Regional Metamorphic Rock: General Rock Facies
An Interactive Poster
Ordinary Limestone
Feldspar hornblende andesite
weak epidote alteration: non-metamorphic
Platy greenstone
green, fine grained, weak foliation\cleavage, fine chlorite
low grade metamorphic: greenschist zone
(similar assemblage as propylite alteration)
Slaty phyllite
Pale green, sheen of slatey cleavage fine chlorite\sericite, greenschist slate (sediment or volcanic??)
Greenstone
Weakly foliated\cleaved greenstone, fine chlorite, sericite
Chlorite Schist\semi-schist Chlorite greenschist
Abundance of fine chlorite suggests a more mafic (basaltic?) original composition.
Chlorite schist
Foliated to lineated chlorite schist. Elongate patches of chlorite\fine biotite? Relict mafic phenocrysts? Light matrix mix of fine chlorite\sericite.
Meta-volcanic
Foliated to lineated chlorite\hornblende\feldspar schist, moderate high temperature-early amphibolite zone?
Gneiss
Biotite\hornblende felspar gneiss. High grade metamorphic zone
Slate
close spaced parallel fracture\cleavage
Slate
close spaced parallel fracture\cleavage
Slate
close spaced parallel fracture\cleavage
Phyllite
strong platy fracture cleavage, fine sheen on cleavage surfaces, fine grained sericite\muscovite, low-medium grade metamorphism
Sericite schist
Fine grained sericite schist\phyllite. Presence of white mica on cleavage develops early metamorphic foliation
Sericite schist
fine rust and thin brown (iron carbonate-ankerite) veinlets of curious note as to origin
Sericite semi-schist to schist
Fine white mica develops good foliation and visible mica and small knots of garnet?
staurolite\muscovite\garnet schist
light grey; micaceous; 70% muscovite; 20% biotite; 10% staurolite
staurolite\muscovite\garnet schist
25% garnet and 20% staurolite (vitreous, brown) as 1-2 cm porphyroblasts; 55% muscovite; recessive; resistant garnet and staurolite produce knobby outcrop
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