Journal of Asian Earth Sciences 100 (2015) 31–59
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Journal of Asian Earth Sciences
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Review Ophiolites of Iran: Keys to understanding the tectonic evolution of SW Asia: (II) Mesozoic ophiolites ⇑ Hadi Shafaii Moghadam a, , Robert J. Stern b a School of Earth Sciences, Damghan University, Damghan, Iran b Geosciences Dept., University of Texas at Dallas, Richardson, TX 75083-0688, USA article info abstract
Article history: Iran is a mosaic of continental terranes of Cadomian (520–600 Ma) age, stitched together along sutures Received 29 May 2014 decorated by Paleozoic and Mesozoic ophiolites. Here we present the current understanding of the Meso- Received in revised form 8 December 2014 zoic (and rare Cenozoic) ophiolites of Iran for the international geoscientific audience. We summarize Accepted 16 December 2014 field, chemical and geochronological data from the literature and our own unpublished data. Mesozoic Available online 13 January 2015 ophiolites of Iran are mostly Cretaceous in age and are related to the Neotethys and associated backarc basins on the S flank of Eurasia. These ophiolites can be subdivided into five belts: 1. Late Cretaceous Keywords: Zagros outer belt ophiolites (ZOB) along the Main Zagros Thrust including Late Cretaceous–Early Paleo- Ophiolite cene Maku–Khoy–Salmas ophiolites in NW Iran as well as Kermanshah–Kurdistan, Neyriz and Esfanda- Neotethys Cimmeria gheh (Haji Abad) ophiolites, also Late Cretaceous–Eocene ophiolites along the Iraq–Iran border; 2. Late Supra-subduction zone Cretaceous Zagros inner belt ophiolites (ZIB) including Nain, Dehshir, Shahr-e-Babak and Balvard–Baft MORB ophiolites along the southern periphery of the Central Iranian block and bending north into it; 3. Late Cre- Iran taceous–Early Paleocene Sabzevar–Torbat-e-Heydarieh ophiolites of NE Iran; 4. Early to Late Cretaceous Birjand–Nehbandan–Tchehel–Kureh ophiolites in eastern Iran between the Lut and Afghan blocks; and 5. Late Jurassic–Cretaceous Makran ophiolites of SE Iran including Kahnuj ophiolites. Most Mesozoic ophi- olites of Iran show supra-subduction zone (SSZ) geochemical signatures, indicating that SW Asia was a site of plate convergence during Late Mesozoic time, but also include a significant proportion showing ocean-island basalt affinities, perhaps indicating the involvement of subcontinental lithospheric mantle. Ó 2015 Elsevier Ltd. All rights reserved.
Contents
1. Introduction ...... 32 2. Geologic background ...... 32 3. Field and structural characteristics of Iranian Mesozoic ophiolites ...... 33 3.1. Zagros outer belt ophiolites ...... 33 3.1.1. Khoy–Maku ophiolites ...... 33 3.1.2. Late Cretaceous Iraqi–Iranian (Kurdistan) Zagros ophiolites ...... 33 3.1.3. Eocene Hasanbag (Kurdistan)–Kermanshah ophiolites ...... 35 3.1.4. Mesozoic Kermanshah ophiolite ...... 35 3.1.5. Neyriz ophiolite ...... 36 3.1.6. Haji Abad (Esfandagheh) ophiolite ...... 36 3.2. Zagros inner belt ophiolites ...... 38 3.2.1. Nain ophiolite ...... 39 3.2.2. Dehshir ophiolite ...... 39 3.2.3. Shahr-e-Babak ophiolite...... 40 3.2.4. Balvard–Baft ophiolite ...... 40
⇑ Corresponding author. E-mail address: [email protected] (H.S. Moghadam). http://dx.doi.org/10.1016/j.jseaes.2014.12.016 1367-9120/Ó 2015 Elsevier Ltd. All rights reserved. 32 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59
