Behavior of argon gas release from manganese oxide minerals as revealed by Ar-40/Ar-39 laser incremental heating analysis

Li, Jianwei W., Vasconcelos, P. M. and Zhang, Jun (2002) Behavior of argon gas release from manganese oxide minerals as revealed by Ar-40/Ar-39 laser incremental heating analysis. Chinese Science Bulletin, 47 18: 1502-1510. doi:10.1360/02tb9331

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Author Li, Jianwei W.
Vasconcelos, P. M.
Zhang, Jun
Title Behavior of argon gas release from manganese oxide minerals as revealed by Ar-40/Ar-39 laser incremental heating analysis
Formatted title
Behavior of argon gas release from manganese oxide minerals as revealed by Ar-40/Ar-39 laser incremental heating analysis
Journal name Chinese Science Bulletin   Check publisher's open access policy
ISSN 1001-6538
0250-7862
Publication date 2002-09
Sub-type Article (original research)
DOI 10.1360/02tb9331
Open Access Status File (Publisher version)
Volume 47
Issue 18
Start page 1502
End page 1510
Total pages 9
Editor Zhou Guangzhao
Place of publication Beijing, China
Publisher Science in China Press
Collection year 2002
Language eng
Abstract Manganese oxides in association with paleo-weathering may provide significant insights into the multiple factors affecting the formation and evolution of weathering profiles, such as temperature, precipitation, and biodiversity. Laser probe step-heating analysis of supergene hollandite and cryptomelane samples collected from central Queensland, Australia, yield well-defined plateaus and consistent isochron ages, confirming the feasibility, dating very-fined supergene manganese oxides by Ar-40/(39) Ar technique. Two distinct structural sites hosting Ar isotopes can be identified in light of their degassing behaviors obtained by incremental heating analyses. The first site, releasing its gas fraction at the laser power 0.2-0.4 W, yields primarily Ar-40(atm), Ar-38(atm), and Ar-36(atm), (atmospheric Ar isotopes). The second sites yield predominantly Ar-40* (radiogenic Ar-40), Ar-39(K), and Ar-38(K) (nucleogenic components), at similar to0.5-1.0 W. There is no significant Ar gas released at the laser power higher than 1.0 W, indicating the breakdown of the tunnel sites hosting the radiogenic and nucleogenic components. The excellent match between the degassing behaviors of Ar-40*, Ar-39(K), and Ar-38(K) suggests that these isotopes occupy the same crystallographic sites and that Ar-39(K) loss from the tunnel site by recoil during neutron irradiation and/or bake-out procedure preceding isotopic analysis does not occur. Present investigation supports that neither the overwhelming atmospheric Ar-40 nor the very-fined nature of the supergene manganese oxides poses problems in extracting meaningful weathering geo-chronological information by analyzing supergene manganese oxides minerals.
Keyword Hollandite
Cryptomelane
40ar/39ar Laser Incremental Heating
Argon Degassing
Tunnel Site
Multidisciplinary Sciences
K-mn Oxides
Mechanisms
Australia
Q-Index Code C1
Q-Index Status Provisional Code
Institutional Status UQ

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Physical Sciences Publications
 
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Created: Tue, 14 Aug 2007, 18:35:45 EST