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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]

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 aim of this article is to examine the geochemistry and geochronology of the Cadomian Mishu granites from northwest Iran, in order to elucidate petrogenesis and their role in the evolution of the Cadomian crust of Iran. The Mishu granites mainly consist of two-mica granites associated with scarce outcrops of tonalite, amphibole granodiorite, and diorite. Leucogranitic dikes locally crosscut the Mishu granites. Two-mica granites show S-type characteristics whereas amphibole granodiorite, tonalities, and diorites have I-type signatures. The I-type granites show enrichment in large-ion lithophile elements (e.g. Rb, Ba and K) and depletion in high field strength elements (e.g. Nb, Ti and Ta). These characteristics show that these granites have been formed along an ancient, fossilized subduction zone. The S-type granites have high K, Rb, Cs (and other large ion lithophile elements) contents, resembling collision-related granites. U–Pb zircon dating of the Mishu rocks yielded238U/206Pb crystallization ages of ca. 550 Ma. Moreover, Rb–Sr errorchron shows an early Ediacaran age (547 ± 84 Ma) for the Mishu igneous rocks. The two-mica granites (S-type granites) show high87Sr/86Sr(i)ratios, ranging from 0.7068 to 0.7095. TheirɛNd values change between −4.2 and −4.6. Amphibole granitoids and diorites (I-type granites) are characterized by relatively low87Sr/86Sr(i)ratios (0.7048–0.7079) and higher values ofɛNd (−0.8 to −4.2). Leucogranitic dikes have quite juvenile signature, withɛNd values ranging from +1.1 to +1.4 and Nd model ages (TDM) from 1.1 to 1.2 Ga. The isotopic data suggests interaction of juvenile, mantle-derived melts with old continental crust to be the main factor for the generation of the Mishu granites. Interaction with older continental crust is also confirmed by the presence of abundant inherited zircon cores. The liquid-line of descend in the Harker diagrams suggests fractional crystallization was also a predominant mechanism during evolution of the Mishu I-type granites. The zircon U–Pb ages, whole rock trace elements, and Sr–Nd isotope data strongly indicate the similarities between the Mishu Cadomian granites with other late Neoproterozoic–early Cambrian (600–520 Ma) granites across Iran and the surrounding areas such as Turkey and Iberia. The generation of the Mishu I-type granites could be related to the subduction of the Proto-Tethyan Ocean during Cadomian orogeny, through interaction between juvenile melts and old (Mesoproterozoic or Archaean) continental crust. The S-type granites are related to the pooling of the basaltic melts within the middle–upper parts of the thick continental crust and then partial melting of that crust. [ABSTRACT FROM AUTHOR]

The Early Miocene high-K I-type plutonic rocks constitute the early products of the Neogene to Quaternary magmatism, and the youngest exposed intrusions in the East Anatolian plateau. Here we deal with the petrogenesis of the Early Miocene Taşlıçay intrusion covering an area of ∼62 km2. The intrusion comprises leucogranite, and minor gabbro-monzodiorite and rhyolite porphyry. U-Pb dating of zircons from the leucogranite, monzodiorite and rhyolite porphyry yielded identical igneous crystallization ages of ∼19 Ma (Early Miocene). According to the modified alkali-lime index, the leucogranite and the rhyolite porphyry are alkali-calcic, while the gabbro-monzodiorite is transitional calcic to calc-alkalic. On variation diagrams, the gabbro-monzodiorite and the leucogranite as well as rhyolite porphyry form distinct bimodal groupings, whereby the leucogranite display well-defined linear differentiation trends, in contrast to the gabbro-monzodiorite. The leucogranite has relatively fractionated rate earth element (REE) patterns with concave-upward shapes and significant negative Eu anomalies; middle REEs are hardly fractionated with respect to heavy REEs. The gabbro-monzodiorite is characterized by high abundances of incompatible elements, slightly fractionated chondrite-normalized REE patterns with feebly negative Eu anomaly. The rhyolite porphyry is compositionally similar to the leucogranite. The geochemical features imply a fractionating mineral assemblage of hornblende, plagioclase and biotite for the leucogranite, and hornblende and ± plagioclase for the gabbro-monzodiorite. All the rock types display a narrow Sr and Nd isotopic variation (initial 87Sr/86Sr = 0.7053 to 0.7065; initial εNd = −0.5 to −3.8). The leucogranite and rhyolite porphyry exhibit gradually slightly higher initial 87Sr/86Sr and lower initial 143Nd/ 144Nd ratios relative to the gabbro-monzodiorite. Similarly, δ18O and initial εHf values of zircons suggest slightly increasing amount of crustal component from the leucogranite to the rhyolite porphyry. The gabbro-monzodiorite is probably related to partial melts from the slightly enriched lithospheric mantle. The magmas of the leucogranite and the rhyolite porphyry, on the other hand, probably resulted from the remelting of a middle- to high-K basic to intermediate rocks, compositionally similar to the gabbro-monzodiorite, and assimilated gradually slightly increasing amount of old high-silica crustal material. Several lines of evidence such as (i) presence of the well-developed dike swarm of rhyolite porphyry at the north eastern margin of the intrusion, (ii) exhumation of the intrusion at the earth's surface by Middle Miocene, (iii) widespread apatite fission tract ages between 22 and 16 Ma from literature, and (iv) the absence of the exposed intrusions younger than the Early Miocene suggest that the Early Miocene represents probably a time of continental extension and exhumation in Eastern Anatolia and NW Iran. • The Taşlıçay intrusion occurs in the East Anatolian Plateau in the Tethyan realm. • It comprises middle to high-K gabbro-diorite, leucogranite and rhyolite porphyry. • All the rock types formed during Early Miocene (ca. 19 Ma). • Formation and exhumation occurred in an extensional setting. • The high-K leucogranite formed mainly by melting of newly underplated mafic rock. [ABSTRACT FROM AUTHOR]