Arizona LaserChron Center

The Arizona LaserChron Center is designed to address problems in Earth Science through the generation of U-Th-Pb geochronologic data and complementary geochemical information by LA-ICPMS. 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 ICP mass spectrometry.
Provide opportunities for researchers and students 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 Nu Plasma HR 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, Li, and B 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 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. All Faraday collectors are equipped with 3x10e11 ohm resistors for enhanced signal/noise at low signal intensity. A New Wave UP193HE laser, refurbished to include an ATL short-pulse excimer laser, is connected to the Nu ICPMS. We also have a GVI Isoprobe MC-ICPMS coupled to a New Wave DUV 193 nm excimer laser ablation system which is used for traditional U-Pb geochronology of zircons. The Isoprobe has been used primarily for U-Pb geochronology of zircons since 2000, and is approaching one million U-Pb analyses!

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.

What's New:

-- Alex Pullen will be the interim Manager of the ALC during Spring 2010. Alex can be contacted at apullen@email.arizona.edu for information about analytical methods, schedules, costs, support letters, etc.

-- We will be searching for a permanent Lab Manager and a post-doc. Stay tuned for position descriptions, and please contact George Gehrels (ggehrels@email.arizona.edu) if interested...

-- We are experimenting with a new system for keeping track of projects, samples, costs, correspondence, etc. If you have an upcoming visit, you can probably find information about your samples and arrangements at our Project Status Page. You will eventually be able to upload information to the site, but for now please contact George Gehrels (ggehrels@email.arizona.edu) for info or input.

-- We are making excellent progress with developing measurement techniques for Hf and Li isotopes of zircon, Nd isotopes of monazite, titanite, and apatite, and U-Pb of apatite, rutile, titanite, and baddeleyite. This development work is being led by post-docs Robinson Cecil, Frank Mazdab, Fernando Barra, and Stuart Thomson, and PhD student Alex Pullen. Our first Hf data set, from the Sierra Nevada and Coast Mountains batholiths, is just coming together and should be ready to present at AGU this fall.

-- 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 U-Pb analyses in light of other available information (e.g., spot location, U concentration, U/Th, degree of discordance, etc.). This should provide opportunites to interrogate data for complications from inheritance, Pb loss, and/or overgrowth of metamorphic zircon. The program also calculates the age ranges and peak ages present within a set of detrital zircon ages. Check it out and send comments!

-- We have recently been funded for the acquisition of a new SEM system, which will be equipped with color CL and integrated EDS/EBSD detectors. This will greatly enhance our ability to image and analyze minerals porior to analysis by LA-ICPMS. For SE/BSE images from recent demos, click here for Hitachi 3400N results and here for FEI Quanta results. Stay tuned for updates!

-- A workshop focusing on reduction, analysis, and archival of U-Th-Pb data acquired by LA-ICPMS was conducted on Dec 12-13, 2009 in San Francsico. The workshop was conducted at the San Farncisco Marriott, with participants from many of the LA-ICPMS labs around the world. Conveners include Matt Horstwood, George Gehrels, and Jim Bowring -- contact any of us for more info!

-- Alex Pullen and Martin Pepper have prepared a very detailed guide to making mounts for LA-ICPMS analysis. Check it out!