Metamorphic Facies. Metamorphic Facies. Metamorphic Facies. ERSC 3P21 Metamorphic Petrology II 03/11/2005. Facies

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1 Metamorhic Facies Facies There is a redictable and common corresondence between the of each rock and its Mineral that define the metamorhic indicate that a state of stable has been over a restricted T and P condition. Metamorhic Facies Several different facies have been formally recognized and have been named according to distinct asects of the facies eg. greenschist = characterized by schists in which green chlorite, talc, serentine, eidote and actinolite are redominant Examine the mineralogical characteristics in metamorhosed mafic (basic) rocks subjected to rograde metamorhism 1 Metamorhic Facies Glaucohane Pumellyite Greenschist Eclogite granite Amhibolite Granulite 0 Deth (km) Px Sanidinite Temerature (C) 1

2 Facies s are a grou of white to colourless silicates, analogous in comosition to Common s are: Laumontite - Ca(Al Si 4 )O 1 4H O Heulandite (Ca,Na) (Al Si 7 )O 1 H O Analcime NaAlSi O H O Assemblage qtz + heulandite + chlorite is diagnostic htt:// htt:// - Pumellyite Facies and umellyite, along with the zeolites, commonly occur as fillings in originally vesicular samles Minerals resent are: Ca Al Si 3 O (OH) Pumellyite Ca MgAl (SiO 4 )(Si O 7 )(OH) H O Assemblage qtz + + Pumellyite is diagnostic htt:// htt:// Glaucohane - Facies AKA - Minerals resent are blue in colour Glaucohane - Na MgAl Si O (OH) - CaAl Si O 7 (OH) H O Jadeite NaAlSi O Characteristic of regions of and metamorhism, near zones Assemblage jadeite + qtz + aragonite is diagnostic

3 htt://geosciences.geol.u-sud.fr/objectifterre/mineralogie/mineroolarisant/glaucohane/glaulp.jg htt://ic.ucsc.edu/~rocks/eart005/metamorhic/green_blue.htm htt:// Formation of Blueschists htt:// 1 Glaucohane Metamorhic Facies Pumellyite granite 0 Deth (km) Temerature (C) 3

4 Greenschist Facies A schist develoed through the metamorhism of a -rich rock basalt Common minerals are: Eidote Ca Fe 3+ Al OSi O 7 (SiO 4 )(OH) Actinolite Ca (Mg,Fe + ) 5 Si O (OH) Chlorite (Mg,Al,Fe) 3 (Si,Al) 4 O (OH) (Mg,Al,Fe) 3 (OH) Albite + Eidote + Actinolite + Chlorite + Calcite in mafic rocks Pyrohyllite in elitic rocks Amhibolite Facies Abundant and little, as such they do not roduce quartz and micas Named for abundant Common minerals are: Hornblende Ca (Mg,Fe,Al) 5 Si O (OH) Plagioclase (Ca,Na) (Al,Si)AlSi )O»>An 0 Garnet (Ca,Mg,Fe +,Mn) 3 (Al,Fe 3+,Cr) (SiO 4 ) 3 Kyanite (Al SiO 5 ) in elites Assemblage hornblende + lagioclase is diagnostic 4

5 o a b o Samle Amhibolite (metamorhosed gabbro) under (a) lane light and (b) crossed olars. Minerals resent include lagioclase (), clinoyroxene () (note the variable colour (leochroism) of the brown and green), hornblende () and oaques (o). (FOV =.5mm) 1 Metamorhic Facies Glaucohane Pumellyite Greenschist granite Amhibolite 0 Deth (km) Temerature (C) 5

6 Granulite Facies Characteristic of Cx + Ox + Pl + (Fe,Mg) Garnet Eclogite Facies Lower or uer (deeest material samled on a regular basis) Feldsar-free assemblage, Jadeite + yroe (Mg ) is diagnostic clinoyroxene clinoyroxene gt gt.0 mm.0 mm Samle PT-79: Eclogite. This samle is equivalent to the basalt, gabbro and amhibolite, excet that it has been metamorhosed to a higher degree (~ C and > kbars). This samle consists of medium to coarse grained clinoyroxene () which exhibits a weak green leochroism and (gt), an isotroic mineral. Hornblende, light green to dark green leochroism, is resent in this samle (not visible in this view). Minor amounts of lagioclase and quartz make u the fine grained matrix.

7 1 Metamorhic Facies Glaucohane Pumellyite Greenschist Eclogitegranite Amhibolite Granulite 0 Deth (km) Px Sanidinite Temerature (C) Characteristics of regionally metamorhsed mudstones Grade Rock Name Grain Size Key Minerals Features Protolith Very Low Low Mudstone Slate Phyllite Very fine grained, Clays, quartz clay sized articles Very Fine, recrystallized articles Fine Clays, chlorite, quartz, Fe-oxides Micas, chlorite, quartz, Fe-oxides Fissile, shale, bedding or massive, mudstone texture Bedding, slaty cleavage Bedding, hyllitic foliation Medium High Very High Schist Schist/gneiss Gneiss Fine to medium, with random isolated large orhyrobalsts Medium to coarse Medium to coarse Micas, chlorite, quartz, lag,, staurolite, kyanite, Fe-Ti oxides Biotite, quartz, lag.,, cordierite, sillimanite, Fe-Ti oxides Biotite, quartz,lag., orthoclase, sillimanite,, cordierite, Fe-Ti ox. Schistosity, orhyroblasts, rare bedding Schistosity or gneissosity, segregation layering, orhyroblasts Gneissosity, segregation, layering, orhyroblasts, migmatitic layering 7