The sheet-like body that cuts across rock layers and is produced when magma injected into a fracture is called a dike.

Here's why:

* Dike: A tabular (flat, sheet-like) intrusive igneous rock body that cuts across existing rock layers (strata). They are formed when magma forces its way through fractures or pre-existing cracks in the surrounding rock.

* Sill: A tabular intrusive igneous rock body that is parallel to the existing rock layers. They are formed when magma intrudes between layers of rock.

Let me know if you'd like more information about dikes or sills!