Thanks for joining the Graphics community.
I understand you have an Apple computer and you are looking for Thunderbolt information on 4K displays.
Please bear in mind, Intel does not provide support for Apple computers, this type of issue is handled by Apple. I recommend checking for support at Contact Apple Support - Apple Support
I have been checking on this matter and I found the following link Using 4K displays and Ultra HD TVs with Mac computers
that talks about 4k resolution support for Thunderbolt.
Please check with Apple support to confirm if 4K resolution is handled by your computer model..