A
breccia pipe, also referred to as a
chimney, is a mass of
breccia (rock composed of broken fragments of
minerals or rock cemented together by a fine-grained matrix), 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
Silicification. They usually consist of fragments of the host rock (the rock layer they are contained in) cemented together by
silica. They can also be cemented by finely ground host rock called rock flour. These formations are often hosts for
ore deposition especially in
copper and
uranium mining districts.
[ Descriptive Model of Solution Collapse- Breccia Pipe Uranium Deposits
] They are sensitive to
oxidation, 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 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 contain many examples of breccia pipes include Copper Creek, Arizona, which contains approximately 500 mineralized breccia pipes,[
]
See also
