CRJ700 Captain experiences a 'slats fail' CAS message during approach and goes around. Crew complies with checklist procedures and returns for a no slat approach and landing.

Narrative

When executing the visual approach the slats failed to extend when we put the flaps to 8 degrees and we received an associated 'SLATS FAIL' amber CAS message. I leveled the aircraft off at 3;000 FT in preparation for a missed approach and the First Officer informed the Tower of our need to go missed. We were vectored out to the west; switched to Departure who vectored us to the north for another approach. We ran the appropriate QRH checklist. When it became clear that the 'SLATS FAIL' message would not clear and the slats were remaining in the 0 degree position; I declared an emergency. Approach Control asked for and was given the souls on board; total fuel and hazmat information. I then talked to the Flight Attendants and to the passengers and told them what was wrong with the plane and explained that we had declared an emergency and they should not be too surprised by the crash fire rescue vehicles chasing the aircraft down the runway. A message was also sent to Dispatch advising them of the problem and letting them know we were landing in an emergency condition. We were brought about 20-25 miles north of the airport and vectored in for the visual. The rest of the approach and landing was uneventful. After landing I stopped the aircraft off the runway. The emergency vehicles were told that no further assistance was required.We spent some time talking to maintenance while they were working on the plane and the diagnostic computer showed a mechanical jam. I'm not sure if that was true or not; but they were still fiddling with the aircraft when we got off. They seem to think initially that there was a problem with one of the slat actuators; whether or not that was the case remains to be seen.