Figure 32. Radiometric ages of minerals in sample 8B7: A, Internal isochron showing mineral age of the bastnaesite (555+-11 Ma), which replaced the host dolostone marble; B, 40Ar/39Ar plateau showing age (395.5+-4.4 Ma) of the coexisting alkali amphibole.
This page is http://pubs.usgs.gov/bulletin/b2143/fig32.html
Maintained by John Watson
Last updated 01.26.98