I noticed those weird looking contacts on an Emirates Boeing 777-300 flight's headphone jack.
Any idea what those additional contacts do?
This appears to be a type of MJU (Magnetic Jack Unit) as seen here:
According to the literature at that site the silver-like contacts are magnets that allow for easy break-away if a passenger puts too much strain on the jack, say when getting up from their seat (which apparently is a big maintenance issue for the airlines) and avoids damaging the jack.
As for the gold-like contacts, they appear (as lrked states above) to power noise cancellation headphones. Some of these jacks support automatic noise reduction with regular headphones (the grey circle at the top of the jack might be the microphone that would be needed to do this). The website also state that with their other jacks that have more contacts, they can supply digital audio and even VOIP (Voice Over IP, or telephone service using Internet Protocol). It looks like there are also companies that supply special higher-end headphones for these types of IFE (In-Flight Entertainment) connections as well, and most of them support noise reduction.