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 rocks cemented together by a fine-grained matrix. The word has its origins in the Italian language, in which it means "rubble". A breccia may have a variety of ...

(rock composed of broken fragments of

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

or rock cemented together by a fine-grained

matrix Matrix most commonly refers to: * ''The Matrix'' (franchise), an American media franchise ** '' The Matrix'', a 1999 science-fiction action film ** "The Matrix", a fictional setting, a virtual reality environment, within ''The Matrix'' (franchi ...

), 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, petrifaction or petrification () is the process by which organic material becomes a fossil through the replacement of the original material and the filling of the original pore spaces with minerals. Petrified wood typifies this p ...

. 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 , most commonly found in nature as quartz and in various living organisms. In many parts of the world, silica is the major constituent of sand. Silica is ...

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

copper Copper is a chemical element with the symbol Cu (from la, cuprum) 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 pink ...

and

uranium Uranium is a chemical element with the 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. Uranium is weak ...

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

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

, 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.

Occurrence

Areas that contains many examples of breccia pipes include Copper Creek, Arizona, which contains approximately 500 mineralized breccia pipes,Geology And Geochemistry of the Mammoth Breccia Pipe, Copper Creek Mining District, Southeastern Arizona
/ref> and the

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile ...

mining area of

Cripple Creek, Colorado Cripple Creek is a statutory city that is the county seat of Teller County, Colorado, United States. The city population was 1,155 at the 2020 United States Census. Cripple Creek is a former gold mining camp located southwest of Colorado Sprin ...

which contains breccia pipe ore deposits associated with a

volcanic A volcano is a rupture 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 found where tectonic plat ...

diatreme A diatreme, sometimes known as a maar-diatreme volcano, is a volcanic pipe formed by 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 wate ...

References

{{reflist Igneous petrology Economic geology

Characteristics

Origin

Occurrence

See also

References