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I. The late Oligocene to Miocene collision of Arabia and Eurasia was preceded by ~175 My of subduction of Neotethyan oceanic crust. Associated magmatic activity includes late Triassic(?) to Jurassic plutons in the Sanandaj-Sirjan zone of southern Iran, limited Cretaceous magmatism in the Alborz Mountains of northern Iran, and widespread Eocene volc...
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Citations
... 2006; Moritz et al., 2006;Verdel, 2009Verdel, , 2013Alirezaei and Hassanzadeh, 2012). ...
Middle Cretaceous sedimentary carbonates of Alvand Mountain host Pb-Zn-Ba veins. This mineralization occurs mainly as veins, breccia fillings, and to a lesser extent disseminated and host rock replacements. Ore mineralogy is simple and consists of sphalerite, galena, and barite, with minor pyrite, rare chalcopyrite, and tetrahedrite. Host rock dolomitization and hydrothermal silicification are typically associated with ore. Two types of primary liquid-vapor fluid inclusions were distinguished in sphalerite, quartz, and barite. Type I (salinity, 17-23 wt% NaCl; Th, 130±30°C) is dominant in sphalerite, whereas type II (salinity, 4.5-10 wt% NaCl, Th, 190±40°C) is dominant in quartz and barite; these fluids have characteristics of basinal brines and show a negative mixing trend in an evolving process of sulfide and gangue saturation. The δ¹⁸O and δ¹³C values for host rock and altered minerals range from 22 to 12.9 ‰ and 3.8 to -3.2 ‰, respectively, which suggest the influence of increased temperature fluids, presence of organic carbon and fluid mixing. The δ³⁴S values of sulfides and barite varies from 2 to 17 ‰ and 23 to 24 ‰, respectively, suggesting that reduced sulfur could be derived by thermochemical reduction of Paleogene seawater sulfate in the presence of organic matter; however, the wide ranges of δ³⁴S sulfide values (15‰) exhibits that reduction of sulfur probably originated by different sulfur reduction process. The data present in this study suggest that during increased tectonic activity in the late Cretaceous-Paleogene, mixing of basinal brines and water-rock interaction resulted in Pb-Zn-Ba deposition in carbonate host rocks. Therefore, it may represent low- temperature mineralization, possibly analogous to MVT depositional systems.
... Specifically, the volcanic member of the Browns Hole Fm serves as a distinctive stratigraphic marker unit with the potential to provide geochronologic control to improve regional stratigraphic correlations and insights into rifting [10,[15][16][17][18]. To date, however, volcanic and volcaniclastic materials from this unit have yielded sparse, uncertain, and conflicting geochronologic results (Figures 2 and 3) [12,13,19]. Hornblende from a volcanic clast in an agglomerate, located~40 m above the base of the contact between the Browns Hole and underlying Mutual formations near Huntsville, UT, yields a maximum depositional age of 580 ± 14 Ma (2σ) from total 40 Ar/ 39 Ar gas analysis [12,13]. ...
... Hornblende from a volcanic clast in an agglomerate, located~40 m above the base of the contact between the Browns Hole and underlying Mutual formations near Huntsville, UT, yields a maximum depositional age of 580 ± 14 Ma (2σ) from total 40 Ar/ 39 Ar gas analysis [12,13]. But, apatite grains from a thin basalt flow located 30 m above the agglomerate at this location have an isotope dilution-thermal ionization mass spectrometry (ID-TIMS) U-Pb date of 609 ± 25 Ma (2σ) (Figures 2 and 3) [19]. Although these dates overlap at the tails of their uncertainties, the juxtaposition of the younger maximum depositional age stratigraphically well below the older mean absolute age is problematic for interpreting the timing of deposition for the Browns Hole volcaniclastics and related strata. ...
... Approximate location of measured section (Figure 3) denoted by red bar. Radiometric dates are from (a) Isakson [47], (b) Fanning and Link [46], (c) Balgord et al. [40], (d) Crittenden and Wallace [13] and Christie-Blick and Levy [12], and (e) Verdel [19]. ...
