Petrogenesis of Early Paleozoic lamprophyre in North Qinling Orogenic Belt and their implications

Early Paleozoic tectonic evolution of Qinling Orogenic Belt and Shangdan Ocean remains an argument because of the different understandings of Early Paleozoic geological records, including the petrogenesis of magmatic and metamorphic rocks and formation setting of Liuling Groups. In this paper, we present zircon U–Pb data and geochemical and isotopic compositions of the lamprophyres in the southern part of North Qinling Orogenic Belt. The lamprophyres yield zircon U–Pb ages of ca. 470 Ma and are coeval with the Early Paleozoic potassium–rich mafic rocks (Fushui complex). The lamprophyres belong to calc-alkaline series and are characterized by enrichment in large-ion lithophile elements and light rare earth elements and depletion in high field strength elements. Lamprophyre and mafic rocks, etc, the crust-like geochemical signatures represent a source feature. The lamprophyres also have high initial Sr ratios of 0.706859 to 0.713288 and enrich Nd isotopic composition with ε Nd ( t ) values of − 6.8 to − 8.3, implying that they are derived from the enriched subcontinental lithospheric mantle. In addition, the lamprophyres intrude into the supracrustal Luohansi Formation, representing their shallow intrusive level, and cross through the crust and carry the key information. In the lamprophyres, there are many Neoproterozoic zircon xenocrysts with ages of 813.3 to 825.6 Ma, which is affinity with South Qinling Orogenic Belt. This is an implication of the closure of Shangdan Ocean and collision between North Qinling Orogenic Belt and South Qinling Orogenic Belt during the formation of lamprophyre.