Geochemistry of upper Palaeozoic ‘thin-layer’ limestones in the southern North China Craton: implications for closure of the northeastern Palaeotethys Ocean

Abstract

During the late Palaeozoic Era, a series of related marine strata dominated by multi-layer limestones were deposited in the southern North China Craton. In order to gain new insights into the systematic geochemistry of the carbonate succession of the representative formation (Taiyuan Formation), we examined 59 limestone samples collected from the Huaibei Coal Basin (HCB), with a view towards quantitatively determining the major and trace elements and stable isotope compositions. The data obtained can provide essential evidence for reconstruction of the depositional palaeo-environment and tectonic setting of the Taiyuan Formation. Both X-ray diffraction analyses and palaeoredox proxies (e.g. V/Cr, V/(V + Ni) and authigenic U) indicated that the limestone layers were deposited in an oxic–dysoxic zone, with calcite as the main component. Moreover, palaeomagnetic evidence provided support for the conclusion that these limestones were laid down within an epicontinental sea depositional environment under a warm or hot palaeoclimate during the transition between late Carboniferous and early Permian time. Additionally, evidence obtained from our analyses of trace and rare earth elements revealed that the tectonic setting of the Taiyuan Formation (L1–L5) in the HCB transited from an open ocean to a passive continental margin, thereby indicating that this transformation stemmed from the subduction closure of the northeastern Palaeotethys Ocean. The findings of this study would be of interest to those working on the upper Palaeozoic marine strata in the southern North China Craton.

Characterization of the Govanda Formation limestones: chemostratigraphy and tectonic setting of the last marine carbonate rocks in the Arabia–Eurasia suture zone, NW Zagros fold-thrust belt

“…Hydrothermal alteration and burial metamorphic can occur during the early and late stages of diagenesis, leading to the destruction of the original depositional information in carbonate rocks (Knauth & Kennedy, 2009;Li et al, 2022). The findings of our chemical analyses of major oxides in the present study revealed that calcite is the main mineral component of limestones of the Govanda Formation, which is consistent with the average content of CaO (51.6%).…”

“…REEs patterns in carbonate rocks are not affected by alteration or strong weathering (Webb & Kamber, 2000). However, the behavior of certain elements, such as Ce and Eu, may vary due to differences in valence states under different redox conditions, leading to anomalies in their behavior and differentiation in rare earth element associations (Webb & Kamber, 2000;Tribovillard et al 2006;Li et al 2022). According to Webb & Kamber (2000), in this study, we assessed the correlations between Ce/Ce*;…”