Petrogenesis of Rabor-Lalehzar magmatic rocks (SE Iran): Constraints from whole rock chemistry and Sr-Nd isotopes

Miocene adakitic rocks are characterd by relatively enrichmented in incompatible elements, high (Sr/Y)(N) (>40), and (La/Yb)(N) (>10) ratios with slightly negative Eu anomalies (EuN/Eu*≈ 0.9), depletion in HFSEs, and relatively non-radiogenic Sr isotope signatures (87Sr/86Sr = 0.7048-0.7049). In contrast, the Oligocene granitoids exhibit low Sr/Y (<20) and La/Yb (<9) ratios, negative Eu anomalies (EuN/Eu* ≈ 0.5), and enrichment in HFSEs and radiogenic Sr isotope signatures (87Sr/86Sr = 0.7050-0.7052), showing affinity to the island arc rocks. Eocene volcanic rocks which crusscut the younger granitoid rocks comprise andesites and dacites. Geochemically, lavas show calc-alkaline character without any Eu anomaly (EuN/Eu* ≈ 1.0). Based on the geochemical and isotopic data we propose that melt source for both calc-alkaline and adakitic rocks from the RLMC can be related to the melting of a sub-continental lithospheric mantle (SCLM). Basaltic melts derived from a metasomatized mantle wedge might be emplaced at the mantle-crust boundary and formed the juvenile mafic lower crust. However, some melts fractionated in the shallow magma chambers and continued to rise forming the volcanic intermediate-mafic rocks at the surface. On the other hand, the assimilation and fractional crystallization in the shallow magma chambers of may have been responsible for the development of Oligocene granitoids with calc-alkaline affinity. In the mid-Late Miocene, following the collision between Afro-Arabia and Iranian block the juvenile mafic crust of UDMA underwent thickening and metamorphosed into garnet-amphibolites. Subsequent upwelling of a hot asthenosphere during Miocene was responsible for partial melting of thickened juvenile crust of the SE UDMA (RLM complex). The adakitic melts ascended to the shallow crust to form the adakitic rocks in the KMB.