Genesis of clinopyroxene-amphibole xenoliths from Birket Ram: trace element and petrologic constraints

The xenolith suite of Birket Ram is composed of a mafic granulite series and an ultramafic series of clinopyroxene-amphibole (CA) nodules. The petrographic characteristics of the CA nodules show that they were formed as crystal fractionates from a basaltic melt. The trace element data on the nodules show that the xenoliths could have been crystal fractionates from an evolved Golan basalt magma. The trace element data require that more than one parent magma was responsible for the formation of the CA nodule series. In particular, the lack of coherence between the mineralogy of the nodules and the trace element abundances plus the dispersion of the trace element data argue for the involvement of several parent magmas. Rare contact relationships between the granulites and the CA nodules indicate that at least some of the CA nodules were formed within the lower crust. The pressure of formation is estimated to have been in the range 550–800 MPa based on geophysical models for the crustal structure in the region.