The role of magma recharge and mixing in producing compositional modality in post-collisional volcanic rocks, Konya Volcanic Field, Central Anatolia (Türkiye)

Abstract

The Neogene Erenlerdağ-Alacadağ (ErAVC) and Sulutas (SVC) volcanic complexes in the Konya Volcanic Field, Türkiye have distinctly different unimodal and bimodal compositional variations, respectively. They occurred in graben-like extensional basins behind the retreating Cyprus subduction zone between the African and Eurasian plates. We here investigate their compositional modality by using new and published whole-rock major and trace element and Sr-Nd-Pb isotope data.

Both complexes are characterized by basaltic to rhyodacitic high-K calc-alkaline rocks with the geochemical signatures of orogenic volcanism, except for minor alkaline rocks in the SVC. Mass-balance models suggest that major element variations can be largely explained by the fractional crystallization of amphibole, plagioclase, and Fe-Ti oxides. However, Sr-Nd-Pb isotopes show correlations with SiO₂ indicating that open-system processes played a role in their differentiation. Modeling of AFC (Assimilation and Fractional Crystallization) involving a recharge situation shows that low degrees of crustal assimilation (rate of assimilation/rate of fractional crystallization, r < 0.2 and crust/magma ratio, ρ: 15–16 %) of lower and upper crust-like rocks was involved in the differentiation of the ErAVC and SVC, respectively. However, the modeling suggests that magma recharge (β: rate of magma recharge/rate of assimilation) was more efficient in the ErAVC (β: 3.45, % ∼52.5 rate of recharge) relative to that of the SVC (β: 2.15, % ∼36.55 rate of recharge). We conclude that for the ErAVC and SVC, different parental magmas derived from the subduction-modified mantle source followed distinct differentiation paths in the crust, and their compositional modality was mainly controlled by the magma recharge and mixing process.