What are the Weathering Products of Rock?



The products of weathering usually include the following

(i) The first products of weathering is a mantle of broken and decomposed material of varying thickness and composition, called the regolith which covers the areas except those from which it is removed as soon as formed.

(ii) Soluble salts, which are produced, are carried away along with the transporting media in solutions.

(iii) Colloidal substances like Al(OH)3 and Fe(OH)3 which are the products of weathering, are carried away by ground water and streams.

(iv) Insoluble products, which include clay minerals, quartz grains, undecomposed feldspars and some resistant minerals like zircon, tourmaline, quartz etc. are usually found at the site of weathering and later transported to the sites of deposition.

All the weathering products are grouped into two categories as:

(a) Transported or mobile and

(b) Residual or sedentary

The products of weathering belonging to the first category are those which are transported over varying distances by mechanical, chemical and biochemical means.

They include various types of clastic and nonclastic sedimentary rocks. The products belonging to the second category are those which are accumulated at the site of destruction of rocks.

These are usually the insouble products of rock-weathering and they still mantle the rocks from which they have been derived.

The most important and immediate results of the weathering processes is the formation of soil. This may be residual or transported.

Weathering also gives rise to residual concentration of minerals of economic importance. Residual concentration results in the accumu­lation of valuable minerals when the undesired constituents of rocks and minerals are removed during weathering.

Bauxite deposits, iron deposits (in the form laterite concretion), manganese, nickel and cobalt deposits are formed in this fashion.

Weathering gives rise to infiltration-deposits through oxidation and secondary enrichment. In such processes, oxidation, solution (leaching) and consequent downward movement of the valuable ore minerals lead to their concentration below the water table due to the existence of reducing condition there. Copper deposits are sometimes formed in this manner.