Central Age
The central age is calculated from the geometric mean U-Th-(Sm)-He composition.
To calculate this composition, HelioPlot employs a non-linear optimisation
algorithm (using Newton's method) that simultaneously takes into account the
internal and external reproducibilities of the data. Convergence of this algorithm
is communicated to the user via the console. If the algorithm fails to converge,
HelioPlot uses one of two alternative methods. If the compositional MSWD < 3,
the program uses a 'conventional weighted mean algorithm taking into account
only the assigned analytical errors. If the compositional MSWD > 3,
the analytical errors are ignored and the error propagation uses only the
empirical overdispersion. Again, the specific algorithm will be reported to
the console.
See MSWD