igneous petrology francis 2013. lectures: tues & thurs: 11:30 - 12:30 pm lab: thursday...
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IgneousPetrology
Francis 2013
Lectures: Tues & Thurs: 11:30 - 12:30 pm Lab: Thursday 2:30-5:30pm Room: FDA 315
Documents: www.eps.mcgill.ca/~courses/c423/
Topics: The Nature of Silicate MeltsReview of Thermodynamics and Simple Phase Diagrams
Phase Equilibria in Complex Systems at elevated P-TRole of VolatilesBehaviour of Trace ElementsImplications of IsotopesCrust / Mantle Reservoirs Fractionation ProcessesMid-Ocean Ridge Basalts Ocean Island Basalt Suites Flood Basalt VolcanismCalc-Alkaline Magmatism Ultra-Potassic and Carbonatitic Magmatism Troctolite - Anorthosite Magmatic SuitesKomatiites and Archean Greenstone - Tonalite Terranes Magmatism on the Moon, Venus, and Mars
Grading: Final Theory Exam 50% Lab Reports 50%
TA’s: Grant Cox - FDA 311 ([email protected]) Ryan Libbey - FDA 312
([email protected])Jason Coumans - FDA 202a
Igneous Petrology: EPSC 423A, 2013 [email protected]
Labs – reports worth 50% A typed report will be required for each lab, typically due the following Thursday
before the next Lab.
You Will Work in Teams of ~2
1. Review of Common Rock Forming Minerals2. Meteorites and the Mantle3. Volcanic Textures, Cooling Rates, and Primary Magmas 4. Classification of Basalts: Baffin Island and Fort Selkirk5. Plutonic Equivalents: The Monteregian Hills (with associated field trip)6. Small Intrusions – the Dash Dyke7. Large Layered Intrusions – Muskox, Bushveld, Raudot. 8. Graphical & Numerical Analysis of Crystal Fractionation 9. Eocene Calc-Alkaline Volcanism10. Eocene Granitoid Plutonism11. Kimberlites, carbonatites, and other exotica12. Precambrian greenstones and granitoids
NB: Get Microscope and download AlphaMelts program during the first lab, Thursday, Sept. 5.All questions such as: my microscope does not work, where are the thin sections, who has the rock samples, etc. should be directed to the TA’s.
Francis, Igneous Petrology EPSC 423A, 2013
Mount St. Hilaire
RougemontMount
Yamaska
Field Trip Saturday, Oct. 5
The Monteregian Hills
References on Reserve in PSE Library and/or my Office
Theory:
Winter, J.D.; 2001: An Introduction to Igneous and Metamorphic Petrology. Prentice
Hall, QE461.W735 2001.
Philpotts,A.R., & Ague, J.J.; 2009: Priciples of Igneous and Metamorphic Petrology.
Cambridge University Press, QE461.P572
Ehlers, E.G.; 1972: The Interpretation of Geological Phase Diagrams. Freeman, San Francisco, QE364 E35
Rocks in Thin Section:
Nesse, W.D., 2004: Introduction to Optical Mineralogy, 348p. Oxford University, Press, QE369.06 N47
Williams, H., Turner, F.J., & Gilbert, C.M.; 1982: Petrography: An introduction to the study of rocks in thin section. Freeman, San Francisco, QE434 W73.
Francis, Igneous Petrology EPSC 423A, 2013
Required Component of Course Outlines Jane Everett, Dean of Students.
Integrity:
McGill University values academic integrity. Therefore all students must understand the meaning and consequences of cheating, plagiarism and other academic offences under the Code of Student Conduct and Disciplinary Procedures (seewww.mcgill.ca/students/srr/honest/ for more information).
Language:
In accord with McGill University’s Charter of Students’ Rights, students in this course have the right to submit in English or in French any written work that is to be graded.
Francis, Igneous Petrology EPSC 423A, 2013
Igneous Petrology
The study of rocks that form by the:crystallization of a cooling melt (“liquid”) or magma
Fundamental challenge : to understand high temperature
crystal-liquid processes
by studying cold solid rocks
Francis, Igneous Petrology EPSC 423A, 2013
Solid(xyl) Liquid(liq)
Cxyli / Cliq
i = Ki
Elemental partitioning between coexisting solid and liquid
followed by the physical separation of solid(s) and liquid 0livine
glass
K
constanttemperature
Diversity of igneous rocks reflects the action of
crystal – liquid fractionation
processes at high temperature
(Fe/Mg)oliv / (Fe/Mg)liq ~ 0.3
Francis, Igneous Petrology EPSC 423A, 2013
Two Kinds of Igneous Rocks:
Basalt/gabbro: dark or mafic rocks dominated by Fe-Mg silicates, such as olivine, and pyroxenes.
Constitute the oceanic crust.
Granitoids: light or felsic rocks dominated by feldspar and quartz that
Constitute the continental crust.
Black/Dark
White/Light
Basalt
Granite
Igneous Rocks reflect magmatic processes in an evolving Earth
Francis, Igneous Petrology EPSC 423A, 2013
Composition of the Sun and the Cosmic Abundances of the Elements:
The Sun constitutes 99.98 wt.% of the solar system, thus the chemical composition of the Sun is also that of the solar system.
To determine the proportion of the elements in the Sun, we make use of the energy levels between the electron orbitals of the atoms of the different elements. The electromagnetic spectra of the Sun was noted to contain dark lines in 1802 by Wollaston and later studied by Fraunhofer (early 1800's), indicating adsorption at selective wavelengths or energies. Radiation emerging from the Sun's interior passes though the gas of its photosphere (outermost visible layer), in which the different elements selectively absorb radiation whose wavelength corresponds to the difference in the energy (E = hc/) levels of its electron orbitals. The intensity of the absorption lines is a measure of the proportion of each element.
