东秦岭造山带两类元古宙地壳基底及其地壳增生

通过研究南秦岭地区陡岭群、武当群和北秦岭地区秦岭群的变质基性岩等的铅同位素和微量元素组成，揭示出东秦岭造山带分布有两种性质及不同归属的元古宙地壳，指出中、古元古代时可能一个统一的地壳基底；南秦岭的中、古元古代地壳是在扬子陆地基底上通过岛弧的侧向加积形成和，北秦岭元古宙地壳则可能垂向增生于一个富入射性成因铅同位素组成的、具古洋壳幔性质的微地块之上，研究还表明陡岭群不是北秦岭地区的秦岭群，而应属于南秦

TWO KINDS OF PROTEROZOIC CRUSTAL BASEMENTS AND CRUSTAL GROWTH IN EAST QINLING OROGENIC BELT

Two kinds of Proterozoic crustal basements are recognized in the study of Pb-isotope ratios and trace elements of the mafic rocks from Douling Group,Wudang Group of South Qinling area and Qinling Group of North Qinling area in East Qinling orogenic belt.The Proterozoic crustal basements of North and South Qinling might,respectively,belong to different continental blocks.It seems that an integrated crustal basement in Proterozoic did not exist in East Qinling area.The crust of South Qinling was originated from the arc above the northern continental margin of Yangtze craton by side-accretion in Meso-Paleoproterozoic.However,Proterozoic crust of North Qinling might have been formed by vertical accretion above North Qinling block which might consist of paleo-oceanic crust and mantle with high radiogenic Pb-isotope composition.The geochemical data indicate that Douling Groupin South Qinling area is different from Qinling Group of North Qinling area,and so the former should be a part of Proterozoic crustal basement of South Qinling.