蛇绿岩研究的最新进展

关于蛇绿岩的形成、定义和分类争论了近200年。早期蛇绿岩被认为是有成因联系的几种岩石的组合，发育在优地槽的核部。在板块构造中它被看作形成于洋脊的古洋壳残片。经过几十年的研究，发现导致蛇绿岩多样性的因素很多，一个新的定义和分类方案被提出。新定义强调了蛇绿岩形成的构造环境，认为在威尔逊旋回的各个阶段都会形成性质不同的蛇绿岩,并根据生成环境将蛇绿岩分为两大类，即与俯冲作用无关和与俯冲作用相关的蛇绿岩，两大类型还可以划分出不同的亚类。这些类型的蛇绿岩有其特有的地球化学、岩石学指标和内部结构。最近的研究还发现蛇绿岩产生的主要时段与全球超大陆的形成、裂解，以及巨型地幔柱活动的时间吻合。根据新分类方案，一部分前寒武纪绿岩应属于蛇绿岩，表明在太古宙时期地球已进入板块构造体制。新的定义和分类为蛇绿岩研究指出了新的方向。

New advances in the study of ophiolites

The dispute on the origin, definition and classification of ophiolites has lasted for two hundred years. In the early period, ophiolite was interpreted as a rock assemblage which was developed from a consanguineous igneous process and intruded into the axial part of the geosynclines. In the plate tectonics, it is regarded as the relic of the subducted oceanic plates produced in the middle ocean ridges. However, based on tens of years' studies, people have found that factors affecting the origin of the ophiolites are varied, and a new definition and new classification of the ophiolites have been put forward recently. This new definition emphasizes the tectonic setting in which the ophiolites were developed, and argues that ophiolites with different characteristics could have been developed at every stage of the Wilson cycle. The new classification is based on the tectonic environment in which the ophiolites were developed. Two groups have been classified, i.e., subduction-related ophiolites and subduction-unrelated ones. The two groups could be divided into several subgroups respectively. All these ophiolites have their own characteristic geochemical and petrological indexes and internal structures. Recent studies also reveal the main periods in which the ophiolites originated were consistent with the development and breakup of the super-continents and superplumes. Some recent studies also show that some pre-Cambrian greenstones should belong to the ophiolites based on the new classification. This means that the plate tectonic movement occurred during the Archean. The new definition and new classification point to the new direction for the study of ophiolites.