简介:TheCarboniferousvolcanicrocksinwesternHainanIslandconsistofaseriesofoceanictholeiteandrhyoporphyrite,showingbimodalnature.Similargeochemicalcharacters,intermsofabun-dacesandrelativerationsofincompatibleelementsandREEandtheREEpatterns,betweenthebasaltandcontinentalrift-associatedtholeiiteindicatetheoccurrenceofLatePaleozoicriftinginthearea.Thebasalticmagma,withalowdegreeofevolution,wasoriginatedfromdeepmantle,show-ingcontaminationbylowcrustalmaterial.Therhyoliteisthoughttobeformedfrompartialmeltingofthecontinentalcrustbyhigherthermalflowinariftenvironmentratherthanfromfractionalcrystallizationofabasalticmagma.