Baddeleyite U-Pb geochronology and geochemistry of Late Paleoproterozoic mafic dykes from the Kongling complex of the northern Yangtze block, South China

•Ca. 1.87 Ga mafic dykes occur in the northern Yangtze block.•The dykes were derived by partial melting of metasomatised lithospheric mantle in a post-orogenic setting.•Tectonic regime switching from convergence to extension in the Yangtze block could have occurred at ~1.87 Ga.•It infers a southern Siberia-Yangtze-northern Laurentia connection during Columbia evolution. Baddeleyite LA-ICP-MS U-Pb geochronology, major and trace element geochemistry and Nd-Pb isotope analysis of Late Paleoproterozoic mafic dykes from the northern Yangtze block, South China craton are used to investigate their petrogenesis and tectonic implications. The dykes mainly consist of fine-grained dolerite. Baddeleyite U-Pb dating indicates that the dolerites formed at 1866 ± 21 Ma. These rocks are alkaline in composition with high TiO2 contents (2.21–3.17 wt%) and display LREE enrichments ((La/Yb)N = 6.0–6.4) with slight positive Eu anomalies (Eu/Eu* = 1.06–1.14). On primitive mantle normalized multi-element diagrams they generally show convex upward curves with weak negative Nb-Ta anomalies. All of the samples have similar Nd-Pb isotopic compositions with negative εNd(t) values ranging from −4.3 to −3.2, (206Pb/204Pb)i from 14.91 to 15.31, (207Pb/204Pb)i from 14.99 to 15.08, and (208Pb/204Pb)i from 34.75 to 35.58. Geochemical features such as EM1-like isotopic compositions suggest the dolerites were derived from partial melting of metasomatised subcontinental lithospheric mantle. The mafic dykes are inferred to have formed in a post-orogenic extensional setting. We suggest that the northern Yangtze block experienced a tectonic switch from convergence to extension at ~1.87 Ga. A comparison of Paleoproterozoic magmatic, metamorphic, and sedimentary events in the Yangtze block with the southern Siberian craton and northern Laurentia supports a Paleoproterozoic position of the Yangtze block adjacent to southern Siberia and northern Laurentia within the Columbia supercontinent.