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The Ghohroud granitoids (GG), containing mafic microgranular enclaves (MMEs) are located in the central part of the Urumieh‐Dokhtar Magmatic Arc (UDMA) in central Iran. They are associated with the subduction‐related magmatism in the Alpine‐Himalayan orogenic belt. The GG are comprised of a variety of intermediate and felsic rocks, including tonalite, granodiorite, granite, diorite porphyry and monzodiorite. The MMEs are gabbroic diorite and tonalite in composition and characterized by a fine‐grained hypidiomorphic microgranular texture with occasional chilled margins. They show rounded, sharp or irregular contact with the host granitoids. The occurrences of quartz, K‐feldspar and corroded plagioclase indicate that MMEs are the products of mixing between mantle and crust‐derived magmas. New ages of zircon U–Pb dating reveal that the GG in the Kashan area emplaced at ca. 19–17 Ma (Burdigalian). All the samples of MMEs and granitoid host rocks in this study are metaluminous and calc‐alkaline with I‐type affinities. They are enriched in light rare earth elements (LREEs) and show slight negative Eu anomalies (Eu/Eu* = 0.36–0.95). These features in a combination with the relative depletion in Nb, Ta, Ti and P, indicate the granitoids and MMEs are closely associated with subduction‐related magmas at an active continental margin. The host rocks yield relatively homogeneous isotopic compositions of initial 87Sr/86Sr ratios ranging from 0.706036 to 0.707055, εNd(t) values varying from −2.25 to 0.8, and the Nd model ages (TDM) vary in a limited range of 0.70–0.96 Ga. The MMEs show similar initial 87Sr/86Sr ratios (0.706420–0.707366), εNd(t) values (−1.32 to −0.27), TDM (0.68–1.09 Ga) and Pb isotopic compositions with host granitoids, which imply they attained isotopic equilibration during magma mingling and mixing. In combination with the petrographic, chemical and isotopic results, we suggest that the origin of MMEs and their host rocks were related to the interaction between crust‐derived melts and mantle‐derived mafic magmas. The magma‐mixing event possibly occurred during the transition from subduction to collision in the UDMA along with the closure of the Neotethyan ocean. [ABSTRACT FROM AUTHOR]

Mineralization of the southern Chah-Palang W (Cu–Au) deposit in the Yazd Block, central Iran are ore-bearing veins and veinlets commonly hosted by Jurassic sandstone and shale rocks of the Shemshak Formation that is intruded by younger dacitic domes. Tungsten and gold are temporally and spatially related to NW-trending, subvertical hydrothermal breccias veins with silicic–chloritic alterations. The deposit formed during granitic magmatism. Three stages of veins–veinlets are recognized: early-stage quartz 1, wolframite, scheelite 1, pyrite 1, chalcopyrite 1, and arsenopyrite1 vein–veinlets; intermediate stage: quartz 2, scheelite 2, gold, pyrite 2, chalcopyrite 2, arsenopyrite 2, pyrrhotite, bornite, native bismuth, niccolite, cobaltite, and sphalerite vein–veinlets; late-stage hematite: quartz and carbonate vein–veinlets. The first two stages are economic significance. The homogenization temperatures (Th) and salinities of fluid inclusion groups from the early stage (milky quartz) range from 260 to 288 °C and 5.1 to 12.7 wt.% NaCl equiv., respectively. In the intermediate stage (white quartz), the fluid temperature and salinity range from 223 to 247 °C and 3.5 to 9.5 wt.% NaCl equiv. The δ34Sfluid values of pyrrhotite and chalcopyrite range between 5.7 and 9.2‰. The southern Chah-Palang mineralization is related to a magmatic geothermal system. δ18Ofluid (8.61 to 3.44‰ values) suggest that the early-stage ore-forming fluids were primarily extracted from magmatic fluid, with the addition of meteoric water in the intermediate stage. Early-stage apatite precipitated mainly from a volatile-rich magmatic fluid. The oxygen isotopic data, fluid inclusions, and mineral chemistry of the apatite samples indicate that the ore-forming fluids of the vein-type southern Chah-Palang deposit were dominated by magmatic-hydrothermal fluids during the early stage and that meteoric water was added during fluid evolution. [ABSTRACT FROM AUTHOR]

The Kashan plutons are situated in the central part of Urumieh-Dokhtar magmatic arc recording subduction-related magmatism within the Alpine-Himalayan orogeny in Iran. These rocks consist of different calc-alkaline plutonic rocks including gabbro, gabbroic diorite, microdiorite, monzodiorite, tonalite, granodiorite, and granite. The plutons were emplaced into the Jurassic sedimentary units (Shemshak Formation) and the Eocene calc-alkaline volcanic and pyroclastic rocks. New U-Pb zircon ages show that the Kashan plutons formed during two main periods at 35.20±0.71 Ma in the Late Eocene (Priabonian) and at 18.90±0.84, 19.26±0.83, 19.30±1.2, and 17.3±1.8 Ma in the Early Miocene (Burdigalian). The reported events in the Kashan plutons imply the final phases of subductionrelated magmatism before the collision which happened between the Arabian and Iranian plates in the Middle Miocene. The plutonic activity in the Kashan region occurred during the transition from Eocene subduction-related setting to Middle Miocene collisional setting. [ABSTRACT FROM AUTHOR]

