Rare-earth patterns of Mid-Atlantic Ridge gabbros: Continental nature?

Abstract

Five gabbros from the Mid-Atlantic Ridge near 30°N were analyzed for the rare-earth elements. The pattern analysis indicates that these gabbros represent the solid-type materials which were separated from the melt with mutually almost unfractionated RE abundances relative to chondrite. The bulk partition coefficient functions pertaining to those rocks have the common feature in an inflection at Tb (Lm - 8.0). It is noted that the RE pattern of the North American shale (HASKIN et. al, 1966) reflects the similar partition coefficient function. Thus this allows us to speculate that the Mid-Atlantic Ridge gabbros ever underlay the continental crust. Meanwhile, it is difficult to consider that the abyssal tholeiites had the direct genetic relation with the gabbros studied. The systematic notation to express the RE bulk partition coefficient function is presented at the same time. © 1973, GEOCHEMICAL SOCIETY OF JAPAN. All rights reserved.