Preprints
https://doi.org/10.5194/gchron-2020-19
https://doi.org/10.5194/gchron-2020-19

  26 Jun 2020

26 Jun 2020

Review status: a revised version of this preprint is currently under review for the journal GChron.

Towards in-situ U–Pb dating of dolomites

Bar Elisha1,3, Perach Nuriel1, Andrew Kylander-Clark2, and Ram Weinberger1 Bar Elisha et al.
  • 1Geological Survey of Israel, Jerusalem, Israel
  • 2Department of Earth Sciences, University of California, Santa Barbara, CA, USA
  • 3Department of Natural Sciences, The Open University of Israel

Abstract. Recent U–Pb dating by laser ablation ICP-MS has demonstrated that reasonable precision (3–10 % 2σ) can be achieved for high-resolution dating of texturally distinct calcite phases. Absolute dating of dolomite, for which biostratigraphy and traditional dating techniques are very limited, remains challenging but may resolve many fundamental questions related to the timing of mineral-rock formation by syngenetic, diagenesis, hydrothermal, and epigenetic processes. In this study we explore the possibility of dating dolomitic rocks via recent LA-ICP-MS dating techniques developed for calcite. The in-situ U–Pb dating was tested on a wide range of dolomite rocks of various origins (i.e., syngenetic, early diagenetic and epigenetic) from the Cambrian to Pliocene age – all of which from well-constrained stratigraphic sections in Israel. We present in-situ U–Pb results of dolomitic rock samples, together with imaging techniques and chemical characterizations. We show that dolomite dating is highly sensitive to textural differences and highlight parameters such as crater morphology and roughness, calcite zoning and impurities that may affect the interpretation of the resulted ages. Textural examination indicates zonation and mixing of different phases at the sub-millimeter scale (< 1 µm), and thus Tera-Wasserburg ages may represent mixing dates of early diagenesis and some later epigenetic dolomitization event(s). We conclude that age mixing at the sub-millimeter scale is a major problem in dolomite dating that need to be further studied and note the necessity of matrix-matched standards for accurate dating.

Bar Elisha et al.

 
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Status: final response (author comments only)
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Bar Elisha et al.

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Latest update: 27 Feb 2021