A layer of soft, pulverized clay or crushed rock found along a fault plane or at the contact between an ore vein and the host rock. It forms from the grinding action of tectonic movement and often acts as a lubricating layer or an impermeable barrier to groundwater flow.
The hanging wall is going to be treacherous here because there's a thick layer of gouge right on the contact.
Finding gouge usually means you are looking at a fault zone, which implies weak ground conditions that will require extra support.
Also heard as
- fault gouge
- clay gouge
Related terms
Fault
A planar fracture in a rock volume across which there has been significant displacement.
Hanging wall
The block of rock that lies above an inclined fault plane or ore body.
Footwall
The block of rock that lies on the underside of an inclined fault or mineral vein.
Selvage
The boundary layer of altered rock or clay between a mineral vein and the surrounding country rock.