Geol-7081 – Stable isotope Geochemistry: Principle and application

Instructor: Dr. Huiming Bao (Phone: 8-3419)
Office: E338 Howe-Russell, LSU
E-mail: bao@lsu.edu; Website: http://www.geol.lsu.edu/Faculty/Bao/
Pre-requirements: Geol-4085 (or Geol-4083 or Geol-4081)

 

Statement of Purpose

The application of stable isotope ratios to physical, chemical, and biological problems has been enjoying a great expansion for over half a century. Stable isotope ratios are one of the most useful “detective” tools for understanding processes in nature, especially for events that occurred in the distant past. The goal of this course is to introduce key concepts, principles, methodologies, and cases of applications on the distributions of stable isotopes (e.g., C, O, S, N, and H) in nature with applications on geological, environmental, and biological problems. I will focus on universal principles that are applicable to isotopes of different elements, and on quantitative understanding and handling of fractionation processes.

Structure

There will be no designated textbooks, but we will have several important reference books (listed below). Key reference papers will be distributed in class or on reserve in Middleton Library. There will be reading assignments, problem sets, and discussion sessions. Each one of you will play a leading role in discussing one particular topic of your choice at least ONCE in the semester (mostly in the second half of the semester). We will have a mid-term exam and a final term paper.
We will have two classes (1.50 hrs each) per week, in which  ~ 6 hrs is on laboratory demonstration and trainning.
 
Reference books

      1. Robert E. Criss: Principles of Stable Isotope Distribution, 1999
2. Jochen Hoefs, Stable Isotope Geochemistry, 4th edition, 1997
(I recommend you purchase the above two textbooks.)

3. Gunter Faure, Principles of Isotope Geology, 2nd Edition, 1986
4. P. W. Rundel, J. R. Ehleringer, and K. A. Nagy, eds: Stable Isotopes in Ecological Research, 1998, ASIN: 3540967125
5. David S. Schimel: Theory and Application of Tracers (Isotopic Techniques in Plant, Soil, and Aquatic Biology), 1993
6. Pier de Groot, Handbook of Stable Isotope Analytical Techniques, in press. See website http://users.pandora.be/handbook/index.html

(more to come … …)


 

Grading

  1. Problem sets: 25% (total 6-7 sets)
  2. Late Midterm exam: 35%
  3. Class preparation and Attendance: 15%
I expect everyone read the weekly reading assignment and prepare to discuss the subject in depth. Informal class discussion is a major component of the course. Your grade will be judged by your performance in class discussion (10%) and the session you chair (5%).
4. Final term paper: 25% (~ 10 pages -- size 11 and double-spaced) -- 
Your paper can be a proposed project using stable isotopes in your research area. It can also be an “authoritative” review paper on a topic (sample topics shown below). It will be judged from the layout of the history of the problem, hypothesis, major progresses, current debates, gaps of knowledge, and possible frontiers for further study. The topic can not be the same one that you have chaired in the Discussion session.
 
Sample topics for your term paper (you can have a much more focused topics than listed):
Isotopic evidence for early life
Processes that could result in extremely negative d13C in carbonates

Processes that could result in large positive d13C shift in short geological interval

Processes that could result in large negative d13C shift in short geological interval

Isotopic evidence for the rising of molecular oxygen in the atmosphere

Kinetic isotopic fractionation during calcite precipitation

Oxygen isotope geothermometer

The standardization of isotopic ratios

Carbon isotope fractionation during photosynthesis

Kinetic isotopic effect during bacterial sulfide oxidation and sulfate reduction
Mass-independent isotope fractionation
Extraterrestrial oxygen isotope compositions
Nitrogen isotope variation and its application in ecosystem
What controls the sulfur and oxygen isotopic compositions of seawater sulfate?
Exchange or no exchange (kinetics of isotopic equilibrium)
(more to add … …)


 

Syllabus:

Week 1

Introduction: Basic concepts and history – isotopes, abundances, d, R, a, absolute ratio, standard, and isotope-ratio mass spectrometers (lab tour).

Problem set I out

Week 2
Cases showing the wide spectrum of applications, key literature and journals, major players in the past and present: older generation, current generation

Problem set I due and Problem set II out

Week 3
Mechanisms of isotopic fractionation: Unified separation theory
Molecular models
Problem set II due and Problem set III out
Week 4
Equilibrium and kinetic isotopic fractionation

Equilibrium: Geothermometer.

Problem set III due

Week 5

Kinetic: 

Rayleigh Distillation model, open- vs. close-system fractionation

Case study: hydrological system, biological sulfur oxidation and sulfate reduction

Problem set IV out

Week 6

Kinetic: carbon isotope fractionation during photosynthesis

Labile and non-labile ions in solution and isotope exchange kinetics

Problem set VI due

Week 7: 

Relations between a17 and a18, or a33 and a34

Changing isotope ratios of O and H in water, S and O in sulfate, N and O in nitrate, and C and O in carbonate.

Problem set V out

Week 8:

Mass-dependent vs. mass-independent isotope fractionation

O and S Photochemistry

Week 9: 

1. Student-chaired Discussion session I--- Problem set V due

Week 10

Application of oxygen and sulfur isotope ratios in atmospheric chemistry
Week 11:
Fall Break
Week 12
Mid-term exam (sometimes at the end of October or early November)

1. Origin of soil carbonate nodules, calcrete, and lake carbonates

2. Student-chaired Discussion session II

Week 13

  1. Student-chaired Discussion session III
  2. Wild carbon isotope swings in the Neoproterozoic and their causes
Week 14: 
  1. Student-chaired Discussion session VI
  2. Oxygen revolution in the end of Archean eon
Week 15: 
  1. Student-chaired Discuss session V
  2. To be arranged
Week 16: 
New analytical techniques, plus Discussion session VI
Week 17: Perspectives and emerging fields in stable isotope geochemistry

Final term paper due at 5:00 pm Dec. 10, 2005.