Thermochronology GEOS 459/559 University of Arizona

Thermal histories of natural materials are central to understanding a wide range of problems in Earth and planetary science including the timing and rates of erosion and faulting in orogenic systems, the development and evolution of sedimentary basins, and the histories and dynamics of impacts on extraterrestrial bodies. This course will equip students with a understanding of and skills in analytical approaches and diffusion theory, the ability to interpret and model cooling ages and thermal histories of rocks and minerals in the context of tectonic, geomorphic, and basinal histories, and the freedom to explore innovative applications of thermochronology through their own work. A wide variety of both high- and low-temperature radioisotopic systems (and other approaches) will be covered. There will be a few problem sets, and graduate students will be required to do and present an original project, hopefully involving original analyses and definitely involving original interpretations.

Organizational meeting: Wed 16 Jan 2008, 12:00 pm GS 303
Tentative meeting time: Mon & Wed 12:00 to 1:30 pm GS 303
Details: 3 units, regular grades, cross listed for undergrads (459) and grads (559).
Instructor: Peter Reiners; 626-2236; reiners at u.arizona.edu; GS 521.
Readings : To be assigned from papers and chapters.
On-line resources: http://www.geo.arizona.edu/~reiners/geos459-559/

Course Rationale and Logistics

Readings from chapters, papers, and other sources will serve as starting points for lectures and discussions. To reinforce your understanding and quantitative grasp of the concepts, there will be several complementary components to the class meetings:

• Several problem sets dealing with diffusion, thermal modeling, data reduction/interpretation, and applications.

• Students will lead at least one class discussion on a current issue or paper.

• Students will write a short final paper and make an oral presentation to the class on a final project. For graduate students, the project will involve original data and thermochronologic interpretation. Proposals for this final project will be due before Spring Break.

Tentative Schedule

Day	General topic	Specific topic	Reading
1/16	Introduction	Current issues, decay/growth
1/21	no class
1/23	Diffusion	Constant T	M&H, Braun
1/28	Diffusion	Changing T, Closure	M&H, Braun
1/30	Heat transport	Crustal thermal structure	M&H, Braun
2/4	Thermal modeling	Transience, Topography	Braun; TBA
2/6	Thermal modeling	Transience, Topography	Braun; TBA
2/11	Models	Store-bought and homemade	Braun; MSA volume
2/13	⁴⁰Ar/³⁹Ar dating	Micas, hornblendes	McDougall & Harrison
2/18	K-spar ⁴⁰Ar/³⁹Ar dating and MDD	Multi-domain diffusion models, modeling t-T paths	McDougall & Harrison
2/20	(U-Th)/He dating	Methods/application examples	MSA volume
2/25	Case studies	TBA	TBA
2/27	4He/3He thermochron	Methods/application examples	Shuster & Farley, 2005
3/3	Fission-track dating	Methods/application examples	Braun, MSA volume
3/5	High-T thermochron	U/Pb, Sm/Nd, Rb/Sr, etc.	TBA
3/10	Garnet Sm/Nd	Methods/application examples	TBA
3/12	Analytical techniques	Mass-spectrometry, ICP-MS	TBA
3/17	Spring Break
3/19	Spring Break
3/24	no class
3/26	Non-radioisotopic approaches	Diffusion profiles, organic maturity indices, etc.	TBA
3/31	Extensional settings	slip rates, footwall t-T histories	MSA volume; TBA
4/2	Convergent settings	horizontal and vertical age patterns	TBA
4/7	Detrital thermochron	Provenance, lag time, pdfs and catchment-wide analyses	MSA volume, Braun
4/9	Basin analysis	Thermal histories of basins	TBA
4/14	UHP rocks	fast exhumation, excess Ar, and heat/fluid pulses	TBA
4/16	Paleotopography	interpreting spatial age patterns and detrital ages	TBA
4/21	Shallow-level processes	volcanism, wildfire, fault heating, etc.	TBA
4/23	Meteorite evolution	TBA	TBA
4/28	catch-up
4/30	catch-up
5/5	Final presentations
5/7	Final presentations

Problem Sets

Problem Set 1. Basic practice manipulating and reducing data
Problem Set 2. Diffusion at constant temperature exercises
Problem Set 3: Diffusion at varying temperature: Step-heating experiment, Tc, domains, etc.
PS3 Data Set 1 (epidote)
PS3 Data Set 2 (tooth enamel)
Problem Set 4: Modeling the shallow crustal thermal field, with topography, and influences on cooling ages
Problem Set 5: ⁴⁰Ar/³⁹Ar stuff
PS Data Set 5 (xenolithic phlogopite)

Discussion Papers
Flowers et al., in press, GSA Bull
Brewer et al., 2003, Basin Res.
Zeitler et al., 2001, GSA Hoy
Wobus et al, in press, EPSL

M&H: Geochronology and Thermochronology by the ⁴⁰Ar/³⁹Ar Method , 2nd Ed. , by McDougall, I., and Harrison, T.M., 1999, Oxford University Press, 269 pp.
MSA Volume: Low-Temperature Thermochronology: Techniques, Interpretations, and Applications , Reviews in Mineralogy & Geochemistry v. 58, 622 pp.
Braun: Braun, J., van der Beek, P., and Batt, G., 2005, Quantitative Thermochronology , Cambridge University Press, 258 pp.

In addition to the three books listed above (M&H, MSA Volume, and Braun), here are some more references which you will find useful in, and long after, this class:

Radiogenic Isotope Geology , 2nd Ed., by A. P. Dickin, 2005, Cambridge University Press, 492 pp.
Isotopes: Principles and Applications , 3rd Ed., by G. Faure and T.M. Mensing, 2005, John Wiley & Sons, 897 pp.
Geodynamics, 2nd Ed., by D.L. Turcotte and G. Schubert, 2002, Cambridge University Press, 589 pp.