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+ Cordierite
muscovite + Mg chlorite => cordierite + biotite
Zone de la cordiérite
A1 - Na - 2 Ca - 3 K
fixed T, P, Pf
fixed Na/Ca Pl
+ garnet
muscovite + Fe chlorite =>garnet + biotite
exces of quartz,
muscovite and fluid
Cordierite
garnet zone
A1 - Na - 2 Ca - 3 K
chlorite
+ Staurolite
garnet + chlorite + muscovite => staurolite + blolite
Staurolite - chlorite zone
A1- Na - 2 Ca -3 K
Staurolite
cordierite
Fe
Mg
chlorite
garnet
Chlorite
Cordierite
Fe
Mg
garnet
biotite
Fe
Mg
- chlorite
chlorite + muscovite =>
cordierite + staurolite + biotite
Staurolite
+ cordierite zone
A1 - Na - 2 Ca - 3 K
staurolite
biotite
biotite
cordierite
+ andalusite
staurolite + cordierite + muscovite
=> andalusite + biotite
garnet
andalusite
=> sillimanite
-staurolite
staurolite => sillimanite + garnet
sillimanite + garnet zone
sillimanite
A1 - Na - 2 Ca - 3 K
Fe
Mg
andalusite zone
andalusite/sillimanite
A1 - Na - 2 Ca - 3 K
sillimanite
+ staurolite
zone
Staurolite
cordierite
garnet
cordierite
biotite
garnet
Fe
Mg
Fe
Mg
biotite
biotite
Figure 3.29 Succession of the metamorphic facies in Saint-Ponais (Montagne Noire,
Hérault, France).
We give in Figure 3.29 the example of an intermediate low pressure
metamorphism, observed in Saint-Ponais, on southern slope of Montagne
Noire (France, Demange and Gattoni, 1976, Demange, 1982). Diagrams are
built in actual size from mineral analyses with the microprobe.
The pattern of the Thompson's diagram established for a given zone of
metamorphism, is only valid if the following conditions are fulfilled: fixed
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