This page is for the promotion of sharing and cooperation between labs united under the common goals of EARTHTIME. It should be used for the posting of longer technique-oriented papers, data templates, suggestions etc. Dialogue should still be done on the FORUM page. Please submit content for this page to Sam Bowring
Two New Calibration Papers
Two papers on the EARTHTIME tracer have been submitted for review to Geochimica Cosmochimica Acta.
Metrology and Traceability of U-Pb Isotope Dilution Geochronology (EARTHTIME Tracer Calibration Part I)
Evaluating Uncertainties in the Calibration of Isotopic Reference Materials and Multi-Element Isotopic Tracers (EARTHTIME Calibration Part lI)
The two manuscripts are undergoing external peer review. Together they outline the metrologic underpinning of the tracer calibration and the algorithm developed to combine the data and quantify the uncertainty for derived U-Pb dates. If you have any comments on the manuscripts please contact the corresponding authors. Check out the poster: A Traceability Schematic for the Calibration of (EARTHTIME) U-Pb Isotope Dilution Geochronology.
Latest calibration of ET535 and ET2535 tracers
You can download the Excel fil fith the latest tracer calibration here. If you are a Tripoli and Redux user, the latest tracer calibrations are automatically updated.
How to qualify for an aliquot of EARTHTIME 205Pb-233U-235U tracer solution (EARTHTIME tracer #1)
Demonstrate that you can calibrate your existing spike accurately with the ET and JMM gravimetric standards available from EARTHTIME.
Develop a data set for synthetic zircon solutions (available from Dan Condon, mailto:email@example.com) ideally with sub per mil reproducibility on single analyses.
Develop a data set of single crystal analyses using chemical abrasion (Mattinson 2005) for one or preferably more internationally recognized zircon standard material (e.g. TEMORA, R33, FC1, 91500, or similar), which demonstrates per mil accuracy and precision on single analyses, and less on weighted mean dates.
Demonstrate low total common Pb for zircon analyses. If a lab’s only has a 205Pb/235U or a 208Pb/235U tracer we would like to see a discussion of tracer calibration and limitations on determining total common Pb with the assumption that for natural zircons all common Pb comes from the laboratory. Small aliquots of calibrated enriched 208Pb tracer can be made available for labs that need to trace sources of blanks. Once low blanks and reasonable reproducibility mixed tracer available for final testing, in some cases we will provide small quantities of non EARTHTIME 205Pb-233U-235U tracer.
Send all of this data fully documented, either via Redux (Bowring et al., 2011) or the “yourlab” spreadsheet (Schmitz and Schoene, 2007) to Sam Bowring for committee review.
These are demonstrations of performance that ensure the benefit of using the EARTHTIME U-Pb tracers will be realized. If you have any questions please contact us (email Sam Bowring) and we will work with you.
How to qualify for an aliquot of EARTHTIME 202Pb-205Pb-233U-235U tracer solution (EARTHTIME tracer #2)
In addition to the criteria above, you must have published or had accepted for publication three papers using the EARTHTIME tracer #1 solution.
There is much less of EARTHTIME tracer #2 than the #1 and thus you must agree to use it only for studies where the fractionation is the dominant source of your total analytical uncertainty.
CIRDLES: the computing arm of EARTHTIME
EARTHTIME's goals for improving the precision of uranium-lead geochronology depend on developing robust software systems for data-handling. The Cyber Infrastructure and Development Lab for the Earth Sciences (CIRDLES.org) is leading this effort on behalf of EARTHTIME. CIRDLES.org develops open source software and provides community forums to support EARTHTIME and EarthChem. The software packages "Tripoli" and "U-Pb_Redux" currently support ID-TIMS. Software support for LA-ICP MS is under development.
Excel workbook for ICE
Data reduction Excel workbook for U-Pb ID-TIMS interlaboratory experiment - see U-Pb Forum for more information. Get the .xls file here.
Additional ICE news
We have just finished blank checking the first batch of 3ml hex Savillex, 41 of the 51 checked were clean. At present there are 15 labs who requested solutions so we are just waiting for the next batch of clean and checked beakers. We will start sending the solutions out in the next couple of weeks, so I just thought I'd take this opportunity to clarify some points regarding what we will be sending, and the expectations for the interlab experiment. Everyone involved or interested should read the more detailed document available as a PDF here.
