Petrogenesis of Mesoproterozoic mafic rocks in Hainan (South China) and its implication on the southwest Hainan-Laurentia-Australia connection

New U-Pb geochronological, elemental and Nd-Hf isotopic data for the metamorphic mafic rocks from the Baoban Complex in southwest Hainan provide new constraints on their petrogenesis and geodynamic setting. Magmatic zircons from the representative samples yielded weighted mean Pb-207/Pb-206 ages of 1441-1424 Ma, representing their crystallization ages. These samples show subalkaline to alkaline characteristics and can be geochemically subdivided into three groups in spite of similar formation time. Group 1 has TiO2 of 2.85-3.18 wt.%, Nb of 20.5-21.6 ppm, Nb/U of 45-49, Nb/La of 1.22-1.37, epsilon(Nd) (t) of +6.8-+6.9 and zircon epsilon(Hf) (t) of +9.3-+12.7, suggestive of the derivation from OIB-like source. Group 2 shows Nb contents ranging from 1.0 ppm to 12.6 ppm, epsilon(Nd) (t) values from +5.5 to +5.9 and zircon epsilon(Hf) (t) values from +10.3-+12.4 with right-sloping REE-normalized pattern, indicative of an E-MORB source. Group 3 is characterized by negative Nb-Ta anomalies with Nb/La ratios of 0.51-0.88 and epsilon(Nd) (t) value of similar to+5.1, indicative of the derivation from a previously-metasomatized mantle source. The coeval mafic and felsic rocks in the Baoban Complex are geochronologically and geochemically comparable to the Mesoproterozoic intra-plate magma in southwest Laurentia. The Mesoproterozoic Baoban igneous rocks are generated in a syn-rift setting in response to the Columbia breakup. Southwest Hainan might connected with west Laurentia and Australia at similar to 1.43 Ga.