Breccia

ASEMINAR ON

BRECCIAPresented By

Durgesh SharmaM.Sc. (Tech) semester II

Date: 29th March 2016

ContentSr. No. Topic

1 Introduction2 Types of breccia2 2.1 Sedimentary breccia2 2.2 Igneous breccia ● Volcanic

● Intrusive2 2.3 Hydrothermal breccia2 2.4 Tectonic breccia2 2.5 Impact breccia3 Composition of breccia4 Uses of breccia5 Summary6 References

Breccia exposed in the walls of mosaic canyon, Death valley, California, (U.S.A.)

BrecciaBreccia is a rock composed of broken fragments of minerals or rock

cemented together by a fine-grained matrix that can be similar to or different from the composition of the fragments.

Breccia

SEDIMENTARY

IGNEOUSHYDROTHERMAL

TECTONIC

IMPACT

• Sedimentary breccia is a type of clastic sedimentary rock which is made of angular to subangular, randomly oriented clasts of other sedimentary rocks.

• Sedimentary breccias comprise more than 30% gravel-size (>2mm) angular clasts produced by mechanical weathering or brittle deformation of nearby rocks.

• Their angular shape implies minimal transport.

Breccia vs conglomerates

Fig. 1. Chert Breccia: The angular clasts in this breccia are chert fragments. The matrix is an iron-stained mix of clay through sand-size particles. The specimen is about two inches (five centimeters) across.

Fig. 2. Chert conglomerate: The rounded clast in this conglomerate are chert fragments.

Breccia

SEDIMENTARY BRECCIA

IGNEOUS HYDROTHERMAL TECTONIC IMPACT

• Igneous breccias can form during the emplacement of igneous bodies by explosive exsolution of volatile phases and/or explosive interaction of magma with groundwater .

• Intrusive breccias (such as associated with kimberlite pipes) often contain fragments of both intrusive and host rocks.

• Igneous breccia dykes may contain a wide range of rock fragments sampled during magma ascent and thus, provide information about the composition of rocks at deeper levels.

Fig. 3. Basalt breccia; green groundmass is composed of epidote

Fig. 5. Black dibase or diorite brecciated and surrounded by younger, intrusive white granetic material. Specimen from the Hermitage Peninsula, southern Newfoundland

BrecciaSEDIMENTARY

IGNEOUS BRECCIAHYDROTHERMAL TECTONIC IMPACT

Fig. 4 . Igneous breccia

• Hydrothermal breccias are usually formed by hydrofracturing of rocks by highly pressured hydrothermal fluids. Hydrothermal breccias usually form at shallow crustal levels (<1 km) between 150 to 350 °C,

• when seismic or volcanic activity causes a void to open along a fault deep underground. The void draws in hot water , and as pressure in the cavity drops, the water violently boils . In addition, the sudden opening of a cavity causes rock at the sides of the fault to destabilise and implode inwards, and the broken rock gets caught up in a churning mixture of rock, steam and boiling water.

• Volatile gases are lost to the steam phase as boiling continues, in particular carbon dioxide . As a result, the chemistry of the fluids changes and ore minerals rapidly precipitate. Breccia- hosted ore deposits are quite common.

Fig. 6. Hydrothermal breccia in the Cloghleagh Iron Mine, near Blessington in Ireland, composed mainly of quartz and manganese oxides , the result of seismic activity about 12 Ma ago

Fig. 7. Silicified and mineralized breccia. Light gray is mostly dolomite with a little translucent quartz. Dark gray is jasperoid and ore minerals. Veinlet along lower edge of specimen contains sphalerite in carbonates. Pend Oreille mine, Pend Oreille County, Washington

BrecciaSEDIMENTARY IGNEOUS

HYDROTHERMAL BRECCIATECTONIC IMPACT

• In fault zones, where rocks or even continents slide past each other, breccia zones can be created that can vary from inches across to tens of meters across.

• Fault breccia results from the grinding action of two fault blocks as they slide past each other. Subsequent cementation of these broken fragments may occur by means of the introduction of mineral matter in groundwater

Fig. 9. Boulder of a tectonic breccia in the Sous River valley near Alouz, Morocco,derived from Haut Atlas.

Fig. 8. Schematic cross section across fault zones, A shallow fault zone with fault breccia, After Mason (1978).

BrecciaSEDIMENTARY IGNEOUS HYDROTHERMAL

TECTONIC BRECCIAIMPACT

• Impact melt-breccias form by the fracturing and fusion of rocks under extreme pressures and temperatures rapidly induced during meteorite impacts.

• Breccia of this type may be present on or beneath the floor of the crater, in the rim, or in the ejecta expelled beyond the crater.

• Impact breccia may be identified by its occurrence in or around a known impact crater, and/or an association with other products of impact cratering such as shatter cones, impact glass, shocked minerals, and chemical and isotopic evidence of contamination with extraterrestrial material (e.g. iridium and osmium anomalies).

• Impact-melt breccias containing clastic debris and glass fragments produced by meteorite bombardment have been collected from the surface of the Moon during Apollo missions.

