Ophiolites: Identification and tectonic significance in space and time

Abstract

Ophiolites are fragments of oceanic lithosphere that are produced at spreading centers at ocean ridges, back arc basins, or forearcs during subduction initiation, and are key indicators of plate tectonics. Although it is widely agreed that ophiolites are remnants of oceanic crust and associated depleted mantle preserved in orogens, the recognition of ophiolites and their tectonic significance is still a topic of discussion and disagreement. We propose that ophiolites can be recognized in the geologic record by some combination of genetically related pillow basalt, layered gabbro, sheeted dykes, podiform chromite, harzburgite or/and dunite. Mafic igneous rocks have either ocean-ridge basalt or immature oceanic arc basalt chemical compositions. Using a scoring system of 1–11 for ophiolite confidence level, scores of ≥ 8 are considered confident, 6–8 probable, and 900 Ma ophiolites is probably real.

Keywords

• Ophiolite
• Plate tectonics
• Subduction initiation
• Forearc
• Ocean ridge
• Tectonic setting