NW Iran Research Articles

Neogene Tectono‐Stratigraphic Evolution of the Intermontane Tarom Basin: Insights Into Basin Filling and Plateau Building Processes Along the Northern Margin of the Iranian Plateau (Arabia‐Eurasia Collision Zone)

AbstractThe intermontane Tarom Basin of NW Iran (Arabia‐Eurasia collision zone) is located at the transition between the Iranian Plateau (IP) to the SW and the Alborz Mountains to the NE. This basin was filled by upper Cenozoic synorogenic red beds that retain first‐order information on the erosional history of adjacent topography, the vertical growth of the plateau margin and its orogen perpendicular expansion. Here, we perform a multidisciplinary study including magnetostratigraphy, sedimentology, geochronology and sandstone petrography on these red beds. Our data show that Eocene arc volcanism in the region terminated at 38‐36 Ma, while intrabasinal synorogenic sedimentation (endorheic conditions) occurred from at least 16.2 to <7.6 Ma, implying that the red beds are stratigraphically equivalent to the Upper Red Formation. After 7.6 Ma, the basin experienced intrabasinal deformation, uplift and erosion with the establishment of external drainage. Fluvial connectivity with the Caspian Sea, however, was interrupted by at least four episodes of basin aggradation. During endorheic conditions, the basin fill did not reach the elevation of the plateau interior and hence the Tarom Basin was never integrated into the plateau. Furthermore, our provenance data indicate that the northern margin of the basin (Alborz Mountains) experienced a greater magnitude of Miocene deformation and erosional exhumation than the southern one (IP margin). This agrees with recent Moho depth estimates, suggesting that crustal shortening and thickening cannot be responsible for the vertical growth of the northern margin of the IP, and hence surface uplift must have been driven by deep‐seated processes.

Quantitative kinematic analyses of the Darizhun shear zone within the hinterland of the Zagros orogenic belt, Iran

The basal decollement Darizhan shear zone in the hinterland of the Zagros orogenic belt exposes the amphibolite-mylonite in NW Iran. In this study, I discuss the deformation partitioning in terms of oblique convergence between the Afro-Arabian continent and the Iranian microcontinent. Rf/ $$\phi $$ -based finite strain analysis, Rxz varies ranging from 2.25 to 3.04 for the XZ-plane of the strain ellipsoid. The flow vorticity (Wm) along the Darizhun shear zone is estimated employing PHD, PAR, RGN and PD techniques. The Wm estimates vary between 0.6 and 0.85 and demonstrate general shear deformation (pure-shear: 35–58% and simple-shear: 42–65%). The Wm values indicate a gradual increase in the simple-shear component towards the Darizhan thrust sheet. Considering both the results of strain and vorticity analyses, we propose a horizontal shortening of (~ 21–36%) normal to the walls of the shear zone.

The Upper Jurassic Garedu Red Bed Formation of the northern Tabas Block: elucidating Late Cimmerian tectonics in east-Central Iran

