Pb pb dating method Realfreechatnocharge
In reality the comparison is made with the Global Strandard Strontium Curve using a “look up” table.
The assumption that the Sr ratio of the world’s oceans has fluctuated uniformly through time has enabled a Global Standard Strontium Curve (GSSC) to be established (Howarth and Mc Arthur, 1997).
Results obtained usually signify the "date" of the metamorphism, but they may also yield the "age" of the original volcanic (or sedimentary) rock.
The "age" or "date" is calculated from the amount of the daughter isotope produced by radioactive decay of the parent isotope.
The model K-Ar ages for each of the samples ranged from 405.1±10 Ma to 2574.2±73 Ma.
Furthermore, the seven samples from the small amphibolite unit near Clear Creek, which should all be the same age because they belong to the same metamorphosed basalt lava flow, yielded K-Ar model ages ranging from 1060.4±28 Ma to 2574.2±73 Ma.