AT&G - Spotila's active
tectonics and geomorphology research
Radiogenic helium dating [(U-Th)/He] of apatite
Scope: (U-Th)/He dating is a technique developed
only over the last decade or so, which is proving very useful for studies of
mountain building, landscape evolution, volcanology, and the thermal evolution
of the crust. Based on the in situ radiogenic growth and subsequent
thermal diffusion of 4He in minerals, this thermochronometer
constrains the cooling history of rocks. By using different mineral
phases (e.g. apatite, titanite, zircon), different segments of the
time-temperature curve can be determined. I specialize in the dating of
apatite, which is sensitive to the lowest temperature cooling (50-90oC).
By having a lab here in the department, we can employ this important technique
to estimate exhumation rates from samples in any location that we study.
So far this technique has helped our work California, the Appalachians, and
southeast Alaska. For more information on the technique, check out the
links to other helium dating experts below.
Funding: the Instrumentation and Facilities
branch of the National Science
Foundation (EAR-NSF) (award #EAR9906357, 10/99-9/02).
Status: The lab is outputting quality data,
after being calibrated and reproducing ages of known samples (Durango
fluorapatite) to within ~5%. We are currently using a resistance furnace,
but hope to upgrade to a Nd:YAG laser furnace in 2005. We currently work with Peter Reiners at
Yale U. for U and Th analysis using ICP-MS. During 2005 we will be running samples from the Chugach/St.
Elias Range and Fairweather Range of Alaska, the northern San Gabriel Mountains
of California, Siberia, and reconnaissance samples from Tibet and the
Himalayas.
Links to some other helium daters: Ken Farley
(Caltech), Pete
Reiners (Yale), Peter Zeitler
(Lehigh), Des Patterson (Patterson Instruments), Suzanne Baldwin and Paul
Fitzgerald (SUNGIRL
- Syracuse), Danny Stockli
(Kansas), Kip
Hodges (MIT)
Photo of the lab (as of 2002)
Comments to: spotila@vt.edu