- 40Ar/39Ar provides isotopic ages that
are used to derive thermal histories of geologic materials. Samples
of any age throughout Earth's history may be dated accurately
and precisely by the 40Ar/39Ar method,
but a practical minimum age is about 10,000 years. Before present.
This technique, particularly when applied to various minerals
within a single sample and used in conjunction with other geochronologic
techniques, can provide not only the age of formation, but also
its post-formation thermal and alteration history (based on argon
"closure" temperatures in various minerals, the technique
can delineate thermal history over a range of approximately 100-550°C).
The capabilities described are available as both analytical and
scientific/technical collaborative support. The facilities represent
a state of the art argon geochronology laboratory equipped with
three modern high sensitivity automated mass spectrometers, CO2
(infrared) and Nd:YAG (in UV) lasers (for total fusion and in-situ
analyses of < milligram samples), and low blank furnaces (for
age spectra and very young samples). Samples are irradiated in
the Denver TRIGA reactor before mass spectrometer analysis of
Whole rock slates
Whole rock basalts
- extract and clean, analyze for argon isotopic composition
on mass spectrometer as 'cleaned' argon thermally released from
irradiated sample material.
- Typically ±0.25% to 0.5% - 0.1% to 0.2% for sanidine
and anorthoclase. With optimal sample conditions, an age # 10,000
years is possible.
- Numerical dating of rock and mineral samples for studies
of timing of:
- geologic mapping in igneous and metamorphic terrains
- stratigraphic relationships
- sediment provenance
- timing of evaporite formation
- timing of faulting
- timing of metamorphism
- cooling trajectories in metamorphic and igneous rocks
- differential uplift and timing
- hazards assessment in recently active volcanic terrain
- timing of bolide impacts
- the geologic time scale
- argon concentration and isotopic composition in metals and
other man made inorganic materials.
- CO2 laser, frequency quadrupled Nd:YAG laser operating
in the UV range, argon ion lasers, low blank furnaces, ultrahigh
vacuum extraction lines, custom fabricated SAES getter pumps.
Located in Denver.
- Yes - VG1200b (36-50 analyses/day), MAP 216 (40-72 analyses/day),
with multiple analyses per age determination. MAP 215 currently
- MAP 215, min = 10-12
moles 40Ar, typical = 10-11
- MAP 216, min = 10-16
moles 40Ar, typical = 10-14
- VG1200b, min = 10-12 moles
40Ar, typical = 10-11