I think Romeo's use of the word cannot is to imperative... Partly or wholly decayed organic matter often goes through a stage which creates an activated form of carbon that is known to attract and capture metallic gold.
This is the reason why most coal seams contain small amounts of gold, and so do many peat bog deposits. Even the compacted partly decomposed organic matter underneath swamps have been found to contain unusually pure form of gold. Plants, particularly certain trees, bushes and cat tails, can draw gold out of the soil through their roots. Once inside the plant, the gold is pushed out into the leaves where it can reach concentrations sufficient to be detected and measured by sensitive assay technology.
It is true, however that the nature of most coal deposits tends to make it unlikely that any significant amount of native gold would be released into the environment in spite of carbon-induced concentrations within the coal itself. There are stories about small amounts of placer gold being found in the natural drainage from coal seams, but these deposits are generally not economically sufficient to warrant investment...