Course Outline

GEOS3101/3801 Earth’s Structure and Evolution: unit outline Semester 1, 2014 6 credit points Aims: The Earth’s crust and upper mantle, or lithosphere, are a consequence of tectonic and geodynamic pro-

cesses operating since Earth’s formation. This unit focuses on information and techniques that enable an understanding of these processes. The main topics presented in this unit include: the formation and evolution of oceanic and continental lithosphere; struc¬tural deformation, magmatism and metamorphism at plate boundaries; the mesoscopic and microscopic analysis of igneous and metamorphic rocks; mechanisms of heat and mass transfer, and the mechanical behavior (i.e. rheology) of Earth materials. Practical classes are designed to enable students to be competently and independently identify the common crystalline rocks in hand-specimen; to gather and interpret the structural field data which enables the determi¬nation of the structural style and deformational history presented in particular tectonic settings, and to understand and interpret petrological and structural data in terms of thermal and mechanical processes. The concepts and content presented in this unit are essential knowl¬edge for geologists and geophysicists and provide a conceptual framework for their professional practice. There will be a three-day excursion to the South Coast of NSW in the first few weeks of semester to examine relevant themes in a field setting. Students wishing to specialize in the field and become professional geologists will normally need to expand upon the knowledge gained from this unit and either complete an honours project or progress to postgraduate coursework in this field.

Unit Outcomes

After completing Geos3101/3801, you are expected to be able to: • identify common rock forming minerals in hand specimen and thin sections; • interpret common mineral textures and rocks fabrics, including finite strain and kinematic indicators; • understand the tectonic, metamorphic and geochemical processes involved in key geodynamic settings, their products and be aware of assumptions underlying their interpretation; • calculate the continental geotherm from observation of surface heat flow and rock content in heat producing radiogenic elements; • understand how lithospheric deformation affects the temperature and pressure evolution of metamorphic rocks; and • when presented with a geological problem, observe and interpret the key data and relationships and provide a satisfactory explanation or interpretation.

Lectures will be delivered at 10 am on Monday in Carslaw room 408. Students must attend all lectures

to derive benefit from this unit of study. Most lectures will have assigned reading, to be completed in preparation, and some will require group presentations. To maximize learning outcomes and promote a dynamic and collaborative learning environment, students are requested to read the lecture material prior to attending the lecture.

Practical classes will be delivered between 1 and 3, and 3 and 5 pm on Monday in Madsen room 336; you need

attend one of these. The practical exercises are oriented toward solving problems relevant to the unit objectives and all exercises should be completed. The use of a laptop in the classroom is encouraged. Although simple tools such as Excel and Livemath (no programming required) are sufficient, students are invited to use during the practicals their knowledge of Matlab or Mathematica, or their open source equivalents: Octave, Freemat or SciLab.

Lecture notes and supporting material will be available on-line through Blackboard.

Assessment:

40% two hour exam covering theoretical concepts mostly addressed in lectures 30% practical test (week 8; 15%) and presentations (15%) 15% South Coast Field excursion: Friday March 28 - Monday March 31 15% student presentation (week 13) Portions of the unit will be weighted by contact time proportion.

Presentations: Student pairs will be assigned one or two topical research papers on a theme relevant to the

unit. Together you will prepare a 4 minute computer video presentation on that topic for delivery during week 13, and a typed 1-2 page synopsis of the topic that should include diagrams. Please attach to the synopsis a signed statement indicating the contribution made by each person. Topics will be assigned by week 5 to give you time to prepare the material; you are encouraged to consult the teaching staff between weeks 5 and 12 with respect to preparation of the talk and synopsis. Your talk should explain the significance of the topic at an introductory level that could be understood by, for example, an interested first year student, and cover sufficient detail to engage your peers (i.e. fellow third year students). It may be a video of yourself delivering the presentation, or mix diagrams and/or animations with such material - its nature is flexible. The material will be placed on a server and made available for comment from an audience outside the University.