3.3. Sabzevar–Torbat-e-Heydarieh ophiolitic belt ...... 40 3.3.1. Sabzevar ophiolite ...... 41 3.3.2. Oryan–Bardaskan ophiolite ...... 41 3.3.3. Torbat-e-Heydarieh ophiolite...... 42 3.4. Birjand–Nehbandan (Eastern Iranian) ophiolitic belt ...... 42 3.5. Makran ophiolites (SE Iran) including Kahnuj ophiolites ...... 45 3.5.1. Makran ophiolites...... 45 3.5.2. Kahnuj ophiolites ...... 47 4. Age constraints of Iranian ophiolites ...... 47 4.1. Zagros outer belt ophiolites ...... 47 4.2. Zagros inner belt ophiolites ...... 47 4.3. Sabzevar–Torbat-e-Heydarieh ophiolitic belt ...... 47 4.4. Birjand–Nehbandan (Eastern Iranian) ophiolitic belt ...... 48 4.5. Makran ophiolites ...... 49 5. Summary of compositional variations in Iranian Mesozoic ophiolites ...... 49 5.1. Khoy–Maku and Zagros outer belt ophiolites ...... 49 5.2. Zagros inner belt ophiolites ...... 49 5.3. Sabzevar–Torbat-e-Heydarieh ophiolitic belt ...... 49 5.4. Birjand–Nehbandan (Eastern Iranian) ophiolitic belt ...... 50 5.5. Makran ophiolites ...... 51 6. Discussion...... 51 6.1. Comparison with other Mesozoic Tethyan ophiolites...... 51 6.1.1. Comparison with Jurassic ophiolites ...... 51 6.1.2. Comparison with Late Cretaceous ophiolites ...... 51 6.1.3. Importance of Eocene ophiolites ...... 51 6.2. Petrological diversity of Iranian Mesozoic ophiolites ...... 52 6.2.1. Passive continental margin-type ophiolites ...... 53 6.2.2. MORB-type ophiolites ...... 53 6.2.3. Plume-type ophiolites ...... 53 6.2.4. Supra-subduction zone-type ophiolites...... 53 6.2.5. Volcanic arc-type ophiolites...... 53 6.2.6. Accretionary prism-type ophiolites ...... 53 6.3. Tectonic evolution of Iranian Mesozoic ophiolites ...... 53 6.3.1. Zagros ophiolites ...... 53 6.3.2. Khoy–Maku ophiolites ...... 55 6.3.3. Sabzevar–Torbat-e-Heydarieh ophiolites ...... 55 6.3.4. Birjand–Nehbandan ophiolites...... 55 6.3.5. Makran ophiolites...... 55 7. Conclusions...... 57 Acknowledgments ...... 57 References ...... 57
1. Introduction reviewed by multiple authors (e.g., Knipper et al., 1986; Moores et al., 2000; Robertson, 2002; Dilek and Furnes, 2009) but a modern Late Paleozoic–Early Mesozoic time was a period of continental review of Iran Mesozoic ophiolites is lacking. rifting, oceanic crust formation and accretion across Iran and other In this paper, we review modern understanding of Mesozoic Cimmerian blocks including Afghanistan and Turkey, Lhasa and ophiolites of Iran for the international geoscientific audience. We Karakoram. This is when the Paleotethys Ocean was consumed have learned a lot since the last review of Iranian ophiolites by beneath the southern margin of Eurasia and when Neotethys began Delaloye and Desmons (1980), a third of a century ago. This review to open along the northern margin of Gondwana (Shafaii – which should be regarded as a progress report – complements Moghadam et al., 2014). our recent review of Paleozoic ophiolites of Iran (Shafaii Neotethyan ophiolites define a 7000 km long belt across Moghadam and Stern, 2014). We incorporate our own results southern Eurasia and can be divided into two groups (Fig. 1; and field observations plus data from the literature. We use the Abbate et al., 1980): (1) Jurassic ophiolites in the west (e.g., Dina- timescale of Walker et al. (2012) to relate biostratigraphic ages rides and Ligurian ophiolites) with MORB geochemical signature to radiometric ages. Below, we first outline the major features of and (2) mostly Cretaceous ophiolites in the east, which typically Iranian basement geology (Section 2), then we focus on 6 great show SSZ geochemical signatures. Southwest Asia is littered with belts of Iran Mesozoic ophiolites, first summarizing their field ophiolitic relicts of Neotethyan oceanic lithosphere, which delin- relations (Section 3), then age constraints (Section 4), and finally eate sutures between continental blocks rifted from Gondwana, their petrology and geochemistry (Section 5) before briefly including Arabia and India as well as the Cimmerian blocks of Ana- discussing the broader significance of Iran Mesozoic ophiolites tolia, Iran, and Afghanistan. Most Neotethyan ophiolites in Cyprus, (Section 6). Turkey, Iran, Pakistan, Afghanistan, Oman and in the Tibetean Pla- teau have Late Cretaceous ages but some are older (e.g., ophiolites in Caucasus and Iranian