Question

Age of granitic rocks can be determined using Rb-Sr whole rock radioactive dating method and the following age equation, \[ (^{87}Sr/^{86}Sr) = (^{87}Sr/^{86}Sr)_0 + (^{87}Rb/^{86}Sr) (e^{\lambda t} - 1) \] For a suite of representative co-magmatic granitic rocks, the Rb-Sr whole rock isochron plot and relevant data are shown in the diagram. The age of granite is calculated at (1 Ga = 10⁹ yrs), (give answer in one decimal place). 

Hint:

In radiometric dating, the age is calculated based on the isotope ratios and the decay constant. Ensure correct values are used for accurate results.

Answer 1

Step 1: Understanding the question.
The Rb-Sr whole rock method is used for radiometric dating of granitic rocks. The question provides the necessary data, including the value of \(\lambda\) (decay constant), tan(θ), and Sr₀.
Step 2: Analyzing the solution.
The age can be calculated using the formula provided for the Rb-Sr dating method, with the given values of \(\lambda\), tan(θ), and Sr₀. By substituting the values into the equation, the calculated age of the granite is 1200 million years.
Step 3: Conclusion.
The correct answer is 1200.0 million years.