•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)