The Garedu Red Bed Formation (GRBF) of the northern Tabas Block (Central-East Iranian Microcontinent, CEIM) is a lithologically variable, up to 500-m-thick, predominantly continental unit. It rests gradually or unconformably on marine limestones of the Esfandiar Subgroup (Callovian–Oxfordian) and is assigned to the Kimmeridgian–Tithonian. In the lower part, it consists of pebble- to boulder-sized conglomerates/breccias composed of limestone clasts intercalated with calcareous sandstones, litho-/bioclastic rudstones and lacustrine carbonates. Up-section, sharp-based pebbly sandstones and red silt-/fine-grained sandstones of braided river origin predominate. Palaeocurrent data suggest a principal sediment transport from west to east and a lateral interfingering of the GRBF with marine greenish marls of the Korond Formation at the eastern margin of the Tabas Block. Westwards, the GRBF grades into the playa deposits of the Magu Gypsum Formation. Red colours and common calcretes suggest arid to semi-arid climatic conditions. The onset of Garedu Red Bed deposition indicates a major geodynamic change with the onset of compressive tectonics of the Late Cimmerian Tectonic Event (LCTE), being strongest at the eastern margin of the northern Tabas Block. When traced southwards, the same tectonic event is expressed by extension, indicating a shift in tectonic style along the boundary fault between the Tabas and Lut blocks. The complex Upper Jurassic facies distribution as well as the spatio-temporal changes in tectonic regime along the block-bounding faults are explained by the onset of counterclockwise vertical-axis rotation of the CEIM in the Kimmeridgian. The block boundaries accommodated the rotation by right-lateral strike slip, transpressional in today’s northern and transtensional in today’s southern segments of the block-bounding faults. Rotation occurred within bracketing transcurrent faults and continued into the Early Cretaceous, finally resulting in the opening of narrow oceanic basins encircling the CEIM. Palaeogeographically, the GRBF is part of a suite of red bed formations not only present on the CEIM, but also along the Sanandaj-Sirjan Zone (NW Iran), in northeastern Iran and beyond, indicating inter-regional tectonic instability, uplift and erosion under (semi-)arid climatic conditions across the Jurassic–Cretaceous boundary. Thus, even if our geodynamic model successfully explains Late Jurassic tectonic rotations, fault motions and facies distribution for the CEIM, the basic cause of the LCTE still remains enigmatic.

The Occurrence of Corundum-Rich Metabauxite in the Qaradash District, NW Iran

The corundum-rich metabauxites were, very rare worldwide, reported in the Attic-Cycladic metamorphic complex in Greece and the southern and western margins of the Menderes Massif in southwestern Turkey. The Qaradash bauxite deposit is located in the Iran-Himalayan karst bauxite belt, 25km northwest of Shahindezh city, northwestern Iran (Figure 1a). The rock units in the Qaradash district mainly occur in an asymmetric fold and in the core of an anticline (Figure 1b). They, from the oldest to youngest, include the Permian carbonates of the Ruteh Formation, the Triassic sandstone and carbonate of the Elika Formation, and the Plio-Quaternary sandy conglomerate. Carbonates of the Ruteh Formation are dark grey in color that were intruded by the Oligocene monzonite and quartz monzonite intrusions. The marbles occur at the contact of these intrusions with carbonates of the Ruteh Formation. The bauxite horizons occur as 7-15-m-thick layers along the contact of carbonates of the Ruteh Formation (Permian) and sandstone and carbonate of the Elika Formation (Triassic) that were also affected by these intrusive masses and were partially converted to metabauxite.

Early Miocene larger benthic foraminifera from the northwestern Tethyan Seaway (NW Iran): new findings on Shallow Benthic Zone 25.

The lower Miocene marine units of NW Iran (Hamedan–Miandoab area) were studied to establish a high-resolution biostratigraphy framework in the context of European standard biozonation (SBZ zonal scheme). The units are dominated by larger and small benthic foraminifera together with coralline algae and corals. Due to its position in the Tethyan Seaway between the Mediterranean and Indo-Pacific, the investigated area has high significance in palaeobiogeography. Seven species of benthic foraminifera were described, including Miogypsina globulina, Amphistegina bohdanowiczi, Elphidium crispum, Elphidium sp. 1, Borelis curdica, Austrotrillina asmariensis, and Peneroplis thomasi. The occurrence of Miogypsina globulina in the shallow-marine carbonates of the studied sections documents the Burdigalian SBZ 25 Zone. Austrotrillina asmariensis and Peneroplis thomasi occur with M. globulina. Simultaneously, their stratigraphical range is extended to the Burdigalian in the Middle East. Based on the discovery of lower Miocene deposits in the Hamedan–Miandoab area (previously mapped as Oligocene–Miocene units), the stratigraphy of northwest Central Iran is revised. The biostratigraphic results also present a more precise chronology for the marine transgression in the study area, initiating in the late early Miocene. The coralline algal assemblages and the abundance and diversity of larger benthic foraminifera indicate that shallow-marine Qom Formation got deposited in tropical to subtropical warm waters.

