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[Display omitted] • Detrital zircon data show an extensive Cadomian arc magmatism in Iran-Anatolia. • Abundant 2.6–2.4 Ga zircons show exhumation of a local crust during the Ediacaran. • Zircon and bulk-rock isotope data show Gondwana rifting in early Paleozoic. Understanding crustal growth, reworking, and geodynamics of the northern continental margin of Gondwana during Ediacaran to Silurian times plays an important role in Gondwana's paleogeographic reconstruction. This study uses a combination of bulk-rock geochemistry, magmatic and detrital zircon geochronology, zircon trace element, and O-Hf isotope data to evaluate the Ediacaran-early Paleozoic magmatic history of northern Gondwana. Our detrital zircon data from Ediacaran to Ordovician sedimentary successions of central Iran show that the 620–500 Ma detrital zircon likely originates from the erosion of the Cadomian arcs in Iran and Anatolia. This zircon shows variable εHf (t) and δ18O values and Nb/Yb, U/Yb, and U/Nb, resembling arc rocks. The Cryogenian (1000–620 Ma) detrital zircon with juvenile εHf (t) and mantle-like δ18O values could have been supplied from erosion of the juvenile crust of the ANS. The youngest age peaks of 488–450 Ma for detrital zircon, in upper Cambrian-Ordovician sedimentary rocks, are considered to show the rifting of Gondwana and Paleotethys opening. Abundant unrounded 2.5 Ga detrital zircon from Ediacaran sandstones probably shows uplift and exhumation of a local source, i.e., the Archean crust of Iran. The Neoproterozoic igneous rocks formed firstly during the subduction of oceanic lithosphere (Mozambique Ocean) beneath northern Gondwana around 880 Ma to form the ANS juvenile crust. Later, the magmatism moved from the ANS toward the northern territories of Gondwana, with peak magmatism at 570–525 Ma. In Cambrian to Ordovician, the Cadomian magmatic arc was uplifted and eroded, and the geodynamic setting switched into juvenile magmatism following rifting of northern Gondwana. [ABSTRACT FROM AUTHOR]

Post-collisional volcanism contains important clues for understanding the processes that prevail in orogenic belts, including those in the mantle and the uplift and collapse of continents. Here we report new geochronological and geochemical data for a suite of post-collisional Miocene to Pleistocene volcanic rocks from northwest Iran. Four groups of volcanic rocks can be distinguished according to their geochemical and isotopic signatures, including: (1) Miocene depleted lavas with high Nd and Hf but low Pb and Sr isotopic ratios, (2) less depleted lavas with quite variable Pb isotopic composition, (3) lavas with non-radiogenic Nd and Hf isotopic values, but highly radiogenic Sr and Pb isotopic composition, and (4) Pleistocene adakitic rocks with depleted isotopic signatures. The isotopic data reveal that the Miocene rocks are derived from asthenospheric and highly heterogeneous sub-continental lithospheric mantle sources. Evidence suggests that the lithospheric mantle contains recycled upper continental material and is isotopically similar to the enriched mantle two (EMII) end-member. Analysis of Sr-Nd-Pb-Hf-O isotopes in both mineral and rock groundmass, in conjunction with energy-constrained assimilation and fractional crystallization (EC-AFC) numerical modeling, demonstrates that the incorporation of continental crust during magma fractionation via AFC had an insignificant impact on the isotopic composition of the Miocene lavas. Moreover, adakites are the youngest rocks and show a geochemical signature consistent with the partial melting of a young and mafic continental lower crust. Both seismological data and geochemical signatures on these Miocene to Pleistocene volcanic rocks indicate the initiation of asthenospheric upwelling and orogen uplift in the Arabia-Eurasia collision zone, which occurred after slab break-off, following the Neotethyan closure. [ABSTRACT FROM AUTHOR]

