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<p>The Ordos Block (OB), a cratonic terrane with Archean-Paleoproterozoic crystalline basement in the western North China Craton (NCC), has long been considered tectonically stable. However, its basement architecture and Precambrian evolution remain poorly constrained due to extensive sedimentary cover and limited basement exposure. Here we present the first integrated petrological-geochemical-geochronological study of the previously unreported Maxia diabase from the southwestern OB margin. Outcropping in an abandoned quarry, the diabase is unconformably overlain by Ediacaran microclastic-carbonate sequences, preserving a well-developed paleoweathering surface. Whole-rock geochemical data suggest magma generation in an intracontinental rift setting. Both chondrite- and primitive mantle-normalized trace element patterns show remarkable similarities to regional Paleoproterozoic rift-related mafic suites. Laser ablation-inductively coupled plasma–mass spectrometry (LA-ICP-MS) baddeleyite U–Pb dating yields a discordia with an upper intercept age of 1643 ± 23&#xa0;Ma and a lower intercept age of 122 ± 75&#xa0;Ma. The upper intercept age of 1643 ± 23&#xa0;Ma, representing the first documented evidence of ca. 1.64&#xa0;Ga mafic magmatism along this cratonic margin, combined with regional geological constraints, indicates prolonged extensional tectonism (ca. 2.01–1.64&#xa0;Ga) during the Columbia supercontinent assembly. The lower intercept age of 122 ± 75&#xa0;Ma correlates with Early Cretaceous lithospheric thinning and NCC destruction during regional extensional reactivation. The paleoweathering surface between the diabase and Ediacaran strata records approximately 1 billion years of subaerial exposure (1643–635&#xa0;Ma), attesting to prolonged regional weathering and exhumation. These results demonstrate that the Maxia diabase serves as an excellent archive for probing multiple magmatic events and early tectonic evolution since the Proterozoic at the southwestern margin of the OB.</p>

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Geochemical and baddeleyite U–Pb geochronological characteristics of the 1.64 Ga diabase in the Southwestern Ordos Block: Implications for Paleoproterozoic extension, Neoproterozoic uplift and erosion, and Early Cretaceous extension

  • 期刊论文

  • 发表日期：

    2025年11月23日

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  • Yinglei Chang,
  • Jinhai Luo,
  • Zhuo Chen,
  • Haotian Zhi,
  • Bo Ji

摘要

The Ordos Block (OB), a cratonic terrane with Archean-Paleoproterozoic crystalline basement in the western North China Craton (NCC), has long been considered tectonically stable. However, its basement architecture and Precambrian evolution remain poorly constrained due to extensive sedimentary cover and limited basement exposure. Here we present the first integrated petrological-geochemical-geochronological study of the previously unreported Maxia diabase from the southwestern OB margin. Outcropping in an abandoned quarry, the diabase is unconformably overlain by Ediacaran microclastic-carbonate sequences, preserving a well-developed paleoweathering surface. Whole-rock geochemical data suggest magma generation in an intracontinental rift setting. Both chondrite- and primitive mantle-normalized trace element patterns show remarkable similarities to regional Paleoproterozoic rift-related mafic suites. Laser ablation-inductively coupled plasma–mass spectrometry (LA-ICP-MS) baddeleyite U–Pb dating yields a discordia with an upper intercept age of 1643 ± 23 Ma and a lower intercept age of 122 ± 75 Ma. The upper intercept age of 1643 ± 23 Ma, representing the first documented evidence of ca. 1.64 Ga mafic magmatism along this cratonic margin, combined with regional geological constraints, indicates prolonged extensional tectonism (ca. 2.01–1.64 Ga) during the Columbia supercontinent assembly. The lower intercept age of 122 ± 75 Ma correlates with Early Cretaceous lithospheric thinning and NCC destruction during regional extensional reactivation. The paleoweathering surface between the diabase and Ediacaran strata records approximately 1 billion years of subaerial exposure (1643–635 Ma), attesting to prolonged regional weathering and exhumation. These results demonstrate that the Maxia diabase serves as an excellent archive for probing multiple magmatic events and early tectonic evolution since the Proterozoic at the southwestern margin of the OB.