Geochronology, geochemistry and zircon Hf-isotopes of the early Mesoproterozoic Yaopengzi dolerite in SW Yangtze block (Sichuan, SW China): implications for the Columbia supercontinent breakup

Magmatism in the Huili area (SW margin of the Yangtze block) was active during the early Mesoproterozoic, and has important implications on the early tectonic evolution of the Yangtze block. We report new data in petrology, whole-rock geochemistry, zircon U-Pb and Hf isotopes for the Yaopengzi dolerite in the Huili area. LA-ICP-MS zircon U-Pb dating of the dolerite yielded an early Mesoproterozoic age of ca. 1515-1513 Ma, coeval with the Columbia supercontinent breakup. The dolerite belongs to the alkali basalt series, and is enriched in light rare earth elements (LREE) and large ion lithophile elements (LILE), resembling typical oceanic island basalt (OIB) in geochemistry. Zircons from the Yaopengzi dolerite yielded Hf-176/Hf-177 = 0.28192-0.28203 and epsilon(Hf(t)) =-0.3 to 5.3. Our integrated study suggests that parental magma of the Yaopengzi dolerite may have originated from the enriched mantle, and was slightly contaminated by crustal materials during its evolution. Combining with regional tectonic background, the early Mesoproterozoic mafic magmatism at/ around Yaopengzi may have formed in a mantle plume-related intracontinental rift setting. This reflects that the early Mesoproterozoic extension in the Yangtze block may have resulted from mantle plume activities led by the Columbia supercontinent breakup.