Gold contained in Tertiary deposits are called ancient placers. These ancient river placers (including those of the Quaternary age) account for the spectacular gold deposits found in California, Alaska, Australia, and South Africa. The older deposits were eroded and reconcentrated and provided the bulk of past gold rush deposits in Northern California Mother Load country.
In some areas, an entire mountain range would have been eroded away over a period of millions of years, leaving what has been called "white" channels which contain only the most resistant materials. These materials would have been quartz, gold, chert, and the platinum materials. The rest of the material would be ground into a fine powder and washed away through river channels and eventually the ocean.
| To the right is a graphic representation of an old Tertiary river deposit that has been covered with another deposit. |  |
Many of these old river channels were extensive and as river channels do today, they included bench gravels and terrace gravels that are of interest to the small scale miner today. These structures if identified can contain more placer gold deposits than the current river channels do. For a quick survey, try using a metal detector to search the side of the exposed deposit.
For more on tertiary deposits see El Paso Mts. visit
References: California Mining Journal, Oct. 1987, pages 53-57.
|
 |
 |