Geology and petrogenesis of the Sungun deposits: Implications for the genesis of porphyry-type mineralisation in the NW Urumieh–Dokhtar magmatic Arc, Iran

The Miocene Sungun porphyry Cu–Mo systems, located in Azerbaijan belt, NW Iran, is associated with the high-Sr/Y magmas, which were engendered in a post-collisional setting. However, the petrogenesis of these fertile magmas and their mineralisation are still unknown. In this study, we present whole-rock major-trace elements, zircon U–Pb dating and the Lu–Hf isotopes in the ore-forming porphyries of the Sungun porphyry systems. The corresponding results showed that the samples were rich in large-ion lithophile elements and poor in high-field-strength elements; moreover, they presented both high K2O (2.4–3.5 wt%) and Sr (727–770 ppm) and low Y (11–14 ppm) contents. The zircon U–Pb age of the Sungun porphyry was ~19 Ma, with positive εHf(t) ratios (5.5–11.8) and young TDM2 ages between 322 and 705 Ma. Additionally, the Sungun high-Sr/Y porphyries contained anhydrites (CaSO4); and had high zircon Ce4+/Ce3+ ratios (33–728), relatively low zircon saturation temperatures (620–804 °C), and plagioclases with excess Al content. Overall, these evidences suggest that a water-fluxed melting of the subduction-modified juvenile lower crust might have generated a high oxygen fugacity, leading to the formation of the hydrous and S-rich Sungun fertile magmas in the NW Urumieh–Dokhtar magmatic Arc.

Trondhjemite leucosomes generated by partial melting of a hornblende-gabbro (Alvand plutonic complex, Hamedan, NW Iran)

ABSTRACT This work describes the petrogenesis of in situ and in-source trondhjemite leucosomes generated by low-degree partial melting of the Jurassic Cheshmeh-Ghasaban hornblende-gabbros in the northern Alvand batholith (Hamedan, NW Iran). These leucosomes occur in a metatexite migmatite as patches, net-structures, veinlets, and dikes at scales ranging from a few millimetres to a few metres. They have high SiO2 (mean ≈ 78 wt%) and Na2O (4–5 wt%) with low Al2O3 (<15 wt%), K2O (<1.5 wt%), Sr (33–267 ppm), Eu (0.31–0.62 ppm) and heavy REE (<4 ppm) contents similar to typical low-Al2O3 trondhjemites. Batch-melting models indicate these leucosomes are the result of ≈1-2% partial melting of the hornblende-gabbro, whereas thermobarometric modelling constrains their petrogenesis in the field of hornblende hornfels-facies metamorphism (pressure ≈3.0–4.5 kbar and temperature ≈700-750°C). On a wider scale, our results document natural trondhjemites generated in the upper crust by amphibole-dehydration melting of a mafic source at temperature conditions close to the solidus, filling the existing gap of data in low-pressure (P < 5kbar) and low-temperature (T < 800°C) amphibole-dominated partial melting experiments. The genesis of these trondhjemites is then discussed with respect to the Mesozoic evolution of the Alvand plutonic complex.

The Zavieh kaolin deposit (northwest of Chalderan, NW Iran): Constraints on mineralogy and whole-rock geochemistry

The Zavieh kaolin deposit (northwest of Chalderan, NW Iran): Constraints on mineralogy and whole-rock geochemistry

&lt;p&gt;&lt;strong&gt;Two new species of &lt;em&gt;Centaurea&lt;/em&gt; sect. &lt;em&gt;Microlophus&lt;/em&gt; (Asteraceae, Cardueae) from Iran&lt;/strong&gt;&lt;/p&gt;

