Modification of the lithospheric mantle induced by recycled crustal components: Insights from Early Cretaceous appinites from the Liaodong Peninsula, NE China

The term "appinites" refers to amphibole -rich mafic rocks, as one of the most typical products of partial melting of a metasomatic lithospheric mantle. This paper presents results of integrated geochemical and isoto-pic analyses for six Early Cretaceous (125- 119 Ma) appinitic plutons from the Liaodong Peninsula, northeastern North China Craton (NCC), to not only investigate the proper-ties of the metasomatic lithospheric mantle induced by variable recycled crustal com-ponents but also to discuss a hydrous mantle source. The appinites originated from par-tial melting of sub-continental lithospheric mantle (SCLM), and can be geochemically categorized into three groups distinguished by the input of different recycled crustal components (e.g., terrigenous sediments and delaminated lower continental crust) on the basis of two distinct Hf-O isotopic arrays. Based on the occurrence of voluminous amphiboles (50-60 vol%) and minor clino-pyroxene remnants, a petrogenetic model was proposed to interpret the formation of appinites. Asthenospheric upwelling caused by the subduction and roll-back of the Paleo-Pacific plate firstly resulted in partial melt-ing of the SCLM to yield basaltic magmas. Subsequently, numerous hydration reactions between early anhydrous minerals (e.g., olivine and pyroxene) of basaltic magmas and hydrous melts derived from terrigenous sediments and delaminated lower continental crust occurred to produce the studied appin-ites. Ultimately, the recycled crustal materi-als can serve as the metasomatic agent not only to transfer the enriched isotopic signa-tures into the studied appinites but also to represent hydrous components to play the part of hydrous reactions. The high abun-dance of amphibole in the studied appinites is indicative of a hydrous lithospheric mantle beneath the eastern NCC.