Problems with dating metamorphic rocks
In principle, sedimentary rocks may be divided into two groups according to the nature of the Rb-bearing phase present.
Allogenic (detrital) minerals are moderately resistant to open-system behaviour during burial metamorphism, but problems arise from inherited isotopic signatures.
Sedimentary rock on the other hand consists of sedimentary particles which were removed and deposited somewhere else by some sort of fluid (generally wind and water).
The sedimentary particles predate the rock which they form.
In the case of Rb Sr dating of sediments, this rests on the assumption that Sr isotope systematics in the rock were homogenized during deposition or early diagenesis, and thereafter remained as a closed system until the present day.
However, we will see that these two requirements may be mutually exclusive.
Precise corrections can be made for the amount of pre-existing daughter product, if any, incorporated in the mineral at the time of its formation, and the amounts of the isotope introduced in the lab procedure.
Carbonates deposited from, and calcareous organisms living in these waters will have distinctive The presence of uranium-rich accessory minerals (e.g., zircon, monazite, sphene and apatite) in acid to intermediate igneous and metamorphic rocks enables the uranium-lead technique to be applied to the problems of precisely defining crystallization ages of such minerals.But last Sunday, her Bible teacher stated emphatically that God made Earth only six thousand years ago. The age assigned to the fossils in front of her seems to contradict the creation account, and Janet’s heartbeats accelerate at the implication. Credible answers to common misconceptions about radiometric dating and a proper understanding of Scripture can help people like Janet reconcile creation accounts regarding the age of Earth. Scientists agree that radiometric-dating techniques offer the most concrete evidence of any dating system for answering questions about the age of Earth.Ages can be measured with an analytical uncertainty of 1 to 2% for rocks as young as 100 Ka or older than 3000 Ma.Rubidium, because of its geochemical association with potassium, is also found in a wide range of rocks and minerals.
Radiometric dating can be compared to an hourglass.