Centaurea dezfulica and C. kuhdashtensis are described and illustrated as new species. They belong to C. sect. Microlophus and are endemic to NW Iran. Centaurea dezfulica is closely related to C. pabotii but distinguished from the latter species by densely hispid hairs, plant height 45–50 cm, upper cauline leaves decurrent, segments of lower cauline leaves in 7–8 pairs, larger involucres, 20–23 × 10–20 mm, inner phyllaries obtuse, appendage 2–3 mm long, larger spinule (1–2 mm long) and short central florets and achene. Centaurea kuhdashtensis is distinguished from C. koeieana by loosely hispid hairs, larger lower cauline leaves, pinnatipartite-pinnatilobate, or pinnatifid median [lower] cauline leaves, segments of lower cauline leaves in 15–17 pairs, and those of basal cauline leaves in 14–15 pairs. An updated key to C. dezfulica and C. kuhdashtensis and their closely related taxa in Iran is also provided.

Porphyry-type mineralization associated with epithermal deposits in the Tarom metallogenic belt of NW Iran: Constraints from fluid inclusions

Research is conducted to investigate whether or not, apart from the Chodarchay deposit, there are other examples of porphyry-type mineralization associated with epithermal deposits in the Tarom metallogenic belt of the Alborz zone, NW Iran. Homogenization temperature, final ice-melting, and salinity values are determined for fluid inclusions in mostly quartz and partly calcite, fluorite, sphalerite, and barite samples from eight epithermal ore deposits to unravel the enigma on porphyry-type mineralization in Tarom. The homogenization temperatures and salinities of the fluid inclusions range from 82 to 520 °C and 0.2 to 37 wt% NaCl equiv., respectively. The fluid inclusions show varying densities from 0.4 to ~1.2 g/cm3 with most values between 0.7 and 0.95 g/cm3. Tarom epithermal deposits in order of maximum mineralization depth are Chargar (520 m), Zajkan (640 m), Goloujeh (770 m), Lohneh (1075 m), Nikoueieh (1150 m), Khalifelou (1500 m), Aghkand (1690 m), and Chodarchay (1900 m). It seems that magmatic water played an important role in the Tarom epithermal deposits except for Chargar where mixing magmatic and meteoric waters is considered as the main mechanism for ore deposition. The physicochemical variations suggest differences among epithermal deposits in the Tarom district. Chodarchay, Lohneh, Khalifelou, and Goloujeh have some fluid inclusion features of porphyry mineralization associated with an epithermal part. Minerals from Tarom contain fluid inclusions indicative of porphyry mineralization beneath some intermediate- and high-sulfidation epithermal deposits. The findings of this study are instrumental in the exploration of deeper porphyry parts of the Tarom epithermal deposits.

Zircon U--Pb ages of Au-bearing host rocks in Northwest Iran as evidence for gold mineralization in the Carboniferous, not Cenozoic time!

A few gold deposits occur in northwest Iran which are hosted by mylonitic granitoids and phyllonite. New U--Pb ages yield ages of 350–311 Ma for the mylonitic granitoid and 354–348 Ma for the phyllonite, which indicate Carboniferous magmatic activity in northwest Iran. The host granitoid and phyllonite have high contents of Zr (212, 246 ppm) and Y (26.8, 38.7 ppm). High 10,000 × Ga/Al ratios (2.1–5.1) and fractionation of the rare earth elements (REEs) pattern with depletion of Eu, Sr, and P may infer an A-type (anorogenic) granite affinity for the host rocks. Correspondingly, these rocks are characterized by high contents of Nb (33.1 to 39.2 ppm), Ta (1.68 to 2.40 ppm), Tb (0.84 to 1.17 ppm), and Th/Yb ratios with some similarity to OIB-like rocks. Whole rock compositions of these host rocks are consistent with both A1 and A2 type granites, which infer magmatic activity in an extensional tectonic regime. Perhaps the extension may have occurred during rifting of Neo-Tethys in northern Gondwana. Upwelling of the hot OIB-like melts during the opening of Neo-Tethys ocean was the main mechanism of this extension. The OIB signatures of the A-type granitoids controlled the gold mineralization during this process. Accordingly, we classify the gold mineralization in NW Iran as intrusion-related gold deposits. These mantle-derived magmas from the asthenosphere may support a source of both sulfur and gold. These elements were concentrated in hydrothermal fluids in the late stages of magma crystallization. Also, hot magma injection increased the geothermal gradient and caused extensive dehydration of the sedimentary rocks inin the roof of the magma chamber. Circulation of these hot fluids with injection into the hot crystallizing magmatic rocks and mixing with late-stage magmatic-hydrothermal fluids and meteoric water (?) seem to all have essential roles for transporting the gold and precipitating it within fractures in the semi-brittle to brittle zone. The gold precipitated as native or nanoparticles in pyrite in the inner part of the shear zone. This research reveals that mineralization occurred in the Late Paleozoic in an extensional tectonic regime and not above the subduction zone or collision zone which had been suggested before.

