Well I call it kerosine mainly because of the smell...fuel..not definitive enough for me.
The disc thingy
was exploded out because the oil/air was on fire inside the bearing case.
Now you want to know how the turbine oil got mixed in with the kero...
Well if you look at the photo you will see that the fracture on the part nearest the camera is old. So that pipe has been porous for enough time for the surface to be discoloured.
We know this bearing was in the mid section of the engine. The oil is sent around in pipes which we know are subject to fracture. Air and oil was mixing.
So we have fractured pipes feeding hot oil into the engine domain. The reason why I am convinced this happened is the premature wear on the spline shaft.
Thank you for your comment on my imagination. I can see why the disc exploded out,but I use my imagination to apply a reason for the spline wear. All comments welcome by return.