This happened to my friend today.
He went 10/11/3 in a match with score 13-10 and got 114 elo which is just absurd( For the unknown, 100 in a tier=Rank up). Plus he ain't the only one. Saw many other posts where others experienced as well. Is this some sort of bug that might get fixed soon?
Or is Riot trying to push people in upper ranks?