A tabular, nearly vertical intrusion of igneous rock that forces its way through fractures in pre-existing rock strata. Unlike sills, which run parallel to the bedding planes, dykes cut across the grain of the host rock. In mining, they often act as hard barriers that disrupt coal seams or ore bodies, sometimes altering the surrounding minerals through contact metamorphism.
The main seam pinches out where we hit that basalt dyke, so we'll have to drive through it to pick up the coal on the other side.
Miners often curse dykes because they mean drilling through barren, exceptionally hard rock just to get back into the pay zone.
Also heard as
- dike
Related terms
Fault
A planar fracture in a rock volume across which there has been significant displacement.
Country rock
The pre-existing, non-mineralized rock that surrounds and encloses an orebody or igneous intrusion.
Trouble
A geological disruption such as a fault or washout that interrupts a coal seam or ore body.