What does it mean if someone says that "you're a minefield of information" - after you gave them some useful information. Perhaps they meant "mine of information"? What do both those phrases mean?
Minefield is often used figuratively to refer to something dangerous – to something that may seem harmless, but really isn't. NOAD reads:
There's also a common idiom: he knows just enough to be dangerous, which is used when someone has just a little bit of knowledge about something, but is not very proficient. That little bit of knowledge can give a person a false sense of confidence that can eventually lead to trouble. (For example, if you know a little bit about engines, you might start taking one apart, only to find out you're not going to fix the engine – and you might even have trouble putting it back together again.)
Minefield of information is not an established idiom; it might have been misspoken, misheard, or else it's someone trying to say something humorous, playing off of mine of information, which is used to refer to a person or database where much valuable information can be gleaned. If that information is sometimes faulty, one might say something like:
which I think reads rather clever, but it's not an established idiom. That said, it's not completely original, either; others have used it.
The idiom I'm used to is "a gold mine of information about X," meaning someone who's willing and able to tell you a whole bunch about X. Here's a (not very detailed) verifying link.