LA-ICPMS zircon U-Pb ages and geochemistry of Neoproterozoic low-grade metavolcanic rocks in Wuyuan-Dexing area of northeastern Jianxi Province
赣东北婺源-德兴地区新元古代浅变质火山岩的地球化学和锆石U-Pb年龄

Low-grade metamorphosed volcanic rocks consist mainly of metamorphic basalt, dacite and rhyolite in the Wuyuan to Dexing region of the northeastern Jiangxi Province. Whole-rock geochemical analyses reveal that the metabasalt has chemical features of the tholeiite, and the basaltic magma originated from low-degreed partial melting of a spinel lhezolite in disturbed deleted mantle. However, the dacitic magma was derived from a partial melting of a meta-greywacke, and the rhyolite was produced by the fractionation of the dacitic magma. LA-ICP-MS zircon U-Pb isotope dating indicates low-grade meta-dacite from the Wuyuan area was formed at 861±8Ma, and meta-rhyolite and tuffaceous slate from the Dexing area at 860±3Ma and 860±6Ma, respectively, which indicate that these metamorphic volcanic rocks erupted at Neoproterozoic Tonian era. Meanwhile, these samples also preserved some signatures of Neoarchean (2.8~2.5Ga), Middle-Late Paleoproterozoic (2.0~1.7Ga) and Mesoproterozoic (~1.0 Ga) inherited and/or captured zircon ages. Integrated the whole-rock geochemistry, petrogenesis and zircon ages, we suggest that these metamorphic volcanic rocks formed under an Early Neoproterozoic tectonic background of back-arc basin in Andes-type actively continental margin.