High temperature hydrothermal activity in the deep oceanic crust: Experiments and investigations on natural rocks in the Oman ophiolite

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The Oman ophiolite is regarded to present the best proxy of fast-spreading oceanic crust on land. Most petrologists/geochemists built on the evidence from Oman ophiolite and favour a general accretion model for fast-spread oceanic crust that deep plutonic crust is formed by multiple intrusions of gabbroic sills. A requirement for this model, however, is a substantial cooling of the deep oceanic crust, and many scientists believe that a seawater-derived high-temperature hydrothermal circulation system must exist. Recent studies based on experimental work revealed that Oman gabbros show characteristic parageneses indicating that partial melting triggered by water-rich fluids proceeded in the deep crust. These can be interpreted as result of hightemperature hydrothermal convection, implying that the distinction between primary magmatic and seawater-induced metamorphic processes is blurred. The present study will combine the investigation of natural rocks of the Oman ophiolite and experimental work on relevant natural systems, and finally theoretical work on thermal modelling, in order to understand one important aspect of fast-spread ocean crust generation: the interplay between magmatic accretion and hydrothermal processes ongoing at high temperatures, and the way how the hydrothermal cooling of the deep crust proceeds.