Several Mesozoic ophiolites in Iran formed in response to Late Cretaceous subduction initiation. Here we review the geology, petrography, mineralogy and geochemistry of mantle rocks from the Nain, Neyriz, Khoy, Esfandagheh and Fannuj ophiolites. They are remnants of Neo-Tethys ocean lithosphere formed during subduction initiation and were emplaced onto the southern flank of Eurasia. Most show SSZ-type geochemical affinity. We summarize the composition of mantle sections from these five representatives, which comprise lherzolites and harzburgites with minor dunite lenses and sometimes chromitites. Spinels in lherzolite from all regions are characterized by low chromium number [Cr# = Cr/(Al + Cr)] of 0.09 to 0.56 and plot in the abyssal peridotite field, whereas spinel in harzburgite and dunite-chromitite have Cr# of 0.41 to 0.73 and 0.45 to 0.86, respectively, showing geochemical affinities with forearc peridotites and boninites, respectively. Lherzolites and harzburgites have low rare earth element (REE) contents and experienced around 15% and 25% partial melting, respectively. Ophiolitic peridotites from the Nain (inner Zagros ophiolitic belt), Khoy, and Neyriz (outer Zagros ophiolitic belt) complexes are depleted in light REE and show flat heavy REE patterns. By contrast, peridotites from the Fannuj (Makran ophiolitic zone) and Esfandagheh (outer Zagros ophiolitic belt) complexes are characterized by flatter and U-shaped REE patterns, respectively, similar to those of SSZ peridotites. Based on the compositions of olivine and spinel, we infer that chromitites and their dunite envelopes experienced wider variations in oxygen fugacity (fO2), equilibrium temperatures, and spinel Cr# values than those of the surrounding lherzolites and harzburgites, suggesting interaction between residual mantle harzburgites and H2O-rich and highly oxidized SSZ melts. Lherzolites from all regions and harzburgites of Nain, Neyriz and Fannuj are MOR-type peridotites that plot in the overlapping space of MOR peridotites and were generated in an extensional environment. These are forearc peridotites that were in equilibrium with tholeiitic melts generated during early proto-forearc or back-arc spreading during subduction initiation, whereas spinels of dunites and high-Cr chromitites were in equilibrium with boninitic melts. [ABSTRACT FROM AUTHOR]

[Display omitted] • A magmatic flare-up occurred in NE Iran during the Early to Middle Eocene. • Magmatic flare-up was dominated by melts from a metasomatized mantle wedge. • Change in slab dip and upwelling of the asthenosphere caused the magmatic flare-up. Most continental arcs are built up over a long time (≥100 myr), and while subduction may be ongoing throughout this interval, magmatism appears to be highly episodic. This episodic behaviour is characterized by high-flux magmatic events but an overall low rate of magmatism. The causes of high-flux magmatic events ("flare-ups") are enigmatic in many continental arcs. Bulk-rock Sr, Nd, and Pb isotopes, as well as zircon O and Hf isotopes, imply that the mantle and the continental crust can be involved in magmatic flare-ups. However, the relative contributions of mantle vs. crust with changes in eruption rates can differ from arc to arc. The Cenozoic magmatic arcs of Iran, built on mature continental crust, are an excellent candidate for studying the geochemical-isotopic feedback of magmatic pulses to understand the triggers for a flare-up. Our new data constrain the timing of the flare-up in NE Iran to the Early to Middle Eocene (51–43 Ma). This flare-up is characterized by the outpouring of high-K calc-alkalic to shoshonitic magmas at ∼110 ± 8 km3/myr - km. Geochemical modelling using the "Arc Basalt Simulator version 3″ shows that the high-K trachybasalts, moderately to extremely depleted in high-field strength elements, can be derived from the shallower (3.0 GPa; 870 °C) to deeper parts (5.0–5.4 GPa; 965–980 °C) of a subducting slab with ∼1.0 to 5.5 % slab melt flux. Mixing modelling using Sr, Nd, and Pb isotope data indicates that the Torud mafic-intermediate magmatic rocks can be generated by adding ∼ 1% to <6% of slab components (50% AOC: 50% sediment) to an Indian MORB-like mantle. Our results suggest that the high magmatic fluxes in NE Iran were instigated mainly by Eocene slab steepening after Paleocene flat-slab subduction, resulting in enhanced upwelling and melting of a volatile-enriched asthenospheric mantle. [ABSTRACT FROM AUTHOR]

