Prolonged magmatism and growth of the Iran-Anatolia Cadomian continental arc segment in Northern Gondwana

Much of the crust of Iran and Anatolia, including their oldest exposed rocks, formed during an episode of intense convergent margin (arc) magmatism as a result of subduction of oceanic lithosphere beneath northern Gondwana from ca 620 Ma to ca 500 Ma, the Cadomian crust-forming event. Most igneous rocks formed between ca 570 and 525 Ma. Cadomian crust is well-known from western and southern Europe and from eastern North America but is much less well-known from Iran and Anatolia. We use published age and compositional data and contribute new data in order to better understand this ancient magmatic system. Cadomian magmatism included calc-alkaline igneous rocks of arc affinity in the main arc and alkalic igneous rocks that formed in a back-arc setting; these igneous rocks are associated with sedimentary rocks. Geochemical and isotopic modelling reveals that basaltic magmas were the main input, that these formed by partial melting in the upper mantle, and that basaltic magmas evolved further in deep crustal hot zones to form granitic magmas through a combination of assimilating older continental crust and fractional crystalization of basaltic magmas.This study was funded by the “ National Key Research and Development Program of China ( 2016YFE0203000 )” and by “ Chinese Academy of Sciences , President's International Fellowship Initiative (PIFI, 2019VCB0013 ). Financial support was also received from the Alexander von Humboldt Foundation in the form of a senior research grant and GEOMAR Helmholtz Centre while preparing these results for publication. FL gratefully acknowledges the PRIN2017 Project 20177BX42Z_001 (Intraplate deformation, magmatism and topographic evolution of a diffuse collisional belt: Insights into the geodynamics of the Arabia-Eurasia collisional zones) and the grant to Department of Science, Roma Tre University (MIUR-Italy Dipartimenti di Eccellenza, ARTICOLO 1, COMMI 314 – 337 LEGGE 232/2016 ). We thank Semih Gürsu for providing us bulk rock data from Derik complex of Turkey. Zircon U–Pb geochronology and and Lu–Hf isotope data were obtained using instrumentation funded by DEST Systemic Infrastructure Grants, ARC LIEF, NCRIS/AuScope, industry partners, and Macquarie University. All logistical support for field studies came from Damghan University. This is contribution 1544 from the ARC Centre of Excellence for Core to Crust Fluid Systems ( http://www.ccfs.mq.edu.au ) and 1412 in the GEMOC Key Centre ( http://www.gemoc.mq.edu.au ), and 1380 from UTD Geosciences and is related to IGCP-662. from the ARC Centre of Excellence for Core to Crust Fluid Systems ( http://www.ccfs.mq.edu.au ), xxxx from the GEMOC Key Centre ( http://www.gemoc.mq.edu.au ), and xxxx from UTD Geosciences and is related to IGCP-662

Neotethyan Subduction Ignited the Iran Arc and Backarc Differently

Most arcs show systematic temporal and spatial variations in magmatism with clear shifts in igneous rock compositions between those of the magmatic front (MF) and those in the backarc (BA). It is unclear if similar magmatic polarity is seen for extensional continental arcs. Herein, we use geochemical and isotopic characteristics coupled with zircon U‐Pb geochronology to identify the different magmatic style of the Iran convergent margin, an extensional system that evolved over 100 Myr. Our new and compiled U‐Pb ages indicate that major magmatic episodes for the NE Iran BA occurred at 110–80, 75–50, 50–35, 35–20, and 15–10 Ma. In contrast to NE Iran BA magmatic episodes, compiled data from MF display two main magmatic episodes at 95–75 and 55–5 Ma, indicating more continuous magmatism for the MF than for the BA. We show that Paleogene Iran serves as a useful example of a continental arc under extension. Our data also suggest that there is not a clear relationship between the subduction velocity of Neotethyan Ocean beneath Iran and magmatic activity in Iran. Our results imply that the isotopic compositions of Iran BA igneous rocks do not directly correspond to the changes in tectonic processes or geodynamics, but other parameters such as the composition of lithosphere and melt source(s) should be considered. In addition, changes in subduction zone dynamics and contractional versus extensional tectonic regimes influenced the composition of MF and BA magmatic rocks. These controls diminished the geochemical and isotopic variations between the magmatic front and backarc

