what are the icons on the mini map? (The Witcher 3: Wild Hunt)

Portals

portals, they are in the cave

Ah, got it

They are portals only in the cave.

from this zoom !!!

Man, you're a real pro in taking photos.
SpoilerNo

The screenshot is just agony ...))) And on-topic - a red triangle under the icon hints that the element associated with the icon is below Geralt's location. If the triangle is depicted with its apex up, then it is correspondingly higher than Geralt.

Yes portals. Most likely below is a quest location.