Cenozoic temporal variation of crustal thickness in the Urumieh-Dokhtar and Alborz magmatic belts, Iran

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 (fO2) 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 fO2 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

Crustal architecture studies in the Iranian Cadomian arc: insights into source, timing and metallogeny

The Jalal Abad magmatic rocks, situated at the southern edge of the Saghand-Bafgh-Zarand district, include a thick pile of Cadomian extrusive and pyroclastic units intruded by younger granitoid stocks. New zircon U–Pb ages show eruptions at ∼552 Ma, followed by emplacement of granodiorite at ∼537 Ma. The Jalal Abad magmatic rocks have typical high-K and shoshonitic signatures, and are characterized by enrichment in large-ion lithophile elements (LILEs) and depletion in high-field-strength elements (HFSE). Zircon ɛHf(t) from the Jalal Abad magmatic rocks ranges from +3.9 to −3.9 for volcanic rocks and −1.2 to +8.1 for granodiorite. Zircon δ18O values for the Jalal Abad are variable from +5.1 to +8.8‰, progressively higher than those of mantle-derived melts. The whole-rock ɛNd(t) values range between −7.7 to −7.4 for granodiorite, −4.6 to −3 for volcanic rocks and −6.2 to −8.2 for ignimbrites/tuff. The whole-rock Nd and zircon Hf crustal model ages (TDMC) for the Jalal Abad magmatic rocks range between 0.8 and 2.3 Ga. All of the Jalal Abad magmatic rocks have quite similar trace element patterns, and slightly different whole-rock Nd and zircon Hf isotopic composition, indicating the involvement of the thick continental crust during the formation of these rocks. Modeling of zircon Hf–O data, bulk-rock trace elements, and Sr–Nd isotopes suggest the magmas were generated by interaction of mantle–derived melts with thick continental crust through assimilation/fractional crystallization (AFC) processes. However, crustal architecture studies in the Iranian Cadomian arcs show that AFC processes were more important during the Mesoarchean–Early Neoproterozoic (3000–1000 Ma), whereas juvenile magmas became increasingly important to the Cadomian (600–500 Ma) magmatism. Early Cambrian intrusive magmas seemingly intruded sedimentary sequences in the study region and provided magmatic constituents and a heat source for hydrothermal processes and mineralization

Petrogenesis of arc-related peridotite hosted chromitite deposits in Sikhoran-Soghan mantle section, South Iran: evidence for proto-forearc spreading to boninitic stages

The Soghan-Sikhoran ophiolite in southeast Iran (Outer Zagros Ophiolite Belt) is a remnant of a series of Upper Triassic–Cretaceous supra-subduction zone (SSZ) ophiolites that formed along the Zagros suture zone, which is considered as the southern border of the Neo-Tethyan sea. These SSZ ophiolites are older than the Late Cretaceous Zagros ophiolites. The main part of the Soghan-Sikhoran ophiolite comprises layered ultramafic cumulates including dunites, wehrlites, and pyroxenites, and a tectonized mantle section including residual lherzolites, and depleted harzburgites with foliated/discordant dunite lenses. Podiform chromitites are common and are typically surrounded by thin dunitic haloes. Spinels in lherzolite–harzburgite are geochemically characterized by a low Cr# (42.0 to 52.6), and plot in an abyssal peridotite field on geochemical discrimination diagrams, whereas spinel in dunites and high-Cr chromitite spinels (Cr# = 52.4 to 76.4) show geochemical affinities to boninites. Lherzolites and harzburgites have low REE contents and experienced >17 vol% partial melting. The Soghan-Sikhoran ophiolite contains both high Cr# and low Cr# podiform chromitite types. Trace and REE element patterns of Soghan-Sikhoran rocks are similar to those in SSZ peridotites. The studied ophiolites show relatively moderate to high oxygen fugacities (ƒO2), with log units ranging from −0.4 to +0.4 for harzburgites, +0.2 for lherzolites, from − 0.7 to + 2.5 for pyroxenites, from +0.8 to +2.2 for dunites, and from + 0.6 to + 0.8 for chromitites. The moderate to high oxidation state of the studied upper-mantle ophiolitic complexes also suggests a boninitic source in the mantle wedge of the arc setting. The two-pyroxene thermometer yields mean equilibrium temperatures of 879 °C, 895 °C, 912 °C and 912 °C for harzburgites, lherzolites, dunites and pyroxenites, respectively. We therefore interpret that the spinels in the lherzolite-harzburgite crystallized from tholeiitic melt generated due to proto-forearc spreading and formation of the infant arc, whereas high-Cr# spinel in dunites and high-Cr# chromitite crystallized from boninitic melts during the mature arc stage, with an increasing contribution of slab-derived fluids at high ƒO2

Coeval calc-alkaline and alkaline Cadomian magmatism in the Bafq, central Iran: Insights into their petrogenesis

The Chah-Gaz and Mishdovan areas in the Bafq magmatic complex, central Iran, contain thick series of terrigenous sediments (the Rizu-Dezu complex), and arc-related calc-alkaline and alkaline igneous rocks. Geochemical analyses of igneous rocks from both areas indicate two distinct rock clans: (1) high-K, calc-alkaline-shoshonitic rocks with strong depletions in Nb, P, and Ti, and (2) an alkaline quartz gabbro-diorite, with trace element patterns resembling oceanic island basalts (OIB). New geochronological data reveal that magmatic rocks of both clans crystallized almost simultaneously, with zircon U[sbnd]Pb ages of 534 Ma and 537 Ma, respectively. The whole-rock Nd[sbnd]Sr isotopic data ((87Sr/86Sr)(I) = 0.7052 to 0.7064 and ɛNd(t) = +1.3 to +2.7) of alkaline quartz gabbro-diorite indicate an enriched OIB-like mantle source, while the high-K, calc-alkaline-shoshonitic rocks have εNd(t) = −5.5 to −7.6, clearly reflecting significant contributions from pre-existing Proterozoic basement. Apatite in both the Chah-Gaz and Mishdovan magmatic rocks is of magmatic origin, with light rare earth element (LREE) enrichment patterns. The low Sr/Y and Eu/Eu⁎ values in apatite demonstrate the non-adakitic character of the investigated rocks, while the moderately negative Eu anomaly and inverse correlation between δCe and δEu in the analyzed apatites may reflect reduced parental magmas. The geochemical and isotopic results presented here indicate that slab rollback and opening of an extensional basin could have initiated concurrent Cadomian arc-related calc-alkaline and rift-associated alkaline magmatism in the Chah-Gaz and Mishdovan areas

