Preprints
https://doi.org/10.5194/gchron-2021-27
https://doi.org/10.5194/gchron-2021-27

  20 Sep 2021

20 Sep 2021

Review status: this preprint is currently under review for the journal GChron.

Calcite U-Pb dating of altered ancient oceanic crust in the North Pamir, Central Asia

Johannes Rembe1, Renjie Zhou2, Edward R. Sobel1, Jonas Kley3, Chen Jie4, Jian-xin Zhao2, Yuexing Feng2, and Daryl L. Howard5 Johannes Rembe et al.
  • 1Institute of Geosciences, University of Potsdam, 14476 Potsdam-Golm, Germany
  • 2School of Earth and Environmental Sciences, The University of Queensland, St. Lucia QLD 4072, Australia
  • 3Department of Structural Geology and Geodynamics, Georg-August-Universität Göttingen, 37077 Göttingen, Germany
  • 4State Key Lab. of Earthquake Dynamics, Xinjiang Pamir Intracontinental Subduction National Field Observation and Research Station, Institute of Geology, China Earthquake Administration, X9GJ+RV Chaoyang, Beijing, China
  • 5The Australian Synchrotron, 800 Blackburn Rd Clayton, VIC 3168, Australia

Abstract. The North Pamir, part of the western syntax of the India-Asia collision zone, preserves remnants of a poorly investigated Paleozoic intra-oceanic subduction zone. To constrain the age of this ancient ocean floor, we analyzed calcite phases in vesicular basalt and basaltic volcanic breccia with U-Pb geochronology using laser-ablation inductively-coupled-plasma mass-spectrometry (LA-ICP-MS). Calcite dating yielded Mississippian ages, mostly overlapping each other within errors. REE + Y data reveal that the basaltic host rock of the calcite and oxidizing seawater are major sources of trace elements during calcite precipitation. U-Pb ages seem to be independent of REE + Y concentrations. Our results demonstrate the potential of calcite dating to constrain the age of ancient ocean floors and provide a test of the hypothesis that a continuous early Paleozoic Kunlun Terrane extended from northern Tibet into the North Pamir.

Johannes Rembe et al.

Status: open (until 08 Nov 2021)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • CC1: 'RC – Comment on gchron-2021-27', Dimitry Konopelko, 03 Oct 2021 reply
    • AC1: 'Reply on CC1', Johannes Rembe, 06 Oct 2021 reply
  • RC1: 'Comment on gchron-2021-27', Alexander Robinson, 05 Oct 2021 reply
    • AC2: 'Reply on RC1', Johannes Rembe, 06 Oct 2021 reply

Johannes Rembe et al.

Johannes Rembe et al.

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Short summary
Calcite is frequently formed during alteration processes in the basaltic, uppermost layer of juvenile oceanic crust. Weathered oceanic basalts are hard to date with conventional radiometric methods. We show in a case study from the North Pamir, Central Asia, that calcite U-Pb age data – supported by geochemistry and petrological microscopy – has the potential to date sufficiently old oceanic basalts, if the time span between basalt extrusion and latest calcite precipitation (~ 25 Ma) is considered.