ThegeochemistryofthebasicvolcanicrocksatthesouthmarginoftheQinlingorogenicbelt(SMQOB)suggeststhattheywereformedinanintraplatetectonicsetting.TheREEdistributionpatternsshowtheserocksarestronglyenrichedinLREEwithhigh∑REE,andtheirtraceelementsgeochemistryissimilartothatofcontimentalfloodbasalt.AlltheaboveevidencesuggeststhattheCaledonianbasicvolcanicrocksintheSMQOBweretholeiiticbasaltsformedinanintraplatespreading-initialrifttectonicsetting.Thecharacteristicsofregionalgeologyandgeochemistryindicatethattherewasanintraplatespreading-rifttectonicsettingbetweentheSouthQinglingblockandtheYangtzeblockintheCaledonianepoch.ThedynamicspreadinginthisdistrictbeganintheEarlyCaledonianandthentheintraplatespreadinginitialriftswereformedintheLateCaledonian.AsaresultofspreadingoftheTethysandgeodynamicprocessesindeepmantle,theMianlue-HuashanoceanicbasinwasformedbetweentheQinlingblockandtheYangtzeblockinDevonian,andtheQinlingmicroplatewasseparatedfromthenorthernpartoftheYangtzeplate.