Granite on the moon

 There's a huge chunk of granite on the moon. On the dark side. It's 50km wide and it doesn't make any sense.

Granite requires one of two things to form: Plate tectonics or a lot of water. The moon has neither. So, where did this granite come from? Or is it something else...we're guessing granite based on a 9 degree Celsius hotspot likely caused by radiation. (Yes, granite is radioactive, that's why places with lots of it have radon problems).

The lead theory is that there was a mantle plume under it a long time ago that, without plate tectonics, just sat there making more granite.

But to find out, we're going to have to send a robot there to take an actual look.