The major difference between the two types of lavas

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.

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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
(