Synthetic U-Pb solutions for assessing ID-TIMS intra- and inter- laboratory reproducibility
As part of the EARTHTIME Initiative, NIGL is involved in development and calibration the ET535 and ET2535 tracers, as well as development of new standard materials. In particular, we prepared and calibrated a series of synthetic U-(Th)-Pb solutions that have 206Pb-238U and 207Pb-235U ratios that yield “concordant” 206Pb-238U and 207Pb-235U ages at 10 Ma, 100 Ma, 500 Ma and 2 Ga.
The synthetic solutions were prepared in quantities sufficient that they can be used as long term standards, with the aim that they can be used for (1) assessment of long-term intra-laboratory reproducibility and (2) assessment of inter-laboratory agreement. We are currently using these solutions to assess the long-term reproducibility of U-Pb ID-TIMS data generated at NIGL and for direct comparison with similar data generated in other labs.
The solutions permit easily variable load size making them suitable to inter- calibrating detection modes (such as dynamic ion counting or static faraday measurements) and assessing accuracy of various corrections.
The solutions were prepared by iterative mixing of natural uranium (SRM 950a), 206Pb (SRM 991) and 207Pb (metal from Cambridge Isotopes) solutions. Determination of the 206Pb-238U and 207Pb-235U ratios is being achieved via calibration against the ET535 tracer.
In that these solutions do not require any chemical purification, combined U- Pb loads can be prepared by mixing in a pre-cleaned beaker, meaning that the exposure to laboratory blank, and effort in preparing loads is reduced, compared to a mineral standard. We believe these solutions will augment natural mineral standards (such as R33 and Temora) for ID-TIMS, allowing for greater evaluation of mass-spectrometry as post-crystallisation Pb-loss and natural variation in zircon crystallisation will not be factors.
We are currently cleaning vessels for the transport of these solutions to other labs and hope to begin shipping materials in the next several weeks. If you are interested in obtaining these materials please contact Dan Condon for more information.
Tripoli is now Shareware.
Tripoli, a powerful new program for viewing, filtering, and interpreting cycle-by-cycle mass spectrometer data, is now available free of charge. For more information, click here.
EarthChem Workshop on Geochronology for U-Pb
EarthChem is a community driven project to facilitate the compilation and dissemination of geochemical data of all types. EarthChem will likely be a major repository of U-Pb geochronological data. EARTHTIME is working with EarthChem to design readily exportable output from U-Pb data reduction programs that can be readily input into the EarthChem data base.
A meeting was held to discuss the minimum data requirements for archiving U-Pb data and the report as well a proposed data entry template are posted here as a pdf. Please look at the report and the list of minimum reportable parameters and provide feedback either to EARTHTIME and/or EarthChem. Your input is crucial!.
Schmitz adds labshare page
Mark Schmitz added a labshare page to his website. There's lots of good stuff there. Check it out!
Data Sucker is available. Learn about it here.
EARTHTIME U-Pb spike
EARTHTIME U-Pb spike is available!!! Get yours here!!
Learn more about zircons from Permian-Triassic Boundary at Meishan and get your samples here!!
Get zircons & baddeleyite from Duluth complex. Look here!!
McClure Mountain syenite
U-Pb systematics of the McClure Mountain syenite: thermochronological constraints on the age of the 40Ar/39Ar standard MMhb Get a preprint here
Reassessing the uranium decay constant for geochronology using ID-TIMS U-Pb data: Get your preprint of this new and exciting paper here.
As described at the EARTHTIME II meeting:
Here is Jim Mattinson's paper documenting his revolutionary breakthrough in the creation of concordant zircons: Zircon U–Pb chemical abrasion ("CA-TIMS") method: Combined annealing and multi-step partial dissolution analysis for improved precision and accuracy of zircon ages.
U-Oxide correction protocol for 233U/235U double spike
U-Pb reduction program for Mac's or PC's
U-Pb Calibration Solutions
As discussed at the EARTHTIME II workshop, Jim Mattinson, Randy Parrish, and MIT have made their calibration solutions available for the community. Many aliquots have been distributed and there are more available. please request from Sam Bowring. Below, are the details for all three solutions. Please send requests for Randy's solution directly to him. If anyone else has a good solution that can be used for the intercalibration of our spikes, please feel free to let us know.
Mattinson Calibration solution
MIT Calibration solution
EARTHTIME is supported by the National Science Foundation.