You broke a shear pin. It is a small pin that goes through the shaft that the tines are welded onto. It's purpose is to prevent damage to the machine from a foreign object being scooped up by the tines. Rather than damaging the engine and drive shaft the shear pin breaks allowing the drive shaft to continue to spin unfettered. You should be able to get new shear pins from any Ariens dealer for around $10 and it should take about 5 minutes to fix this problem.