Debris rocks (also clastic rocks , clastolites ) are sedimentary rocks of exogenous origin , which mainly contain fragments of other rocks or minerals .
Content
Education and composition
The detrital rocks are diverse in origin and deposition methods. Debris is formed as a result of weathering , volcanism , tectonic and man-made processes. Sorting and rounding debris associated with their transfer under the influence of streams of water, wind and ice movement.
In the clastic rocks, there are fragments of igneous , metamorphic , sedimentary and technogenic rocks, as well as fragments of many minerals, including quartz , feldspar , mica , amphibole , pyroxenes , and occasionally glauconite . Organic rocks are also found in the rocks - shells, fragments of skeletons and tree trunks.
Fragments in clastic rocks can be bonded with a “cement” aggregate (“cemented” rocks), if there is no cement, the rocks are called uncemented (“loose”). According to their composition, cements are flint (for example, opal , chalcedony , quartz ), ferric oxide ( limonite , goethite ), carbonate ( calcite , dolomite ), clayey , bituminous .
Since the debris has a more ancient origin than the rocks themselves, their material suggests sources of demolition, and the particle size parameters help determine the sedimentation regime.
Classification
Debris is classified according to external signs ( granulometric and cemented):
| Group of rocks | Debris size | Not cemented | Cemented | ||
|---|---|---|---|---|---|
| Rolled | Not rounded | Rolled | Not rounded | ||
| Coarse clastic rocks ( psephytes ) | 10 - 1 m | Block boulders | Lumps | - | - |
| 1 m - 10 cm | Boulder | Break off (blocks) | Boulder conglomerate | Breakaway (block) breccia | |
| 10 - 1 cm | Pebble | Rubble | Pebble conglomerates | Macadam breccia | |
| 1 cm - 2 mm | Gravel | Dressva | Gravelites | Dresvyaniki | |
| Sands ( psammites ) | 2 - 0.05 mm | Sands | Sandstones | ||
| Dusty rocks ( silts ) | 0.05 - 0.005 mm | Aleurite | Alevrolity | ||
| Clay rocks ( pelites ) | <0.005 mm | Elah , clay | Clay , mudstone | ||
Since debris of different sizes are usually mixed, they release:
- monomichtic (unmixed) rocks with 90% or more predominance of one type of debris (examples are monomineral sands, many breccias);
- oligomiktovye (weakly mixed) with a predominant component in the amount of 75-90%, (oligomiktovy argillite and sandstone conglomerates);
- mesicic (medium-mixed) with a content of the predominant component of 50-75%, (volcanite-sementite tresheniki);
- polymictic (multicomponent, strongly mixed) rocks without a predominant component.
Monomiktovye rocks are less common, polymictic - most often.
Within categories, grouped by appearance, clastic rocks are also subdivided according to their composition, some petrographic types have their own names, for example, arkosa , greywacke .
Prey
The detrital rocks enclose minerals (for example, as collectors for oil and gas fields and groundwater deposits) and are developed by themselves as building materials (gravel, sand, sand and gravel, strong conglomerates, breccias, sandstones), raw materials for the production of building materials ( quartz sands for glass, siltstones for cement, expanded clay ), a molding material in metallurgy (sands).
The types of deposits of fragmental rocks associated with the features of their accumulation:
- colluvial plumes at the bottom of the slopes;
- proluvial and alluvial exhaust cones created by the flow of water, alluvial ribbon-like bodies along the river bed;
- “Seas” of desert sands in deserts created by the wind;
- belt in the surf zone of the seas and oceans.
Literature
- Clastic rocks / V. Frolov // Nikolay Kuzansky - Ocean. - M .: The Great Russian Encyclopedia, 2013. - (The Great Russian Encyclopedia : [in 35 tons.] / Ch. Ed. Yu. S. Osipov ; 2004–2017, vol. 23). - ISBN 978-5-85270-360-6 .
- Debris rocks // Geography. Modern illustrated encyclopedia. - M .: Rosman. Edited by prof. A. P. Gorkina. 2006
- Clastic rocks // Brockhaus and Efron Encyclopedic Dictionary : 86 tons (82 tons and 4 extra). - SPb. , 1890-1907.
From BDT:
- Proshlyakov B. K., Kuznetsov V. G. Lithology. M. , 1991.
- Frolov V. T. Lithology. M. , 1993. T. 2.