EPSC 445: Metamorphic PetrologyLecture 1: An introduction to metamorphism

Vincent van Hinsberg Department of Earth and Planetary Sciences, McGill University, Montréal, Québec, Canada

Course practicalities - aims

EPSC 445: Metamorphic Petrology

The aim of this course is to get familiar with metamorphic processes and rocks, their minerals and textures, and the tools that have been developed to convert these observations into the P-T conditions under which these rocks formed and the path they have taken through the Earth.

Lectures will focus on processes and more theoretical aspects of metamorphism, whereas this knowledge will be applied in the labs.

Course prerequisites: EPSC 212 and 312 - you are expected to know the basics of Petrology, Mineralogy and Microscopy

Course practicalities - subjects covered

causes of metamorphism:

effects of metamorphism:

metamorphic facies:

mineral stability:

geothermobarometry:

rock metamorphism:

effects of temperature, pressure and strain; contact, regional and subduction style metamorphism; heating from pluton intrusion

development of fabric and texture; changes in mineral assemblage; metasomatism and devolatilisation; over-growths and relicts

characteristic mineral assemblages for different P-T domains and P-T-t paths; low to high grade rocks; prograde and retrograde paths

phase diagrams; terminal and sliding reactions; effect of bulk composition; solvi and exsolution; pseudo-section calculations

constraining P-T conditions from mineral equilibria and assemblages; garnet-biotite thermometer; GASP baro-meter; solubility thermometers

characteristics of metamorphism of pelites, mafic rocks, carbonates and calc-silicates, and granites

Course practicalities

Lectures; Monday and Wednesday 9:30 to 10:30 in FDA 211

Labs; Monday afternoon from 14:30 to 17:30 in FDA 315 labs will consist of rock and mineral identification + description in hand specimens and thin-sections; descriptions + drawings of minerals and textures; construction of P-T and mineral stability diagrams

work in groups of 3, will need at least 1 laptop, will be given 1 good scope

Office hours; Wednesday 13:30 to 14:30 in FDA 341

Examination - the practical skills of identification and description are most important: 1. lab reports (there will be three): 60% of final grade2. formal written exam on theory: 40% of final gradeNo late submission will be accepted for lab reports.

for more information, see: http://eps.mcgill.ca/~hinsberg/Metamorphic/

Course practicalities

Books; Philpotts and Ague (2009) Principles of Igneous and Metamorphic Petrology Winter (2010) An Introduction to Igneous and Metamorphic Petrology

Chapters;

Thermodynamics introPhase rule and Schreinemakers Thermodynamics of solid solutionsCause and effect in metamorphism, metamorphic faciesTextures of metamorphic rocksProjectionsGeothermobarometry, reactionsReactions involving CO2MetasomatismPressure-Temperature-time paths

W 5; W 6; W 9; W 21; W 22; W 23; W 24; W 25; W 26; W 27; W 28; W 29; W 30;

P&A 7;P&A 8; P&A 9; P&A 16;

P&A 17; P&A 18; P&A 19; P&A 20; P&A 21;P&A 22;

ThermodynamicsThe phase ruleIsotopes and datingCause and effect in metamorphismMetamorphic rock nomenclatureTextures of metamorphic rocksProjectionsMetamorphic faciesMetamorphic reactionsThermodynamics in metamorphic reactionsPelite metamorphismMetamorphism of impure limestones and UMsMetasomatism

Course practicalities

Suggested additional reading;

• Bucher and Frey (2010) Petrogenesis of Metamorphic Rocks: nice textbook on metamor-phic petrology with 4 chapters of general concepts followed by detailed descriptions of metamorphism in different rock compositions

• Frank Spear (1994) Metamorphic Phase Equilibria and Pressure-Temperature-Time Paths. Comprehensive overview of all aspects of metamorphism. Both an excellent textbook and reference work

• MacKenzie and Adams (1994) Rocks and Minerals in Thin Section (A Colour Atlas): photographs of most common rock forming minerals in thinsection

• Yardley, MacKenzie and Guilford (1990) Atlas of Metamorphic Rocks and Their Textures: similar to previous, but dedicated to metamorphic rocks. Beautiful images.

• Perkins and Henke (2003) Minerals in Thin Section: a detailed guide to microscopy with lots of pictures and drawing of minerals and textures in thinsection

• Philpotts (2003) Petrography of Igneous and Metamorphic Rocks: detailed guide to micro-scopy of igneous and metamorphic rocks with lots of figures and a CD with images

Labs and lab reports

Labs consist of three sections:1. Thinsection mineral and texture ID, description and illustration. This involves the

ability to recognize metamorphic minerals and textures, and their reporting in text and drawings.

2. Assessing the P-T conditions for each sample based on their mineralogy and mineral phase stability as read from pseudosections.

3. Calculations (this section varies per lab, but includes heat flow calculations and P-T)

In the lab reports you provide a summary of your observations, drawings, calculation results and a final interpretation of the sample suite and its history.

