Oceanic island basalts in ophiolitic melanges of the Central China Orogen: An overview

We present an overview of the internal structure of the 10 ophiolitic melanges in the Central China Orogen (CCO) with a focus on the geochemical character and tectonic evolution of the ophiolitic melange-related ocean island basalt (OIB) and mafic rock assemblages. The ophiolitic melanges in CCO are generally complicated and usually consist of metamorphic peridotites (serpentinite), cumulates, gabbros, basaltic lavas (pillows), and abyssal radiolarian cherts. The ages of ophiolitic melanges range from Mesoproterozoic to Carboniferous. The OIB-type basalts and mafic rocks in CCO occur as tectonic blocks within the melanges that are composed of limestones, radiolarian cherts, and turbidites, possessing formation characteristics of seamounts (oceanic islands/plateau). The mafic rocks in ophiolitic melanges of CCO display uniform chondrite-normalized rare earth element (REE) patterns with light REE enrichment and heavy REE depletion, no obvious Eu anomalies or negative Nb, Ta, and Ti anomalies, and primitive mantle-normalized trace element patterns with significant large-ion lithophile element enrichment, similar to those of modern OIB and the Hawaiian alkaline basalts. The OIB-type basalts and mafic rocks are considered as accreted seamount fragments in an accretionary complex of CCO and may represent plume-related magmatism within the Proto-Tethys Ocean and Paleo-Tethys Ocean. Our study provides further insights into the processes of multiple subduction and long-lasting accretionary histories with seamounts in the CCO.