I think I found the culprit: Its BIOS setting which allows fan speed control according to CPU temperature. I disabled it and now the fan is spinning at around 3.5k RPM and the temp is around 30C.
I can't understand why the BIOS allows the CPU temp to shoot to 65C before kicking in the fan. Wrong settings by Gigabyte I suppose.
may be a future bios update will fix this .. anyway, nice to know that your issue has been solved.