IgneousPetrology

Jean-François Moyen

Practical informations

• Venues, dates, times• Contact• Textbooks• Outline

Outline1. Classification of igneous rocks2. Analytical techniques; major and trace

elements3. Isotopes4. Magma genesis: melting processes5. Magma evolution: cristallization, mixing, etc.6. Geochemical signature of mgmatic processes7. Magma transport and emplacement8. Volcanic processes

Outline

9. Basalts10. Andesites11. Granites12. Alkaline complexes13. Igneous rocks in a plate tectonic context14. Revisions etc.

April break: 2 days field trip

Introduction to igneous petrology

Stromboli (Italy)

Etna (Italy)

Piton de la Fournaise (Réunion, Indian Ocean)

Torres del Paine, S. Chile

Ploumanac’h, France

Cantal extinct volcano, France

« Ignimbrites », Turkey

Bournac volcanic pipe, France

Montserrat, Lesser antilles (1997)

The upper part of the solid Earth

Crust•Oceanic

•Continental

Mantle•Lithosphere

•Astenosphere

The Pressure Gradient

• P increases = gh• Nearly linear through

mantle~ 30 MPa/km 1 GPa at base of ave crust

• Core: incr. more rapidly since alloy more dense

Figure 1-8. Winter, From Dziewonski and Anderson (1981).Phys. Earth Planet. Int., 25, 297-356. © Elsevier Science.

Heat Sources in the Earth

1. Heat from the early accretion and differentiation of the Earth still slowly reaching surface

2. Heat released by the radioactive breakdown of unstable nuclides

The Geothermal Gradient

Figure 1-11. Winter, from Green and Falloon ((1998), Green & Ringwood (1963), Jaupart and Mareschal (1999), McKenzie et al. (2005 and personal communication), Ringwood (1966), Rudnick and Nyblade (1999), Turcotte and Schubert (2002).

Active volcanoes

The Geothermal

Gradient

Pattern of global heat flux variations compiled from observations at over 20,000 sites and modeled on a spherical harmonic expansion to degree 12. From Pollack, Hurter and Johnson. (1993) Rev. Geophys. 31, 267-280.

Cross-section of the mantle based on a seismic tomography model. Arrows represent plate motions and large-scale mantle flow and subduction zones represented by dipping line segments. EPR =- East pacific Rise, MAR = Mid-Atlantic Ridge, CBR = Carlsberg Ridge. Plates: EA = Eurasian, IN = Indian, PA = Pacific, NA = North American, SA = South American, AF = African, CO = Cocos. From Li and Romanowicz (1996). J. Geophys. Research, 101, 22,245-72.

Figure 1-9. Estimated ranges of oceanic and continental steady-state geotherms to a depth of 100 km using upper and lower limits based on heat flows measured near the surface. After Sclater et al. (1980), Earth. Rev. Geophys. Space Sci., 18, 269-311.

Plate Tectonic - Igneous Genesis

1. Mid-ocean Ridges2. Intracontinental

Rifts3. Island Arcs4. Active Continental

Margins

5. Back-arc Basins6. Ocean Island Basalts7. Miscellaneous Intra-

Continental Activity kimberlites, carbonatites,

anorthosites...

Plates and plate boundariesGeological activity is concentrated on plate boundaries