Constraining the depositional age of Neoproterozoic stratigraphy in the North American Cordilleran margin informs global connections of major climatic and tectonic events in deep time. Making these correlations is challenging due to a paucity of existing geochronological data and adequate material for absolute age control in key stratigraphic sequences. The late Ediacaran Browns Hole Formation in the Brigham Group of northern Utah, USA, provides a key chronological benchmark on Neoproterozoic stratigraphy. This unit locally comprises <140 m of volcaniclastic rocks with interbedded mafic-volcanic flows that lie within a 3500 m thick package of strata preserving the Cryogenian, Ediacaran, and the lowermost Cambrian history of this area. Prior efforts to constrain the age of the Browns Hole Formation yielded uncertain and conflicting results. Here, we report new laser-ablation-inductively-coupled-mass-spectrometry U-Pb geochronologic data from detrital apatite grains to refine the maximum depositional age of the volcanic member of the Browns Hole Formation to 613±12 Ma (2σ). Apatite crystals are euhedral and pristine and define a single date population, indicating they are likely proximally sourced. These data place new constraints on the timing and tempo of deposition of underlying and overlying units. Owing to unresolved interpretations for the age of underlying Cryogenian stratigraphy, our new date brackets two potential Brigham Group accumulation rate scenarios for ~1400 m of preserved strata: ~38 mm/kyr over ~37 Myr or ~64 mm/kyr over ~22 Myr. These results suggest that the origins of regional unconformities at the base of the Inkom Formation, previously attributed to either the Marinoan or Gaskiers global glaciation events, should be revisited. Our paired sedimentological and geochronology data inform the timing of rift-related magmatism and sedimentation near the western margin of Laurentia.
... 2006; Moritz et al., 2006;Verdel, 2009Verdel, , 2013Alirezaei and Hassanzadeh, 2012). ...
Nickel laterites are supergene deposits derived from the weathering of ± serpentinized ultramafic rocks and they commonly accounts for over 70% of world land-based Ni resources. Serpentinized ultramafic rocks outcrop extensively in Iran as result of collision between Afro-Arabian and Iranian micro-plate during the Late Cretaceous. Two Ni-bearing laterite belts developed on the ultramafic rocks of the Neyriz ophiolite have been recently discovered in the Bavanat region (South Iran). The Chah-Gheib deposit, as the biggest Ni-bearing laterite in the Bavanat area, hosts a total estimated reserve mineralization of about 102000 tons of ore at 0.92 % Ni and 180000 tons at 1.63% Cr.
This study focuses on elemental fractionation and mineralogical control of major, trace and rare earth elements in a selected profile from the Chah-Gheib Ni-laterite, in order to assess the conditions of ore formation and its paleo-environmental significance.
Four distinct horizons, including saprolite, lower limonite, upper limonite, and lateritic duricrust, have been recognized from the bottom to the top of the studied profile. Iron oxy-hydroxides are the dominant phases found in the laterite profile. Overall, Fe and other first raw transition metals (i.e. Cr, Ni, V, Co, Cu, and Zn) show abundances higher than those of the bedrock. The main Fe and Cr carriers in the laterite deposit are Fe oxy-hydroxides and chromite, respectively, although authigenic Ni- and Cr-bearing palygorskite is also common throughout the profile.
Elemental mobility, estimated using Th as immobile element, showed that the major oxides are largely depleted with the exception of Fe2O3 and CaO. Among trace elements, Cr is the element resulting strongly enriched in those levels where large chromite crystals occurs while V, Co, Ni, and Zn are enriched only in some levels of the upper limonite horizon and in the lateritic duricrust, likely as adsorbed cations onto iron oxy-hydroxides and as a consequence of an alkaline pH environment. Alkaline pH conditions can also explain the Cu depletion observed throughout the profile. Such a condition during lateritization appears further supported by both the occurrence of carbonates and palygorskite and by the distribution of the Ba/Sr ratio. Carbonates and palygorskite, as well as secondary quartz, require dry climate to form and alternating wet-dry climate may allow lateritization. This study suggests that the Chah-Gheib laterite formed in a subtropical climate, possibly during the Late Cretaceous-Late Paleocene period, in a roughly 25°-35° latitude range, promoting Si and Mg mobilization during the wet season and carbonates, quartz, and Mg-rich silicate precipitation during the drier periods.
... As a result, much of the Sanandaj-Sirjan Terrane is deeply exhumed, and characterized by high-, medium-, and low-pressure regional metamorphic facies that are variably overprinted by contact metamorphism. The terrane is also affected by normal faulting, and later folding, thrusting, and strike-slip faulting that have resulted in deformation and extensive cover (Baharifar et al., 2004;Berberian et al., 1982;Mohajjel et al., 2003;Verdel, 2009). 4.1.1.2. ...
