U thhe dating of phosphates apatite monazite and xenotime dating agency richmond surrey
It is easy to imagine diffusion in liquid phase as ink spreading in water.
Solid-state diffusion of Pb is the net exchange of Pb in the solid mineral with the external environment, which is usually a fluid.
However, as the mineral cools and the crystal structure becomes more complete, the diffusions of parent and daughter isotopes slows down and finally become insignificant at a certain temperature.
Monazite is characterised for its high Pb retention ability even at high temperatures for a prolonged period.
The closure temperature of monazite in U-Th-Pb system is higher than 800 °C, much higher than the other common minerals.
Successive growth of monazite grain by fluid-assisted dissolution-precipitation.
Geological age represents the time when a geological event occurs.Manipulating the isotopic ratios can only give us radiometric age.To obtain the geological age, we need to know the relationship between the two.(1) Monazite (orange) dissolves along reaction front the contact with the fluid (yellow) (2) Monazite reprecipitates as an altered monazite with a new chemical composition (pink) (3) Reaction continues with fluid being transported to the reaction front by infiltration paths.(A) Reaction ceased due to recrystallisation of precipitating phase (dark orange).