Your tree has Tar Spot. While it looks terrible, it is a cosmetic problem and does not injure your tree. http://www.extension.umn.edu/garden/diagnose/plant/deciduous/maple/leavesspots.html  This only becomes a problem if this occurs for several years in a row. More than likely you will not have the same problem next year.  A combination of humidity and fungi combine to cause this disease.  Sanitation will be important.  Make sure to pick up all leaves and dispose of them.  Do not mulch them into the soil or add to a compost pile.