New geochronological and geochemical data for Late Neoproterozoic to Mesozoic intrusive rocks from NW Iran define major regional magmatic episodes and track the birth and growth of one of the Cimmerian microcontinents: the Persian block. After the final accretion of the Gondwanan terranes, the subduction of the Prototethyan Ocean beneath NW Gondwana during the Late Neoproterozoic was the trigger for high magmatic fluxes and the emplacement of isotopically diverse arc-related intrusions in NW Gondwana. The Late Neoproterozoic rocks of NW Iran belong to this magmatic event which includes intrusions with highly variable εHf(t) values. This magmatism continued until a magmatic lull during the Ordovician, which led to the erosion of the Neoproterozoic arc, and then was followed by a rifting event which controlled the opening of Paleotethys. In addition, it is supposed that a prolonged pulse of rift magmatism in Persia lasted from Devonian-Carboniferous to Early Permian time. These magmatic events are geographically restricted and are mostly recorded from NW Iran, although there is some evidence for these magmatic events in other segments of Iran. The Jurassic rocks of NW Iran are interpreted to be the along-strike equivalents of a Mesozoic magmatic belt (the Sanandaj-Sirjan Zone; SaSZ) toward the NW. Magmatic rocks from the SaSZ show pulsed magmatism, with high-flux events at both ~176–160 Ma and ~130 Ma. The SaSZ magmatic rocks are suggested to be formed along a continental arc but a rift setting is also considered for the formation of the SaSZ rocks based on the plume-related geochemical signatures. The arc signatures are represented by Nb-Ta depletion in the highly contaminated (by upper continental crust) plutonic rocks whereas the plume-related signature of less-contaminated melts is manifested by enrichment in Nb-Ta and high εHf(t) values, with peaks at +0.6 and +11.2. All these magmatic pulses led to pre-Cimmerian continental growth and reworking during the Late Neoproterozoic, rifting and detachment of the Cimmerian blocks from Gondwana in Mid-Late Paleozoic time and further crustal growth and reworking of Cimmeria during the Mesozoic. Unlabelled Image • U-Pb zircon ages define Late Neoproterozoic, Paleozoic and Mesozoic magmatic events in NW Iran. • Late Neoproterozoic magmatism is characterized by highly variable εHf(t) values. • Late Paleozoic magmatic pulses show rift-related geochemical signatures with radiogenic εHf(t) values. [ABSTRACT FROM AUTHOR]

The Cadomian orogen of NW Iran includes a series of metamorphic rocks with zircon U-Pb ages between ca 562 and 505 Ma (Ediacaran to middle Cambrian). The Ediacaran-Cambrian basement is intruded by a series of Late Eocene-Late Oligocene I-type granitic rocks. U-Pb geochronology, integrated with geochemical and isotopic data for the basement rocks in NW Iran, provides further evidence of a Cadomian (562-505 Ma) arc-related magmatic event lasting ∼ 60 Myr. Cadomian magmatism in Iran was a part of a ∼ 100 Myr long episode of subduction-related arc magmatism at the northern margin of Gondwana. Zircon Hf-isotope compositions show that during Cadomian magmatic arc activity, juvenile arc magmas interacted with reworked Archean crust to generate the Ediacaran-Cambrian igneous rocks. Our results document both inheritance of old zircons and the presence of zircons with juvenile signatures in NW Iran, suggesting that the geotectonic setting for the Cadomian rocks was an Ediacaran continental magmatic arc and probably a neighboring back-arc basin. The occurrence of Ediacaran ophiolitic slices in NW Iran may provide evidence of back-arc basin opening at that time. Cenozoic plutonism in NW Iran is part of an Eocene-Oligocene magmatic 'flare-up' along the Urumieh-Dokhtar Magmatic Belt in central Iran, which lasted for ca 30 Myr. The melts responsible for the formation of these rocks had an essentially juvenile signature with minor contamination by Archean to Cadomian middle-lower continental crust. Continuous convergence between Arabia and Iran was accompanied by the transition of SW Eurasia from a compressional to an extensional convergent plate margin in Eocene-Oligocene times, leading to orogenic collapse, core-complex formation, exhumation of Cadomian crust and a major increase in arc magmatism. [ABSTRACT FROM AUTHOR]