... Magmatism. Late Cretaceous to late Eocene magmatism in eastern Turkey, the Lesser Caucasus, and northwestern Iran consists of Late Cretaceous-Paleocene island and continental arc magmatism in front of and on the Bitlis-Pötürge and Sanandaj-Sirjan terranes, and associated Late Cretaceous to late Eocene intra-oceanic arc and backarc magmatism in the eastern Anatolide-Tauride and Central Iranian terranes (Kaymakci et al., 2010;Şengör and Yılmaz, 1981;Verdel, 2009). ...
... Several workers further distinguish the existence of two subduction zones operating in the southern Neo-Tethys Ocean southwest of the Sanandaj-Sirjan Terrane, and one between the Sanandaj-Sirjan and Central Iranian terranes (Arfania and Shahriari, 2009;Azizi and Moinevaziri, 2009;Babaie et al., 2001;Ghasemi and Talbot, 2006;Ghazi and Hassanipak, 2000). These subduction zones were individually responsible for the generation of Late Cretaceous island arc magmatism between the Afro-Arabian Plate and the Sanandaj-Sirjan Terrane (preserved in the Neyriz and Kermanshah ophiolite complexes), Late Cretaceous continental arc magmatism on the Sanandaj-Sirjan and Bitlis-Pötürge terranes (the Border Folds tract above), and Late Cretaceous to late Eocene intra-oceanic arc magmatism between the Sanandaj-Sirjan and Central Iranian terranes (preserved in the Nain-Baft and Khoy ophiolite complexes) ( Fig. 1) (Alavi, 1994;Ghorbani, 2006;Shahabpour, 2007;Verdel, 2009) (Fig. 2D). ...
Abstract
Exploration in the central Tethys region of Turkey, Armenia, Azerbaijan, Georgia, Iran, and western Pakistan has led to the identification of the giant Reko Diq (24 Mt Cu and 1300 t Au), Sar Cheshmeh (8.9 Mt Cu and 0.46 Mt Mo), Sungun (5.1 Mt Cu and 0.20 Mt Mo), and Kadjaran (4.6 Mt Cu, 0.94 Mt Mo, and 1100 t Au), and 10 other large (1–2 Mt Cu) porphyry deposits including Saindak, Cevizlidere, Teghout, Meiduk, and Halilağa. Continued exploration efforts have also resulted in the development of porphyry-related gold deposits such as Kişladağ (9.6 Moz Au), Çöpler (3.7 Moz Au), Aği Daği (1.7 Moz Au), and Sary Gunay (3.0 Moz Au), and in the generation of several other promising exploration projects.
The distribution in space and time of porphyry deposits in the central Tethys region was shaped by complex pre- to post-mineral tectonic, igneous, collisional, uplift and burial events. These events are represented by a partially-overlapping and variably exhumed and covered collage of twenty-six Early Jurassic to Holocene magmatic belts permissive for the occurrence of porphyry deposits (porphyry tracts and sub-tracts). Twelve tracts or sub-tracts are characterized by compressional continental arcs that formed on drifting terranes or continental margins, 10 developed in compressional to extensional intra-oceanic arc and backarc-rift settings, and 4 formed in extensional post-collisional environments over amalgamated terranes. Eight of these belts were variably affected by coeval and younger metamorphic, fold-and-thrust, and extensional faulting events.
Fifty-four porphyry Au-(Cu), Cu-Au, Cu-Mo, Mo-Cu deposits, 15 porphyry-related Au, Au-(Mo) and W-(Mo-Au) deposits, 239 porphyry prospects, and 68 other porphyry-related mineral sites were identified in the study region. Of the 376 porphyry and porphyry-related sites, about 11% formed in island arc, 42% in continental arc, 20% in backarc, and 27% in post-collisional settings. Of the 69 porphyry and porphyry-related deposits, 7% developed in intra-oceanic arc, 41% in continental arc, 27% in backarc, and 25% in post-collisional settings. The largest occur in either compressional continental arc (18 deposits including the Reko Diq and Sar Cheshmeh giants) or post-collisional (13 deposits including the Kadjaran and Sungun giants) environments. Ninety percent of the largest porphyry or porphyry-related deposits occur in only 9 of the 26 permissive porphyry tracts or sub-tracts. Moreover, 88, 90, and 77% of the identified Cu, Mo, and Au resources are contained in porphyry deposits that occur in only 4 of these 9 tracts. Of these 4 tracts, 3 outline arc settings, and one delimits a post-collisional environment.