Data for: Repeated Magmatic Build-up and Deep "Hot Zones" in Continental Evolution: the Cadomian Crust of Iran

These files include mineral geochemistry, bulk rock major, trace and isotope data, zircon U-Pb age data and zircon Lu-Hf isotopes from all Cadomian rocks in Iran

Data for: Repeated Magmatic Build-up and Deep "Hot Zones" in Continental Evolution: the Cadomian Crust of Iran

These files include mineral geochemistry, bulk rock major, trace and isotope data, zircon U-Pb age data and zircon Lu-Hf isotopes from all Cadomian rocks in Iran.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Data for: Prolonged Magmatism and Growth of the Iran-Anatolia Cadomian Continental Arc Segment in Northern Gondwana

Much of the crust of Iran and Anatolia, including their oldest exposed rocks, formed during an episode of intense convergent margin (arc) magmatism as a result of subduction of oceanic lithosphere beneath northern Gondwana from ca 620 Ma to ca 500 Ma, the Cadomian crust-forming event. Most igneous rocks formed between ca 570 and 525 Ma. Cadomian crust is well-known from western and southern Europe and from eastern North America but is much less well-known from Iran and Anatolia. We use published age and compositional data and contribute new data in order to better understand this ancient magmatic system. Cadomian magmatism included arc-like igneous rocks in the main arc and alkalic igneous rocks that formed in a back-arc setting; these igneous rocks are associated with sedimentary rocks. Geochemical and isotopic modelling reveals that basaltic magmas were the main input, that these formed by partial melting in the upper mantle, and that basaltic magmas evolved further in deep crustal hot zones to form granitic magmas through a combination of assimilating older continental crust and fractional crystalization of basaltic magmas.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Data for: Tracking the birth and growth of Cimmeria: Geochronology and origins of intrusive rocks from NW Iran

New geochronological and geochemical data for Late Neoproterozoic to Mesozoic igneous 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. An additional, 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 show both arc- and plume-related geochemical signatures. The plume-related signature of less-contaminated melts is manifested by 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.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Data for: Zircon U-Pb, Geochemical and Isotopic Constraints on the Age and Origin of A- and I-type Granites and Gabbro-Diorites from NW Iran: Implication for Continental Crust Growth

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 isotope (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 signature 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 distinct 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 Fe2O3, K2O, Na2O, Al2O3, 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 resulting from a sub-continental lithospheric mantle, but with interaction 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 compression melting of SCLM. Rising mantle-derived magmas assimilated middle-upper crust. Fractionating mantle-derived magmas and contamination with crustal components produced evolved gabbro-diorites and I-type granites. In contrast, asthenosphere upwelling during Paleocene provided heat and melt for melting of- and interacting with SCLM to generate A-type granite precursor melts.THIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

Geochemistry and petrogenesis of the Late Cretaceous Haji-Abad ophiolite (Outer Zagros Ophiolite Belt, Iran) : implications for geodynamics of the Bitlis-Zagros suture zone