We present regional variations of whole-rock Sr/Y and (La/Yb) N ratios of magmatic rocks along the Cenozoic Urumieh-Dokhtar and Alborz magmatic belts, Iran. Both the magmatic belts are located at the north of the main Zagros Neo-Tethyan suture. The Urumieh-Dokhtar magmatic belt (UDMB), which trends NW-SE for 1000 km across Iran, was characterized by the intensive volcanism and plutonism, and defined the magmatic front (MF) of the Zagros orogenic belt. The Alborz magmatic belt (AMB) is situated to the north, and characterized by less intense magmatic activity. The Alborz magmatic belt was formed behind it in the rear-arc (RA) domain. A striking feature of the both magmatic belts is the transition from normal calc-alkaline arc magmatism during the Eocene–Oligocene to adakite-like calc-alkaline magmatism during the Middle to Late Miocene–Pliocene. The late-Cenozoic magmatism of the UDMB and AMB shows higher Sr/Y and (La/Yb) N. However, it should be noted that crustal thickening event is intensive in the UDMB than AMB during Late Cenozoic. Using the composition of the Lale-Zar zircons from the SE UDMB we determined the oxygen fugacity (f O 2) during zircon crystallization to be between FMQ (fayalite–magnetite–quartz buffer) -0.69 to +2.41, whereas those of the Hashroud-Teckmdash-Gormolla zircons from NW AMB range from −1.22 to +5.99. The f O 2 estimates suggest relatively more oxidized conditions for the Late Cenozoic igneous rocks of the AMB. Compiled data from the UDMB and AMB intrusions show an increase in average zircon crystallization temperatures with decreasing age. These outcomes have been interpreted in terms of variation of the crustal thickness, from 30 to 35 km during Eocene-Oligocene to 40–55 km during the middle-late Miocene. We propose the increase in crustal thickness is associated with the collision between the Arabian plate and Iran and subsequent convergence during the middle-late Miocene. • Increasing in average zircon crystallization temperatures, and f O 2 from Eocene-Oligocene to Miocene. • Variation of the crustal thickness from 30 to 35 km to 40–55 km during the Cenozoic • Thickening was likely due to collision between the Arabian plate and Iran and subsequent convergence [ABSTRACT FROM AUTHOR]

The Sanandaj-Sirjan Zone of western Iran is characterized by significant Mesozoic magmatic activity (from the early Jurassic to the late Cretaceous), with Cenozoic rocks being less common. Granitoids are prevalent in this zone, displaying A-, I-, and S-type geochemical characteristics. Despite several studies on these granitoids, there are still some questions regarding their sources– especially the S- and A-type granitoids – and the crustal growth and recycling in this zone, which require further studies using isotopes. This study focuses on the Aligoodarz, Kolah-Ghazi, and Golpayegan granitoids from the central SaSZ to better understand crustal growth and recycling in the Sanandaj-Sirjan Zone. The Aligoodarz and Kolah-Ghazi granitoids are identified as S-type granites, showing strong peraluminous signatures. Geochemical evidence suggests a mixture of melts from sub-crustal metasedimentary and meta-igneous sources, with factors such as source diversity and disequilibrium melting contributing to their formation. in contrast, the Golpayegan granitoids exhibit high total alkali (Na 2 O + K 2 O) contents and high field strength elements, indicating alkaline magmatic affinity. Their geochemical signatures suggest derivation from an enriched portion of an Indian MORB-like protolith. Golpayegan syenites share similarities with within-plate A1 granites, suggesting they are related to anorogenic silica-oversaturated granitoids. Golpayegan A-type granites probably originated from high-degree fractionation of alkali basic magmas. Golpayegan gabbros may be derived from a MORB or OIB-like mantle source, with characteristics indicating the presence of garnet in the mantle source and potentially deep melting from a mantle plume. Newly compiled zircon U Pb data from the Sanandaj-Sirjan Zone show a complex magmatic chronology spanning from approximately 