Using the 230Th/U and 234U/238U methods, this lab is capable of dating samples ranging in age from about a million years old to less than 100 years. On suitable materials, the 230Th/U method is sufficiently precise and reliable that it is used as the ultimate calibration of the radiocarbon dating method for samples older than about 10,000 years.
Using the U-Pb method, this laboratory also provides precise dates for rocks and minerals ranging in age from billions of years to about a million years. Because of the extreme resistance of such minerals as zircon to age resetting, the U-Pb system has proven more reliable than other dating methods for rocks that have been strongly reheated, sheared, or exposed to hydrothermal fluids.
The Uranium-Daughter Laboratory features: 1) a MicroMass Sector 54 thermal-ionization mass spectrometer (TIMS), equipped with a WARP filter for very high abundance sensitivity, eight Faraday collectors (for high precision analyses of large samples), and an ion-counting collector (for analyses of extremely small samples), and 2) a Thermo-Fisher NEPTUNE Plus multi-collector inductively coupled plasma mass spectrometer (ICP-MS) with nine Faraday collectors, and an axial, discrete dynode ion counter with a tunable repelling potential quadrupole energy filter (for increased abundance sensitivity). Associated with the Neptune ICP-MS are two sample introduction devices, a Cetac Aridus II system for solution analyses, including a desolvation nebulizer and automated sample handling system, and a Photon Machines programmable laser ablation system including a 193 nm excimer laser and a two-volume, ANU-type sample cell, which provides the capability to analyze samples with spatial resolutions of 10s of microns.
Samples for the TIMS and ICP-MS are prepared in a clean lab, equipped with a highly-filtered, positive-pressure air supply, and four ultraclean HEPA-filtered laminar-flow workstations. Routine contamination levels in the lab for zircon analyses have been reduced to less than a trillionth of a gram of lead, permitting U-Pb dating of single crystals of zircon finer than a grain of sand and of almost any age.