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Igneous Petrology Francis 2013
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Igneous Petrology: EPSC 423A, 2013
Lectures: Tues & Thurs: 11: :30 pm Lab: Thursday 2:30-5:30pm Room: FDA 315 Documents: Topics: The Nature of Silicate Melts Review of Thermodynamics and Simple Phase Diagrams Phase Equilibria in Complex Systems at elevated P-T Role of Volatiles Behaviour of Trace Elements Implications of Isotopes Crust / Mantle Reservoirs Fractionation Processes Mid-Ocean Ridge Basalts Ocean Island Basalt Suites Flood Basalt Volcanism Calc-Alkaline Magmatism Ultra-Potassic and Carbonatitic Magmatism Troctolite - Anorthosite Magmatic Suites Komatiites and Archean Greenstone - Tonalite Terranes Magmatism on the Moon, Venus, and Mars Grading: Final Theory Exam % Lab Reports 50% TA’s: Grant Cox - FDA 311 Ryan Libbey - FDA 312 Jason Coumans - FDA 202a
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You Will Work in Teams of ~2
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 Review of Common Rock Forming Minerals Meteorites and the Mantle Volcanic Textures, Cooling Rates, and Primary Magmas Classification of Basalts: Baffin Island and Fort Selkirk Plutonic Equivalents: The Monteregian Hills (with associated field trip) Small Intrusions – the Dash Dyke Large Layered Intrusions – Muskox, Bushveld, Raudot. Graphical & Numerical Analysis of Crystal Fractionation Eocene Calc-Alkaline Volcanism Eocene Granitoid Plutonism Kimberlites, carbonatites, and other exotica 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
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Field Trip Saturday, Oct. 5 The Monteregian Hills Mount St. Hilaire
Yamaska Rougemont
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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.W 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, QE 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
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Required Component of Course Outlines Jane Everett, Dean of Students.
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. 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). Francis, Igneous Petrology EPSC 423A, 2013
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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
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crystal – liquid fractionation
Diversity of igneous rocks reflects the action of crystal – liquid fractionation processes at high temperature K Solid(xyl) Liquid(liq) glass Elemental partitioning between coexisting solid and liquid followed by the physical separation of solid(s) and liquid Cxyli / Cliqi = Ki 0livine constant temperature (Fe/Mg)oliv / (Fe/Mg)liq ~ 0.3 Francis, Igneous Petrology EPSC 423A, 2013
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Igneous Rocks reflect magmatic processes in an evolving Earth
Two Kinds of Igneous Rocks: White/Light Granitoids: light or felsic rocks dominated by feldspar and quartz that Constitute the continental crust. Granite Black/Dark Basalt/gabbro: dark or mafic rocks dominated by Fe-Mg silicates, such as olivine, and pyroxenes. Constitute the oceanic crust. Basalt Igneous Rocks reflect magmatic processes in an evolving Earth Francis, Igneous Petrology EPSC 423A, 2013
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Composition of the Sun and the Cosmic Abundances of the Elements:
The Sun constitutes 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/l) 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
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O, Si, Mg, Fe constitute more than 91%
of Condensed Sun’s Composition The Sun constitutes wt.% of the solar system, thus the chemical composition of the Sun is also that of the solar system. >92% Major Elements Chondritic Meteorites have the same solid composition as the Sun ~ Solar System Francis, Igneous Petrology EPSC 423A, 2013
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Mantle Xenoliths: Olivine – rich Peridotite nodules of the Earth’s mantle brought to the surface by volcanoes. Francis, Igneous Petrology EPSC 423A, 2013
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Sun - Chondritic Meteorites - Earth’s Mantle
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 SiO2 + MgO + FeO ~ 91% basalt or granite crust peridotite mantle Fe-Ni metallic core Francis, Igneous Petrology EPSC 423A, 2013
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Iron olivine Chondritic Meteorite = Sun + Iron Metal Mantle Xenoliths
basalt or granite crust feldspar peridotite mantle Iron olivine Chondritic Meteorite = Sun + Iron Metal Mantle Xenoliths Francis, Igneous Petrology EPSC 423A, 2013
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Crust represents only ~0.7 wt.% of the Earth
Terrestrial Planets basalt or granite crust peridotite mantle Crust represents only ~0.7 wt.% of the Earth Fe-Ni metallic core Francis, Igneous Petrology EPSC 423A, 2013
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Oceanic crust - MORB basalt p
Mantle Ocean Continent crust crust SiO TiO Al2O MgO FeO CaO Na2O K2O Total Cations normalized to 100 cations Si Ti Al Mg Fe Ca Na K O Mineralogy (oxygen units, XFe3+ = 0.10) Quartz Feldspar Clinopyroxene Orthopyroxene Olivine Oxides Oceanic crust MORB basalt p Continental crust granite e Francis, Igneous Petrology EPSC 423A, 2013
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Refractory Mantle + Oceanic
Partial Melting of the Mantle Solid Source Refractory Solid Liquid Restite Fertile Mantle Refractory Mantle Oceanic Crust Cpx-rich Peridotite Lherzolite Olivine-rich Peridotite Basalt Harzburgite Whole = Σ Parts Lever Rule: p/R = x/y amount of basalt (P) in fertile mantle = x/(x+y) ~ 15-20% y x R Francis, Igneous Petrology EPSC 423A, 2013
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Crystal Fractionation of Basalt
Parent Magma Crystal Cumulate + Residual Magma Plutonic or Intrusive Rocks Volcanic Rocks Mafic Magma Gabbroic Cumulate + Felsic Magma Whole = Σ Parts Lever Rule: e/C = x/y 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. amount of granite in basalt = x/(x+y) ~ 10% C x y Francis, Igneous Petrology EPSC 423A, 2013
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Continental Crustal Granitoids Second 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
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Oceanic crust - MORB basalt p
Mantle Ocean Continent crust crust SiO TiO Al2O MgO FeO CaO Na2O K2O Total Cations normalized to 100 cations Si Ti Al Mg Fe Ca Na K O Mineralogy (oxygen units, XFe3+ = 0.10) Quartz Feldspar Clinopyroxene Orthopyroxene Olivine Oxides Spectrum of Igneous liquids Oceanic crust MORB basalt p Continental crust granite e Francis, Igneous Petrology EPSC 423A, 2013
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