How to judge whether there is placer gold in a river?

The formation of placer gold mainly depends on three factors: placer gold supply source, hydrodynamic conditions and landform characteristics. This paper focuses on the comprehensive analysis of the distribution characteristics of placer gold from these three aspects

1. The distribution of placer gold is strictly controlled by gold-bearing bodies.

"Gold-bearing body" is the material basis of placer gold formation, which directly affects the distribution of placer gold. The so-called "gold-bearing bodies" mainly include rock-gold mineralized bodies, associated gold deposits (points) and strata and rock bodies with high gold abundance.

Actual data show that:

(1) The distribution of most placer gold deposits is closely related to the genesis of rock gold deposits, but a few are limited by other geological conditions. Although the distribution of rock gold deposits does not necessarily form placer gold deposits. For example, Xiaoqinling is a rock gold metallogenic area, and due to the limitation of topography and other conditions, placer gold deposits cannot be formed. On the contrary, in the northern Daxing 'anling and Altay areas, placer gold is dense, and some primary gold deposits or mineralization points have been found.

(2) The placer gold metallogenic areas are mostly distributed in ancient basement strata with high gold abundance and large intrusive rock denudation areas.

(3) The material source of most placer gold deposits is multi-source. For example, the material source of placer gold deposits in the gold basin is mainly the gold-bearing conglomerate layer of the Lower Cretaceous, followed by the dispersed gold-bearing quartz veins and Jurassic gold-bearing conglomerate in Erdaowa Group. Another example is that the gold-bearing quartz veins in the medium-acid magmatic rocks distributed in a large area on both sides of the Hunchun River, the associated gold deposits around the gold-bearing fractured alteration zone and the tertiary gold-bearing conglomerate are the supply sources of placer gold.

(4) Placer gold deposits are mainly formed by enrichment in water basins. For example, the average content of all rivers is 0.0 1g per cubic meter. The content of matrix sometimes exceeds 20 grams per cubic meter.

Extended data:

The process of panning for gold in the sand by Pan Chuan;

Because the density of gold is much higher than that of sand, the sand particles in placer gold mine are carried away by the current under the impact of water, and the gold particles remain in the boat. This is the principle of gold mining with sand. Because of its stable chemical properties, gold generally does not interact with other substances, so it exists in sand in a free state. Under the action of natural weathering, rocks are broken and eventually sand is formed.

The gold is buried in it. Under the action of water flow, sediments and gold particles move with water, and their moving speed and state are different. Therefore, in a certain area of the river bed, a belt rich in gold sands can be formed, which is the gold mining field that people are eager to find. People set up a pan boat here, dug river sand into a gold bucket, and then used a pump to wash away the sand in the bucket. A lot of sand was taken away by the water, leaving golden gold in the bucket.

References:

Baidu encyclopedia-placer gold mine