Spontaneous Formation of Mandalas
I've had similar experiences. Though Buddhism doesn't directly talk about the Kundalini system or even use the terminology (though Tibetan Vajrayana Buddhism has something close or maybe the same in Thummo), reading about it was useful from a systemic analysis perspective.

Regardless of any explanation I found, it was ultimately only for curiosity satisfaction. 

I think the best approach is to continue to practice and to not get carried away by this. Especially not obsessively, as you state. Just observe, remain equanimous and go on about your meditation.

One could term it a nimitta in the  Theravada tradition, I suppose.

In any case, it is a good sign of powerful concentration, keep at it.