Le Geotop - Dr. Steven W. Denyszyn : High-Precision U-Pb ... (16-11-2017)

Dr. Steven W. Denyszyn : High-Precision U-Pb ... (16-11-2017)

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Dr. Steven W. Denyszyn (University of Western Australia, Perth)

High-Precision U-Pb Geochronology:
A Window into Igneous Petrology, Geodynamics, and Ore Deposit Geology

Jeudi 16 novembre 2017 à 12h00/ Thursday, November 16, 2017, 12:00pm

Local PK-6601, 201 ave. Président-Kennedy, UQAM

Résumé / Abstract:

In order to reconstruct Earth history, we need to achieve a robust understanding of the timing of geological events. In recent years, there have been great advances in in situ methods of U-Pb geochronology, allowing for high spatial resolution and the ability to make many analyses quickly, with steady improvement in precision and accuracy. However, these methods lack the time resolution required to precisely determine the age of a geological sample (typically zircon or baddeleyite) in order to, for example, establish the rates of Earth processes or environmental changes, or to distinguish discrete pulses in a rapidly-evolving magmatic system. For these problems, the methodology of Isotope Dilution – Thermal Ionization Mass Spectrometry (ID-TIMS) U-Pb geochronology remains the only option to provide the high-precision age information that is required.

This presentation will describe the methods and applications of ID-TIMS U-Pb geochronology, particularly with respect to igneous samples, with a focus on recent work carried out at the radio-isotopic research facility at the University of Western Australia.

Several examples will be provided of the potent combination of high-precision U-Pb geochronology with other geological, geochemical, and isotopic information as it can be applied to the study of igneous petrology, economic geology, and geodynamics (and the many linkages between these). Important questions ranging from the study of continental growth at arcs, to the formation of magmatic ore deposits and the metal and sulphur fertilization of the lower crust, to the reconstruction of paleocontinents through time, can be addressed to a significant degree with the addition of high-resolution geochronological analyses to other types of data sets. Across the diverse range of the Earth sciences, from saving millions of dollars in mineral-exploration costs by narrowing the search space to constraining the timing and tempo of biotic evolution and the configuration of continents, the question of when, and for how long, these processes occurred is an essential one, but it must always be kept in an appropriate geological context.