Part 6- Sm-Nd Decay System Flashcards
What does 143Nd stand for?
Neodymium (mass = 143)
What does 147Sm stand for?
Samarium (mass = 147)
What group of elements do Sm and Nd both belong to?
REE
What is the half life of the Sm-Nd decay system?
106Gyr
What compatibility do Sm and Nd have?
Moderate incompatibility. Nd is more incompatible than Sm.
Is the system easily affected by fluids.
No the elements are fluid-immobile.
What types of rocks are well dated with the Sm-Nd decay system?
Mafic and Ultramafic rocks.
Which of Goldschmidt’s classifications do Sm and Nd belong to?
Lithophile
Are Sm and Nd refractory or volatile?
Refractory.
What is the Sm/Nd ratio in the BSE and BE?
The same as the solar system (CI carbonaceous chondrites).
How do the concentrations of Sm and Nd differ in the BSE relative to chondrites and why?
They’re enriched in the BSE relative to chondrites due to loss of volatiles on Earth and the loss of siderophiles on the BSE due to core formation.
Which reservoirs are particularly enriched in Sm and Nd?
OIBs and the CC.
Why is the Sm-Nd system good for studying the temporal evolution of terrestrial reservoirs?
The isotope compositions of older rocks have not been affected by weathering/metamorphism due to the fluid-immobility of the elements.
What does CHUR stand for?
What is it?
Chondritic Uniform Reservoir
It is defined by the average present day Sm/Nd ratio and Nd composition of chondritic meteorites.
What do εNd values denote?
Relative differences in Nd isotope compositions relative to CHUR in pp 10,000.
