The Key to Geologic Dating- How Do We Know The Rock's Initial Isotope Composition? GEO GIRL

When determining the age of a rock using radiometric dating, we assume the rock started off with 100% parent isotope and 0% daughter isotope... But how does this work? How do we know the rock starts off without any daughter isotopes?

In todays video, I go through all the processes that govern radioactive (parent) isotope and radiogenic (daughter) isotope behavior in melts and high T and P conditions within Earth's interior. For the most part, diffusion allows the movement of these isotopes under these conditions, which allows the inclusion of parent isotopes in the crystallizing rock and the exclusion of daughter isotopes. But why this selectivity? How does the rock know what is parent and what is daughter isotope? The concept of compatible and incompatible elements helps with this one. Most parent isotopes are compatible elements, meaning they fit into the crystal structures of the minerals that we use for radiometric dating. Daughter isotopes, however, are incompatible, meaning they do not fit into these crystal structures. Thus, while parent isotopes are incoroporated into the rock, daughter isotopes are left in the melt, until a different mineral with a structure favorable for those isotopes crystallizes and incoroporates them. Then we just make sure we use the correct mineral and isotope combinations when using these dating techniques. Simple as that! ;) Hope you enjoy learning about this as much as I did! ;D

References:
Radiogenic Isotope Geochemistry: https://amzn.to/3QWHWHC
Stable Isotope Geochemistry: https://amzn.to/3ud82gZ
Essentials of Igneous Petrology by Ronald and Carol Frost: https://amzn.to/37Zs9AL
Earth Materials by Cornelis Klein and Anthony Philpotts: https://amzn.to/3z5sCxe
Earth System History: https://amzn.to/3v1Iy0G

0:00 What is an isotope?
2:32 How radiometric dating works
5:16 What rocks can be radiometrically dated?
6:08 What does ‘resetting’ mean?
7:11 How ‘resetting’ works
10:12 Not all isotope systems ‘reset’
11:42 Different ‘resetting’ temperatures
13:38 Isotope + mineral selection is key
14:34 Problem w/initial daughter isotopes
15:07 Mineral/isotope selection helps minimize this
15:57 Loss/gain models helps minimize this
16:17 Isochrons helps minimize this
18:07 Multiple samples helps minimize this
19:14 Why daughter isotopes are ‘rejected’ during formation
22:11 Where do all the daughter isotopes go?
23:40 Correcting’ isotope data
25:09 Reliability of peer-reviewed journals
26:07 Repetition also helps

GEO GIRL Website: https://www.geogirlscience.com/ (visit my website to see all my courses, shop merch, learn more about me, & donate to support the channel if you'd like!)

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Non-textbook books I recommend:
Oxygen by D. Canfield: https://amzn.to/3gffbCL
Brief history of Earth by A. Knoll: https://amzn.to/3w3hC1I
Life on young planet by A. Knoll: https://amzn.to/2RBMpny
Some assembly required by N. Shubin: https://amzn.to/3w1Ezm2
Your inner fish by N. Shubin: https://amzn.to/3cpw3Wb
Oxygen by N. Lane: https://amzn.to/3z4FgwZ
Alien Oceans by K. Hand: https://amzn.to/3clMx1l
Life's Engines: https://amzn.to/3w1Nhke

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Geology field notebook: https://amzn.to/3lb6dJf
Geology rock hammer: https://amzn.to/3DZw8MA
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Camera: https://amzn.to/3l6fGRT
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