The compositional diversity of porphyry intrusions in these tectono-magmatic environments generally varies from island arc settings with the most restricted range (partly alkaline but mainly calc-alkaline dioritic to granodioritic-tonalitic), to continental arc (calc-alkaline dioritic-quartz dioritic, granodioritic, quartz monzonitic-granitic, and less commonly mildly alkaline), to backarc (mildly alkaline and calc-alkaline dioritic to granitic), to post-collisional settings with the most expansive range (alkaline and calc-alkaline mafic to felsic, and weakly peraluminous). Metal associations also vary broadly as a function of porphyry intrusion composition from weakly peraluminous to metaluminous felsic (Mo[±W ± Cu]; <2% of porphyry-related systems [i.e., Tyrnyauz]), to metaluminous felsic and intermediate (Cu-Mo[±Au]; 85% [i.e., Cevizlidere, Haft Cheshmeh, Kahang, Sar Cheshmeh, Sungun, Teghout, Reko Diq, Saindak]), to mildly alkaline felsic and intermediate (Cu-Au[±Mo] [i.e., Agarak, Kadjaran, Kale Kafi]) and mafic (Au-Cu; 12% [i.e., Çöpler]), and to alkaline felsic (Au-Mo; 1% of porphyry-related systems [i.e., Kişladağ).
Tectonic changes were critical in triggering the formation of large porphyry deposits in the region. Large porphyry deposits were preferentially emplaced in continental arc settings shortly before major collisional events (Dar Alu, Kahang, Meiduk, Now Chun, and the giant Sar Cheshmeh and Reko Diq deposits), or in post-subduction environments shortly after collision (Bakirçay, Güzelyayla, Haft Cheshmeh, Masjed Daghi, and the giant Kadjaran and Sungun deposits) or during periods of prominent extension (Aği Daği, Halilağa, Kişladağ, Sari Gunay, and Zarshuran porphyry-related deposits). Collision-induced uplift, erosion, and removal of coeval volcanic rocks favorably exposed the hypabyssal level of subduction-related porphyry deposits. Extensional structures that developed parallel and orthogonal to the compressional principal stress component along transtensional or transpressional strike-slip faults or in pull-apart basins commonly controlled porphyry-related deposits in post-collisional settings. The latter deposits typically exhibit shallow epithermal levels of emplacement because of preservation by burial.
Seventeen porphyry deposits and one porphyry-related deposit in the study region are reported to contain significant supergene resources. Relatively mature levels of secondary copper enrichment in dominantly granodioritic to granitic porphyry deposits occur in areas where large pyrite-rich quartz-sericite alteration zones have been preserved and exposed to surface oxidation (Güzelyayla and Ulutaş in northeastern Turkey; Agarak, Ankavan, Dastakert, Kadjaran, and Teghout in Armenia; Ali Javad in northern Iran; Kale Kafi in central Iran; Darreh Zar, Meiduk, Now Chun, and Sar Cheshmeh in southeastern Iran; and Tanjeel in southwestern Pakistan). Chalcocite blankets also developed over porphyry deposits in regions where significant post-mineral faulting has occurred (Muratdere and Sarıçayıryayla in western Turkey). Normal faulting also enhanced secondary enrichment of gold in the Halilağa porphyry and Sary Gunay porphyry-related deposits located respectively in western Turkey and northern Iran.
Evaluation of provincial as well as local controls strongly suggests that continued exploration in the region will lead to the identification of additional porphyry and porphyry-related deposits. These deposits will likely be found under younger cover formations in porphyry belts that are already known, and in association with superjacent high- and intermediate-sulfidation epithermal deposits, or increasingly peripheral skarn, carbonate-replacement, and sediment-hosted deposits. Application of suitable exploration techniques to detect concealed and/or deformed deposits in porphyry belts that remain under-explored may also prove productive.
... The rocks of the NW-SE trending SSZ were highly deformed during the Zagros Orogeny (Stöcklin, 1968;Berberian and King, 1981;Hooper et al., 1994;Mohajjel et al., 2003;Agard et al., 2005). Metallogeny of the SSZ is complicated and includes Paleozoic metamorphosed iron deposits, Triassic to Cretaceous shale and carbonates that host Ba-F mineral ization, Lower Cretaceous carbonate-hosted Pb-Zn mineralization, Upper Cretaceous iron mineralization related to plutonic rocks, and Eocene gold deposits hosted by metamorphosed rocks (Stöcklin, 1968;Förster, 1974Förster, , 1978Moritz et al., 2006;Verdel, 2009Verdel, , 2011Verdel, , 2013Nabatian et al., 2015). ...
