How do I determine if my contribution to an area of research merits publication?
If you don't submit a paper, you're never going to find out it's publishable—unless someone beats you to it. Basically, if you and your colleagues believe you have a publishable advance, then write it up and submit it. 

On a related note: have you solicited feedback from colleagues in the field? Has it been presented at a conference somewhere? What have you heard and done to "talk the work up" with colleagues? Has anyone told you it is (or is not) publishable?