Fig. 11. Alamo bolide impact breccia (Late Devonian , Frasnian) near Hancock Summit, Pahranagat Range, Nevada

Fig. 10. Impact crater

BrecciaSEDIMENTARY IGNEOUS HYDROTHERMAL TECTONIC

IMPACT BRECCIA

Apollo 11 breccia

Breccias & Metamorphic clastic rocks

• Clastic metamorphic rocks include breccias formed in faults, Metamorphic rocks can be brecciated via hydrothermal fluids forming a hydrofracture breccia

Fig. 12. Breccia structure in agmatite.

• Agmatite shows breccia like structure

Class - breccia can be divided into two broad classes:

• Clast supported - where the clasts touch each other and the matrix fills the voids;• Matrix supported - where the clasts are not in contact and the matrix surrounds each clast;• Sorting - a breccia comprising a mixture of clast sizes is poorly sorted, while one comprising

mostly clasts of the same size is well sorted;

Fig. 13. Spectrum of grain frameworks of aggregation fragmentites (A-breccias), resulting from deposition and diagenesis (including a post-lithification pressure solution).

What is Composition of Breccia?

• Breccia has many compositions. Its composition is mainly determined by the rock and mineral material that the angular fragments were produced from.

• The climate of the source area can also influence composition. Most breccias are a mix of rock fragments and mineral grains.

• The type of rock that the fragments were produced from is often used as an adjective when referring to the rock. Some examples: sandstone breccia, limestone breccia, granite breccia, chert breccia, basalt breccia and others.

• A breccia where the clasts represent more than one rock type is termed polymictic (or petromictic), while one where the clasts are of a single rock type are monomictic (or oligomictic).

Fig. 14. Polymictic Limestone Breccia: A breccia that contains clasts of multiple types of limestone. Specimen is about four inches (ten centimeters) across.

Fig. 15. Unusual breccia cemented by azurite and malachite , Morenci Mine , Arizona

Fig. 16. Tertiary breccia at Resting Springs Pass, Mojave Desert, California

Fig. 17. Highland breccia, Apollo 16Plagioclase (white)Impact melt? (black)

Uses of Breccia• Breccias have very unique angular textures and

are prized as ornamental rocks for buildings, monuments, grave stones, tiles and many other ornamental uses.

• They have been used by people for centuries for many ornamental uses and some breccias are even considered to be semi-precious and have found uses in jewelry.

• Breccia was used on a limited scale by the ancient Egyptians ; one of the best- known examples is the statue of the goddess Tawaret in the British Museum.

• It was regarded by the Romans as an especially precious stone and was often used in high-profile public buildings.

Fig. 18. Breccia statue of the Ancient Egyptian goddess Tawaret

SUMMARY

• Breccia is a rock formed from angular gravel and boulder-sized clasts cemented together in a matrix.

• Sedimentary breccia: Sedimentary breccia is a type of clastic sedimentary rock which is made of angular to subangular, randomly oriented clasts of other sedimentary rocks.

• Igneous Breccia: A term used for a rock composed angular fragments of igneous rocks. "Flow breccia" and "pyroclastic breccia" could be called "igneous breccia".

• Hydrothermal Breccia: The interaction of hydrothermal fluids with tectonically brecciated rock produces hydrothermal breccias

• Fault Breccia: Broken rock found in the contact area between two fault blocks and produced by movement of the fault.

• Impact Breccia: A deposit of angular rock debris produced by the impact of an asteroid or other cosmic body.

• Composition of breccias : Its composition is mainly determined by the rock and mineral material that the angular fragments were produced from. The climate of the source area can also influence composition.

• Uses of breccia: Building material, decorative stones, tiles, tombstones, monuments, jewelry, aquifers, natural gas and petroleum reservoirs

References

• Buckland, A.J., (1819). Breccia in Staffordshire. Trans. Geol. Soc., 1st Ser., vol. 5 (2), pp. 507.• Geikie, A., (1902). The geology of eastern Fife. Mere. Geol. Surv. Scotland, Nos. 40a, 41, 48a, 49a,

520 pp.• Laznicka, P., (1989). Breccias and ores. Part 1: History, organization and petrography of breccias.

Ore Geol. Rev., vol. 4, pp. 315-344.• Ramsay, A.C., (1855). On the occurrence of angular, subangular, polished and striated boulders in

the Permian Breccia of Shropshire, Worcestershire etc. and on the probable existence of glaciers and icebergs in the Permian Epoch. Q. J. Geol. Soc. London, vol. 11, pp. 185-205.

• Sedgwick, A., (1835). On the geological relations and internal structure of the Magnesian Limestone, and the lower portions of the New Red Sandstone series in their range through Nottinghamshire, Derbyshire, Yorkshire and Durham, to the southern extremity of Northumberland. Trans. Geol. Soc. London, vol. 3, pp. 37-124.

• Web Links:• http://en.m.wikipedia.org/wiki/Breccia• http://www.galleries.com/rocks/breccia.htm• http://www.encyclopedia.com/topic/Breccia.aspx• http://geology.com/rocks/breccia.shtml• https://flexiblelearning.auckland.ac.nz/rocks_minerals/rocks/breccia.html• http://www.impact-structures.com/impact-rocks-impactites/the-impact-breccia-page/

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