The major difference between the two types of lavas in a level of incompatible trace element differ by a factor of >5x for La, Nb, Zr and Ta; this explains differences in the level of partial melting or the magma were generated from the source with different trace element composition. Chondrite-normalized rare earth element diagrams of both lavas of the area shows LREE (light rare earth element) enrichment over HREE (heavy rare earth element); the enrichment history of LREE over HREE is more pronounced on the melanephelinite lavas.
The very high enrichment of LREE over the heavy one of the melanephelinite lava crosses the basalt lavas Chondrite-normalized diagram and together with non-correlation trend on a variation diagram between them; reflecting their derivation from various mantle source region.
Bothlavasof Hirna characterized by high La/Sm ratio (for the basalt = ~ 2.7; for the Melanephelinite = ~ 7), Sm/Y ratio (for the basalt = ~ 3.4; for the Melanephelinite= ~ 6.4) relatively fractionating HREE pattern (Tbn/Ybn = 2.03 to 2.7) and together with Lan/Ybn ratiovalue(5 to 28) which most likely suggest mantle source containing garnet rather thanspinel. The lavas of Hirna exhibit enrichment of Ba and depletion of Rb and K relative to other elements with a similar degree of incompatibility in their primitive mantle-normalized variation diagram (fig. 5). Such depletion and enrichment are thought to be related to amphibole/phlogopite in the mantle source (e.g. Furman and Grham, 1999; Ayalew et al., 2006; Jung et al., 2005; 2012; Mayer et al., 2014; Rooney et al., 2014).
Rb and Ba are compatible with phlogopite while Sr, Rb and Ba are moderately compatible with amphibole. Melts in equilibrium with phlogopite are expected to have significantly higher Rb/Sr and lower Ba/Rb values whereas melt in equilibrium with an amphibole-bearing source are expected to have a higher Baand Ba/Rb value. Furman et al.(1999) presented lava from many volcanic areasthat have low K2O/Na2O (