... Although the age of the volcanic rocks has already been reported as 54.7-44.3 Ma (Verdel, 2009) and as 26.0 ± 1.6 Ma (Ghorbani, Graham, & Ghaderi, 2014), no information exists on the crystallization age of the plutonic rocks. Most studies in this part of the UDMA have focused on volcanic rocks, whereas the origin of the associated plutonic rocks is not well characterized. ...
This paper presents UPb zircon dating and element compositions for Miocene intrusive rocks in NE Tafresh situated in the central Urumieh‐Dokhtar Magmatic Arc. These intrusive rocks, consisting of granodiorite and diorite, were emplaced during the Early Miocene (19.07–20.37 Ma), following extensive submarine volcanic activity in the Eocene. In normalized multi‐element diagrams, all the analysed rocks are characterized by enrichments in large ion lithophile elements (e.g., Ba, Rb, and Sr) and depletions in high field strength elements (e.g., Nb, Ta, and Hf) and display geochemical features typical of subduction‐related calc‐alkaline arc magmas. The enrichment of light rare earth elements and flat heavy rare earth elements patterns reflect amphibole fractionation from relatively hydrous, calc‐alkalic magmas. The geochemical features and ages of the Tafresh intrusive rocks suggest that the Neo‐Tethys Ocean did not close completely in the region until the Miocene and is consistent with a diachronous collision starting in the NW and closing later in the SE.
... The Isfahan porphyry tract is delimited by permissive units of a broad Late Cretaceous to late Eocene extensional back-arc rift that formed across central Iran, but that also propagated over time to the north into the Alborz, and to the southwest over the arc axis into the Sanandaj-Sirjan terranes (Fig. 2). Extensional tectonics and associated magmatism, as well as formation of cordilleran metamorphic core complexes of Eocene age have been recognized in the central Iranian, Sanandaj-Sirjan and Yazd terranes (Verdel et al., 2007(Verdel et al., , 2011Verdel, 2009). ...
ABSTRACT
Tectonic, geologic, geochemical, geochronologic, and ore deposit data from the U.S. Geological Survey-led assessment of 26 porphyry belts identified in the central Tethys region of Turkey, the Caucasus, Iran, western Pakistan, and southern Afghanistan relate porphyry mineralization to the tectonomagmatic evolution of the region and associated subduction and postsubduction processes. However, uplift, erosion, subsidence, and burial of porphyry systems, as well as post-mineral deformation, also played an essential role in shaping the observed metallogenic patterns.
We present a methodology that systematically evaluates the relationship between the level of erosion, the extent of cover, and the number of known porphyry occurrences in porphyry belts. Porphyry belts that exhibit coeval volcanic-to-plutonic rock aerial ratios between 33 and 66 and limited cover contain numerous identified porphyry occurrences. These belts are relatively well explored because porphyry systems are not eroded or buried. Porphyry belts with volcanic-to-plutonic ratios that are greater than 66, but are modestly covered, contain fewer identified porphyry occurrences. Current exploration in these belts is increasingly identifying porphyry systems under associated epithermal deposits. Porphyry belts that show volcanic-to-plutonic ratios that are greater than 66, but are extensively covered, contain few identified porphyry occurrences. These belts have not been extensively explored but have potential for discoveries under cover. Deformed porphyry belts exhibit variable volcanic-to-plutonic ratios that are typically below 33, but can be as high as 60. Commonly, these deformed belts are extensively covered.
