If I'm a new KF member with, say 24000 miles and take a 10000 mile flight then do the additional 9000 miles normally carry forward?
I believe the OP is enquiring about qualifying for Gold Elite status, since he talks about being a new member. So in that case, congratulations on reaching Silver Elite status, and yes, the additional 9,000 miles count towards the 50,000 miles you need to reach in the next twelve months to achieve Gold Elite status.
In fact, your original 24,000 miles might also count towards Gold Elite status- if you can fly 50,000 miles within a 12 month period, even looking back, you will get Gold Elite status. KF has a "hidden counter" that looks at miles flown in a 12 month window.
See you in the lounge!
Friendly