isochronplots7

[@louisalou2121]

So well explained, totally understood now. Thank you so much!

[@sciencegeek691]

Thank you. This was extremely helpful and really clearly explained.

[@mat16006]

8:20 was groundbreaking for my learning, wish I saw this earlier.

[@GhostRyder2008]

4:27 so only during this crystallization process can these different minerals absorb the Samarium parent atom? They can't absorb it before crystallization or afterward?

[@geohubliverpool651]

Hi, Sorry it has taken so long to reply. This method of dating is only used for igneous rocks and the minerals found in the rocks did not exist before crystallisation. Everything is 'locked in' once the mineral has crystallised and formed. Since the magma is cooling it is never going to reach a temperature where it meltsand can absorb the parent atoms. After their formation, original igneous rocks may be changed by heat during metamorphism and may reach temperatures that alter their original compostion. Metamorphic rocks are very difficult to date because if this. Regards, GeoHubLiverpool

[@dr.nandeibamnilimachanu22r57]

Thank you very much .

[@sciencenerd7639]

very informative, thanks so much

[@tacoman202]

Doesn't Nd-144 decay as well? Wouldn't you want the isotope in the denominator to be a stable isotope?

[@geohubliverpool651]

144 Neodymium has a half life of 2.3 x 10 to the power 15 years so, although it is not stable, its half life is so long that at the age of the Solar System 99.999% of the original isotope would be unchanged. This means to all intents and purposes it can be considered to be stable.

[@blue4172]

this was so clear! thank you so much :)

[@MaximumEdits]

Why did the graph start at 350 million years ago? Or in other words, how do you go about determining where a certain sample should start on a specific time scale when this dating technique is suppose to determine how old said sample is? Or am I completely missing something?

[@geohubliverpool651]

When you make an isochron plot for a rock of unknown age it will take a sloping line. The slope for a very old rock will be steep and for a recent rock it will be shallow. Measuring the gradaaient of the line tells you how old the rock is. I chose to start 350 million years ago as an example to show you how the slope alters with time. (In the video, the formula used gives you the gradient or slope of the line)

[@WillzyFilms]

Sorry, I'm probably missing something, but is the dotted line respresentive of the Nd144 content in the samples?

[@geohubliverpool651]

The vertical axis on the graph is showing a ratio of 2 isotopes of Neodymium. Whatever the ratio of these isotopes is in the melt in the magma chamber when the crystallisation takes place both isotopes will behave in the same way chemically. Crystallisation is a chemical process, so the ratios will be the same in each mineral as it crystallises. The actual amounts of Neodymium will get less as the cooling takes place because here will be less left in the melt. The horizontal dotted line emphasises that the ratio stays the same for the Neodymium isotopes in olivine, feldspar and pyroxene.