A shield is generally a large area of exposed Precambrian crystalline igneous and high-grade metamorphic rocks that form tectonically stable areas.
It can be found in high-grade metamorphic rocks, xenoliths and in the groundmass of rhyolite and dacite.
Igneous and high-grade metamorphic rocks are associated with the orogeny.
The low-grade components of the greywackes were derived primarily from volcanic rocks; the high-grade rocks are coarser-grained and contain minerals that reflect higher temperatures.
There is high-grade metamorphic rock originated from nepheline syenite that is characterized by gneiss texture of very rare occurrence.
A common type of granulite found in high-grade metamorphic rocks of the continents contains pyroxene, plagioclase feldspar and accessory garnet, oxides and possibly amphibole.
The eastern portion has high-grade arc-derived rocks ranging in age from 841 to 632 million years ago.
It is rare, but is found in high-grade metamorphic rocks on Madagascar.
These are high-grade metamorphic rocks, but their metamorphism is unrelated to the (later) formation of the Alps.
It is a window (in German fenster) in the Austroalpine nappes where high-grade metamorphic rocks of the underlying Penninic nappes crop out.