A Breccia Pipe in the Deseret Limestone, South Flank of the Uinta Mountains, Northern Utah

A breccia pipe is a cylindrical- or irregular-shaped mass of brecciated rock. A breccia consists of broken, angular fragments of rock cemented together by a fine-grained matrix. Hydrothermal breccia pipes form when hydrothermal solutions force their way towards the surface through zones of weakness or fracture zones and naturally break up the rocks in the process, i.e., hydrofracturing; breccia pipes can also form by collapse. Hydrothermal breccia pipes can contain ore deposits and, as will be discussed later, are associated with some large oil and gas accumulations in southeastern Utah.