A remnant of continental lithospheric mantle above subduction zone: geochemical constraints on ultramafic rock from Raobazhai area, Anhui Province

摘要

Raobazhai ultramafic rock (RUR) consists mainly of harzburgite. Their two distinct characteristics are: (ⅰ) mylonitization of harzburgite is quite strong; (ⅱ) metasomatism of mantle is developed. Trace element, REE, Nd- and Sr-isotope geochemistry show that the RUR is much similar to that of continental lithospheric mantle (CLM) rather than oceanic lithospheric mantle (OLM). Melt composition calculated by cumulate demonstrates that the characteristics of island are basalt, which implies that the source of mantle flow might be related to the subduction process. It is possible that RUR represents a remmant of CLM above the Praterozoic subduction zone.