ERSC 3P21 Metamorphic Petrology II 24/08/2011
Metamorphic Facies
• Facies – ______• There is a predictable and common correspondence between the ______of each rock and its ______• Mineral ______that define the metamorphic ______indicate that a state of stable ______has been ______over a restricted T and P condition.
ERSC 3P21 - Brock University Greg Finn
Metamorphic Facies
• Several different facies have been formally recognized and have been named according to distinct aspects of the facies – eg. greenschist = characterized by schists in which green chlorite, talc, serpentine, epidote and actinolite are predominant • Examine the mineralogical characteristics in metamorphosed mafic (basic) rocks subjected to prograde metamorphism
ERSC 3P21 - Brock University Greg Finn
Metamorphic Grade Calculated 14 Geothermal Water Gradient saturated 40 granite 12 solidus Diagenesis
10 30
Liquid 8 VERY LOW or+ab+q HIGH GRADE 20 GRADE Depth (km) 6 Pressure (kbar) LOW 4 GRADE MEDIUM 10 GRADE mu + q 2 or+Al2SiO5+H2O
100 200 300 400 500 600 700 800 900 1000 Temperature (C) ERSC 3P21 - Brock University Greg Finn
1 ERSC 3P21 Metamorphic Petrology II 24/08/2011
Metamorphic Facies Calculated 14 Geothermal Water Gradient saturated 40 Eclogite granite 12 solidus Diagenesis
Glaucophane 30 10 Lawsonite
8
Granulite 20
Amphibolite Depth (km) 6 Prehnite
Pressure (kbar) Greenschist Pumpellyite
4 10 Zeolite
2 Px Hornfels Hornfels Sanidinite 100 200 300 400 500 600 700 800 900 1000 Temperature (C) ERSC 3P21 - Brock University Greg Finn
Zeolite Facies • Zeolites are a group of white to colourless ______
silicates, analogous in 2005/gold2005/images/zeolite.jpg composition to ______• Common Zeolites are: http://www.the-conference.com/
• Laumontite - Ca(Al2Si4)O12·4H2O
• Heulandite – (Ca,Na)2(Al2Si7)O18·6H2O
• Analcime – NaAlSi2O6·H2O • Assemblage qtz + heulandite + chlorite is diagnostic
http://www.curiogrove.com/Zeolite/gfx/ze002.jpg
ERSC 3P21 - Brock University Greg Finn
Prehnite - Pumpellyite Facies • Prehnite and pumpellyite, along with the zeolites, commonly occur as ______fillings in originally vesicular samples • Minerals present are:
• Prehnite – Ca2Al2Si3O10(OH)2
• Pumpellyite – http://www.dsuper.net/~marcouet/images/prehnite.jpg
Ca2MgAl2(SiO4)(Si2O7)(OH)2·H2O
• Assemblage qtz + Prehnite + Pumpellyite is diagnostic
http://www.asahi-net.or.jp/~ug7s-ktu/e_pumpel.htm ERSC 3P21 - Brock University Greg Finn
2 ERSC 3P21 Metamorphic Petrology II 24/08/2011
Glaucophane - Lawsonite Facies
• AKA - ______• Minerals present are blue in colour
• Glaucophane - Na2MgAl2Si8O22(OH)2 • Lawsonite - CaAl2Si2O7(OH)2H2O • Jadeite – NaAlSi2O6 • Characteristic of regions of ______and ______metamorphism, near ______zones • Assemblage jadeite + qtz + aragonite is diagnostic
ERSC 3P21 - Brock University Greg Finn
http://geosciences.geol.u-psud.fr/ObjectifTerre/Mineralogie/mineropolarisant/Glaucophane/GlauLP.jpg
http://ic.ucsc.edu/~rocks/eart005/Metamorphic/Green_Blue.htm
http://www.tulane.edu/~sanelson/images/fransican.gif
ERSC 3P21 - Brock University Greg Finn
• Formation of Blueschists
http://www.uwgb.edu/dutchs/graphic0/platetec/metzone.gif
ERSC 3P21 - Brock University Greg Finn From: http://www.uwgb.edu/dutchs/platetec/orogeny.htm
3 ERSC 3P21 Metamorphic Petrology II 24/08/2011
Metamorphic Facies Calculated 14 Geothermal Water Gradient saturated 40 granite 12 solidus Diagenesis Glaucophane 10 30 Lawsonite
8
20 Depth (km) 6 Prehnite Pressure (kbar) Pumpellyite
4 10 Zeolite
2
100 200 300 400 500 600 700 800 900 1000 Temperature (C) ERSC 3P21 - Brock University Greg Finn
Greenschist Facies
• A ______schist developed through the metamorphism of a ______-rich rock – basalt • Common minerals are: 3+ • Epidote – Ca2Fe Al2OSi2O7(SiO4)(OH) 2+ • Actinolite – Ca2(Mg,Fe )5Si8O22(OH)2