Exploration efforts for porphyry deposits in these variably exhumed belts have been limited. Exploration has resulted in the identification of 62.7 million tonnes (Mt) of copper, 2.0 Mt of molybdenum, and 4.200 t of gold in the 45 porphyry deposits contained in the 26 porphyry belts of the region: (1) 54.7 Mt of copper (87% of total), 1.74 Mt of molybdenum (87%), and 3,370 t of gold (80%) occur in the 25 deposits of the four porphyry belts that exhibit coeval volcanic-to-plutonic ratios between 33 and 66 and limited cover; (2) 5.44 Mt of copper (9%), 0.148 Mt of molybdenum (7%), and 581 t of gold (14%) are contained in the 11 deposits of the 11 porphyry belts that display volcanic-to-plutonic ratios greater than 66 and modest cover; (3) 2.08 Mt of copper (3%), 0.110 Mt of molybdenum (6%), and 244 t of gold (6%) occur in the seven deposits of the three porphyry belts that have volcanic-to-plutonic ratios that are greater than 66 and extensive cover; and (4) 0.388 Mt of copper (1%), 0.006 Mt of molybdenum (<<1%), and 6 t of gold (<<1%) are contained in the two deposits of the eight deformed and covered porphyry belts with variable but typically low volcanic-to-plutonic ratios.
The central Tethys region is receiving considerable exploration attention. It hosts the Kadjaran (4.6 Mt Cu), Sungun (5.1 Mt Cu), Sar Cheshmeh (8.9 Mt Cu), and Reko Diq (23.0 Mt Cu) world-class porphyry deposits. Continued exploration for porphyry deposits in the region will likely lead to new discoveries in known porphyry belts, particularly under cover and below high- and intermediate-sulfidation epithermal systems.
... The Alborz range, SSZ and UDMA are interpreted as products of the Neotethys oceanic subduction beneath the Iranian microcontinents (e.g., Stocklin, 1974;Berberian et al., 1982;Verdel, 2009). Geochronological studies revealed three main magmatic phases in the late Cretaceous, Paleogene, and Miocene in the Alborz belt (Rezaeian, 2008). ...
... The only source for late Cretaceous zircons in the drainage basin of the Sefidrud river system are volcanic rocks, mostly of mafic (basic to andesitic) (Stocklin and Eftekharnezhad, 1969;Davies, 1977;Annells et al., 1985;Azizi and Jahangiri, 2008;Verdel, 2009). The small number of late Cretaceous zircon grains reflects the nature of the magmatism at this time (Rezaeian, 2008). ...
... -20 -consistent with magmatic activity during Paleogene, especially its highest activity in middle Eocene (Rezaeian, 2008;Ballato, 2009;Verdel, 2009 (Ballato, 2009;Verdel, 2009). In addition, there are several plutonic bodies and basic lava flows of this age in the Sefidrud catchment area (Guest et al., 2007;Hassanzadeh et al., 2008;Rezaeian, 2008;Chiu et al., 2013;Nabatian et al., 2014;Honarmand et al., 2015). ...
In order to improve techniques for provenance studies, and especially to address the question of sediment recycling, morphological changes of two minerals with contrasting durability (zircon and apatite) were tracked during both fluvial transport and littoral reworking. The Sefidrud river system in northern Iran, which drains the Alborz volcano-sedimentary range into the Caspian Sea, and the Sarbaz river system in southeastern Iran, which drains the Makran Accretionary Prism into the Oman Sea, were chosen for this study. To determine source rocks of the grains, and thus their nature in terms of sedimentary cycles, zircon geochronology was conducted on both rivers. The zircon data indicate that most of the Sefidrud sediments are first cycle, derived from crystalline rocks, and the Sarbaz sediments are generally recycled from older wedges of the Makran. Results from SEM analysis show significant differences between the roundness of associated zircon and apatite grains. Zircon grains remain unrounded through several cycles, while apatite grains show abrasion from the early stages of their first cycle.
... In contrast, LILE/HFSE ratios, interpreted as an indication of subduction signature, increase to the south-southwest of the central Lut block (Fig. 11), where Neotethyan oceanic crust was subducted beneath Iran along a northeast dipping subduction zone from approximately Late Triassic (Berberian and Berberian 1981) to Late Oligocene time (Fakhari et al. 2008). Verdel (2009) also suggested the mantle source of the Eocene-Oligocene volcanism in the north-central Lut block was metasomatized by slabderived fluids over the course of ~150 million year, from the time of subduction initiation in the late Triassic until the late Eocene-early Oligocene. Convergence rates of around 3 cm/yr during this period , would have limited the volume of fluids released to the mantle wedge over any given period of time, but this supply of fluids was still sufficient to partially hydrate and alter the trace element composition of the mantle wedge, including both the subcontinental lithosphere and asthenosphere (Verdel 2009). ...
