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Re-Os dating of paleozoic organic-rich black shales by LA-ICP-MS/MS

Jay M. Thompson·Stijn Glorie·Amanda Kate Souders·Sarah E. Gilbert·Timothy Paton·Poul Emsbo
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Abstract

We present a new in-situ method for Re- Os geochronology of black shales using LA-ICP-MS/MS that is rapid, cost-effective, and sufficiently accurate and precise to address many geological questions. The method is tested on Paleozoic organic-rich black shales with independently constrained stratigraphic or radiometric ages. Results demonstrate that LA-ICP-MS/MS analysis yields Re- Os dates and initial Os isotopic compositions generally within uncertainty of published values using a laser spot size of 100 to 120 μ m in diameter. Despite low Os abundances in many samples, high-density microscale sampling compensates through large numbers of analyses, enabling robust inverse isochron regressions. The approach also allows contemporaneous acquisition of trace- element data (V, Ni, Mo and Re), providing insight into metal distribution in a sample, degree of metal enrichments, and serve as a proxy for open-system behavior for Re- Os. As a result, LA-ICP-MS/MS Re- Os analysis can serve both as a stand-alone geochronological tool and as an efficient screening method prior to conventional ID-N-TIMS, helping to identify optimal intervals and exclude isotopically disturbed material. Together, our study demonstrates that in-situ Re- Os geochronology of organic-rich shales is technically viable, geologically informative, and broadly applicable, opening new opportunities to investigate basin evolution, metallogenesis, hydrocarbon systems, and Earth-system processes across deep time.

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Jay M. Thompson, Stijn Glorie, Amanda Kate Souders, Sarah E. Gilbert, Timothy Paton, Poul Emsbo. 2026-08-13. Re-Os dating of paleozoic organic-rich black shales by LA-ICP-MS/MS. https://doi.org/10.5066/p13zty3i

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