Studies on chemical composition and trace elements and REE geochemistry of mantle peridotite in opholites of Shexian County show that its chondritenormalized patterns are of LREE--enriched type, quite different from mantle peridotite from other orogenic belts of China. The crustal sequence of Shexian ophiolites belongs to the transitional series behaeen calc-alkaline basalt and tholeiite and all through has similar trace elements and REE ratios and chondrite-normalized REE patterns, with high enrichment of large-ion lithophile elements and LREE. In Zr-Ti-Y and Hf-Ta-Th diagrams, compositional ponits of basic lava of Shexian ophiolites all fall into the area of calc-alkaline basalt. This, combined with petrological and regional geological data, has led the authors to believe that Shexian ophiolites were formed in a back-arc (interarc) basin environment.