... Verdel (2009) also suggested the mantle source of the Eocene-Oligocene volcanism in the north-central Lut block was metasomatized by slabderived fluids over the course of ~150 million year, from the time of subduction initiation in the late Triassic until the late Eocene-early Oligocene. Convergence rates of around 3 cm/yr during this period , would have limited the volume of fluids released to the mantle wedge over any given period of time, but this supply of fluids was still sufficient to partially hydrate and alter the trace element composition of the mantle wedge, including both the subcontinental lithosphere and asthenosphere (Verdel 2009). To account for the presence of subduction components derived from this subducting slab magmatism some 800 km inboard of the convergent plate margin active along the southwest margin of central and eastern Iran during the Paleogene time, low angle sub-horizontally subduction is required (Fig. 12a). ...
... In summary, the Neogene mafic rocks along the margins of the Lut block represent only the last manifestation of a much more extensive mid-Tertiary magmatic event. Fig. 12. Diagram, modified from Verdel (2009), summarizing the sequential development from Late Cretaceous/Late Eocene flat slab subduction stage, followed by a Late-Eocene/Early Miocene extentional flare-up stage as subduction geometry changes in response to the closure of Neotethys, and subsequent OIB-type Neogene/Quaternary magmatism along the margins of the Lut block. Abbreviations: UD-Urumieh-Dokhtar magmatic arc, CL-Central Lut, WL-Western Lut, EL-Eastern Lut. ...
The Lut block in eastern Iran is a micro-continental block within the convergent orogen between the Arabian, Eurasian and Indian plates. Large areas of the north-central, eastern, and western Lut block are covered by volcanic rocks of Paleogene, Neogene and Quaternary age. Peak volcanic activity took place in the north-central part of the Lut block during the Eocene, and then dramatically decreased, becoming more restricted to the eastern and western margins of the block during the late Miocene and Quaternary. There is also significant variation in chemistry between the Paleogene igneous rocks from the north-central part compared to the Neogene and Quaternary volcanic rocks from the western and eastern margins of the Lut block. The Neogene and Quaternary olivine basalts, which were erupted along both margins of the Lut block, are similar in trace element chemistry to the average composition of oceanic island basalt. In contrast, the Paleogene volcanic units of the north-central Lut block, which include basalts through rhyolites, follow both calc-alkaline and alkaline trends. Low TiO2 and high Ba/Nb and La/Nb ratios for both Paleogene basalts and andesitic samples from the north-central Lut block suggest affinities, at least for some of these samples, with convergent plate boundary arc magmas. LILE/HFSE ratios, interpreted as an indication of subduction signature, increase to the south-southwest of the central Lut block, where Neotethys oceanic crust was subducted beneath Iran in a northeastern direction from approximately Late Triassic to Late Oligocene time. We suggest that components derived from low angle subduction of this crust during the Mesozoic and early Tertiary were stored in the mantle lithosphere below the north-central Lut block until the Paleogene, when changing subduction geometry, associated with the collision of Arabia with Iran and the closing of Neotethys, caused hot asthenosphere to well up under the Lut block. This created the Eocene peak in volcanic activity, generating basalts from asthenospheric mixed with lithospheric melts, with both alkaline and calc-alkaline affinities. After this volcanism waned, becoming restricted during the Neogene to OIB-type alkaline basalts erupted through deep lithospheric structures along both the western and eastern margins of the Lut block.
... Flat-lying normal sense shear zones those were cut with the high-angle normal faults, as a result of late-stage extension in the early to middle Eocene, as is well documented in the north Muteh Mine area by Moritz et al. (2006). Verdel (2009, 2013) postdated the existence of the structural elements of a metamorphic core complex in the Muteh-Golpaygan area and compared it with the Funeral Mountain Complex in the western United States. ...
... A mid to Late Cretaceous exhumation of HP metamorphic rocks in the Sanandaj-Sirjan zone has been documented by using 40 Ar/ 39 Ar age data (Monié and Agard, 2009). The voluminous Eocene volcanism in the Urumieh-Dokhtar magmatic arc was attributed to subduction (e.g., Dewey et al., 1973;Farhoudi, 1978;Berberian et al., 1982;Omrani et al., 2008;Verdel, 2009) but other researchers (Takin, 1972;Amidi, 1975) related it to melting of sialic crustal material during rift system. A late Eocene-early Oligocene partitioning of strike-slip and reverse components of brittle transpressional deformation was documented along the SW edge of the northern Sanandaj-Sirjan zone (Agard et al., 2005). ...