• Chlorite – (Mg,Al,Fe)3(Si,Al)4O10(OH)2·(Mg,Al,Fe)3(OH)6 • Albite + Epidote + Actinolite + Chlorite + Calcite in mafic rocks • Pyrophyllite in pelitic rocks
ERSC 3P21 - Brock University Greg Finn
ERSC 3P21 - Brock University Greg Finn
4 ERSC 3P21 Metamorphic Petrology II 24/08/2011
Amphibolite Facies
• Abundant _____ and little ____, as such they do not produce quartz and micas • Named for abundant ______• Common minerals are:
• Hornblende – Ca2(Mg,Fe,Al)5Si8O22(OH)2 • Plagioclase – (Ca,Na)2(Al,Si)AlSi2)O8 »>An20 2+ 3+ • Garnet – (Ca,Mg,Fe ,Mn)3(Al,Fe ,Cr)2(SiO4)3 • Kyanite (Al2SiO5) in pelites • Assemblage hornblende + plagioclase is diagnostic
ERSC 3P21 - Brock University Greg Finn
ERSC 3P21 - Brock University Greg Finn
hb hb
cpx cpx
hb hb p p
cpx cpx
op p op p p p a b
Sample 99-3 - Amphibolite (metamorphosed gabbro) under (a) plane light and (b) crossed polars. Minerals present include plagioclase (p), clinopyroxene (cpx) (note the variable colour (pleochroism) of the cpx brown and green), hornblende (hb) and
opaques (op). (FOV = 8.5mm) ERSC 3P21 - Brock University Greg Finn
5 ERSC 3P21 Metamorphic Petrology II 24/08/2011
Metamorphic Facies Calculated 14 Geothermal Water Gradient saturated 40 granite 12 solidus Diagenesis
Glaucophane 30 10 Lawsonite
8
20
Amphibolite Depth (km) 6 Prehnite
Pressure (kbar) Greenschist Pumpellyite
4 10 Zeolite
2
100 200 300 400 500 600 700 800 900 1000 Temperature (C) ERSC 3P21 - Brock University Greg Finn
Granulite Facies
• Characteristic of ______• Cpx + Opx + Pl + (Fe,Mg) Garnet
ERSC 3P21 - Brock University Greg Finn
Eclogite Facies
• Lower _____ or upper ______(deepest material sampled on a regular basis) • Feldspar-free assemblage, • Jadeite + pyrope (Mg garnet) is diagnostic
ERSC 3P21 - Brock University Greg Finn
6 ERSC 3P21 Metamorphic Petrology II 24/08/2011
cpx cpx
clinopyroxene clinopyroxene
garnet garnet
gt gt cpx cpx garnet garnet
cpx cpx cpx cpx 2.0 mm cpx 2.0 mm cpx
Sample PT-279: Eclogite. This sample is equivalent to the basalt, gabbro and amphibolite, except that it has been metamorphosed to a higher degree (~500-700°C and >10 kbars). This sample consists of medium to coarse grained clinopyroxene (cpx) which exhibits a weak green pleochroism and garnet (gt), an isotropic mineral. Hornblende, light green to dark green pleochroism, is present in this sample (not visible in this view). Minor amounts of plagioclase and quartz make up the fine grained matrix. ERSC 3P21 - Brock University Greg Finn
Metamorphic Facies Calculated 14 Geothermal Water Gradient saturated 40 Eclogitegranite 12 solidus Diagenesis
Glaucophane 30 10 Lawsonite
8 Granulite 20
Amphibolite Depth (km) 6 Prehnite
Pressure (kbar) Greenschist Pumpellyite
4 10 Zeolite
2 Px Hornfels Hornfels Sanidinite 100 200 300 400 500 600 700 800 900 1000 Temperature (C) ERSC 3P21 - Brock University Greg Finn
Characteristics of regionally metamorphsed mudstones
Grade Rock Name Grain Size Key Minerals Features
Protolith Mudstone Very fine grained, Clays, quartz Fissile, shale, bedding or clay sized massive, mudstone particles texture Very Low Slate Very Fine, Clays, chlorite, Bedding, slaty cleavage recrystallized quartz, Fe-oxides particles Low Phyllite Fine Micas, chlorite, Bedding, phyllitic foliation quartz, Fe-oxides
Medium Schist Fine to medium, Micas, chlorite, Schistosity, with random quartz, plag, garnet, porphyroblasts, rare isolated large staurolite, kyanite, bedding porphyrobalsts Fe-Ti oxides High Schist/gneiss Medium to Biotite, quartz, plag., Schistosity or coarse garnet, cordierite, gneissosity, segregation sillimanite, Fe-Ti layering, porphyroblasts oxides Very Gneiss Medium to Biotite, quartz,plag., Gneissosity, segregation, coarse orthoclase, layering, porphyroblasts, High sillimanite, garnet, migmatitic layering cordierite, Fe-Ti ox. ERSC 3P21 - Brock University Greg Finn
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