摘要
地壳交代作用是洋壳俯冲带板片-地幔界面的普遍现象,由于地幔楔样品的缺乏,其识别存在困难。而碰撞造山带广泛出露的地幔楔来源的造山带橄榄岩则是理想的研究对象。本文对大别-苏鲁造山带橄榄岩的已有研究成果进行了系统总结。这些成果表明这些橄榄岩在大洋俯冲向大陆碰撞转换的不同阶段经历了多期地壳来源流体的交代作用。地壳交代作用不仅改变了地幔楔橄榄岩的地球化学成分,而且导致了交代矿物的生长以及超镁铁质交代体的形成。这些交代体或作为同碰撞和碰撞后镁铁质火成岩的地幔源区,或将地壳组分传输到深部地幔,或释放流体交代大陆俯冲隧道中的俯冲陆壳。本文对地壳交代作用研究中存在的重要问题和解决思路提出了建议。
The crustal metasomatism is a common process in the slab-mantle interface in the oceanic subduction zone. It is difficult to be identified due to the lack of mantle-wedge samples. The mantle wedge-derived orogenic peridotites widely outcropped in collisional orogens provide us excellent samples to investigate the crustal metasomatism at the slab-mantle interface in subduction zones. This paper has systematically reviewed petrographical,whole-rock and mineral geochemical researches on the crustal metasomatism of orogenic peridotites from the Dabie-Sulu orogenic belt. The mantle wedge peridotites had experienced multi-stage crustal metasomatisms by crustal sourced fluids through the fluid-peridotite reaction at different stages of the tectonic transition from oceanic subduction to continental collision. The crustal metasomatism had not only changed geochemical composition of the mantle wedge peridotite,but also resulted in the growth of metasomatic minerals and formation of ultramafic metasome. These metasome would either serve as mantle sources of syn-and post-collisional mafic igneous rocks,or transport crustal components into deep parts of the mantle,or release fluids for metasomatizing the subducted crust in the continental subduction channels. Therefore,we have pointed out some important questions existed in researches on the crustal metasomatism and then proposed some suggestions for solving those questions in this paper.