Formation of the Chah-Gaz iron oxide-apatite ore (IOA) deposit, Bafq District, Iran: constraints from halogens, trace element concentrations, and Sr-Nd isotopes of fluorapatite

The textures, chemistry and Sr-Nd isotopic compositions of apatite from the Chah-Gaz iron-oxide apatite (IOA) deposit in the Bafq metallogenic belt, central Iran, were studied to investigate the formation of this ore deposit. Two generations of apatite were recognized based on Cl/F and Cl/OH ratios. Primary fluorapatite, which is coeval with magnetite in the massive ore bodies, is chemically homogeneous and characterized by Cl/F < 0.05 and Cl/OH in the range of 0.01–0.07. By contrast, F-depleted apatite rims are present in apatite hosted in veinlets that crosscut the massive ore bodies and are disseminated in the igneous host rocks, and have Cl/F and Cl/OH-apatite ratios of 0.08–0.12 and 0.15–0.79, respectively. The F-depleted rims are also depleted in LREEs, Th and U, consistent with the presence of secondary monazite, xenotime and thorite that formed by coupled dissolution-reprecipitation. The whole-rock Nd–Sr isotopic data ((87Sr/86Sr)(I) = 0.7052 to 0.7064 and ɛNd(t) = +1.3 to + 2.7) of gabbro-diorite indicate an mantle source, while the high -K, calc-alkaline-shoshonitic volcanic host rocks have εNd(t) = − 5.5 to − 7.6, clearly reflecting mixing between mantle-derived mafic magmas and assimilated Proterozoic basement. The initial 87Sr/86Sr ratios and ɛNd values of both F-rich and -depleted apatites (0.7038 to 0.7050 and −0.3 to + 6.5, respectively) are similar to gabbroic rocks and support a magmatic source for primary fluorapatite, with minimal or no crustal contribution, and indicate that the magmatic event with negative ɛNd values did not affect the whole-rock Sm-Nd signature of the ore. Petrography plus geochemical and Nd-Sr isotopic data of both studied fluorapatite, which come from iron oxide stage, are consistent with a combined igneous/magmatic-hydrothermal genesis for the Chah-Gaz IOA deposit, with low degrees of hydrothermal overprint, as evidenced by the formation of F-depleted (Cl-rich) apatite rims. The relatively constant Sr-Nd data in apatite are consistent with superimposed, episodic hydrothermal fluids from the same, evolving, magmatic-hydrothermal system

Neogene calc-alkaline volcanism in Bobak and Sikh Kuh, Eastern Iran: implications for magma genesis and tectonic setting

The Neogene post-collisional volcanism in eastern Iran is represented by the Sikh Kuh and Bobak high-Na rocks including trachybasalt, trachyandesite, trachydacite, and dacite. We report whole rock geochemistry and Nd–Sr isotopic data which constrain the characteristics of the mantle source. The rocks are highly enriched in incompatible trace elements, suggesting a metasomatized subcontinental lithospheric mantle (SCLM) as the magma source. Felsic rocks record abundant petrographic evidence, major and trace element data, and isotopic (87Sr/86Sr(i) = 0.70727–0.70902) signatures indicative of fractional crystallization, and potentially, crustal assimilation. Such processes however, have not significantly affected the isotopic signatures (87Sr/86Sr(i) = 0.70417–0.70428) of the mafic members, suggesting that they are derived from a mantle source. The geochemical and isotopic data for the Sikh Kuh and Bobak volcanic rocks suggest that these Neogene magmas were derived from a small degree of partial melting (~ 2–10 vol%) of a spinel-bearing subcontinental lithospheric mantle source in a post-collisional setting. The generated more unfractionated mafic magmas erupted during an episode of extensional tectonics, presumably caused by extension that followed Eocene collision between the Lut and Afghan continental blocks. These melts interacted with continental crust during ascent, experiencing crystal fractionation, and crustal assimilation, to produce more evolved felsic volcanic rocks

SUT-Crack

The SUT-Crack dataset contains high-quality images of asphalt pavement cracks, specifically curated for crack detection using deep learning techniques like classification, object detection, and segmentation. Careful consideration was given during dataset creation to encompass various crack detection challenges, such as oil stains, shadows, and different lighting conditions. The images were captured from a fixed height of 672 mm above the pavement surface, facilitating calibration for real-world crack length measurements. Notably, the dataset also includes geotags, providing precise latitude and longitude coordinates for each image.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

SUT-Crack

The SUT-Crack dataset contains high-quality images of asphalt pavement cracks, specifically curated for crack detection using deep learning techniques like classification, object detection, and segmentation. Careful consideration was given during dataset creation to encompass various crack detection challenges, such as oil stains, shadows, and different lighting conditions. The images were captured from a fixed height of 672 mm above the pavement surface, facilitating calibration for real-world crack length measurements. Notably, the dataset also includes geotags, providing precise latitude and longitude coordinates for each image.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