UCL  IRIS
Institutional Research Information Service
UCL Logo
Please report any queries concerning the funding data grouped in the sections named "Externally Awarded" or "Internally Disbursed" (shown on the profile page) to your Research Finance Administrator. Your can find your Research Finance Administrator at http://www.ucl.ac.uk/finance/research/post_award/post_award_contacts.php by entering your department
Please report any queries concerning the student data shown on the profile page to:

Email: portico-services@ucl.ac.uk

Help Desk: http://www.ucl.ac.uk/ras/portico/helpdesk
Publication Detail
HelioPlot, and the treatment of overdispersed (U-Th-Sm)/He data
  • Publication Type:
    Journal article
  • Publication Sub Type:
    Journal Article
  • Authors:
    Vermeesch P
  • Publication date:
    30/03/2010
  • Pagination:
    108, 111
  • Journal:
    Chemical Geology
  • Volume:
    271
  • Issue:
    3-4
  • Status:
    Published
  • Print ISSN:
    0009-2541
Abstract
More often than not, (U-Th-Sm)/He ages are overdispersed with respect to the formal analytical uncertainty. The Mean Square of the Weighted Deviates (MSWD) is a useful tool for assessing the amount of overdispersion. If the MSWD is significantly greater than one, the ages can be parameterised by a (log)normal distribution with two sources of variance, which can be iteratively solved using the method of maximum likelihood. The overdispersion of replicate (U-Th-Sm)/He ages is caused by the overdispersion of the underlying U-Th-Sm-He compositions, the geometric mean of which gives rise to the so-called 'central age'. These compositions can be normalised to unity and parameterised by a multivariate logistic normal distribution with two sources of variance, which can be iteratively solved by a multivariate generalisation of the aforementioned age-averaging algorithm. Exact and asymmetric confidence intervals for the central age are obtained using a deterministic Bayesian algorithm. HelioPlot is a Java application developed for the purpose of plotting U-Th-(Sm)-He data on ternary diagrams and logratio plots that implements all these calculations. The program can be downloaded from http://pvermees.andropov.org/helioplot. © 2010 Elsevier B.V. All rights reserved.
Publication data is maintained in RPS. Visit https://rps.ucl.ac.uk
 More search options
UCL Researchers
Author
Dept of Earth Sciences
University College London - Gower Street - London - WC1E 6BT Tel:+44 (0)20 7679 2000

© UCL 1999–2011

Search by