Teaching Staff: Geoffrey Clarke

[email protected] Patrice Rey [email protected] unit coordinator Jonathan Aitchison

GEOS3101/3801 Earth’s Structure and Evolution Timetable

Lecture title Practical title

Clarke: Earth’s mineralogical evolution W1 Introduction; asymmetry in petrology Metapelitic rocks and the PT spectrum W2 Petrofabrics and parents Timing mineral growth W3 The subduction factory Subduction metamorphism W4 Equilibria and equilibration Petrography and field relationships W5 South Coast excursion W6 The extremes of metamorphism Trial practical test and review W7 Petrology in field work Corona Reaction Textures Easter W8 Practical test W9 W10 W11 W12

Rey: Earth’s geodynamics and evolution: Tectonic and Geodynamic approaches Heat generation and transfer Continental Geotherm Tectonic forces and gravitational forces Isostasy and Earth’s surface elevation The Notion of Rheology Map analysis and cross-section The Deformation of the Earth’s lithosphere Interpretation of rock fabrics

W13

Student Presentations

Student Presentations

This unit focuses on information and techniques that enable an understanding of how oceanic and continental lithosphere form and evolve through tectonic and geodynamic processes. The unit is divided into petrology (weeks 1–8) and tectonics (weeks 9–13), with a component of fieldwork (week 3) and a group 4 minute video presentation (week 13). Petrology is a core subject in Geosciences, and relates closely to mineralogy, geochemistry, geo¬physics, tectonics, economic geology and planetary sciences. It is thus a required component of the undergraduate geology cur¬riculum. There are three components to petrology: (i) observation and analysis; (ii) experimental; and (iii) theoretical. Its fundamen¬tal principles are embedded in the disciplines of physical chemistry, mechanics and transport processes, and material sciences. Geological information comes from the mineralogy, fabric, physical properties and geochemical characteristics of rocks. Rock fabric, mineralogy, geochemistry and physical properties evolve in response to changes in stress, pressure, temperature, fluid abundance and composition. These parameters are, in turn, driven by geodynamic and tectonic processes, including subduction, seafloor spreading, continental collision and plate aggregation. In this unit, you will build on material covered in junior and intermediate years to learn fundamental principles of both qualitative and quantitative approaches in petrology and structural geology, to be able to solve geological problems on diverse scales. Using a combination of conceptual and problem-based learning, you will examine the structural, metamorphic and magmatic evolution of the oceanic and continental lithosphere at active plate margins. The structural, metamorphic and magmatic evolution of the lithosphere mostly unfolds over time scales several orders of magnitude longer than our lives, limiting our ability to directly observe many key processes. Thus, we study it by analyzing the end products (what we can see: structural fabrics and regional finite strain, mineralogical assemblages, chemical and isotopic composition etc) from which lithospheric tectonic evolution and changes in the intensive physical variables can be unraveled. In the first eight weeks of Geos3101/3801, Geoff will lead practical classes where you will perform mesoscopic and microscopic analysis of igneous and metamorphic rocks and become competent in the identification of the common crystalline rocks through solving mesoscopic and microscopic problems that reflect macroscopic processes. Related lectures will address the fundamental parameters of how and why mineral equilibria change, and, as we can only rarely observe the changes, methods that let us anal¬yse and track such processes. Having a sound understanding of rocks at the mesoscopic and microscopic scale, you will jump to the macroscopic scale in weeks 9 to 12 to learn, in Patrice’s classes, the physical principles and processes driving petrologic changes and to understand the interplay between plate boundary forces, internal forces, continental geotherm, and crustal flow. In his lectures, Patrice will emphasize the important role of heat generation and transfer in the definition of the continental geotherm, and the origin of plate boundary forces and that of volume forces. Finally you will learn about the rheology of the mantle, the continental lithosphere and the oceanic litho¬sphere. At completion of this part of the course you will have a sound understanding of the interdependence between tectonic processes, heat transfer and metamorphic evolution. Throughout the semester you will also complete independent research by preparing a 4 minute video and a 2-page synopsis on an assigned topic. To complete this task, you will need to access the University library and download appropriate material relevant to the course of weeks 1 to 12. Presentations will be delivered in week 13.

understanding of geochemical methods bearing on models for upper mantle and crustal geodynamic processes.

Demonstrate the ability to account for major geochem-

ical distinctions between Earth’s core, mantle and

crust, and the major processes leading to elemental

variation in common crustal rocks.

