I've seen trees completely enclose chains, fences, wires, etc. It isn't necessarily a death sentence if the cambium grows back together over the wire. Can you post photos?
How old is "old"? Did you plant this tree, and can you also send a photo of the entire tree, with a good look at the base of it?
There is a sick tree treatment
that is good on general principles, and there may be girdling roots if this tree once was in a black plastic pot from a nursery. You can size down digital photos to about 1000px wide that should fit on this site (it doesn't like very large photos, hence reducing it to 72dpi and making it screen size) or host them to an account like Flickr or Picasa or Photobucket. Link back from there using the IMG button.