaltechAUTHORS:20130501-112334127
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Official Citation:R. K. Eby, J. Janeczek, R. C. Ewing, T. S. Ercit, L. A. Groat, B. C. Chakoumakos, F. C. Hawthorne, and G. R. Rossman Metamict and chemically altered vesuvianite Can Mineral, June 1993, v. 31, p. 357-369
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:38209
Deposited By: Ruth Sustaita
Deposited On:01 May 2013 20:58
Last Modified:03 Oct 2019 04:55

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