If you read the Georgia State Parks "Park Rules and Regulations" nothing is said about metal detecting. http://gastateparks.org/rules?s=14418.104.22.168&genstatic=1
It is important to note that Georgia lists some thing like seventy State Parks in its system.
There is a whole page devoted to restrictions for bothhobbyists and professional archaeologists.
1. It is legal to collect artifacts from the surface of dry land on privately owned property if the land is not posted, gated, or fenced against entry. We recommend obtaining written permission from the landowner to protect the property owner's rights and to protect the visitor from trespassing. (OCGA 12-3-621)
2. It is not legal to surface collect, dig, or metal detect on state property. This includes Civil War sites. (OCGA 12-3-10(n), [12-3-52)
1. With the exception of burials and associated objects, archaeological sites belong to the landowner. Landowners can dig archaeological sites - with the exception of burials - that are on their property. DNR recommends that you preserve any archaeological sites that you may own for future generations.
2. On privately-owned land, it is legal to dig for artifacts (including when artifacts have been found by metal detecting) if you have written permission of the landowner. All lands in Georgia are either owned privately or by the local, state, or federal government. This includes Civil War sites. Hobbyists and professional archaeologists alike must determine who owns the land and ask their permission first, before undertaking any activity.
3. It is not legal to surface collect, dig, or metal detect on state property. This includes Civil War sites. (OCGA 12-3-10(n), 12-3-52)