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.