Need Help GTX 680 4K @60HZ

Hey guys I was just wondering if anyone knows if I can get 4K at 60HZ instead of 30HZ .

I have a Mac Pro 2009 4.1
Nvidia gtx 680 2gb

hooked up to the asus PQ321Q 31 4k monitor via display port 1.2

But MacOS is locked at 30HZ with no option available for 60HZ only with 1080p

Thanks