Part 1 is to be handed in individually, whereas parts 2 and 3, as well as the interpretation are handed in as a group. Lab attendance and lab reports are not mandatory. However, reports make up 60% of the final grade.

Labs focus on thinsections and you will make abundant use of the petrographic microscope. You can obtain an EPS microscope by agreeing to its terms or rent one externally.

Metamorphic minerals and an introduction to PerpleX(2 weeks)

Meta-mafic rocks(3 weeks, lab reportdue Feb 7, 9:00)

Meta-pelites(3 weeks, lab reportdue March 7, 9:00)

Subduction zone metamorphism(3 weeks, lab reportdue March 28, 9:00)

The impact of protolith on metamorphic mineralogy(2 weeks)

Lab topics

Revision of metamorphic minerals in hand specimen and the petrographic microscope; introduction to thermodynamic modelling with PerpleX

Explore and describe how the mineralogy and texture of mafic (basalt) and pelitic (clay) protoliths changes with evolving meta-morphic conditions; thermodynamically model the P-T stability of these minerals with PerpleX pseudosections; determine the P-T conditions of the specimens using these pseudosections and geothermobarometers; determine the metamorphic histories of these suites of samples and present this in a report.

Investigate the mineralogy and textures of subduction zone rocks; determine prograde versus retrograde parageneses; position the samples in P-T space; calculate the physical properties of the samples along their metamorphic path using PerpleX; present your findings in a report.

Explore the effect of protolith composition on mineralogy using a suite of samples including meta-carbonates, meta-ultramafics, meta-granites, meta-BIFs, etc.

Course practicalities - McGill policy statements

“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. This does not apply to courses in which acquiring proficiency in a language is one of the objectives.”

“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” (see www.mcgill.ca/students/srr/honest/ for more information).

“© Instructor-generated course materials (e.g., handouts, notes, summaries, exam questions, etc.) are protected by law and may not be copied or distributed in any form or in any medium without explicit permission of the instructor. Note that infringements of copyright can be subject to follow up by the University under the Code of Student Conduct and Disciplinary Procedures.”

Lecture 1: An introductionLecture 1: An introductionLecture 1: An introduction

Lecture 1: An introduction

Lecture 1: An introduction

Lecture 1: An introduction

MetamorphismRock texture:- sedimentary bedding + crossbedding preserved- minerals overgrow and randomly oriented

Mineralogy:- matrix: quartz, chlorite, oxide, graphite- overgrowing: andalusite, cordierite, biotite with quartz, graphite and oxide still stable

Mineral textures:- matrix minerals are happy with perfect grain boundaries + angles- andalusite has sector zoning -> chiastolite- cordierite is being replaced- biotite full of relic inclusions

P-T constraints:- matrix: chlorite + no biotite -> greenschist facies (300-400 ˚C)- overgrowing: and + crd + bt -> 550 ± 50˚C and 1.5 kbar

Interpretation:Coarsening upward river sediment metamorphosed to greenschist facies, probably by burial metamorphism given the good preservation of sedimentary textures and lack of a clear fabric, and subsequently subjected to contact metamorphism at about 550˚C and 1.5 kbar (~5 km depth). During cooling, the cordierite broke down to a second generation of biotite.

MetPet Lab 1: A review of metamorphic minerals

The main purpose of this lab is to re-familiarize yourself with the main metamor-phic minerals in hand specimen and thin-section, and to work on recording your observations in drawings and descriptions. Next week there will also be an intro into thermodynamic modelling of mineral stability using PerpleX.

Make use of this opportunity - in the coming labs you simply don’t have time to work on mineral ID. And ask questions, not all minerals are easy to identify !

Microscopes will be handed out from 14:30 to 14:45

Lab reports are to be handed in as groups of 3, please let me know by the end of today who your group members are

Look after your microscope and these samples. These are fragile and very hard to replace. Have one thin-section out at a time and please store them carefully.

Thinsection drawings

A key component of the labs is making sketches of minerals and textures in thinsection.

A sketch is NOT the same as a photograph !!!

A sketch is a summary representation of the complete sample and should include all key features, wherever they occur in the sample, in one, or maybe two sketches.

A sketch is intended to show and highlight the key features of the sample and leave out any unnecessary information.

As a result, a sketch contains much more information than a photograph in a way that is easier to understand and interpret by your audience

Sketches take time and practice, but you do not need to be artist. The only requirement is that you are precise and accurate.

Thinsection drawings - precision and accuracy

Accuracy: sketch only what you see, not what you would like to see

Precision: Almost everything has meaning in a thinsection, so make sure that you sketch things as precise as possible, for example;

Thinsection drawings - precision and accuracy

Accuracy: sketch only what you see, not what you would like to see

Precision: Almost everything has meaning in a thinsection, so make sure that you sketch things as precise as possible, for example;