This provides a potential alternate source of the gold in the artifacts. The gold might have come, not from the ancient mine, but from nearby riverbeds. These riverbeds likely have the same element ratios as that of the ancient mine, because the gold is from the same deposit.

If anything, this might strengthen the argument by making the connection between the artifacts and the mine more plausible.

This might strengthen the argument by eliminating the possibility that the ancient mine wasn’t in existence when the artifacts were made.

This suggests the gold in the artifacts might have been taken from earlier artifacts. But this doesn’t affect the original source of the gold; it could have been dug from the ancient mine and simply used in various artifacts over the years.

If anything this might strengthen the argument by suggesting the gold in the mine could have spread far and been used to make various items, potentially including the artifacts that we’re talking about.