安徽歙县蛇绿岩地球化学特征及形成构造环境

岩石化学、微量元素及稀土元素地球化研究表明:歙县蛇绿岩内地幔橄榄岩稀土元素配分为LREE富集型,不同于我国其他造山带地幔橄揽岩。歙县蛇绿岩壳层组合属于钙碱性和拉斑玄武岩间过渡系列,具类似的微量及稀土元素比值和稀土元素配分模型,且大离子亲石元素(LIL)和LREE高度富集。在Zr—Ti—Y和Hf—Ta—Th图解内,蛇绿岩基性熔岩成分点均落入钙碱性玄武岩区。结合岩石及区域地质资料,歙县蛇绿岩应形成于弧后(弧间)盆地环境。

Geochemical Characteristics and Tectonic Setting of Ophiolites in Shexian County,Anhui Province

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