Petrogenesis of Garnet Periodotites and Eclogites in the Bohemian Massif, Czechoslovakia

计划对波希米亚地块捷克部分的石榴石橄榄岩和榴辉岩进行综合实地和实验室调查，该地块是欧洲瓦里斯坎造山带的最东端。摩尔多瑙河带是瓦立斯坎造山带最内部、变质程度最高的构造地层单元。以前的研究表明：(1)两类榴石橄榄岩的产状，表现出不同的起源模式、T-p历史和冷却速率；(2)橄榄岩中a群榴辉岩透镜体的地幔起源，它们是由高压结晶堆积形成的，并被瓦里西造山期构造侵位的封闭橄榄岩带入地壳。进一步的同位素调查将对已被岩石学鉴定的橄榄岩和生态岩样品进行，并将对片麻岩中的额外橄榄岩体和B组榴辉岩透镜体进行综合野外、岩石学、地球化学和同位素研究。研究结果将为确定瓦里斯坎带这部分高压变质作用的时间和性质提供依据，提高我们对造山过程中幔壳相互作用复杂性的认识。

An integrated field and laboratory investigation is planned of garnet peridotites and eclogites in the Czech portion of the Bohemian Massif, which is the easternmost extent of the Variscan Orogen in Europe. These high-pressure rocks occur in sequence of continental crustal rocks in the Moldanubian Zone, which is the most internal and highly metamorphosed tectonostratigraphic unit of the Variscan Orogen. Previous studies have demonstrated: 1) the occurrence of two types of garnet peridotites, which exhibit different modes of origin, T-p histories, and cooling rates, and 2) a mantle origin for Group A eclogite lenses in peridotites, which formed by high-pressure crystal accumulation and were carried into the crust by enclosing peridotites that were tectonically emplaced during the Variscan Orogeny. Further isotopic investigations will be performed on selected peridotite and ecologite samples that have already been characterized petrologically, and integrated field, petrologic, geochemical, and isotopic studies will be made of additional peridotite bodies and Group B eclogite lenses in gneisses. The results should provide a basis for establishing the timing and nature of high-pressure metamorphism in this portion of the Variscan belt, an improve our understanding of the complexities involved in the interaction of mantle and crust during orogenesis.