Metal detecting problem. Mineral overload!?

I was metal detecting on an old river bed. The ground is clay, sand, and quartz beds. I use an IDX Pro with a Black Max 950 Coil. Recently a pond was dug and the dirt spread out over a large area. When I scan the dirt, I get a very strong silver signal over a large area. It seems to be more dense where they dumped the dirt. The mud is streaked with black, white, and yellow. What could this be gold or silver. I live in NW South Carolina, so gold should not be ruled out. Thanks!