Without knowing the specific distance of faulting, we cannot determine the approximate rate of offset. To calculate the approximate rate of offset, we need to determine the total distance of faulting and the time over which this faulting occurred.
If the faulting began immediately after the granite formed and has been ongoing for the past 50 million years, we can assume that the total distance of faulting is proportional to the time elapsed.
Let's assume that the rate of offset is constant over the 50 million years. We can calculate the approximate rate of offset by dividing the total distance of faulting by the time.
However, since the question does not provide information about the actual distance of faulting, we cannot provide a specific rate of offset. The rate of offset would depend on the actual distance that the fault has moved.
Therefore, without knowing the specific distance of faulting, we cannot determine the approximate rate of offset.