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see conglomerateconglomerate,
in geology, sedimentary rock composed largely of pebbles or other rounded particles whose diameter is larger than 2 mm (.08 in.). Essentially a cemented gravel, conglomerates are formed along beaches, as glacial drift, and in river deposits.
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cemented rock composed of angular fragments (sized 1 cm or more). Breccias may be composed of fragments from one rock (monomictic breccia) or several different rocks (polymictic breccia).

Breccias are volcanic (volcanogenic), sedimentary, or tectonic in origin. Volcanogenic breccias originate when the more liquid lava cements together the lava fragments which have formed during the crushing and breakdown of flowing viscous lava (lava breccia), during the agglomeration of tuff and other volcanogenic elastic materials (tuff breccia), and during the diagenesis of mud flow deposits in volcanic regions (lahars). Sedimentary breccias are formed in continental conditions during the cementation of talus deposits and mud-flow deposits from lahars, and during the collapse of the roofs of karstic cavities (karst breccia). A specific type of breccia is bone breccia, which originates in places where the mass destruction and burial of vertebrates has occurred. In maritime areas breccia originates as a result of the destruction of littoral rocks or reefs. Tectonic breccias (friction breccia) are formed in a rock stratum during tectonic movements when rock is crushed along the fractures. Large fragments in this case are usually buried in a finely granulated mass.



A rock made up of very angular coarse fragments; may be sedimentary or may be formed by grinding or crushing along faults.


Any stone composed of angular fragments embedded and consolidated in a finer ground. Numerous marbles owe their distinctive appearance to brecciation.
References in periodicals archive ?
Thermal metamorphism was probably due to a combination of the following heat sources; the decay of short-lived radionuclides, electromagnetic induction during an early T-Tauri stage of the sun, or possibly the brecciated in situ target material being in proximity to an impact-generated melt sheet.
Furthermore, brecciated marbles, given their anomalous colorations, are often used for decorative purposes.
The Raman analyses further revealed that the whitish veins between the brecciated volcanic glass masses consisted of calcite.
The best gold grades are confined within brecciated and altered dolerite with felsic porphyry intercalation and grey quartz vein with fine disseminated pyrite.
A scanning electron microscope (SEM) study of representative drill core samples from the disseminated, massive and brecciated ores has allowed recognition of a number of discrete platinum-group minerals (PGM).
At Planalto, the survey has identified a number of coincident high resistivity and chargeability targets that underlay the silica veined and brecciated rock that has been mapped on surface for a distance of over 2 km.
Following the Namurian sandstone and pelites northwards, another vein deposit has been located at Achmmach, the veins having a quartz-tourmaline brecciated texture lying in an east-west direction.
The 102 channel samples taken across the highly oxidized and brecciated zone returned 2.
All the highly anomalous samples and most of the samples with greater than 20 ppb gold and 5 ppm silver are hosted by highly fractured and/or brecciated quartzite with introduced silica, or by a prominent jasperoid ledge.
The copper mineralization consists of veins of fractured or brecciated quartz with impregnations of ore minerals or their secondary products.
Primary silver mineralization occurs with sphalerite, galena and pyrite in veinlets and in the matrix of a brecciated rhyolite.
Here, a large 3 kilometer zone of sheared and brecciated silicious basalts and sediments occurs that may be analogous to the nearby Ulu deposit.