大别山北部蛇绿岩的地球化学制约

GEOCHEMICAL CONSTRAINS TO THE META OPHIOLITE FROM THE METAMORPHOSED MAFIC ULTRAMAFIC BELT IN THE NORTHERN PART OF THE DABIESHAN OROGEN

常量元素、微量元素、稀土元素、Ｎｄ同位素及氧同位素地球化学特征表明，大别山北部变质镁铁－超镁铁质岩带中存在变质的蛇绿岩，它主要由变质橄榄岩、辉长岩（－辉绿岩？）和基性熔岩三部分组成。其中，变质的基性熔岩的亏损地幔模式年龄ｔＤＭ／Ｍａ＝１０３６．８～１２９３．８，εＮｄ（ｔ）＝７．２～７．７，表明它可能代表１０００Ｍａ左右形成于中等扩张速率（２ｃｍ／ａ左右）洋盆条件下的洋壳残片。

The meta ophiolite from the metamorphosed mafic ultramafic belt in the northern part of the Dabieshan orogen was confirmed by its major, trace and rare earth element geochemical characteristics and is composed of meta peridotite, gabbro ( diabase?) and basic lava. The t DM =1 036.8 Ma￣1 293.8 Ma and ε Nd ( t )=7.2￣7.7 of meta basic lava indicate that it could be relics of paleo oceanic crust formed during ca 1 000 Ma.