Question

where are metamorphic rocks found

Answer 1

Metamorphic rocks form when existing rocks (sedimentary, igneous, or older metamorphic rocks) are changed by heat, pressure, and chemically active fluids. They are typically found in these settings:

- Convergent plate boundaries and mountain belts (regional metamorphism): deep roots of mountains such as the Himalaya, Alps, and Appalachians expose large areas of schist, gneiss and slate.
- Around igneous intrusions (contact or thermal metamorphism): metamorphic aureoles form around plutons; examples include hornfels and contact-metamorphosed marble or skarn near intrusions.
- Subduction zones (high-pressure, low-temperature metamorphism): blueschist and eclogite form in subducting slabs and accretionary prisms.
- Continental shields and cratons (exposed basement): very old metamorphic rocks like gneiss and migmatite are exposed in the Canadian Shield, Scandinavian Shield, and African cratons.
- Metamorphic core complexes and fault zones: deep crustal rocks brought to the surface by extensional faulting can expose metamorphic rocks.
- Near-surface outcrops, quarries and roadcuts: uplift and erosion can expose metamorphic rocks at the surface, where they’re quarried for building stone.

Common types and where they occur: slate (low-grade, from shale) in mountain regions and roof-slate quarries; schist and gneiss in mountain belts and shields; marble where limestone has been heated (often near intrusions); quartzite where sandstone was metamorphosed.

So you’ll find metamorphic rocks both deep in the crust (where they form) and at the surface wherever uplift and erosion have exposed those deeper rocks.