Mineral and rock geochemistry

steady state geotherm; the difference between steady state and transient geotherms; and use a given mathematical recipe to solve a heat problem.

structure and the possible range of temperature at the

Moho. Be able to: calculate the steady state continen-

tal geotherm and the temperature and heat flow at

any depth, and follow a mathematical recipe to solve

of complex relationships. Evidence of independent


may impact on tectonic and gravitational forces; and independently figure out the mathematical solution to

various tectonics forces AND the origin of gravitational volume forces, AND to be able to explain how these forces can oppose or enhance each other; in which circumstances extensional tectonics can be coeval with contractional tectonics; and use a given mathematical recipe aimed at solving a dynamic problem.

forces on Earth. Be able to: draw the various tectonic

forces and gravitational volume force on a realistic

sketch; and follow a mathematical recipe to solve

dynamic problems.

to be able to explain how this transition changes with temperature and strain rate; and independently establish a mathematical solution to a rheological problem.

logical behaviours using concept of strain, strain rate and stress, AND to be able to explain the sensitivity of the various rheological behaviours to pressure, temperature, fluids, etc; and explain and to use a given mathematical recipe aiming at solving a mechanical problem.

structure. Be able to : list the various rheological

behaviours, AND to be able to use simple analogue

models to illustrate them; and follow a mathematical

recipe to solve mechanical problems

As above

As above.

research publications, books ...).

knowledge from other sources (other Unit of Study,

well-articulated and illustrated reports, calling upon

As for Distinction, and be able to write critical,

Notes 1 Common igneous rocks: those defined in the IUGS classification of igneous rocks (Le Bas & Streckeisen, Journal of the Geological Society of London, 148, 825–833, 1991). Common metamorphic rocks: refer to glossary from Vernon & Clarke (2008) given on Blackboard site. Common minerals: those forming common igneous and and metamorphic rocks, as examined in practical exercises.

explain the concept of brittle-ductile transition, AND

able to evaluate their respective integrated strength;

profile for continental and oceanic lithospheres AND be

As for Pass, and be able to explain: the various rheo-

Demonstrate an understaning of Earth’s viscosity

As for Credit, and be able to: construct the rheological

solve a dynamic problem.

of the principle of isostasy; explain how the geotherm

the value of the gravitational forces from application

forces can drive deformation; mathematically derive

forces AND to be able to predict whether or not these

As for Pass, and be able to explain: the origin of the

As for credit, and be able to: calculate the various

solution to solve a heat transfer problem.

crust; and independently figure out the mathematical

PTt paths followed by various part of the continental

therm evolves following a tectonic event and predict

reading and initiative will be shown.

will be indicated from accurate work and the resolution

achievement. As for Credit, and be able to explain: how the geo-

As for distinction. An exceptional level of achievement

well presented argument at an advanced level of


As for credit, with accurate detail, a considered and


indicated from accurate work.



of complex relationships.



of data. An advanced level of achievement will be

will be well constrained with an appropriate amount

As for credit, with accurate detail, lithological variation

indicated.

of data. An advanced level of achievement will be

will be well constrained with an appropriate amount

ture and to know the maximum magnitude of tectonic

Students MUST attain a pass or higher grade in ALL subject areas.

Rheology

demonstrate an exceptional level of understanding

of complex relationships.


will be indicated from detailed and accurate work, and

accurate work indicating a high level of understanding

As for credit, with accurate detail, and the structure


petrogenesis, metamorphic grade variations).

level of achievement will be indicated from careful

of nuanced relationships (timing and growth, igneous

metamorphic grade variations). As for credit and include accurate detail. An advanced

As for distinction, and show a flair in the interpretation

tionships (timing and growth, igneous petrogenesis,

High Distinction

As for credit, and correctly interpret nuanced rela-

Distinction

Demonstrate an understaning of Earth’s density struc-

temperature problems.

of various parameters related to the definition of the

Demonstrate an understaning of Earth’s thermal

Heat

Dynamics

As for Pass, and be able to explain: the significance

Demonstrate the capacity to resolve a best case argument pertaining to common igneous, metamorphic and tectonic issues and present a coherent argument bearing on a case study.

Correctly resolve a best case argument pertaining to common igneous, metamorphic and tectonic issues and present a coherent argument bearing on a case study.

common tectonic environments.

rock associations reflective of common tectonic

environments.

Correctly discriminate rock associations reflective of

Demonstrate the capacity to identify and interpret

As for pass, and be able to interpret the timing of mineral growth stages including prograde, peak and retrograde metamorphic stages.

Logic in incomplete datasets

Tectonic context

As for pass, and be able to demonstrate a critical

Correctly interpret textural and whole rock geochemical relationships in common igneous and metamorphic rocks1, basic petrogenetic dependencies and the effects of metamorphic facies variation on mineral assemblage.

Petrographic analysis

As for pass, and be able predict and account for whole rock compositional depencies on mineral assemblage.

Be able correctly identify and describe common minerals and mineral associations forming common igneous and metamorphic rocks1.

Credit

Pass

Rock and mineral identification

marking criteria

Criteria

Geos3101/3801 Earth’s Structure & Evolution