just found a similar one in the citadel, this is what I did, when you first go in on the left is a block (about the same size as the one in the middle of the cave) I jumped on and crouched/walked towards the chest, there is a gap between that block and the ceiling to floor block that the chest is in, I sprinted and slid towards the middle of that and slid again to the chest, hardest 2 spirit bloom ive ever got :(