really? I never knew that. Green tea doesnt have a lot of caffiene but I dont knw about theine? All teas have tannins but I dont think thats what you're talking about.
Iron shouldn't be too much of a problem though unless you have another medical condition aside from 'vegetarianism' hehe. I am on off vego, and had a friend who had never eaten meat in her life, we drank tea all the time. Iron is something you can build up though, so if you were having problems you could stop drinking tea, take iron tablets for a few weeks and you should be alright again.