Arizona LaserChron Center

The Arizona LaserChron Center is designed to address problems in Earth Science through the generation of high quality U-Th-Pb geochronologic information. Our primary goals are as follows:

Maintain a facility that generates U-Th-Pb ages of the best precision and accuracy available from a Laser-Ablation Multicollector ICP Mass Spectrometer.
Provide opportunities for researchers from around the world (and especially NSF-supported scientists) to use our instruments and expertise to address geologic problems.
Push the development of new applications of laser ablation mass spectrometry.
Provide opportunities for researchers to learn the theory and analytical techniques of U-Th-Pb geochronology while acquiring geochronologic information.

The main instrument utilized at the Arizona LaserChron Center is a Multicollector Inductively Coupled Plasma Mass Spectrometer (GVI Isoprobe) coupled to a 193 nm Excimer laser ablation system (New Wave Instruments and Lambda Physik). These instruments were purchased in 2000 and have been continuously upgraded as new hardware and software became available.

Support for the Arizona LaserChron Center is provided by the NSF Instrumentation and Facilities Program. The center is a multi-user facility, available to all NSF-supported researchers as well as students and researchers from around the world. NSF funding allows us to reduce the cost of NSF-supported research by ~50%, with additional support available to subsidize research conducted by students. We also welcome researchers who are not supported by the National Science Foundation.

What's New:

-- We have received a new Nu Plasma MC-ICPMS which is dedicated to geochronological and geochemical research in the ALC. The instrument was installed in February 2009 and is currently being developed to measure U-Th-Pb ages, Hf and Li isotope ratios, and trace element and REE concentrations. We have worked closely with Nu Plasma engineers to design a new collector block that allows for analysis of U-Th-Pb and Hf isotopes in the same acquisition, from the same laser pit. Twelve faraday collectors are arranged to measure 238U, 232Th, and 180-171 (for Hf, Lu, and Yb), whereas four low-side ion counters measure 208-204Pb. A New Wave UP193HE laser, refurbished to include an ATL short-pulse excimer laser, is connected to the Nu ICPMS.

-- We are very pleased that Robinson Cecil and Frank Mazdab have recently joined the ALC. Robinson is conducting a post-doc primarily on the development of methods for analyzing Hf isotopes, whereas Frank is working mainly on Li isotopes and trace/REE elements in zircon and a variety of other phases.

-- A Short Course for U-Pb geochronologic theory & methods has been developed. Check it out and send comments/suggestions for improvement!

-- A program called "Age Pick" has been developed which helps evaluate whether U-Pb analyses are compromised by Pb loss and/or overgrowth of metamorphic zircon. The program allows users to include or exclude specific analyses from a data set and evaluate the impact both graphically (on plots of 206Pb/238U age versus Uconc and U/Th) and quantitatively (in terms of weighted mean age, uncertainty, and MSWD). It is hoped that this program will provide a more robust method for determining ages and uncertainties of igneous zircons and of clusters of detrital zircons (e.g., youngest age population). The program also calculates the age ranges and peak ages present within a set of detrital zircon ages. Check it out and send comments!

Mount Preparation