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Presented By: Earth and Environmental Sciences

Smith Lecture: Unraveling Potential Biases in U-Pb Detrital Zircon Record Induced by High-temperature Metamorphism (> 850 ºC)

Mahyra Tedeschi, Universidade Federal de Minas Gerais

Zoom Webinar ID#988 7708 8805
The assessment of detrital zircon age records is a key method in modern basin analysis, but it is prone to several biases that can compromise accurate sedimentary provenance investigations. High-temperature metamorphism (> 850 ºC) is herein presented as a natural cause of bias in provenance studies based on U-Pb detrital zircon ages, since zircons from rocks submitted to these extreme and often prolonged conditions frequently yield protracted, apparently concordant, geochronological records. Such spectrum can result from disturbance of the primary U-Pb zircon system, likewise from (re)crystallization processes during multiple and/or prolonged metamorphic events. In this contribution available geochronological data on Archean, Neoproterozoic and Paleozoic metamorphic rocks, acquired by different techniques (SIMS and LA-ICP-MS) and showing distinct compositions, are reassessed in order to demonstrate how these processes may result in age peaks and spectra of unclear geological meaning and exclusively formed by temperature-induced disturbance during high-grade metamorphism. As a consequence, it may induce misinterpretations on U-Pb detrital zircon provenance analyses, depending on the timing of the high-temperature metamorphism relative to the deposition of the studied strata. To evaluate the presence of high-temperature metamorphism-related bias in a given detrital zircon sample, we suggest a workflow for data acquisition and interpretation, combining a multi-proxy approach with: in situ U-Pb dating coupled with Hf analyses to retrieve the isotopic composition of the sources, and the integration of a petrochronological investigation to typify fingerprints of the (ultra)high-temperature metamorphic event.

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February 26, 2021 (Friday) 3:30pm
Meeting ID: 98877088805

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