2016 03 naturalstone petrology blc · igneous (magmatic) rocks sedimentary rocks metamorphic rocks...

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1 Stony materials and conservation of the built heritage – Petrology _ BR /1 Conservation Science Consulting Sàrl NATURAL STONE 2 - PETROLOGY Stony materials and conservation of the built heritage – Petrology _ BR /2 Conservation Science Consulting Sàrl THE THREE CLASSES OF ROCKS Igneous (magmatic) rocks Sedimentary rocks Metamorphic rocks Stony materials and conservation of the built heritage – Petrology _ BR /3 Conservation Science Consulting Sàrl Cours de pétrologie magmatique en ligne http://www.botanic06.com/site/geol/magma1.htm - 23.09.2016

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Page 1: 2016 03 NaturalStone Petrology blc · Igneous (magmatic) rocks Sedimentary rocks Metamorphic rocks Stony materials and conservation of the built heritage – Petrology _ BR /27 Conservation

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Stony m

aterials and conservation of the built heritage–

Petrology _ B

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Conservation Science Consulting Sàrl

NATURAL STONE

2 - PETROLOGY

Stony m

aterials and conservation of the built heritage–

Petrology _ B

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Conservation Science Consulting Sàrl

THE THREE CLASSES OF ROCKS

Igneous (magmatic) rocks

Sedimentary rocks

Metamorphic rocks

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Cours de pétrologie magmatique en ligne

http://www.botanic06.com/site/geol/magma1.htm - 23.09.2016

Page 2: 2016 03 NaturalStone Petrology blc · Igneous (magmatic) rocks Sedimentary rocks Metamorphic rocks Stony materials and conservation of the built heritage – Petrology _ BR /27 Conservation

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IGNEOUS ROCKS(= formed from a magma)

Magma : molten rocks (silicate solutions) located in the Earth crust or in the mantel

T ≈ 1200 –1500°C

plutonic rocks(intrusives)

magmatic chamber

volcanic rocks(extrusives)

crust

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plutonic rocks volcanic rocks

magma granitic basaltic

origin of the material

crust (metamorphic rocks)

mantel (peridotites)

SiO2 high low

viscosity high low

rocks intrusives extrusives

solidification slow fast

cristallization complete incomplete or non-existent

"Schematic" characterization of the igneous rocks

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Concept of fractional crystallization

https://fr.wikipedia.org/wiki/Cristallisation_fractionn%C3%A9e_%28g%C3%A9ologie%29 – 23.09.2016

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Concept of fractional crystallization

http://www.ggl.ulaval.ca/personnel/bourque/s2/r.ign.html - 23.09.2016

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Mineralogical (or chemical) composition

Classification of magmatic rocks

Structure

Coarse grained

Fine grained, vitreous

PlutonicVolcanic

NAME

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Classification of magmatic rocks

Cardinal minerals (light colours):- quartz- Na,K feldspars- plagioclases (Ca,Na feldspars)- feldspathoids

Essential minerals (dark colours):- micas- amphiboles- pyroxenes- olivine

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Classification of magmatic rocks (simplified)

-------------------Light to dark coloured----------------

According to http://www.ggl.ulaval.ca/personnel/bourque/s2/r.ign.html

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PLUTONIC ROCKS(intrusives)

Some characteristics:

- all the cristals are visible with the unaided eye- the cristals have no particular orientation- the porosity is very little or non-existent- cristals are often well formed (automorphes)

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Plutonic rock: granite (≈95% vol.)

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Plutonic rock: diorite

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Plutonic rock: gabbro

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Plutonic rock: peridotite

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VOLCANIC ROCKS (extrusives)

Effusives and pyroclastics rocks

Some characteristics:

- the matrix is always amorphous, glassy or fine grained- the porosity can be very high (vacuoles in pyroclastic rocks => trapped porosity)- If cristals exist, they can be orientated (=> lava flow)

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Effusive volcanic rocks come from effusive volcanos:

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Effusive volcanic rock: rhyolite

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Effusive volcanic rock: obsidian (rhyolite)

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Effusive volcanic rock: andesite

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Effusive volcanic rock: basalt (≈90% vol.)

