A breccia pipe, also referred to as a chimney, is a mass of

breccia Breccia ( , ; ) is a rock composed of large angular broken fragments of minerals or Rock (geology), rocks cementation (geology), cemented together by a fine-grained matrix (geology), matrix. The word has its origins in the Italian language ...

(rock composed of broken fragments of

minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): M ...

or rock cemented together by a fine-grained

matrix Matrix (: matrices or matrixes) or MATRIX may refer to: Science and mathematics * Matrix (mathematics), a rectangular array of numbers, symbols or expressions * Matrix (logic), part of a formula in prenex normal form * Matrix (biology), the m ...

), often in an irregular and cylindrical shape.

Characteristics

When exposed at the surface, a breccia pipe may appear as an iron-stained knob, from several feet to several hundred feet in diameter. Breccia pipes may or may not be

silicified In geology, silicification is a process in which silica-rich fluids seep into the voids of Earth materials, e.g., rocks, wood, bones, shells, and replace the original materials with silica (SiO2). Silica is a naturally existing and abundant com ...

. They usually consist of fragments of the host rock (the rock layer they are contained in) cemented together by

silica Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundant f ...

. They can also be cemented by finely ground host rock called rock flour. These formations are often hosts for

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically including metals, concentrated above background levels, and that is economically viable to mine and process. The grade of ore refers to the concentration ...

deposition especially in

copper Copper is a chemical element; it has symbol Cu (from Latin ) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkish-orang ...

and

uranium Uranium is a chemical element; it has chemical symbol, symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Ura ...

mining districts.Descriptive Model of Solution Collapse- Breccia Pipe Uranium Deposits
They are sensitive to

oxidation Redox ( , , reduction–oxidation or oxidation–reduction) is a type of chemical reaction in which the oxidation states of the reactants change. Oxidation is the loss of electrons or an increase in the oxidation state, while reduction is ...

, and due to their porous nature, may be oxidized to depths far below the ground surface. Breccia pipes that have never reached the Earth's surface are referred to as "blind".

Origin

Although the origin of breccia pipes is disputed, the most commonly accepted theory is that they formed at intersections of fractures. In these areas,

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

solutions forced their way to the surface. However, there are some breccia pipes that are a result of limestone collapse by acidic water or other soluble rock types. Some breccia pipes show evidence of having been associated with magmatic activity; these breccia pipes were possibly formed by

gas Gas is a state of matter that has neither a fixed volume nor a fixed shape and is a compressible fluid. A ''pure gas'' is made up of individual atoms (e.g. a noble gas like neon) or molecules of either a single type of atom ( elements such as ...

explosions.

Occurrence

Areas that contains many examples of breccia pipes include Copper Creek, Arizona, which contains approximately 500 mineralized breccia pipes, and the

gold Gold is a chemical element; it has chemical symbol Au (from Latin ) and atomic number 79. In its pure form, it is a brightness, bright, slightly orange-yellow, dense, soft, malleable, and ductile metal. Chemically, gold is a transition metal ...

mining area of

Cripple Creek, Colorado Cripple Creek is a List of municipalities in Colorado#Statutory city, statutory city that is the county seat of Teller County, Colorado, Teller County, Colorado, United States. The city population was 1,155 at the 2020 United States census. Cri ...

which contains breccia pipe ore deposits associated with a

volcanic A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often fo ...

diatreme A diatreme, sometimes known as a maar-diatreme volcano, is a volcanic pipe associated with a gaseous explosion. When magma rises up through a crack in Earth's crust and makes contact with a shallow body of groundwater, rapid expansion of heated ...

References

{{reflist Igneous petrology Economic geology

Characteristics

Origin

Occurrence

See also

References