Restoring Jarrah out door setting

Hi
trying to restore a Jarrah out door setting - having a problem sanding back to bare timber as the surface is sticky and clogging sandpaper it appears the setting has been treated before. My question: is there a chemical that could remove the previous sticky oil to make sanding easier? or some other method?

First, wash it down with warm water and detergent to get rid of the surface dirt, thentry turps on a rag, but test it first on an area out of sight. If the rag darkens in colour, you will be taking off the coating, probably outdoor furniture oil.