The Zagros Orogen formed during the Cenozoic collision of Arabia with Eurasia and resulted in the closure of the Neo‐Tethys Ocean. Collision was preceded by a complicated tectonic history involving Pan‐African orogenesis, Late Palaeozoic rifting and the formation of Neo‐Tethys, and subsequent Mesozoic convergence on the northern margin of the ocean contemporaneous with ophiolite obduction on its southern margin. The Sanandaj–Sirjan Zone (SaSZ) is a metamorphic belt within the Zagros Orogen of Gondwanan provenance. U–Pb zircon geochronology has revealed the presence of Pan‐African igneous and metamorphic basement complexes, in addition to minor late Palaeozoic plutons and abundant Jurassic plutonic rocks. This study presents a LA‐ICP‐MS U–Pb apatite age of 440.7 ± 3.7 Ma from a gabbroic body on the central north‐eastern margin of the SaSZ (Nodoushan region). Based on petrography and geochemistry, en route fractional crystallization of ascending magma was an important process in the evolution of the intrusive rocks. Geochemical characteristics imply that the south‐west Nodoushan alkaline gabbroic magma was originated from the asthenospheric mantle source, whereas the high ratios of (La/Yb)N and (Dy/Yb)N are related to the low degree of partial melting from the garnet‐bearing mantle source. Enrichment pattern of Nb, Ta, and Ti and depletion of Rb, Th, and Y are similar to the OIB pattern and intraplate alkaline magmatic rocks. High εNd(t) values (+1.29 to +1.50), low initial Sr isotopic ratios (0.703679–0.704098), and trace element ratios (e.g., Nb/La, Ce/Pb, Ba/Nb, and Th/Nb) indicate that crustal contamination was insignificant in its petrogenesis. The petrogenesis of the Nodoushan alkaline gabbroic rocks could be related to the presence of extensional phase, upwelling and decompressional melting of asthenospheric mantle in the rift basin which was associated with the opening of the Paleo‐Tethys Ocean in Late Ordovician to Silurian times. [ABSTRACT FROM AUTHOR]

The interaction of mafic-intermediate and felsic rocks of the Salmas plutonic rocks produced mixed rocks (granodiorites) which contain mafic microgranular enclaves (MMEs). Enclaves ranging from a few millimeters to centimeters in size, and from ellipsoidal to rounded in shape. Based on both field observation and mineralogical compositions, MMEs are composed of quartz diorite whereas the felsic host rocks comprise mainly granodiorite. MMEs are characterized by a microporphiritic texture and revealed some types of microscopic textures, e.g., prismatic-cellular plagioclase with spike zones and rounded plagioclase megacrysts, blade-shaped biotite and acicular apatite. The host rocks show textures such as oscillatory- and reversely zoned plagioclase with spike zone. Compositions of plagioclases (An to An) of MMEs are similar to those of host rocks (An to An) which suggest partial to complete equilibration during mafic-felsic magma interactions. The individual petrographic and microstructural textures and mineral chemistry similarities between the MMEs and their host rocks and diorites indicate that the enclaves are of mixed origin and most probably formed by interaction of lower crust magma (granitic melt) and evolved mantle-derived magmas (diorites). [ABSTRACT FROM AUTHOR]