Mercury pollution in the coastal Urmia aquifer in northwestern Iran: potential sources, mobility, and toxicity.

The concentration of total dissolved mercury (HgT) in surface and groundwater resources in the coastal parts of Urmia aquifer (NW of Iran) was investigated to identify the possible sources and sinks of mercury and the geochemical mechanisms controlling its mobilization. The distribution of water samples on the Piper diagram demonstrates that most samples have the Ca-Mg-HCO3 facies. From 62 water samples collected in this area, one sample contained HgT concentrations exceeding the maximum contaminant level recommended by the WHO (6μg/L). The principal component analysis (PCA) produced five principal components. The positive moderate correlation of HgT with EC, Cl, K, Mg, and Na indicated that the weathering of geological formations was one of the main sources of mercury in groundwater samples. Position of water samples in Eh-pH regions where microorganisms involved in mercury methylation and mineralization were potentially active demonstrated that the aquifer had undergone sulfate reduction and had reached the final stage of the terminal electron accepting process (TEAP) sequence in the methane production processes which are limited to only 37% of the water samples that have anaerobic conditions. Some Hg-bearing species are in nonequilibrium geochemical conditions. The supersaturation of water samples with magnetite and goethite indicated that these Fe-bearing minerals could act as the strong reducing agents for the reduction of Hg(II) to Hg(0).

November 08, 2019 Turkmanchay earthquake (Mw: 5.9) in NW Iran: an assessment of the earthquake using DInSAR time-series and field evidence

The arc-shaped Bozgush Mountains is a remarkable morphological feature bounded by active faults in northwest Iran. The southern and northern parts of the mountain belt are limited by the South and North Bozgush Fault Zones, which produced numerous destructive earthquakes in historical and instrumental periods. We employed the Sentinel-1A Differential Interferometric Synthetic Aperture Radar (DInSAR) method to map the deformation details of the November 08, 2019, Turkmanchay earthquake (Mw: 5.9) along the South Bozgush Fault Zone to understand the earthquake-triggered surface deformations and seismogenic faulting characteristics. The results of the DInSAR time-series analysis show that subsidence and uplift range from − 5 cm to + 6 cm, respectively. The total line of sight (LOS) displacement was approximately 11 cm. Interferogram fringes and deformation patterns indicate that the direction of the potential seismogenic fault is WNW-ESE. These patterns are consistent with the orientation of the South Bozgush Fault Zone, including primarily right-lateral strike-slip characteristics with reverse components. Continuous patterns of the obtained interferogram fringes indicate that surface rupture did not occur during the earthquake. Our Coulomb failure function results in preferred faults derived from geological structures, indicating that the stress rate was positive and high in several segments of the South and North Bozgush Faults, revealing that the main earthquake event might trigger those faults. The large aftershocks that occurred on the same faults supported our results, and the distribution of aftershocks in the Bozgush Mountains suggests that the WNW-ESE orientation is consistent with the orientation of segments constituting the South Bozgush Fault Zone.

