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Abstract:
Lower Jurassic Abshour gabbro (178.3 ± 2.3 Ma and 187.2 ± 4.7 Ma) and Gowd-e-Howz granitoid (180.3 ± 1.3 and 178.9 ± 1.2 Ma) intrusions are exposed in the Esfandaghe area, Kerman province, SE Iran, as part of the southern Sannandaj-Sirjan metamorphic-magmatic zone (SSMMZ). These igneous bodies intruded into Upper Paleozoic-Triassic metamorphic rocks. The Gowd-e-Howz granitoid stock primarily consists of coarse to medium-grained granodiorite, with subordinate diorite, quartz diorite, quartz monzonite, granite, and aplitic-pegmatitic alkali granitic veins, accompanied by a small amount of gabbro and cut by middle Jurassic quartz monzonitic dykes. Mafic microgranular/microgranitoid enclaves (MMEs) of various sizes are present in the stock. The granitoid rocks exhibit a low to medium-K calc-alkaline nature, with enrichment in large ionic lithophile elements (LILEs) such as Rb, Ba, K, and Ce, alongside a depletion in high field strength elements (HFSEs) like Ti, Y, Nb, and Zr. The REE patterns display relatively parallel, smooth LREE-enriched chondrite normalized trends, indicating the influence of fractional crystallization, along with contamination, assimilation, and magma mixing/mingling processes in magma evolution. The type of lithologic association (gabbro, diorite, granodiorite, granite), the presence of MMEs, the prevalence of Fe-Mg silicate minerals (Cpx, Amph. Bt), and the plots of the geochemical data on various whole rock and mineral chemistry discriminant diagrams suggest that the Gowd-e-Howz granitoid stock possesses characteristics of metaluminous to slightly peraluminous, calc-alkaline, magnetite series, I-type granitoids typical of continental volcanic arc settings formed from partial melting of a subducting oceanic slab and lower crust (CI-type granite) in an active continental margin subduction zone. In this model, the initiation of NE-dipping subduction of the Zagros Neotethyan oceanic lithosphere beneath the Central Iran continental lithosphere during the Late Triassic-Early Jurassic (≈180 Ma) may have accounted for the generation of mafic and felsic magmas in the Andean-type arc magmatism of the SSMMZ, where gabbroic and granitoid plutons formed and intruded in metamorphic country rocks. Thermobarometric calculations indicate that magma storage, plumbing, and fractionation occurred at three levels (40–45, 14–16, and 5–7 km) in the base, middle, and upper continental crust, respectively.