We conducted geochemical and isotopic studies on the Oligocene–Miocene Niyasar plutonic suite in the central Urumieh–Dokhtar magmatic belt, in order better to understand the magma sources and tectonic implications. The Niyasar plutonic suite comprises early Eocene microdiorite, early Oligocene dioritic sills, and middle Miocene tonalite + quartzdiorite and minor diorite assemblages. All samples show a medium-K calc-alkaline, metaluminous affinity and have similar geochemical features, including strong enrichment of large-ion lithophile elements (LILEs, e.g. Rb, Ba, Sr), enrichment of light rare earth elements (LREEs), and depletion in high field strength elements (HFSEs, e.g. Nb, Ta, Ti, P). The chondrite-normalized rare earth element (REE) patterns of microdiorite and dioritic sills are slightly fractionated [(La/Yb)n = 1.1–4] and display weak Eu anomalies (Eu/Eu* = 0.72–1.1). Isotopic data for these mafic mantle-derived rocks display ISr = 0.70604–0.70813, ϵNd(microdiorite: 50 Ma and dioritic sills: 35 Ma, respectively) = +1.6 and −0.4, TDM = 1.3 Ga, and lead isotopic ratios are (206Pb/204Pb) = 18.62–18.57, (207Pb/204Pb) = 15.61–15.66, and (208Pb/204Pb) = 38.65–38.69. The middle Miocene granitoids (18 Ma) are also characterized by relatively high REE and minor Eu anomalies (Eu/Eu* = 0.77–0.98) and have uniform initial87Sr/86Sr (0.7065–0.7082), a range of initial Nd isotopic ratios [ϵNd(T)] varying from −2.3 to −3.7, and Pb isotopic composition (206Pb/204Pb) = 18.67–18.94, (207Pb/204Pb) = 15.63–15.71, and (208Pb/204Pb) = 38.73–39.01. Geochemical and isotopic evidence for these Eocene–Ologocene mafic rocks suggests that the magmas originated from lithospheric mantle with a large involvement of EMII component during subduction of the Neotethyan ocean slab beneath the Central Iranian plate, and were significantly affected by crustal contamination. Geochemical and isotopic data of the middle Miocene granitoids rule out a purely crustal-derived magma genesis, and suggest a mixed mantle–crustal [MASH (melting, assimilation, storage, and homogenization)] origin in a post-collision extensional setting. Sr–Nd isotope modelling shows that the generation of these magmas involved ∼60% to 70% of a lower crustal-derived melt and ∼30% to 40% of subcontinental lithospheric mantle. All Niyasar plutons exhibit transitional geochemical features, indicating that involvement of an EMII component in the subcontinental mantle and also continental crust beneath the Urumieh–Dokhtar magmatic belt increased from early Eocene to middle Miocene time. [ABSTRACT FROM PUBLISHER]

The Salmas area, in the northernmost part of the Sanandaj–Sirjan zone of Iran, contains a crystalline mafic–intermediate complex that intrudes into the Precambrian metamorphic basement complex and is composed of gabbroic and gabbrodiorite cumulates and fine-grained non-cumulate gabbronorites and diorites. These rocks have fine- to coarse-grained texture and are mainly composed of plagioclase, pyroxenes, and amphibole. Major element geochemistry indicates that the pluton has a low-K with tholeiitic affinity. Variations of major and trace elements on Harker diagrams, including negative correlations MgO, Fe2O3, CaO, and Co and positive correlations Na2O, K2O, Rb, Ba, and La, with increasing SiO2and chondrite-normalized REE patterns, suggest that fractional crystallization of gabbroic rocks could have played a significant role in the formation of evolved rocks. The chondrite-normalized REE patterns are not fractionated (LaN/LuN= 1.3–5.4) and display strong Eu anomalies (Eu/Eu* = 1.15–1.76) in cumulate rocks, which we attributed to cumulus plagioclase. Sr and Nd isotopic ratios vary from 0.704698 to 0.705866 and from 0.512548 to 0.512703, respectively. Gabbronorites with high143Nd/144Nd ratios, low87Sr/86Sr ratios, and high MgO, Ni, and Cr contents indicate that they were generated from relatively primitive magmas. We used petrogenetic modelling to constrain sources. Trace element ratio modelling indicates that the gabbroic rocks were generated from a spinel-peridotite source via 5–20% degrees of fractional melting at a depth of ∼52 km. Major and REE modelling shows that the diorites are the products of fractional crystallization of gabbronorites. [ABSTRACT FROM AUTHOR]

The Sorkhe- Dizaj iron oxide-apatite deposit in the Cenozoic Alborz- Azarbaijan magmatic belt, NW Iran, is hosted mainly by a Late Eocene to Oligocene quartz-monzonitic body, and subordinately in the Eocene volcanic and volcanoclastic sequences. The Sorkhe- Dizaj intrusive body is an I-type granitoid of the calc-alkaline series. Mineralization is associated with actinolization, K-feldspar, sericitic, propylitic, and tourmaline alteration types. The orebodies are massive, banded, stockwork, and breccia in shape and occur mainly along the fault zones within the quartz-monzonitic intrusion, volcanic, and volcanoclastic rocks. Ore minerals dominantly comprise magnetite, apatite, and monazite, as well as minor amounts of chalcopyrite, bornite, and pyrite. Four major paragenetic stages are discriminated in the mineralization including early, oxide, sulfide, and late stage. The Sorkhe- Dizaj deposit is similar in the aspects of host rock lithology, alteration, and mineralogy to the Kiruna-type deposits associated with minor Cu sulfide minerals. Spatial and temporal association of the mineralization with the Late Eocene- Early Oligocene quartz-monzonite intrusive body suggests that the ore fluid was probably related to magmatic activity. [ABSTRACT FROM AUTHOR]