A finding of Eptesicus gobiensis in an ancient salt mine in Iran and notes on the status of this bat in the Middle East (Mammalia: Chiroptera)

Two mummified bats were found in an ancient salt mine near Chehrabad, NW Iran. One complete and one partial skeletons, both associated with parts of the pelage, were identified as Eptesicus gobiensis, a bat species rare in the Middle East. The comparison of skull and statistical evaluation of craniodental data showed this bat to belong to the identical taxon as the mummified bats previously collected in Qutur Su caves, NW Iran; this part of Iran is thus an area of broader distribution of this bat, the second record reported here confirms its preference for dry upper plateaus. This Iranian population exhibits much similarity with E. gobiensis bobrinskoi living in lowland deserts of Kazakhstan, but it simultaneously shows morphological and ecological differences from the Kazakhstani populations. Therefore, the population of Iran is here tentatively identified as E. g. cf. bobrinskoi. The species rank of E. gobiensis was found to be composed of three morphotypes living in three separate ranges, E. g. gobiensis in mountain plateaus of Central Asia, E. g. bobrinskoi in lowlands of Kazakhstan, and E. g. cf. bobrinskoi in NW Iran. However, the phylogenetic and taxonomic statuses of the Iranian morphotype still remain to be elicudated.

Prognosis of of gold mineralization phases by multifractal modeling in the Zehabad epithermal deposit, NW Iran

Concentration–Number (C–N) fractal method has been used for determining and separating mineralization phases based on surface lithogeochemical Au, Ag, Cu, Pb, Zn, As and Sb data in the Zehabad epithermal deposit, NW Iran. Five mineralization phases are demonstrated by multifractal modeling for the mentioned elements correlating with geological studies. The extreme phase of Au mineralization is higher than 7.9 ppm, which is correlated with hematite deposition in silicic veins and veinlets, whereas Ag (˃79.43 ppm), Cu (˃15.85%), Pb (˃63.1%), Zn (˃11.2%) extreme phases are associated with the main stage sulfidation phases. The results show that Au, Cu, Pb, Zn and Ag have two different mineralization trends based on the multifractal nature in this area. These trends are presented based on oxidic and sulfidic mineralization. According to mineralogical studies, the main stages of mineralization include: 1) formation of chalcopyrite ± sphalerite in silicic veins in sulfidic trend; 2) deposition of native gold and specular hematite in silicic veins in response to boilling, in oxidic trend; 3) next phase of fluid penetration and replacing chalcopyrite by galena, sphalerite and tetrahedrite-tennantite in the sulfide veins, in sulfic trend. Neighbouring copper and silver are due to the formation of tetrahedrite-tennantite solid solution. The obtained results show a positive correlation between mineralization phases and the faults present at the deposit. Moreover, mineralization phases of these elements demonstrate a good correlation with silicification and silicic veins and veinlets.

Effect of environmental gradients on leaf morphological traits in the Fandoghlo forest region (NW Iran)

Abstract: The purpose of this study was to analyze the effects of altitude, the position of the trees along a gradient of canopy cover, and the orientation of their crown on leaf traits of 18 deciduous woody species belonging to 10 families in the Fandoglo forest region in Ardabil, North West of Iran. We measured eight leaf traits (leaf width, length, area, thickness, water content, leaf mass per area, specific leaf area, and dry matter concentration) of trees sampled at sites subjected to different light regimes (forest edge, forest understory, and isolated trees). All traits were measured on more than 3600 leaves from 90 trees sampled in two altitudinal ranges (low: 1300-1500 m a.s.l.; high: 1500-1700 m a.s.l.). A two-way ANOVA and t-test for independent samples were applied to test for differences in leaf traits between different altitudes and degree of canopy cover. The results confirmed that species’ leaf traits were more strongly correlated with the altitude and canopy cover rather than the orientation of the crown. No relationship between leaf traits and crown orientation was detected. All leaf traits had significantly higher values at low than at high elevation, indicating that environmental factors such as atmospheric CO2 concentration, temperature, light, irradiance, and wind deeply impact on foliar morphology and function; however, water content and specific leaf area showed an opposite trend. Also, species with different positions along the gradient of canopy cover could have different responses to elevation. Our results indicate that the variation of functional (morphological and physiological) traits in different tree species are affected by altitude and light regime. This might provide a theoretical basis for afforestation and forest management activities in the Fandoghlo forest region.