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Basalt columns Madagascar

Ireland (Giants Causeway)

Ireland (Giants Causeway)

France (Cessoux)

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Pyroclastic volcanic rocks come from explosive volcanos:

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Pyroclastic volcanic rock: bombs, blocs

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Pyroclastic volcanic rock: pumice (pierre ponce)

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THE THREE CLASSES OF ROCKS

Igneous (magmatic) rocks

Sedimentary rocks

Metamorphic rocks

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Cours de sédimentologie et pétrologie sédimentaire:Prof. Frédéric Boulvain, Uni. Liège BelgiqueCours en ligne:http://www2.ulg.ac.be/geolsed/sedim/sedimentologie.htm - 23.09.2016

Page 10: 2016 03 NaturalStone Petrology blc · Igneous (magmatic) rocks Sedimentary rocks Metamorphic rocks Stony materials and conservation of the built heritage – Petrology _ BR /27 Conservation

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Genesis of the sedimentary rocks

Processes: weathering, transport, sedimentation, diagenesis

Material: terrigenous, allochemical (shells, skeleton,... from the sedimentary basin) orthochemical (chemical precipitation within the sed. basin)

http://www.ggl.ulaval.ca/personnel/bourque/s2/r.sedim.html

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Weathering and erosion

mechanical: mechanical disintegration (freez/thaw, roots of plants)

chemical: the minerals in imbalance with the atmospheric conditions are easily attacked (high temperature minerals or minerals with high solubility)

biochemical: plants take the elements they need from the minerals of the rocks

These 3 mechanisms => erode the preexisting rocks

and produce debris of all dimensions

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Sediment transport

Transporting mediums: rivers, glaciers, wind, ocean currents and tides (marées).

During transportation, edges are smoothed.

Depending on the medium and the energy, transport can last a few hours to several days/weeks/months/years

Deposition occurs when the speed of the transporting medium becomes insufficient to maintain the particles in suspension

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Sedimentation

The transported material accumulates in a sedimentary basin in the form of successive layers whose composition, size of the particles, colour, etc, vary in time => stratifications (cf Gd Canyon, Jura, )

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Sedimentation

Vosgien sandstone (Vosges Mountains, France)

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Diagenesis: transformation of a sediment into a hard rock

Chemical and mechanical processes which modify a sedimentary deposit after its deposition (dehydration, burying, compaction, dissolutions, recrystallizations, neo-formations, cementation)

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Identification criteria of the sedimentary rocks

Stratification:

sedimentary rocks are mostly laminated

(except reef limestone, tuf limestone, glacial moraines)

Fossil content:

presence of substances or objects related to the living world (the hard parts of animals, plants footprints, holes, signs of grazing (pacage) or locomotion)

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- Clastic sedimentary rocks (roches détritiques)

- Biogenic/organic sedimentary rocks (roches biogéniques ou biochimiques)

- Chemical sedimentary rocks (évaporites)

Classification of sedimentary rocks

The classification is based on the formation process.

The subdivisions are based on the chemical composition, the mineralogy or again on the formation process.

(Several classifications exist)

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CLASTIC SEDIMENTARY ROCKS

Composed of fragments of materials derived from other rocks (original rock can be easily identified). Largely composed of quartz with other common minerals (feldspars, amphiboles, clay minerals,…)

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Clastic sedim. rocks / roches sédim. détritiques

Coarse grains

(>2mm)

Rounded clasts (of anyrock type)

CO

NG

LO

RA

TS

S

.L.

Conglomerate(poudingue)

Angular clasts (of any rock type)

Breccia (brèche)

Fine grains

(63μm to 2mm –can be seen / naked eye)

Quartz +/- feldspars, micas, clay minerals –Sandpapery feel and scratches glass

GR

ÈS Sandstone (grès)

Very fine grains

(<63μm –cannot be seen / naked eye)

Quartz + clay minerals

LIT

ES

S.L

.

Siltsone (pélite)

Clay minerals – non laminated

Mudstone (argilite)

Clay minerals –laminated Shale (shale)

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Clastic sedim. rocks / conglomerate (poudingue)

Ex. near Lausanne: the poudingue from the Mont Pelerin

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Clastic sedim. rocks / breccia (brèche)

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Clastic sedim. rocks / sandstone (grès)

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FR, Villarlod, church, May 2009

Clastic sedim. rocks / a kind of sandstone: the molasse sandstone (molasse = grès molassique)

VD, Montheron, church, May 2005

VD, Lausanne, Castel St. Maire, April 2012

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Clastic sedim. rocks / siltstone (pélite)

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Clastic sedim. rocks / mudstone (argilite)

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Clastic sedim. rocks / shale (shale)

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Carbonate rocks: biogenic sedimentary rocks that containcarbonate minerals generated by living organisms (corals, molluscs, foraminifera,…): limestones (calcaires), dolostones (dolomies)

Other organic rocks:

- Siliceous biogenic rocks : diatomite, flint (silex), …

- Carbonaceaous rocks : coal, oil, petroleum…

- Phosphates rocks

Biogenic sedim. rocks= organic or biochemical origin rocks

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Biogenic sedim. rocks / biological

CARBONATE STONES (roches carbonatées)

Mostly calcite (CaCO3)

Fizzes with cold dilute HCl (10%)