180 million years ago to the Eocene epoch, revealing peaks of magmatic activity at various intervals. Distinct phases of A-, I-, and S-type magmatism are identified, and synthesis of zircon U Pb ages and Hf O isotope data reveals the simultaneous occurrence of S-type and I-type magmas during specific periods. Furthermore, our study explores the tectonic settings underlying these magmatic processes and proposes scenarios involving subduction, continental rifting, and asthenospheric upwelling to elucidate the geological dynamics of the SaSZ. • Abundant Jurassic-Cretaceous A-, S-, and I-type granitoids are found in the Sanandaj-Sirjan Zone of Iran. • The granitoids exhibit evidence of mantle and crustal components, defining crustal growth and recycling processes. • The SaSZ rocks are believed to have originated from Jurassic subduction and late Cretaceous asthenospheric upwelling. [ABSTRACT FROM AUTHOR]

Despite diverse geochronological-geochemical studies on Cenozoic igneous rocks from the SE segment of the Urumieh-Dokhtar Magmatic Belt (UDMB) of Iran, the nature of the Oligocene magmatic rocks from the farthermost end of the SE segment- where it is linked to the Makran magmatic belt- has been ignored due to the difficulty of access. In this study, we focus on syn -collisional mafic to felsic igneous rocks of calc-alkaline and high-K calc-alkaline affinities from the SE segment of the Urumieh-Dokhtar Magmatic Belt (UDMB) near Nagisun, south of Bam. The Nagisun rocks have low Sr/Y and La (n) /Yb (n) , similar to igneous rocks from typical arcs. Zircon U Pb ages show comparable ages for plutonic (~ 34–25 Ma) and volcanic (~34–27 Ma) rocks. The εHf(t) values for zircons from plutonic rocks range from −0.3 to +12.8, whereas the εHf(t) values for the volcanic rocks vary from −2.6 to +13. Modelling of trace elements compositions using Nagisan basaltic samples indicate that an 87:2:11 mixture of the depleted MORB mantle, subducting (trench)-sediments and altered oceanic crust with 5% aggregated fractional melting closely matches the trace-element abundances of the Nagisun basaltic rocks. Indeed, the modelling of Sr and Nd isotopic data emphasizes that the Nagisun magmatic rocks could be products of bulk mixing between a depleted MORB mantle and/or a mixed, fertilized mantle with the Cadomian lower and upper continental crust. Furthermore, our compiled data display that the magmatism in the SE segment of the UDMB changed through time from normal calc-alkaline magmatism to adakitic magmatism at ~20 Ma, after the collision with Arabia began ca 27 Ma. • Collision-related, Oligocene magmatic rocks are abundant in the SE segment of the Urumieh-Dokhtar magmatic belt of Iran. • Zircon U-Pb data show ages of 34-25 Ma for plutonic rocks and 34-27 Ma for volcanic rocks from SE UDMB. • Isotope modelling suggests mixing between the mantle and Cadomian crust for the formation of these rocks. [ABSTRACT FROM AUTHOR]

Continental-arc igneous rock compositions change in response to the transition from subduction to collision and these changes can reveal how the crust, lithosphere and magma sources evolved. Neotethys-related Late Cretaceous to Pleistocene subduction- and collision-related magmatic rocks from the ~350 km long southeast Urumieh-Dokhtar Magmatic Belt (UDMB) of Iran provide an excellent natural laboratory to better understand these changes. These igneous rocks are well-exposed and moderately eroded to reveal a nearly complete record since subduction initiation at ~95 Ma. We analyzed new samples for major and trace elements (83 samples), Sr Nd isotopic compositions (47 samples), and U Pb zircon ages (26 samples) and compiled geochemical and geochronological data on the southeast segment of the UDMB. The geochronological data reveal two magmatic pulses at ~80–70 Ma and ~50–0 Ma. Important changes in magmatic compositions reflect initial collision with Arabia at ~32 Ma, changing from normal calc-alkaline to increasingly adakitic immediately after collision began. Five stages can be identified: 1) normal continental-arc magmatism during the Late Cretaceous; 2) arc quiescence in Paleocene and Early Eocene time; 3) Middle-Late Eocene extensional arc magmatism related to slab rollback; 