The Haji-Abad ophiolite in SW Iran (Outer Zagros Ophiolite Belt) is a remnant of the Late Cretaceous supra-subduction zone ophiolites along the Bitlis–Zagros suture zone of southern Tethys. These ophiolites are coeval in age with the Late Cretaceous peri-Arabian ophiolite belt including the Troodos (Cyprus), Kizildag (Turkey), Baer-Bassit (Syria) and Semail (Oman) in the eastern Mediterranean region, as well as other Late Cretaceous Zagros ophiolites. Mantle tectonites constitute the main lithology of the Haji-Abad ophiolite and are mostly lherzolites, depleted harzburgite with widespread residual and foliated/discordant dunite lenses. Podiform chromitites are common and are typically enveloped by thin dunitic haloes. Harzburgitic spinels are geochemically characterized by low and/or high Cr number, showing tendency to plot both in depleted abyssal and fore-arc peridotites fields. Lherzolites are less refractory with slightly higher bulk REE contents and characterized by 7–12% partial melting of a spinel lherzolitic source whereas depleted harzburgites have very low abundances of REE and represented by more than 17% partial melting. The Haji-Abad ophiolite crustal sequences are characterized by ultramafic cumulates and volcanic rocks. The volcanic rocks comprise pillow lavas and massive lava flows with basaltic to more-evolved dacitic composition. The geochemistry and petrology of the Haji-Abad volcanic rocks show a magmatic progression from early-erupted E-MORB-type pillow lavas to late-stages boninitic lavas. The E-MORB-type lavas have LREE-enriched patterns without (or with slight) depletion in Nb–Ta. Boninitic lavas are highly depleted in bulk REEs and are represented by strong LREE-depleted patterns and Nb–Ta negative anomalies. Tonalitic and plagiogranitic intrusions of small size, with calc-alkaline signature, are common in the ophiolite complex. The Late Cretaceous Tethyan ophiolites like those at the Troodos, eastern Mediterranean, Oman and Zagros show similar ages and geochemical signatures, suggesting widespread supra-subduction zone magmatism in all Neotethyan ophiolites during the Late Cretaceous. The geochemical patterns of the Haji-Abad ophiolites as well as those of other Late Cretaceous Tethyan ophiolites, reflect a fore-arc tectonic setting for the generation of the magmatic rocks in the southern branch of Neotethys during the Late Cretaceous.24 page(s

Mantle and crust-driven magmatic flare-up in continental arcs: Northeast Iran example

Mantle and crust-driven magmatic flare-up in continental arcs: Northeast Iran exampleTHIS DATASET IS ARCHIVED AT DANS/EASY, BUT NOT ACCESSIBLE HERE. TO VIEW A LIST OF FILES AND ACCESS THE FILES IN THIS DATASET CLICK ON THE DOI-LINK ABOV

The Dehshir ophiolite (central Iran) : geochemical constraints on the origin and evolution of the inner Zagros ophiolite belt

The Late Cretaceous Dehshir ophiolite is an important element within the Inner Zagros (Nain-Baft) ophiolite belt and contains all components of a complete "Penrose ophiolite," including tectonized harzburgites, gabbros, sheeted dike complexes, pillowed basalts, and rare ultramafic-mafic cumulates. The cumulate rocks of this ophiolite are composed of plagioclase lherzolite, clinopyroxenite, leucogabbro, and pegmatite gabbro. All the massifs in the Inner Zagros ophiolite belt are overlain by Turonian-Maastrichtian pelagic limestones (93.5-65.5 Ma). Clinopyroxene compositions of Dehshir mafic rocks are similar to those of both boninites and island-arc tholeiites. Nearly all spinels from the inner ophiolite belt are similar to those of highly depleted harzburgites from intra-oceanic forearcs, although some Dehshir harzburgite spinels plot within the field for abyssal (mid-ocean-ridge basalt) peridotites. All components of the Dehshir and other ophiolites of this belt show strong suprasubduction-zone affinities, from harzburgitic mantle to ophiolitic lavas. Volcanic rocks have a mixture of dominantly arc-like (island-arc tholeiite, boninite, and calc-alkaline) and subordinate mid-ocean-ridge basalt–like compositional features, usually with mid-ocean-ridge basalt–like rocks at the base and arc-like rocks at the top. Our data for the Dehshir ophiolite and the similarity of these results to those for Iranian inner and outer belt ophiolites compel the conclusion that a geographically long, broad, and continuous tract of forearc lithosphere was created at about the same time during the earliest stages of subduction along the southern margin of Eurasia in Late Cretaceous time.32 page(s