Metamorphic Rocks Francis, 2014

paragoniteNaAl 2 (AlSi 3 O 10 (OH) 2 muscoviteKAl 2 (AlSi 3 O 10 (OH) 2 pyrophylliteAl 2 Si 4 O 10 (OH) 2 andalusiteAl 2 SiO 5 or Al 2 OSiO 4 kyaniteAl 2 SiO 5 or Al 2 OSiO 4 sillimaniteAl 2 SiO 5 or Al 2 OSiO 4 staurolite(Fe,Mg) 2 Al 9 O 6 (SiO 4 ) 4 (O,OH) 2 chloritoid(Fe,Mg) 2 Al 4 O 2 (SiO 4 ) 2 (OH) 4 cordierite(Fe,Mg) 2 Al 3 (Al,Si 5 )O 18.nH 2 O garnet(Fe,Mg) 3 Al 2 (SiO 4 ) 3 chlorite (Mg,Fe) 3 (Al,Si 3 )O 10 (OH) 2  (Mg,Fe) 3 (OH) 6 biotiteKFe 3 (AlSi 3 O 10 (OH) 2 zoisite - epidote Ca 2 (Fe,Al) 3 O(SiO 4 )(Si 2 O 7 )(OH) tremolite/ actinoliteCa 2 (FeMg) 5 Si 8 O 22 (OH) 2 Metamorphic Minerals AFM projection for Metapelites andalusite kyanite sillimanite staurolite

Sillimanite Staurolite Cordierite / Pyrox Andalusite Kyanite Garnet /Biotite Actinolite Hornblende Chlorite Muscovite K-Spar

Metamorphic Facies : A metamorphic facies is the set of mineral assemblages that are stable over a given range of P and T. The actual mineral assemblage within this set that a given rock exhibits is a function of its chemical composition. The delineation of the metamorphic facies commonly used today is a matter of historical development that predates actual experimental determination of pressures and temperatures. The division of the P-T metamorphic regime into the following metamorphic facies developed from field observations on the persistence of certain mineral assemblages for specific bulk compositions in geographic and thus P-T space: Zeolite - zeolites or clay minerals, calcite and/or quartz-filled amygdules Greenschist - green minerals: chlorite, actinolite, epidote Blueschist - blue amphibole, aragonite Amphibolite - dark amphibole (hornblende), garnet Granulite - absence of hydrous minerals and thus schistoscity, granular Eclogite - pyropic garnet & jadeiitic clinopyroxene – high pressure

bedding Slate vs Shale Harder and cleavage at an angle to bedding Extremely fine-grained rock exhibiting a perfect planar cleavage defined by the alignment of sub-microscopic phyllosilicates grains. Distinguished from shale by its greater hardness and the fact that cleavage is generally at an angle to bedding.

Phylites to Schists micaceous foliation with sheen or visible mica xyls garnet muscovite schist cordierite muscovite schist

Schists

Metapelites in the Amphibolite Facies kyanite staurolite schist garnet staurolite schist andalusite kyanite sillimanite No amphiboles because of the lack of Ca

amphibolites basaltic bulk compositions Typically characterized amphibole-defined lineation, rather than mica-defined foliation Hornblende Plag garnet

Amphibolites Hornblende garnet Plag

Gneiss Gneissosity: Compositional layering produced by metamorphic (solid-state) segregation into alternating felsic (leucosomes) and mafic (melanosomes) layers.

Gneiss

granulite garnet-orthopyroxene-cordierite granulite garnet sillimanite gneiss andalusite kyanite sillimanite Feldspar is granular rather than lath-like.

partial melting migmatites and diatextites

diatexite, Hortavaer Complex, Norway partial melting migmatites and diatextites

Metamorphosed Carbonates marble: crystalline metamorphosed limestone. skarn: calcium-rich contact-metasomatic rock – contains abundant calc-silicate minerals ± carbonate formed at the contacts between magmatic intrusions and dirty carbonate rocks. Gross DiopideCaMgSi 2 O 6 GrossulariteCa 3 Al 2 (SiO 4 ) 3 CalciteCaCO 3

andalusite kyanite sillimanite High-pressure rock of basaltic composition dominated by pyropic garnet (Mg 3 Al 2 (SiO 4 ) 3 ) and jadeitic (NaAlSi 2 O 6 ) clinopyroxene  kyanite (never sillimaniteassociated, with of diamonds. More mafic compositions of with similar mineralogy are termed garnet clinopyroxenites. Eclogite

Mylonite / Tectonite Extremely fine-grained rock exhibiting fine parallel gneissic banding over extensive strike lengths, produced by extreme strain. Typically possess a pronounced mineral lineation parallel to the transport direction, commonly have rotated porphyroblasts

Metapelites AFM Projections Shales are typically depleted in Ca and Na because they were lost to solution during the breakdown of tecto-, ino-, and orthosilicates to clay minerals during weathering. Furthermore, quartz and muscovite are typically ubiquitous phases in metapelites. As a result, we can project the compositions of metapelites into a simplified ternary system (end-members: Al 2 O 3 * (A), FeO (F), and MgO (M)), assuming that quartz and muscovite are always present. Components = 6: K 2 O, Al 2 O 3, SiO 2, FeO, MgO, H 2 O With excess quartz & water: C = 4 and F = 4 - P + 2 If muscovite is present, we can project the mineral assemblages onto the Al 2 O 3 – FeO – MgO plane, where: C = 3 and F = 3 - P + 2 thus F = 0 for P = 3, if Press & Temp are fixed

andalusiteAl 2 SiO 5 or Al 2 OSiO 4 kyaniteAl 2 SiO 5 or Al 2 OSiO 4 sillimaniteAl 2 SiO 5 or Al 2 OSiO 4 pyrophylliteAl 2 Si 4 O 10 (OH) 2 paragoniteNaAl 2 (Al,Si 3 )O 10 (OH) 2 muscovite KAl 2 (Al,Si 3 )O 10 (OH) 2 staurolite(Fe,Mg) 2 Al 9 O 6 (SiO 4 ) 4 (O,OH) 2 chloritoid(Fe,Mg) 2 Al 4 O 2 (SiO4) 2 (OH) 4 cordierite(Fe,Mg) 2 Al 3 (Al,Si 5 )O 18.nH 2 O garnet(Fe,Mg) 3 Al 2 (SiO4) 3 chlorite (Mg,Fe) 3 (Al,Si 3 )O 10 (OH) 2  (Mg,Fe) 3 (OH) 6 biotiteK(Mg,Fe) 3 (Al,Si 3 )O 10 (OH) 2 K-feldsparKAlSi 3 O 8 Metapelite Minerals: quartz, muscovite, and :

F = C - P