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Title: In situ dating on Mars: A new approach to the K–Ar method utilizing cosmogenic argon

In this paper, cosmogenic argon isotopes are produced in feldspars via nuclear reactions between cosmic rays and Ca and K atoms within the lattice. These cosmogenic isotopes can be used as proxies for K and Ca, much like nuclear reactor-derived 39Ar and 37Ar are used as proxies for K and Ca, respectively, in 40Ar/ 39Ar geochronology. If Ca and K are uniformly distributed, then the ratio of radiogenic 40Ar ( 40Ar*) to cosmogenic 38Ar or 36Ar ( 38Ar cos or 36Ar cos) is proportional to the difference between the radioisotopic and exposure ages, as well as the K/Ca ratio of the degassing phase. Thus cosmogenic, radiogenic, and trapped Ar isotopes, all of which can be measured remotely and are stable over geologic time, are sufficient to generate an isochron-like diagram from which the isotopic composition of the trapped component may be inferred. Finally, such data also provide a means to assess the extent to which the system has remained closed with respect to 40Ar*, thereby mitigating otherwise unquantifiable uncertainties that complicate the conventional K–Ar dating method.
Authors:
 [1]
  1. Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Publication Date:
Report Number(s):
LLNL-JRNL-636235
Journal ID: ISSN 0094-5765
Grant/Contract Number:
AC52-07NA27344
Type:
Accepted Manuscript
Journal Name:
Acta Astronautica
Additional Journal Information:
Journal Volume: 94; Journal Issue: 1; Journal ID: ISSN 0094-5765
Publisher:
Elsevier
Research Org:
Lawrence Livermore National Lab. (LLNL), Livermore, CA (United States)
Sponsoring Org:
USDOE
Country of Publication:
United States
Language:
English
Subject:
58 GEOSCIENCES; 79 ASTRONOMY AND ASTROPHYSICS; Mars; geochronology; argon; cosmogenic
OSTI Identifier:
1438660

Cassata, William S. In situ dating on Mars: A new approach to the K–Ar method utilizing cosmogenic argon. United States: N. p., Web. doi:10.1016/j.actaastro.2013.07.040.
Cassata, William S. In situ dating on Mars: A new approach to the K–Ar method utilizing cosmogenic argon. United States. doi:10.1016/j.actaastro.2013.07.040.
Cassata, William S. 2013. "In situ dating on Mars: A new approach to the K–Ar method utilizing cosmogenic argon". United States. doi:10.1016/j.actaastro.2013.07.040. https://www.osti.gov/servlets/purl/1438660.
@article{osti_1438660,
title = {In situ dating on Mars: A new approach to the K–Ar method utilizing cosmogenic argon},
author = {Cassata, William S.},
abstractNote = {In this paper, cosmogenic argon isotopes are produced in feldspars via nuclear reactions between cosmic rays and Ca and K atoms within the lattice. These cosmogenic isotopes can be used as proxies for K and Ca, much like nuclear reactor-derived 39Ar and 37Ar are used as proxies for K and Ca, respectively, in 40Ar/39Ar geochronology. If Ca and K are uniformly distributed, then the ratio of radiogenic 40Ar (40Ar*) to cosmogenic 38Ar or 36Ar (38Arcos or 36Arcos) is proportional to the difference between the radioisotopic and exposure ages, as well as the K/Ca ratio of the degassing phase. Thus cosmogenic, radiogenic, and trapped Ar isotopes, all of which can be measured remotely and are stable over geologic time, are sufficient to generate an isochron-like diagram from which the isotopic composition of the trapped component may be inferred. Finally, such data also provide a means to assess the extent to which the system has remained closed with respect to 40Ar*, thereby mitigating otherwise unquantifiable uncertainties that complicate the conventional K–Ar dating method.},
doi = {10.1016/j.actaastro.2013.07.040},
journal = {Acta Astronautica},
number = 1,
volume = 94,
place = {United States},
year = {2013},
month = {8}
}