Muddy matrix with fossils

CA

LC

AIR

ES

s.l

Fossiliferouslimestone(calcaire fossilifère)

Shells or shell fragments (>2mm) poorly cemented => porous rock

Coquina (calcaire coquiller/ lumachelle)

Shells or shell fragments (<63μm) poorly cemented => porous rock

Chalk (craie)

Shells or shell fragments (<4μm) well cemented => dense rock

Micrite (calcaire micritique)

Mostly dolomite CaMg(CO3)2

Fizzes with hot dilute HCl (10%)

Muddy matrix with or withoutfossils

DO

LO

MIE

Ss.l

Fossiliferous

(or not) dolostone(dolomie fossilifère ou non)

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Biogenic sedim. rocks / limestone (calcaire)

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Biogenic sedim. rocks / dolostone (dolomie)

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Biogenic sedim. rocks / fossiliferous limestone

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Petrology _ B

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Biogenic sedim. rocks / coquina (calcaire coquiller ou lumachelle)

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Biogenic sedim. rocks / chalk(made of coccolithophore)

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Biogenic sedim. rocks / Coccolithophore (plankton)

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Petrology _ B

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Biogenic sedim. rocks / micrite

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Biogenic sedim. rocks / biological

SILICEOUS STONES

Mostly quartz (SiO2)

scratches glass

Made of radiolarians, red or green coloured, dense, alternation of dark and bright layers

Radiolarite

Mostly quartz (SiO2)

scratches glass

Made of diatoms, light coloured, extremely light weight, friable

Diatomite

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Biogenic sedim. rocks / radiolarite(made of radiolarians)

http://www.heilsteinforum.de / 18.09.2014

http://www.praehistorische-lithothek.de /18.09.2014

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Biogenic sedim. rocks / radiolarians (plankton)

Fossilized radiolariansx 150

Today’s radiolariansx 150

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Biogenic sedim. rocks / diatomite (made of diatoms)

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Biogenic sedim. rocks / diatoms (plankton)

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Biogenic sedim. rocks / biological

CARBONACEOUS STONES (roches carbonées)

Dull brown and plant-like

Porous and easy to break apart in plant fragments

Peat (tourbe)

Woody appearance, light weight Lignite

Highly altered plant remains (carbon)

Black, dense and brittle or porousand sooty

Bituminouscoal (charbon bitumineux)

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Biogenic sedim. rocks / peat (tourbe)

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Biogenic sedim. rocks / lignite

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Petrology _ B

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Biogenic sedim. rocks / bituminous coal(charbon bitumineux)

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Chemical rocks are mineral sediments- that result from the evaporation of surficial oversaturatedwater or - that precipitated from mineralized oversaturatedsolutions.

This usually happens in an arid environment with a smallsedimentary basin fed by a limited input of water (evaporites: halite, gypsum,…) or in an environmentwhere water undergoes drastic modifications of pressure/temperature conditions (stalactite, stalagmite, travertine,…).

Chemical sedimentary rocks (évaporites)

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Evaporites

Minerals precipitate out of solution in the reverse order of their solubilities. For ex., the order of precipitation fromsea water is:

1. Calcite (CaCO3) and dolomite (CaMg(CO3)2) 2. Gypsum (CaSO4.2H2O) and anhydrite (CaSO4). 3. Halite (NaCl) 4. Potassium and magnesium salts

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Chemical sedimentary rocks

Mostly calcite (CaCO3)

Fizzes withcold dilute HCl

Spherical grains like tiny beads with concentric laminations

Oolitic limestone(calcaire oolitique)

Banded Travertine

Highly porous, recognizable plant debris (mosses, twigs, leaves) and / or angular gravel

Tuf limestone

Very fine grained Chalcedony (SiO2)

Light coloured, scratches glass

Chert(chaille)

Dark coloured, scratches glass

Flint (silex)

Fine to coarse cristalline gypsum (CaSO4,2H2O)

Can be scratched with fingernail

Rock Gypsum(pierre à plâtre)

Fine to coarse cristalline halite (NaCl)

Salty tasteRock Salt(roche saline)

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Chemical sedim. rocks / oolitic limestone(calcaire oolitique)

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Chemical sedim. rocks / travertine (travertin)

Travertin Gerdoo'i (Iran) Roman travertine (Italy)

http://de.wikipedia.org/wiki/Travertin http://de.wikipedia.org/wiki/Travertin

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Ho

t S

pri

ng

s at

Pam

ukk

ale,

Tu

rke

y

Chemical sedim rocks / travertine (travertin)

http://fr.wikipedia.org/wiki/Pamukkale

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Tuf from Corpataux, Escaliers du court chemin, Fribourg

Chemical sedim rocks / tuf limestone(tuf calcaire)

