北秦岭丹凤地区早古生代花岗岩的Pb、Sr、Nd同位素地球化学特征

GEOCHEMICAL CHARACTERISTICS OF Ph, Sr AND Nd ISOTOPES ON EARLY PALAEOZOIC GRANITES IN THE DANFENQ REGION, NORTHERN QINLING BELT

通过对北秦岭丹凤地区早古生代花岗岩的Ｐｈ、Ｓｒ、Ｎｄ同位素地球化学特征的系统研究，结合元素地球化学特征，证明早古生代具成分极性的枣园、黄柏岔、石门花岗岩是由于秦岭群斜长角闪岩和黑云斜长片麻岩部分熔融，近俯冲带以熔体与熔体的混合、远离俯冲带是前者产生的熔体与后者熔融后的残留相以不同比例混合形成的。

hrough systematic research of the geochemical characteristics of Pb, Sr andNd isotopes combined with the geochemical features of elements on Early Palaeozoic granites in the Danfeng region, Northern Qinling Belt, it is proved thatsmall granitic intrusions occurring in ancient island-arc area-southern active margin of North China Platform, were formed in Early Palaeozoic era. By that timethe oceanic crust between North China and Yangtze platforms subduced northward.The compositional regular variation from Zaoyuan in south to Skimen in north similar to magmatic rocks in modern island-arc area was originated from mixtureof magma originated from amphibolite of Qinling Group (Early Proterozoic era) by13%-30% partial melting and magma from biotite-plagioclase gneiss of the groupnear subduction zone represented by Zaoyuan granite or the gneiss's relict Phasesafter partial melting northward from the zone.