Application of in situ U-Pb carbonate geochronology to Stenian-Tonian successions of North China

摘要

Linking geological and biological events requires a robust geochronologic framework, which is especially challenging for poorly fossiliferous Precambrian strata. Although this can be achieved through zircon U-Pb dating, only maximum or minimum ages can typically be obtained, with rare interbedded volcanic ash beds providing precise depositional ages. U-Pb dating of authigenic carbonates could potentially become a more widely applicable geochronometer, but only if carbonate minerals can be dated with sufficient precision. A renaissance in carbonate U-Pb geochronology, utilizing the in situ laser ablation method, has opened new doors in the application of this method to geological problems. Here we apply laser ablation U-Pb dating to carbonate-rich sedimentary strata of likely Meso-Neoproterozoic age on the southeastern margin of the North China Craton, resulting in two meaningful U-Pb ages of 1036 +/- 45 Ma and 1010 +/- 36 Ma (2 sigma), from early diagenetic fine-grained microspar samples. As well as being mutually consistent, these new ages show that precision approaching the limiting uncertainty of the reference material used (similar to 2.5% 2 sigma) can be achieved. Success in this study holds promise for dating other key Precambrian successions.

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