Rare gas systematics in Red Sea Ridge basalts

From south to north, the 4He/³He ratios of submarine basalts from the Red Sea and Gulf of Tadjoura increase from 45,000 (R/Ra=15) in the Gulf of Tadjoura to 84,000 (R/Ra=8.6) in the Mabahiss deep. Our helium isotopic results indicate that the mantle plume proposed in the north of the Red Sea, on the basis of the Sr and Pb isotopic ratios, does not posess a high ³He signature. The neon and Ar isotopic ratios of the Red Sea glasses are explained by mixing between AIR, MORB and a plume with a solar like isotopic Ne signature and low 40Ar/36Ar, similar to that of Loihi.