Ophiolites and ophiolitic mélanges: Archives of Precambrian and Phanerozoic plate tectonics in orogenic belts

Ophiolites and ophiolitic mélanges are among the key tectonic components of both accretionary- and collisional-type orogenic belts around the world, representing significant archives of the evolutionary history of the Earth. These tectonostratigraphic units are not simple rock assemblages; their formation and coexistence require specific geological conditions and environments, internal and external Earth processes, and preservation during certain time intervals in the past. Therefore, they offer most valuable insights and windows into the Earth‟s history. They occur widely in the Precambrian and Phanerozoic accretionary and orogenic belts, delineating major boundaries between disparate terranes, crustal blocks, and even lithospheric plates. Most geoscientists have traditionally considered these boundaries as „suture zones’, and hence ophiolites and mélanges have been accepted as the signature hallmarks of suture zones, and the sites of former subduction and collision zones in orogenic belts (Dewey, 1977; Dilek, 2006; Festa et al., 2010). Unlike their 1972 Penrose definition (Anonymous, 1972), ophiolites do not fit into a simple and uniform template of an oceanic lithosphere template (Dilek, 2003). They are highly diverse structurally, geochemically, and in terms of their tectonic settings of formation (Dilek and Furnes, 2011, 2014). The differences among different ophiolite types reflect variations in seafloor spreading rates, magma budgets, mantle melt sources and melting conditions, the extent of subduction influence on the melt column, and slab dip angle beneath oceanic spreading centers (Dilek and Furnes, 2014). Therefore, the stratigraphic and structural architecture, lithological makeup, and geochemical characteristics of ophiolites can provide significant information about: (i) the mode and tempo of magmatic and tectonic processes during oceanic crust generation; (ii) the pressure–temperature–time paths during the metamorphic evolution of ancient oceanic lithosphere within subduction zones; (iii) the fluid flux and element recycling in subduction–accretion systems. On the other hand, the stratigraphic and structural architecture, lithological makeup, and geochemical characteristics of ophiolitic mélanges can provide significant information about: (i) the processes of mélange formation during the accretion of fragments of oceanic lithosphere at both shallow and deep structural levels at slab interface in subduction zones; (ii) sedimentological, erosional and other physical processes that occur during the accretion of oceanic lithosphere into continental margins (Dilek and Furnes, 2011; Safonova et al., 2016; Festa et al., 2019, 2022; Furnes et al., 2020)