The 31,898 dwt bulk freighter Cosco Jinggangshan collided with the anchored 84,040 dwt tanker Aeolos at Gibraltar.   The freighter had arrived at Gibraltar for bunkering and was leaving the  port when it struck the tanker.   No damage reported on either vessel.   The Cosco Jinggangshan was ordered back to port as authorities conduct an investigation into the incident.   No reports of injuries or pollution being released.