Page 291 - Global Tectonics

276 CHAPTER 9

“Typical continental geotherm”
“Typical continental geotherm” 30 C km 1
1.6
Eclogite
Eclogite 50
30 C km 1
1.4
Blueschist
Blueschist
1.2 40
Pressure (GPa) 1.0 Granulite 30 Depth (km)

0.8
Granulite

0.6 Amphibolite 20
Amphibolite
Greenschist
Greenschist Water-saturated
Water-saturated
Prehnite- granite solidus
Prehnite-
granite solidus
Ky
Pumpellyite
0.4 Pumpellyite Ky Sil
Sil
Zeolite
Zeolite And 10
And
0.2
Hornblende
Hornblende Pyroxene
Pyroxene
Hornfels
Ab-Ep Hornfels Hornfels Sanidinite
Ab-Ep
Sanidinite
Hornfels
Hornfels
Hornfels
0
100 200 300 400 500 600 700 800 900 1000
Temperature ( C)
Figure 9.26 Pressure–temperature diagram showing the approximate limits between the metamorphic facies (from
Winter, John D., Introduction to Igneous and Metamorphic Petrology, 1st edition © 2001, p. 195. Reprinted by
−1
permission of Pearson Education Inc., Upper Saddle River, NJ). Example of an elevated (30°C km ) continental geotherm
and stability ranges of three Al 2 SiO 5 polymorphs commonly found in metamorphosed sedimentary rock (Ky, kyanite;
And, andalusite; Sil, sillimanite) are shown for reference. Ab and Ep are albite and epidote, respectively.
5 160
NE Japan SW Japan 140
4 120
Base of oceanic crust
Base of oceanic crust Eclogite Eclogite 100
3
Pressure (GPa) 80 Depth (km)
Top
Top
2
60
Blueschist
Blueschist Hornblende melting
Top Top 40
Hornblende melting
1 Granulite
Base
Base
Greenschist Wet solidus Dry solidus Dry solidus 20
Wet solidus
Amphibolite
Amphibolite
0 0
0 200 400 600 800 1000 1200
Temperature ( C)
Figure 9.27 Calculated pressure–temperature paths for the top and base of subducted oceanic crust beneath
northeast and southwest Japan (after Peacock & Wang, 1999, with permission from Science 286, 937–9. Copyright by
the AAAS, © 1999). Metamorphic facies and partial melting curves (dark gray lines) for basalt under wet and dry
conditions are shown.