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The Oligocene Nasrand intrusive rocks (NIRs), located in the central part of the Urumieh–Dokhtar magmatic arc, are mainly composed of granite and subordinate diorite and gabbro. These rocks are characterized by the enrichment of light rare earth elements (LREEs), Nb‐Ta negative anomalies, and high LILE/HFSE, suggesting a subduction‐related origin. The felsic rocks with granite compositions have high SiO2 content (69.77–77.88 wt.%), low Mg# (0.02–0.43), low Nb/Ta, and Zr/Hf (Avg: 12.53, and 33.08, respectively). The initial 87Sr/86Sr ratio and εNd(t) values in felsic rocks range from 0.70577 to 0.70576 and 0.4 to −0.3, respectively. These data suggest that these felsic rocks originated from juvenile crust by heat rising from basaltic magmas in an orogenic setting. The mafic‐intermediate rocks and dikes are gabbro, gabbroic diorite, and monzodiorite, with low SiO2 content (48.08–56.11 wt.%) and high Mg# (0.37–0.68), with average ratios of Nb/Ta and Zr/Hf are 27.88 and 39.84, respectively. The initial 87Sr/86Sr ratio and εNd(t) values for mafic‐intermediate rocks and dikes are 0.70583 to 0.70476 and −0.1 to +2.6, respectively. These characteristics indicate magma from a mantle source that had undergone minor mixing with juvenile crust. It seems mantle‐derived juvenile magma underplating played an important role in the crustal growth in the Urumieh–Dokhtar magmatic belt during the Ediacaran to Early Cambrian, relative to other time frames. [ABSTRACT FROM AUTHOR]

The Lower Cretaceous siliciclastic fluvial to shallow marine Shurijeh–Shatlyk formations together form one of the main reservoir successions in the Kopeh Dagh–Amu Darya Basin (NE Iran, Turkmenistan, and north of Afghanistan). Sedimentary facies and thickness changes in the Shurijeh–Shatlyk formations show complex variations throughout the basin, which highlight the importance of understanding the controlling factors on facies distribution and depositional setting for future hydrocarbon exploration. Integration of 3D seismic data, 13 boreholes, and five surface stratigraphic sections led to identification of lithofacies and facies associations. The results allow subdivision of this siliciclastic succession into four stratigraphic units (A, B, C, and D). Our study indicates that base‐level changes interacted with palaeotopography inherited from Middle Jurassic basin rifting, Upper Jurassic carbonate reefs/patch reef distributions, and reactivation of the deep basin faults, to control the Shurijeh–Shatlyk depositional setting and sedimentary facies distribution. Our findings show that the Aghdarband and Badkhyz–Maimana palaeo‐highs affected the Kopeh Dagh–Amu Darya Basin throughout deposition of the Shurijeh–Shatlyk formations. Allogeneic processes and active tectonics, related to the Valanginian Late Cimmerian Orogeny, caused a base‐level fall, exposure of Upper Jurassic carbonate sediments, and deposition of a carbonate pebbly conglomerate unit in the western part of the study area. This base‐level fall led to the deposition of thick evaporites in the western area and conglomerate in the eastern parts of the Kopeh Dagh. Due to a Hauterivian sea‐/base‐level rise, several deltas formed in the basin, which form the main reservoir zone in the Murgab Depression and Khangiran Field in Turkmenistan and Iran. [ABSTRACT FROM AUTHOR]

The Niyasar plutonic complex, one of the Cenozoic magmatic assemblages in the Urumieh-Dokhtar magmatic belt, was the subject of detailed petrographic and mineralogical investigations. The Niyasar magmatic complex is composed of Eocene to Oligocene mafic rocks and Miocene granitoids. Eleven samples, representing the major rock units in the Niyasar magmatic complex and contact aureole were chosen for mineral chemical studies and for estimation of the pressure, temperature, and oxygen fugacity conditions of mineral crystallization during emplacement of various magmatic bodies. The analyzed samples are composed of varying proportions of quartz, plagioclase, K-feldspar, hornblende, biotite, titanite, magnetite, apatite, zircon, garnet, and clinopyroxene. Application of the Al-in-hornblende barometer indicates pressures of around 0.2 to 0.4 kbar for the Eocene-Oligocene mafic bodies and around 0.5 to 1.7 kbar for the Miocene granitoids. Hornblende-plagioclase thermometry yields relatively low temperatures (661-780 °C), which probably reflect late stage re-equilibration of these minerals. The assemblage titanite-magnetite-quartz as well as hornblende composition were used to constrain the oxygen fugacity and H2O content during the crystallization of the parent magmas in the Miocene plutons. The results show that the Miocene granitoids crystallized from magmas with relatively high oxygen fugacity and high H2O content (~5 wt% H2O). The Miocene granitoids show similar range of oxygen fugacity, H2O contents and mineral chemical compositions, which indicate a common source for their magmas. Although the crystallization pressures of the Miocene plutons discriminate various categories of plutonic bodies emplaced at depths of about 5.7-6.5 km (Marfioun pluton), about 4.2 km (Ghalhar pluton) and 1.9-2.3 km (Poudalg pluton), they were later uplifted to the same level by vertical displacement of faults. The emplacement depths of the Niyasar plutons suggest that the central part of the Urumieh-Dokhtar magmatic belt has experienced an uplift rate of ca. 0.25-0.4 mm/yr from the Miocene onwards. [ABSTRACT FROM AUTHOR]