Solar Spectrum
Francis, Igneous Petrology EPSC 423A, 2013
Major Elements
Chondritic Meteorites have the same solid composition as the Sun ~ Solar System
O, Si, Mg, Fe constitute more than 91% of Condensed Sun’s Composition
The Sun constitutes 99.98 wt.% of the solar system, thus the chemical composition of the Sun is also that of the solar system.
Francis, Igneous Petrology EPSC 423A, 2013
>92%
Mantle Xenoliths:
Olivine – rich Peridotite nodules of the Earth’s mantle brought to the surface by volcanoes.
Francis, Igneous Petrology EPSC 423A, 2013
Sun BulkSilicateEarth (~68 wt.%) + Fe-metal core (~31 wt.%)
The Earth’s upper mantle is similar in composition to BSE, and is composed of a rock called peridotite, which consists largely of the minerals olivine and orthopyroxene
basalt orgranite crust
Fe-Nimetallic
core
peridotite mantle
SiO2 + MgO + FeO ~ 91%
Sun - Chondritic Meteorites - Earth’s Mantle
~
Francis, Igneous Petrology EPSC 423A, 2013
Mantle Xenoliths
Chondritic Meteorite
+ IronMetal
Iron
basalt orgranite crust
peridotite mantle
olivine
feldspar
= Sun
Francis, Igneous Petrology EPSC 423A, 2013
Terrestrial Planets
basalt orgranite crust
Fe-Nimetallic
core
peridotite mantle Crust represents only ~0.7
wt.% of the Earth
Francis, Igneous Petrology EPSC 423A, 2013
SiO2 45.2 49.4 60.3
TiO2 0.7 1.4 1.0
Al2O3 3.5 15.4 15.6
MgO 37.5 7.6 3.9 FeO 8.5 10.1 7.2 CaO 3.1 12.5 5.8 Na2O 0.6 2.6 3.2
K2O 0.1 0.3 2.5
Total 99.2 99.3 99.5
Cations normalized to 100 cations Si 38.5 46.1 56.4 Ti 0.5 1.0 0.7 Al 3.6 16.9 17.2 Mg 47.6 10.6 5.4 Fe 6.0 7.9 5.6 Ca 2.8 12.5 5.8 Na 0.9 4.7 5.8 K 0.1 0.5 3.0 O 140.2 153.0 161.3
Mineralogy (oxygen units, XFe3+ = 0.10) Quartz 0.0 0.0 13.0 Feldspar 13.2 57.3 64.3 Clinopyroxene 6.7 25.7 5.9 Orthopyroxene 18.3 4.1 14.7 Olivine 59.9 9.9 0.0 Oxides 1.8 3.0 2.0
Mantle Ocean Continent crust crust
Oceanic crust - MORB basalt p
Continental crust - granite eFrancis, Igneous Petrology EPSC 423A, 2013
Solid Source Refractory Solid + Liquid Restite
Refractory Mantle + Oceanic Crust
Cpx-rich PeridotiteLherzolite
Olivine-rich Peridotite + Basalt Harzburgite
Partial Melting of the Mantle
Fertile Mantle
Whole = Σ Parts
Lever Rule: p/R = x/y
y
x
R
amount of basalt (P) infertile mantle = x/(x+y)
~ 15-20%
Francis, Igneous Petrology EPSC 423A, 2013
Parent Magma Crystal Cumulate + Residual Magma
Volcanic RocksPlutonic or
Intrusive Rocks
Mafic Magma Gabbroic Cumulate + Felsic Magma
Volcanic rocks approximate the compositions of magmatic liquids. They represent aliquots of liquid that have escaped to the surface. The compositional variation observed in the liquids that the volcanic rocks represent is produced by varying degrees of crystal fractionation of a largely “gabbroic” mineral assemblage that now comprises plutonic intrusions.
Crystal Fractionation of Basalt
Whole = Σ Parts
Lever Rule: e/C = x/y
y
x
amount of granitein basalt = x/(x+y) ~ 10%
C
Francis, Igneous Petrology EPSC 423A, 2013
Continental Crustal GranitoidsSecond Stage Melting of Basalt
The majority of crustal granitoids are, however, thought to be liquids
produced at the eutectic point e by the second stage melting of silica-saturated basaltic/gabbroic mafic crust, consisting largely of pyroxene and plagioclase.
e
Francis, Igneous Petrology EPSC 423A, 2013
SiO2 45.2 49.4 60.3
TiO2 0.7 1.4 1.0
Al2O3 3.5 15.4 15.6
MgO 37.5 7.6 3.9 FeO 8.5 10.1 7.2 CaO 3.1 12.5 5.8 Na2O 0.6 2.6 3.2
K2O 0.1 0.3 2.5
Total 99.2 99.3 99.5
Cations normalized to 100 cations Si 38.5 46.1 56.4 Ti 0.5 1.0 0.7 Al 3.6 16.9 17.2 Mg 47.6 10.6 5.4 Fe 6.0 7.9 5.6 Ca 2.8 12.5 5.8 Na 0.9 4.7 5.8 K 0.1 0.5 3.0 O 140.2 153.0 161.3
Mineralogy (oxygen units, XFe3+ = 0.10) Quartz 0.0 0.0 13.0 Feldspar 13.2 57.3 64.3 Clinopyroxene 6.7 25.7 5.9 Orthopyroxene 18.3 4.1 14.7 Olivine 59.9 9.9 0.0 Oxides 1.8 3.0 2.0
Mantle Ocean Continent crust crust
Oceanic crust - MORB basalt p
Continental crust - granite e
Spectrum of Igneousliquids
Francis, Igneous Petrology EPSC 423A, 2013