ANALYSIS OF MANTLE SOURCES FOR MAFIC ASSOCIATIONS ON THE BASIS OF GEOCHEMICAL AND Nd ISOTOPIC DATA
The (La/Nb)<sub>pm</sub>, (Th/La)<sub>pm</sub>, (La/Sm)<sub>pm</sub>, (Nb/Y)<sub>pm</sub> ratios <1 in mafic rocks correspond to a depleted mantle source, while >1 corresponds to an undepleted/enriched source. (La/Nb)<sub>pm</sub> does not change during melting of mantle peridotites, so the Nd minimum is a characteristic feature of the lithospheric mantle metasomatized by fluid/melt. According to the isotopic Nd composition, there are two mantle sources: (1) depleted (+e<sub>Nd</sub>), which corresponds to the asthenospheric and/or lithospheric mantle of restite origin, (2) enriched (-e<sub>Nd</sub>) lithospheric, having a lowered Sm/Nd due to metasomatism. Estimates of the characteristics of the mantle sources of mafic rocks based on their trace element-and isotopic composition can either correlate with each other or differ.