# geology / science

the age of granite can be determind using radiometric dating, explain the basis for the determination of a 238 U- Pb radiometric date of 1120 Ma for a granite.

I have as the answer
238 U decays to Pb with an experimental law, that is the amount of U and Pb in granite are functions of the time. The inverse function allows granite lifetime from its composition considering that radioactive parent elements, the mathamtical expression that relates to radioactive decay to geological time called age equation

Does this answer the question as it is worth 10 marks (which i cant afford to drop)

It is right, however, the wording on the first sentence is cumbersome. Why don't you just write something like U238 decays to Pb in a known rate, so that that knowing the ratio of Pb to U, one can determine time elapsed since the U was placed in the sample of granite.
The function is not an inverse, it is an expontential decay.

You might want to talk about the technique in more detail, for example the use of the key mineral zircon. You could also include a little on the decay equation.

A useful rule of thumb when answering questions is that if 10 marks are available then the marker may expecting up to 10 points to be made.

is this the right equation
t = 1/constant 1n (1 + d/p)
thanks for all your help

thanks for that but i thought it would need to be more as 10 marks are up for grabs, and i didn't think what i wrote would be enough

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