Accumulation of carbonates

Primary processes



Crystallization of carbonates takes place through direct precipitation from the soil solutions. Fundamentally three types of crystals can be distinguished:

 Microcrystals. Crystallization produces, in most cases, very small, equidimensional crystals, generally micrite, because normally the precipitation takes place quickly.


 Acicular crystals. In other cases the crystallization produces acicular crystals (from 2 µm in diameter and up to 30 µm long) of calcite, called whiskers.

They occur inside discrete pores (channels, vughs), forming pseudomycelia, build up of a network of more or less interwoven crystals inside the voids.


They are found preferably in the upper parts of calcitic horizons and represent a very typical case of the crystallization of pedogenic carbonates. They form a first phase of precipitation of carbonates in the soil and are supposed to be formed at the expense of oversaturated solutions.
 Coarser crystals. Occasionally, when conditions are more favorable for crystallization, carbonates precipitate as crystals of large size (>50 microns).




Carbonates may be formed as a result of the weathering of Ca-bearing minerals, as it is frequently the case for feldspars.



Plants and animals can synthetize carbonates as secondary products of their metabolism.



Index | Processes | Previous | Next