Plume-lithosphere interaction, and the formation of fibrous diamonds

This work was financially supported though a JSPS international research fellowship PE 14721 (to MWB) and JSPS KAKENHI grant numbers JP 26287139 and JP15KK0150 (to HS). The work of DAZ and ALR was supported by Russian science foundation (16-17-10067). RB acknowledges funding from the NERC (NE/M000427/1). SM acknowledges funding from the NERC (NE/PO12167/1).Fluid inclusions in diamond provide otherwise inaccessible information on the origin and nature of carbonaceous fluid(s) in the mantle. Here we evaluate the role of subducted volatiles in diamond formation within the Siberian cratonic lithosphere. Specifically, we focus on the halogen (Cl, Br and I) and noble gas (He, Ne and Ar) geochemistry of fluids trapped within cubic, coated and cloudy fibrous diamonds from the Nyurbinskaya kimberlite, Siberia. Our data show Br/Cl and I/Cl ratios consistent with involvement of altered oceanic crust, suggesting subduction-derived fluids have infiltrated the Siberian lithosphere. 3He/4He ranging from 2 to 11 RA, indicates the addition of a primordial mantle component to the SCLM. Mantle plumes may therefore act as a trigger to re-mobilise subducted carbon-rich fluids from the sub-continental lithospheric mantle, and we argue this may be an essential process in the formation of fluid-rich diamonds, and kimberlitic magmatism.Publisher PDFPeer reviewe