Matrix (geology)
The matrix is the fine material between larger grains or particles and is described in the petrography of sedimentary rocks.
In siliciclastic sedimentary rocks, the boundary between the matrix and grains is drawn at 62.5 microns, with limestones, the limit is even smaller, but very different values (> 4 microns and < 20 or <50 microns ). The particles in the matrix can "float" or support each other. The use of the term matrix is only useful when a sand or limestone contains larger or much differently sized particles. Rocks uniform particle size can be according to their grain size indicates ( Lutit, Siltit, arenite or Rudit ) or even after the crystal size ( finely crystalline, coarsely crystalline, etc.). If there is no matrix for particle rocks, the interstitial space with diagenetic precipitates (cement ) or air or water can be filled ( pore space with weakly consolidated sediments or unconsolidated sediments ). The arrangement and distribution of the grains, their texture and structure form a scaffold that document the formation conditions and the Diagenesegeschichte of the rock.
Definition
Some authors describe the concept matrix even further and put it with the term " matrix " is equal, ie also the interstitial, coarse-grained cement ( sparite ) is called the matrix. However, this view contradicts the actual meaning of the matrix, ie the deposition of fine-grained material between particles or the storage of individual larger particles in fine-grained material. The term matrix is thus the overarching term, ie he referred to the case of particle rocks and cement matrix.
However, can not be called between the particles of limestone as a matrix of each fine-grained material. The fine-grained material may also have arisen through intensive Mikritisierung, compaction or diagenesis. Can this development process are proven or probable, it is also called a pseudo -carbonate matrix.
Matrix of igneous rocks
The term matrix is sometimes also used in the petrography of igneous rocks. Since there really are no particles at magmatic rocks in the above sense, but only different sized crystals, here the term is used somewhat differently. Therefore, in this area the designation preferable porphyritic texture.