 |
How do you account for There are over fourty methods
in use for dating rock
samples. Each involves a
radioactive isotope, (the
parent), and a product, (the
daughter) that could easily
wash in or out throwing the
ratio way off.
Water is constantly seeping
through the rocks all the
time. That is how water gets
under the ground into wells.
You cannot find rocks that
this does not happen of has
not happend to.
|
|
 |
|
|
 |
It isn't the percentage of the isotope in the bulk rock material, but the relative percentages of the isotope and daughter product in the mineral making up the rock. Some of the mineral may wash away due to erosion and decomposition, but any mineral with isotope/daughter still in the rock will have the properties needed for analysis. |
|
|
|
|
|
The folks who do the dating go to great efforts to make sure they are using a mineral from a part of the rock that has not been altered by some more recent process, like weathering, which could throw off the isotope ratios. They also conduct a statistically significant number of analyses on the same specimens so they can determine if there are any outliers. The short answer, very carefully, but they do it. |
|
|
|
|
|
The interesting thing about chemistry is that elements do not behave the same among the various constituents in which they are found. It is actually quite easy to establish whether the system has been open to migration of radiogenic components by comparing the mother-daughter relationships in several different mineral species and the bulk rock. When there has been inmigration or leaching or daughter loss, for examples, the various constituents will display this differently and a regular relationship will not be observed. |
|
|
|
|