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Bea

um

e-le

s-M

ess

ieu

rs,

Fra

nce

, Ju

ra

Chemical sedim. rocks / tuf limestone(tuf calcaire)

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Chemical sedim rocks / chert (chaille)

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Petrology _ B

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Chemical sedim. rocks / flint (silex)

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Chemical sedim. rocks / rock gypsum(pierre à plâtre)

Stony m

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Petrology _ B

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Chemical sedim. rocks / rock salt

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THE THREE CLASSES OF ROCKS

Igneous (magmatic) rocks

Sedimentary rocks

Metamorphic rocks

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Metamorphic rocks

A metamorphic rock is the result of the transformation of a pre-existing rock type (protolith), in a process calledmetamorphism. The protolith is subjected to heat, extremepressure and tectonic movements causing profoundphysical and/or chemical change. Protolith = sedimentaryrock, igneous rock or another older metamorphic rock.

Metamorphims ("change in form") = solid state recrystallisation of pre-existing rocks due to changes in heatand/or pressure and/or introduction of fluids withoutmelting. There will be mineralogical, chemical and crystallographic changes

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Limits of the metamorphism

~ 2

00

-3

00

o C

~ 6

50

-7

00

o C

diagenesis melting

solid liquid

metamorphism

Stony m

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Petrology _ B

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Conditions of the metamorphism

Diagenèse

métamorphismerégional

métamorphisme de contact

cond

ition

s no

n ré

alis

ées

dans

la n

atur

e

fusion

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Types of metamorphism

regional m.

contact m.

shock m.

Meteor Crater in Arizona

Stony m

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Cours métamorphisme en ligne :http://christian.nicollet.free.fr/page/enseignement/licencemetam.html -23.09.2016

Cours métamorphisme en pdf:http://christian.nicollet.free.fr/page/Publications/encycl.pdf - 23.09.2016

Stony m

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Petrology _ B

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Orientated or not orientated structures?

Deep in the crust=> isotropic strain=> no orientated structures

Near the surface=> anisotropic strain=> orientated structures

but always very low porosity

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In the compression zones:

- at a shallow depth: onlyfold deformation

- at a medium depth: folddeformation + mechanical flow = schistosity (schistosité)

- at a high depth: schistosity+ alternations of distinct mineral beds = gneisocity(foliation)

- at a very high depth: no orientated structure

http://csmres.jmu.edu/geollab/Fichter/MetaRx/Metatexture.html

DE

PT

H

Orientated or not orientated structures?

Stony m

aterials and conservation of the built heritage–

Petrology _ B

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Classification of metamorphic rocks (simplified)

Schistosity(schistosité)

Clay minerals, micasDense, easy to split into thin sheets

Slate (ardoise)

Micas, chlorite, talc, garnet, kyanite, staurolite, feldspars, quartz, tourmaline,…

Schist

(schiste)

Gneisocity (foliation)

Feldspars, quartz, micas, ferromagnesian minerals –Color banded

Gneiss

Non foliated, non orientated grains

Calcite (CaCO3) Fizzes with dilute HCl Marble

Dolomite (Ca,Mg)(CO3)2Fizzes with dilute HCl only when powdered

Dolomitic marble

Quartz (SiO2) Scratches glass Quartzite

AmphibolesGeneraly black prismatic crystals (2 cleavages 60o/120o)

Amphibolite

Stony m

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Metamorphic sequences

Séquences Roches initialesRoches métamorphiques

(métamorphisme croissant)

pélitique pélites, argilitesschistes -> micaschistes -> gneiss ->

leptynites

arénacée grès, arkoses quartzite -> gneiss -> leptynites

calcaropélitique marnesmicaschistes à mnx -> amphibolites ->

pyroxénites

carbonatéecalcaires et dolomites

calcschistes -> marbres -> cipolins

granitiquegranitoïdes et laves

analogues(protogine) -> gneiss -> leptynites

basiquediorite, gabbros,

basaltesschistes -> prasinites -> amphibolites ->

pyroxénites

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Stony m

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Metamorphic rocks / Slate (ardoise)

Stony m

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Petrology _ B

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Metamorphic rocks / schists

Stony m

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Petrology _ B

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Metamorphic rocks / schists: serpentinite

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Metamorphic rocks / Gneiss

Stony m

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Petrology _ B

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Metamorphic rocks / Marble

Stony m

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Metamorphic rocks / Quartzite

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Conservation Science Consulting Sàrligneous rocks(volcanicrocks)

igneousrocks

(plutonicrocks) sedimentary rocks

metamorphicrocks

magma

melting

rising

crystallization

uplift & exposure

weathering, transportation

depositionin fresh water

deposition in sea water

diagenesis

pressure, temperature & fluid exchange

diagenesis

eruption

+ ++

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