•Cristian Galván Izquierdo •Íker Gil Fabregat •Llàtzer Miguel Valdès

THE METAMORPHIC ROCKS

ÍNDEX●What are the metamorphics rocks?●What are the regional and contact metamorphism?●Which are the metamorphics rocks?●Exemples: Slate, Gneiss, Schist, Marble, Micasquist, Quartzite, Micacita

WHAT ARE THE METAMORPHIC ROCKS?The metamorphic rocks are subjected to metamorphism.Metamorphism is the set of solid state reactions affecting a rock (of any kind be sedimentary, igneous or metamorphic) subject to conditions of pressure and different to its origin temperature.

WHAT ARE THE REGIONAL AND CONTACT METAMORPHISM?

Contact metamorphism is a type of metamorphism in which the change occurs in the rocks by the heat they receive when they are near a magma intrusion.

Regional metamorphism is a type of metamorphism in which the change occurs in conditions of high pressure and sometimes high temperatures.

WHICH ARE THE METAMORPHIC ROCKS?

SLATE (pissarra)It’s formed from metamorphisme of mudstone (argila)

Colour: Black

Fracture: Thin flat layers

Texture: Granular fine and homogeneous

Composition: Crystals not observable to the naked eye

GNEISSIt’s a foliated rock with a banded appearance and granulars mineral grains. It’s formed from granit or clays. It has wavy layers, because of the grains of granit.

Colour: Dark and light stripes

Fracture: Strips

Texture: Planar rude

Composition: Quartz, feldspar and mica.

MICASQUIST

Colour: Gray tones

Fracture: sheet

Texture: Schistose lepidoblastic

Composition: Mica, quartz and other minerals.

SCHIST

Colour: Fairly homogeneous

Fracture: A wavy and irregular structure sheet (schistose structure)

Texture: Flaky

Composition: Muscovite, biotite, chlorite, quartz, plagioclase and chloritoid, staurolite, andalusite, kyanite, garnet, sillimanite

MARBLE It’s formed by metamorphisme of calcareous, so it reacts with hydrochloric acid, and it makes effervescence.

Colour: white, pink, green, … it depends on the impurities.

Fracture: not foliated

Texture: fine to coarse grained,.

Composition: CaCO3, mica, magnesium silicates, graphite, iron oxides

QUARTZITEIt’s formed by metamorphisme of sandstone.

Colour: usually white to gray

Fracture: conchoidal fracture

Texture: coarse texture

Composition: almost entirely of quartz

MICA SCHIST (MICACITA)

Colour: green, grey, dark brown.

Fracture: medium grained.

Texture: foliated, platy.

Composition: quartz and mica (biotite or muscovite)