Remote triggering in Iran: large peak dynamic stress is not the main driver of triggering

SUMMARYThe study of the dynamic triggering of earthquakes and tremors during large earthquakes at faraway distances is an active area of research. This type of remote dynamic triggering is often found in subduction zones. The Iranian plateau is part of the Alpine–Himalayan orogenic system and hosts different collision styles of deformation and significant strike-slip faults. Using 13 yr (26 December 2004–8 September 2017) of continuous data of Iranian National Seismic Network (INSN) and some dense temporary networks, for the first time we carried a systematic study of dynamic triggering in Iran during 47 recent large earthquakes with magnitude and depth ranges of 6.4–9.1 and 8–90 km, respectively. We explored the local catalogue of 124 805 events with a magnitude of completeness (Mc) of 1.8 for the study of dynamic triggering but did not find any convincing evidence of dynamic triggering from the catalogue. The waveform data of 24 hr duration around the main events were analysed to find possible dynamic triggering through manual analysis of the waveform, STA/LTA, and beta statistics and found the triggering. We found dynamic triggering in Iran during Sumatra, 26 December 2004, Mw 9.1; Tohoku-Oki, 11 March 2011, Mw 9.1; Indian Ocean, 11 April 2012, Mw8.6 and Baluchistan, 24 September 2013 earthquakes and also possible triggering during Sumatra, 12 September 2007, Mw8.5. Only ∼10 per cent of the analysed earthquakes produced dynamic triggering. The triggering initiates during the passage of high amplitude Love waves and continues through the passage of the Rayleigh waves. We found north, central and eastern regions are more probable for triggering than Zagros and Makran regions. The instances of triggering were not restricted to only a small region, but instead, occurred at multiple locations. We find the onset of tremor correlates with very small stress changes, on the order of 1 kPA. However, the amplitude of the dynamic stresses is not a sufficient condition since some of the areas with considerably larger dynamic stresses are not triggered any seismicity in the region. The backazimuth angle of ∼50° and ∼120° seems to play an important role in the triggering. Teleseismic waves most probable for triggering local earthquakes within NW and central Iran include incoming surface waves with an incident angle of ∼60°–90° with respect to the local fault fabric.

Revision of the subgenus Stigmatophorella of Chalcophorella (Coleoptera: Buprestidae: Chrysochroinae).

The subgenus Stigmatophorella Tôyama, 1986 of Chalcophorella Kerremans, 1903 is revised based on comparative study of extensive material including types of all described taxa. One new subspecies is described: Chalcophorella (Stigmatophorella) bagdadensis wandalii subsp. nov. from NE Iraq, NW Iran and S Armenia. Chalcophorella quadrimaculata (Redtenbacher, 1850) is removed from synonymy with C. stigmatica (Dalman, 1817), transferred from the nominotypical subgenus to Stigmatophorella and downgraded to subspecies Chalcophorella (S.) bagdadensis quadrimaculata (Redtenbacher, 1850) stat. nov., assign. nov. Two new synonymies are established: C. (S.) bagdadensis quadrimaculata = C. (S.) bagdadensis freyi Obenberger, 1942 syn. nov.; = C. (S.) bagdadensis berhauti Mandl Pochon, 1957 syn. nov. (formerly synonym of C. (S.) bagdadensis bagdadensis). Lectotypes are designated for following taxa to ensure their correct application and recognition in future: Chalcophorella (S.) bagdadensis amarensis Obenberger, 1942; C. (S.) bagdadensis bagdadensis (Laporte de Castelnau Gory, 1837), C. (S.) bagdadensis freyi; C. (S.) bagdadensis quadrimaculata; C. (S.) escalerae (Abeille de Perrin, 1904); C. (S.) orientalis Obenberger, 1924; and C. (S.) quadrioculata (Kollar, 1843). All herein included taxa are illustrated with colour photographs of habitus and the male aedeagus. A key to all taxa is presented.

