Hydrothermal systems in peridotites at slow-spreading ridges. Modeling phase transformations and material balance: Role of gabbroids

This work was aimed on the estimation of role of gabbro in the ore mobilization during hydrothermal transformation of oceanic (gabbro-peridotite) crust at slow-spreading mid-ocean ridges. Kinetic-thermodynamic modeling was used to reconstruct the geochemical and mineralogical trends of evolution of gabbroids during their hydrothermal interaction with marine fluid. The results of our simulation offered a new insight into some problems of material balance and ore formation during hydrothermal process in the slow-spreading mid-ocean ridges. It was shown that the root zones of all known MAR hydrothermal fields related to serpentinites are made up of ultrabasic rocks and located within peridotite protolith near hot and uncooled gabbroic bodies. It was also demonstrated that the observed mineral and geochemical diversity of metagabbros of slow-spreading mid-ocean ridges was provided by the interaction of hydrothermal fluid percolating through the Hess-type oceanic crust with gabbro bodies. It was established that almost cooled gabbroid bodies, being involved in hydrothermal circulation in the shallow root zones, may play an important role in the redistribution of the material within the Hess-type oceanic crust.