Horse (geology)

A horse, in geology, is any block of rock completely separated from the surrounding rock either by mineral veins or fault planes.

In mining, a horse is a block of country rock entirely encased within a mineral lode.

[1] In structural geology the term was first used to describe the thrust-bounded imbricates found within a thrust duplex.

[2] In later literature it has become a general term for any block entirely bounded by faults, whether the overall deformation type is contractional, extensional or strike-slip in nature.

This tectonics article is a stub.

Diagram showing development of thrust-bounded horses within a thrust duplex
A horse sits between the walls of this normal fault located near Upheaval Dome , Utah . The fault plane traces from the upper right to the lower left of the image. The horse is the broad lens-shaped feature in the rock defined by the splitting and rejoining of the trace of the fault plane.