Comment on the Progress in and Problems on Ophiolite Study

According to the concept of ophiolite in 1970s, exposure of mafic-ultramafic rocks in the orogenic zone has been interpreted to represent the relic of fossil ocean lithosphere based on its lithology units consisting with oceanic crust and upper mantle. So the ophiolite is a key evidence of boundary between the fossil plates, and has been played an important role on the formulation and advancement of the plate tectonic theory. Recently, ophiolite is divided into MOR- and SSZ- types based on the formation tectonic setting. MOR-type ophiolite formed at Mid-ocean ridges (MOR), and SSZ-type ophiolite formed on the supra-subduction zone caused by the ocean-continent subduction or intra-ocean subduction, and there are obvious difference in mantle sequence, cumulated assemblage and lavas in petrology, mineralogy and geochemistry between MOR- and SSZ-type ophiolites. This classification explains well the various ophiolites and the difference between the ophiolite and oceanic lithosphere. During the subduction of oceanic lithosphere, the MOR-type ophiolite was subducted, or is preserved only as dismembered thrust sheets or blocks in ophiolitic melange, while SSZ-type ophiolite, as fragments of modified oceanic or rebirth lithosphere caused by fossil oceanic plate subduction, is commonly preserved in the orogenic zone due to it formed above subduction zone. Therefore, SSZ-type ophiolite is major one preserved well in the orogenic zone. Also discussed in this paper are the problems in the ophiolite study, such as the difference between the ophiolite and ocean lithosphere in peridotites, and the methods to solve these problems. And the pre-Rodinia super-continent ophiolite record is still considered poorly understanding, and whether Archean greenstone is ophiolite or not. These are all questions to answer.