That's strange, I can think of a few reasons for that happening.
Do you have Turbo Boost enabled? It must be enabled to maintain your OC to 4.7GHz.
Or, did you change the Turbo power limits or times in the BIOS? I've also heard that disabling SpeedStep (EIST) can cause that to happen.
A processor will reduce its speed if it is too hot, thermal throttling is activated to protect the CPU. The CPU temperatures you posted do not seem to be high enough to cause that to happen, which is usually 100C.