东秦岭虎豹河砾岩砾石的地球化学特征及其构造意义

东秦岭虎豹河砾岩为复成分砾岩层。砾岩中火成央砾石显示了ＬＩＬＥ中等富集，丰富变化不大，Ｂｂ（Ｔａ）有一定亏损，Ｔｈ－Ｔａ比值高，并具有来自岛弧演化不同阶段的两个岩浆源区的地球化学特征，反映它们主要受消减物质影响，且地壳物贡献不大的岛弧钙碱性岩浆的成因特征。

Gcochemical Characteristics and Tectonic Implication of Gravels in the Hubaohe Conglomerate in the East Qinling

The Hubaohe conglomerate in the east Qinling,located in the Heihe area,Shaanxi Province,is a kind of composite conglomerate composed mainly of igneous gravels of basalt ,basaltic andesite,diorite and granodiorite with some of sedimentary gravels of graywacke,pyroclastic rock and carbonate rock.The igneous gravels are geochemically characterized by the intermediate enrichment of restricted LIL,depletion of Nb(Ta) and high Th/Ta ratio as well as distinct material sources,showing a feature of island arc calc alcline magmas affected dominantly by subducted materials and little crust materials.This conglomeratic bed,combined with other geological data,is regarded as a local small scale apron deposit formed in a fore are basin due to the arccontinet collision between the intraoceanic island arc and the North China continent during the transition period from Primitive to normal continental arc.This conglomerate,therefore,is nota mollasse formation resulted ffom the strong continent continent collision.