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Mineral phase variations and compositions of Early Pliocene (Ar-40-Ar-39 ages ranges 5.092 +/- 0.030-4.892 +/- 0.024 Ma) continental alkali basalts cropped out on Mt. Kira, NE of Batman Province, SE Anatolia, and located approximately 75 km east of well-known Karacadag & nbsp;Volcanic Complex (KVC) in Diyarbakir Province, record indications of pre-eruptive assimilation of the lower crust by OIB-like basaltic magmas from Arabian Foreland, which are proved by available data of juvenile lower crustal xenoliths in northern Syria Cenozoic basalts. Diopsitic augites with low Mg#'s (0.65-0.73) in Mt. Kira basalts depict a compositional prone to clinopyroxenes (Mg#, 0.60-0.76) in Syrian lower crustal xenoliths and coexist with Ca-and Mn-rich fayalitic olivines (Fo(63-36)), Ca-poor (An(72-13)) plagioclases, and Fe-Ti oxides. Mt. Kira lavas, classified as hawaiites, are characterized by the narrow ranges of low SiO2 (46.30-47.68 wt%), Al2O3 (13.74-14.41 wt%), MgO (3.48-4.16 wt%), and high total alkali (Na2O + K2O, 5.26-5.89 wt%), Fe2O3 (13.97-15.38 wt%), TiO2 (3.44-3.61 wt%), CaO (7.20-8.99 wt%), and P2O5 (1.54-1.71 wt%) contents, and with low Cr (< 14 ppm) and Ni (< 20 ppm) values. Except for unusual Zr-Hf depletion, they exhibit typical arc-like (or crust-like) sharp negative anomalies of Nb-Ta and Ti and possess high concentrations of Y (45-51 ppm), Sc (28-33 ppm), and Heavy REE (e.g., Dy, 9.25-10.73 ppm; Er, 4.74-5.27 ppm; Yb, 3.79-4.44 ppm). Two-component mixing model, and radiogenic Sr-87/Sr-86 (0.7,044,010-0.705396) and Nd-143/Nd-144 (0.512676-0.512812) isotopic compositions, which overlap with bulk-silicate earth, for Mt. Kira basalts, provide evidence for the mafic juvenile lower crustal assimilation by OIB-like basaltic magmas derived from a common enriched mantle source. High Ba/La, Ba/Ta, Ba/Nb, Zr/Nb, and low Nb/La, La/Sm, Nb/Th, La/Yb, and Dy/Yb ratios, which coincide with those of Syrian lower crustal xenoliths, appears as geochemical hallmarks for decoupling of juvenile lower crust assimilated Mt. Kira, NW Syria and some of KVC basalts from least contaminated ones in Arabian Foreland. The enrichments in Y, Fe, and Ti and depletions in Al and Sr in Mt. Kira lavas, however, are attributed to post-eruptive chemical weathering processes. Based on petrological and tectonic data, it is proposed that the northern Arabian Foreland Cenozoic volcanism was triggered by the combined effect of both collision-and mantle flow-driven forces with a kinematic linkage. Asthenospheric mantle flow and upwelling, which supply a thermal source, caused the deep mantle processes and interaction between asthenosphere and lithosphere, which was formed the amphibole-bearing garnet lher-zolitic (asthenospherized) metasomes (mantle flow-induced metasomatism) at the base of the SCLM accreted from the ductile asthenosphere, prior to partial melting. Partial melting of such re-fertilized metasomes and surrounding wall rock was most likely produced hybrid parental magmas via mixing variable proportions of melt fractions from a garnet lherzolite source with melt fractions from an amphibole-bearing garnet lherzolite source. |
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