4) early collision and crustal thickening during the Early Oligocene; and 5) slab breakoff, asthenospheric upwelling, and associated adakitic magmatism from Middle Miocene onward. Temporal changes in UDMB magmas reflect the response of the overriding plate to changes in the geometry of the subducting Neotethyan lithosphere and to collision between Arabia and Iran. Crustal thickening and arc narrowing during Miocene to Pleistocene post-collisional magmatism caused adakitic magmatism and associated Cu mineralization. Zircon O Hf and apatite O isotopes as well as bulk-rock Nd isotopes of Cu-bearing adakitic rocks are similar to other barren rocks, but nearly all fertile rocks have higher Hf/Y, Eu/Eu⁎ (n) in zircon and higher Sr/Y, V/Y, Eu/Eu⁎ (n) in apatite than barren rocks. • Magmatism in southeast Iran occurred during neotethyan subduction and collision. • Magmatism changed from pre-collision calc-alkaline to Syn -collisional adakitic. • Syn-collisional magmatism at ca 32 Ma was characterized by perturbation of isotopic systems. [ABSTRACT FROM AUTHOR]

The continental crust of NW Iran is intruded by Late Cretaceous I-type granites and gabbro-diorites as well as Paleocene A-type granites. SIMS and LA-ICPMS U-Pb analyses of zircons yield ages of 100–92 Ma (Late Cretaceous) for I-type granites and gabbro-diorites and 61–63 Ma (Paleocene) for A-type granites. Late Cretaceous gabbro-diorites (including mafic microgranular enclaves; MMEs) from NW Iran show variably evolved signatures. They show depletion in Nb and Ta on N-MORB-normalized trace-element spider-diagrams and have high Th/Yb ratios, suggesting their precursor magmas were generated in a subduction-related environment. Gabbro-diorites have variable zircon εHf(t) values of +1.2 to +8, δ18O of 6.4 to 7.4‰ and bulk rock εNd(t) of −1.4 to ~ +4.9. The geochemical and isotopic data attest to melting of subcontinental lithospheric mantle (SCLM) to generate near-primitive gabbros with radiogenic Nd isotopes (εNd(t) = ~ +4.9) and high Nb/Ta and Zr/Hf ratios, similar to mantle melts (Nb/Ta ~ 17 and Zr/Hf ~ 38). These mafic melts underwent further fractionation and mixing with crustal melts to generate Late Cretaceous evolved gabbro-diorites. Geochemical data for I-type granites indicate both Nb-Ta negative and positive anomalies along with enrichment in light REEs. These rocks are peraluminous and have variable bulk-rock εNd(t) (−1.4 to +1.3), zircon εHf(t) (+2.8 to +10.4) and δ18O (4.7–7.3‰) values, but radiogenic bulk rock Pb isotopes. The geochemical and isotopic signatures of these granites suggest interaction of mantle-derived mafic magmas (similar to near-primitive Oshnavieh gabbros) with middle-upper crust through assimilation-fractional crystallization (AFC) to produce Late Cretaceous I-type granites. Paleocene A-type granites have distinctive geochemical features compared to I-type granitoids, including enrichment in Nb-Ta, high bulk rock εNd(t) (+3.3 to +3.9) and zircon εHf(t) (+5.1 − +9.9) values. Alkaline granites are ferroan; they have low MgO, CaO, Sr, Ba and Eu concentrations and high total Fe 2 O 3 , K 2 O, Na 2 O, Al 2 O 3 , Ga, Zr, Nb-Ta, Th and rare earth element (REE) abundances and Ga/Al ratios. These rocks might be related to fractionation of a melt derived from a sub-continental lithospheric mantle, but which interacted with asthenosphere-derived melts. We suggest that subduction initiation and the resultant slab roll-back caused extreme extension in the overlying Iranian plate, induced convection in the mantle wedge and led to the decompression melting of SCLM. Rising mantle-derived magmas assimilated middle-upper crustal rocks. Fractionating mantle-derived magmas and contamination with crustal components produced evolved gabbro-diorites and I-type granites. In contrast, asthenospheric upwelling during the Paleocene provided heat for melting and interaction with SCLM to generate the precursor melts to the A-type granites. • There are Late Cretaceous granitoids and Paleocene A-type granites in NW Iran. • Different mechanisms are suggested for genesis of granitoids and A-type granites. • Subduction initiation and extension generated granitoids during the Late Cretaceous. [ABSTRACT FROM AUTHOR]