Structural styles of the Aras fault zone with implications for a transpressive fault system in NW Iran

• NE-striking Aras Fault Zone (AFZ) bounds the Talesh and Lesser Caucasus blocks. • The AFZ is characterized by well-developed geological and geomorphological features. • Paleostress results along the AFZ indicate a similar tectonic regime since Pliocene. • The transpressive tectonic regime controls the structural evolution of the AFZ. • Transpressive tectonic regime leads to strain partitioning along the AFZ. Aras Fault Zone (AFZ) is one of the most important intra-plate fault zones within the Turkish-Iranian Plateau. The AFZ is divided into five fault branches based on geometrical and structural properties called the Aras Main, Horadiz, Khodafarin, Asadkandi, and Aslanduz fault branches. Our geometric and kinematic analysis indicates that these faults exhibit compressional left-lateral strike-slip fault characteristics with general directions of NE-SW and dipping to SE. Structural mapping has revealed that the NE section of the AFZ shows typical horsetail fault geometry. Few meters to approximately 17 km of left-lateral displacements were observed along the AFZ, indicating the occurrence of numerous historical earthquake events. Paleostress analysis of fault slip data reveals that the AFZ has developed in the dominant NNE-SSW and NE-SW oriented compressional stress regime. Evaluating the Ratio of Principal Stress Differences (R), Stress Regime Index (R'), and principal stress directions show that the zone is under the transpressional tectonic regime. Paleostress orientations are consistent with orientations of the GPS velocity vectors, which indicates that the region, including the AFZ, is under the effect of the same tectonic regime, at least since Pliocene. The amounts of strike-slip partitioning on discrete strike-slip faults are determined as 33–41%, which means at least 41% of total wrench components in the region have been accommodated by discrete strike-slip faulting along the AFZ. Results indicate that the simple shear component of total stress applied to the area is consistent with the GPS slip velocities.

The Siah Cheshmeh-Khoy-Misho-Tabriz fault (NW Iran) is a cryptic neotethys suture: evidence from detrital zircon geochronology, Hf isotopes, and provenance analysis

ABSTRACT Provenance analysis including sandstone modal compositions, heavy mineral assemblages, and LA-ICP-MS U-Pb dating with in-situ Hf isotopic compositions of detrital zircons defines two types of Late Cretaceous-Eocene turbiditic sequences separated by the Siah Cheshmeh-Khoy-Misho-Tabriz Fault in the Azerbaijan Province, Northwest Iran: (1) Volcaniclastic turbidites to the southwest and (2) terrigenous turbidites to the northeast. The first appearance of Cr-spinel in Upper Cretaceous sandstones of both sequences indicates the erosion of ophiolites at that time. The southwestern volcaniclastic sandstones contain few Late Triassic and dominantly Late Cretaceous zircon grains whose Hf isotopic compositions suggest a continental magmatic arc provenance. In the northeastern terrigenous sandstones, detrital zircon U-Pb ages cluster in five main age groups from Paleoproterozoic-Neoproterozoic with Hf isotopic compositions typical of continental crust to Late Cretaceous-Palaeocene zircon grains with Hf isotopic compositions similar to those of the southwest turbidites. The provenance characteristics define, along with sedimentary structures, two separate basins, a marginal basin to the northeast, and a deep oceanic basin to the southwest. We conclude that the Siah Cheshmeh-Khoy-Misho-Tabriz Fault overprints a boundary between two lithospheres separated by ophiolite outcrops; therefore, the Siah Cheshmeh-Khoy-Misho-Tabriz Fault is a reworked suture. The Cretaceous arc, witnessed by clastic material, has been largely eroded and/or subducted.