isochron

English

A diagram showing how isochrons can be used to determine the initial concentration of a radioisotope

iso- +‎ chron.

isochron (plural isochrons)

(geology, geochemistry) A line on a chart linking rock of the same age (as determined from isotope ratios).
- 1997, H.-G. Attendorn, R. Bowen, Radioactive and Stable Isotope Geology, Chapman & Hall, page 163:
  Recapitulating, any suite of comagmatic rocks with an age $t$ defines an isochron if its members all had the same initial ${\ce {^{87}Sr/^{86}Sr}}$ ratio and if it was closed to both ${\ce {Rb}}$ and ${\ce {Sr}}$ since crystallization occurred and neither element was introduced from any extraneous source. […] In this way, whole-rock ${\ce {Rb-Sr}}$ isochrons can produce rather reliable age data for rock samples.
(mathematics, dynamical systems) A collection of points (such as a manifold), each point representing a set of initial conditions for a given dynamical system, such that every set results in the same long-term behaviour of the system.
- 2007, Eugene M. Izhikevich, Dynamical Systems in Neuroscience, The MIT Press, page 446:
  The entire plane is foliated by isochrons.

line on a chart linking rock of the same age

collection of points representing initial conditions of a dynamical system