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Gneiss, a foliated metamorphic rock. Quartzite, a non-foliated metamorphic rock. Foliation in geology refers to repetitive layering in metamorphic rocks. [1] Each layer can be as thin as a sheet of paper, or over a meter in thickness. [1] The word comes from the Latin folium, meaning "leaf", and refers to the sheet-like planar structure. [1]
Geological map of the Hebridean Terrane showing distribution of rocks of the Lewisian complex Undeformed Scourie dyke cutting Lewisian Gneiss, about 1.6 km west of Scourie Scourie dykes (now foliated amphibolites) cutting grey gneiss of the Scourie complex, both deformed during the Laxfordian tectonic event and cut by later (unfoliated) granite veins - road cutting on the A838 just north of ...
Augen gneiss, from the German: Augen, meaning "eyes", is a gneiss resulting from metamorphism of granite, which contains characteristic elliptic or lenticular shear-bound grains (porphyroclasts), normally feldspar, surrounded by finer grained material. The finer grained material deforms around the more resistant feldspar grains to produce this ...
An almandine-garnet growing as a porphyroblast in a quartzitic gneiss. The garnet measures 3 cm. Location: Paraíba, Brazil. Dark-coloured porphyroblasts of garnet in mica schist at Syros, Greece. A porphyroblast is a large mineral crystal in a metamorphic rock which has grown within the finer grained matrix.
The granites pass into gneiss and granulite; the gabbros into flaser gabbro and amphibolite; the slates often contain andalusite or chiastolite, and show transitions to mica schists. At one time these rocks were regarded as Archean gneisses of a special type.
The Acasta Gneiss Complex is a heterogeneous assemblage of foliated to gneissic tonalites, trondhjemites, granodiorites, and granites which contains minor quartz-diorites, diorites, gabbros, and ultramafic rocks.
Amphibolite from Cape Cod, Massachusetts Garnet bearing amphibolite from Val di Fleres, Italy. Amphibolite (/ æ m ˈ f ɪ b ə l aɪ t /) is a metamorphic rock that contains amphibole, especially hornblende and actinolite, as well as plagioclase feldspar, but with little or no quartz.
Foliated metaconglomerate is created under the same metamorphic conditions that produce slate or phyllite, but with the parent rock being conglomerate, rather than clay. [2] The metaconglomerates of the Jack Hills of Western Australia are the source rocks for much of the detrital zircons that have been dated to be as old as 4.4 billion years.