Differences between matrix and cement in sedimentary rocks
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Answer:
Sandstones are composed principally of three fundamental kinds of constituents: framework grains, matrix, and cement. In addition, replacement minerals and open pore space may be present.
Framework grains are coarse silt- and sand-size (0.03–2.0mm) detrital particles that include quartz, feldspars, coarse micas, and heavy minerals.
Matrix is finer-grained material that fills interstitial spaces among framework grains. The upper size limit of material in sandstones considered to be matrix is arbitrary and debatable; however, a maximum size of 0.03mm appears to be favored by many workers. The most common matrix minerals in sandstones are fine silica minerals, feldspars, micas, clay minerals, and chlorite. Matrix may make up trace amounts to a few tens of percent of the total rock volume. Siliciclastic rocks that contain more matrix-size material than framework grains are generally considered to be shales or mudrocks.
Cements are authigenic minerals that fill interstitial areas that were originally open pore spaces. Cement crystals may be any size up to or larger than the sizes of the individual pores they fill. A single crystal of calcite, for example, can fill several adjacent pores. Cements visible under a petrographic microscope rarely make up more than about 30 percent of the total volume of sandstones and commonly are much less abundant. Several minerals may act as cements in sandstones; however, clay minerals, carbonate minerals, and quartz are particularly common cements; see, for example, Morad (1998a) and Worden and Morad (2003).
Because some cements can be composed of very fine-size crystals, an investigator may find it extremely difficult, by standard petrographic examination, to differentiate between matrix and fine-grained cements such as clay-mineral cements. In fact, the difference between such fine-grained cements and matrix tends to become a matter of semantics if the matrix is authigenic. Earlier workers assumed that most matrix in sandstones was detrital; that is, it was sedimented along with framework grains at the time of deposition. That point of view has undergone considerable revision. It now appears that most transport and depositional processes separate clay-size grains from coarser detritus, so that most sand when initially deposited contains very little if any matrix.
Current views suggest that much, if not most, matrix in sandstones originates (1) by postdepositional infiltration of clay into interstitial spaces, particularly in fluvial deposits or (2) as an authigenic filling owing to diagenetic alteration of unstable rock fragments, feldspars, and ferromagnesian minerals. With respect to infiltration, Matlack et al. (1989) conclude on the basis of experimental work that vadose infiltration of muddy water through sand is an effective mechanism for emplacing clay into sand. They suggest that this infiltration occurs most effectively in environments characterized by high suspended sediment concentration, fluctuating water levels, and minimum sediment reworking by waves or currents.
Alteration of framework grains during diagenesis may also produce significant amounts of clay matrix and cement. Alteration takes place mainly by dissolution and replacement of framework grains, and the alteration products are reconstituted as clay minerals, chlorite, micas, and fine quartz and feldspar.
Explanation:
Answer:
The correct answer to this question is the sedimentary material between coarse- and fine-grained particles are called a matrix. Cement, on the other hand, is the binding substance and is either siliceous
Explanation:
Given - Matrix and cement in sedimentary rocks.
To Find - Differences between matrix and cement in sedimentary rocks.
The sedimentary material between coarse- and fine-grained particles is called a matrix. Cement, on the other hand, is the binding substance and is either siliceous or carbonate that has precipitated from the formation's moving fluids. The matrix of sedimentary rocks is made up of bigger grains or clasts that are embedded in finer-grained sedimentary material, such as clay or silt. Additionally, it's used to define the type of rock that a fossil is lodged in.
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