Batholiths and Dikes

Batholiths
Batholiths are huge emplacements of igneous intrusive (also known as plutonic) rock that forms from cooled magma deep in the crust of the earth. Batholiths are almost always made generally of felsic or intermediate rock-types, such as granite, quartz monzonite, or diorite. Batholiths can cover very large areas some of them extend for thousands of miles and have been discovered in Idaho, as well as in the Rocky Mountains and under the Sierra Nevada mountains in California.

Dikes
A dike in geology refers to an intrusive igneous body. The thickness is typically a good deal smaller than the other two dimensions. The thickness can be different from sub-centimeter scale to several meters in thickness and the lateral dimensions can expand over many kilometers.

A dike is an intrusion into a cross cutting crack, in other words a dike cuts across other already existing layers or bodies of rock, this means that a dike is always younger than the rocks that enclose it. Dikes are generally high angle to almost perpendicular in orientation, although succeeding tectonic deformation can alternate the succession of strata through which the dike lies so that the last turns out to be horizontal. Almost horizontal or conformable intrusions along bedding planes between strata are what are known as intrusive sills.

In most cases dikes form as either radial or concentric swarms around plutonic intrusives or around volcanic necks or feeder vents in volcanic cones. These are commonly known as "Ring Dikes”.

Dikes can additionally differ in texture and composition meaning they can be diabase or basaltic or granitic or rhyolitic. Pegmatite dikes are particularly coarsely crystalline granitic rocks frequently connected with late stage granite intrusions or metamorphic segregations. Aplite dikes are fine grained or have a sugary textured intrusive that have a granitic composition.