Petrogenesis of the Maden Complex Volcanic Rocks in the Southeastern Anatolian Orogenic Belt (Malatya- Eastern Türkiye): insight from whole-rock geochemistry, mineral chemistry, and Sr-Nd-Pb isotopes

The volcanic rocks belonging to the Maden Complex are observed along the Southeastern Anatolian Orogenic Belt, and the study area covers the surroundings of Malatya (Türkiye). The Eocene (?) Maden Complex are represented by basalt and diabase dykes cutting them. The studied rocks have high Mg# (51.7-92) values. With increasing Zr ratios, positive trends are observed in CaO, TiO₂, Fe₂O₃, Ba and Sr values, and negative trends are observed in MgO, Al₂O₃, Ni, and Co values. Positive trends in CaO and Sr values ​​indicate the effect of plagioclases in fractional crystallization. Trends in TiO₂, Ni and Fe₂O₃ values ​​indicate fractional crystallization of olivine, pyroxene and Fe-Ti oxides. The Maden Complex have relatively low La/Yb (1.16-6.69) and Nb/La (0.20-1.45) ratios, indicating a lithospheric mantle/lithospheric-asthenospheric mantle origin. In the primitive mantle-normalised multi-element diagram, negative trends are observed in Rb, P, Nb and Ti elements, and positive trends in Sr and Ba values ​​of the rocks belonging to the Maden Complex. A nearly horizontal trend is observed in the chondrite-normalised multi-element diagram. The La_N/Lu_N (LREE/HREE) ratios among the light rare earth elements (LREE) and heavy rare earth elements (HREE) of the studied volcanic rocks range from 0.79 to 4.76, showing weak to moderate fractionation. The basalts and diabases belonging to the Maden Complex show insignificant negative Eu anomalies, and the Eu/Eu* values ​​vary between 0.81 and 1.06.  The Dy/Yb ratios of the studied volcanic rock samples vary between 1.49 and 1.87. These ratios indicate that these rocks were derived from a spinel-bearing lherzolite source representing shallow depths. Mineral chemistry analyses were performed on pyroxene and plagioclase minerals in the studied volcanic rocks. According to pyroxene minerals, the temperature (T) and pressure (P) values ​​of the rocks vary in the range of (1194-1442) and (2.8-20), respectively. According to plagioclase minerals, the T and P values ​​vary between (945-1049) and (26.6-55.7).

The ⁸⁷Sr/⁸⁶Sr_(i) values ​​of the studied volcanic rocks vary between 0.703514 and 0.704958, ¹⁴³Nd/¹⁴⁴Nd_(i) values ​​vary between 0.512861 and 0.512897, and they exhibit a sequence close to the MORB field in the ⁸⁷Sr/⁸⁶Sr_(i) versus ¹⁴³Nd/¹⁴⁴Nd_(i) variation diagram. ƐNd_(t) values ​​range from 5.6 to 6.3, and T_DM(Ga) values ​​vary between 0.45 and 0.83. ²⁰⁶Pb/²⁰⁴Pb_(i) values ​​vary between 18.42267 and 19.39642, ²⁰⁷Pb/²⁰⁴Pb_(i) values ​​vary from 15.54136 to 15.62174, ²⁰⁸Pb/²⁰⁴Pb_(i) values ​​range from 38.40535 to 39.04312. The ²⁰⁷Pb/²⁰⁴Pb_(i) diagram versus ²⁰⁶Pb/²⁰⁴Pb_(i) also shows a sequence close to the MORB field. In light of all data, it is thought that the volcanic rocks of the Maden Complex are derived from a magma source representing shallow depths of MORB origin. This study was supported by the TUBITAK project numbered 123Y070.

Key Words; Geochemistry, Maden Complex,  Mineral chemistry, Sr-Nd-Pb isotopes