Makran) (Fig. 1). Iranian Neotethyan ophi- 2. Geologic background olites are an important part of the 3000 km long ophiolite-rich zone that extends from Troodos (Cyprus) through Turkey An outline of the main tectonic zones of Iran was given by eastwards as far as Semail (Oman). These ophiolites have been Shafaii Moghadam and Stern (2014) and here we present an abbre- H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 33 viated summary. Iran can be divided into 9 major tectonic zones 3.1.1. Khoy–Maku ophiolites (Fig. 2), from N to S including: (1) Kopet-Dagh zone in NE Iran; Information about Khoy–Maku in NW Iran (Figs. 3 and 4)is (2) The southern Caspian Sea basin; (3) Alborz zone in N-NW Iran; summarized in Table 1. The Khoy ophiolite was described by (4) The Central Iranian block or Cimmeria, consisting of three Hassanipak and Ghazi (2000), Ghazi et al. (2003), Khalatbari- major old continental blocks (from E to W): Lut, Tabas, and Yazd, Jafari et al. (2003, 2004, 2006), and Azizi et al. (2005, 2011). separated by major faults (e.g., Alavi, 1991) and similar crust to Hassanipak and Ghazi (2000) concluded that the Khoy ophiolite the NW that is mostly buried beneath Cenozoic deposits; (5) East- is equivalent to the Inner Zagros Ophiolite Belt and formed by clos- ern Iranian suture zone; (6) Urumieh-Dokhtar magmatic belt, (7) ing the northwestern branch of a narrow Mesozoic seaway which The Zagros Fold-Thrust Belt (ZFTB), (8) Sanandaj–Sirjan zone surrounded the Central Iranian microcontinent. Khalatbari-Jafari (SNSZ), and (9) Makran. et al. (2003, 2004) infered five main geological units from NE to Older continental fragments of Iran, including Alborz, Tabas SW in the Khoy region including (Fig. 4): (1) the SW continental Central Iran and Lut blocks contain crust as old as Ediacaran–Cam- margin of the Central Iranian block, (2) the eastern metamorphic brian, also known as Cadomian (Fig. 2). Iranian ophiolites can be unit including a Cadomian meta-ophiolitic complex, (3) the divided into Paleozoic ophiolites (Paleotethys remnants) and supra-ophiolitic turbidites and volcano-sedimentary zone, (4) the Mesozoic and minor Paleogene ophiolites (Neotethys remnants) unmetamorphosed Late Cretaceous Khoy ophiolite, and (5) the (Fig. 2). Paleozoic ophiolites are found in northern Iran, defining western metamorphic unit. The southern margin of the Central Ira- the boundaries between the Turan (Eurasia) block and Cimmeria nian block is composed mainly of Neoproterozoic igneous and (Central Iranian and Alborz blocks) where Paleotethys was con- metamorphic rocks overlain by Cambrian sedimentary rocks, sumed by subduction beneath southern Eurasia (Alavi, 1991; which are disconformably overlain by Permian sediments. These Shafaii Moghadam and Stern, 2014). older sequences are tectonically overlain by Jurassic–Early Creta- Mesozoic and Paleogene ophiolites across Iran can be subdi- ceous sediments. These unconformities are reliable indicators of vided by age and geography into 5 belts (Fig. 2), as discussed in fol- tectonic movements. lowing sections: (a) Late Cretaceous Zagros outer belt ophiolites The eastern metamorphic unit contains four main sub-units (ZOB) along the Main Zagros Thrust including Late Cretaceous– (Khalatbari-Jafari et al., 2003, 2004) consisting of micaschist, Early Paleocene Maku–Khoy–Salmas ophiolites (Khoy–Maku belt amphibolite (MORB to SSZ geochemical affinities), metavolcanic in Fig. 2) in NW Iran as well as Kermanshah–Kurdistan, Neyriz rocks, and gneissic rocks. The supra-ophiolitic volcano-sedimen- and Esfandagheh (Haji Abad) ophiolites, also Late Cretaceous– tary unit includes turbidites and coarse-grained breccias at the Eocene ophiolites along the Iraq–Iran border; (b) Late Cretaceous base grading up into volcanic breccias and pillow lavas intercalated Zagros inner belt ophiolites (ZIB) including Nain, Dehshir, Shahr- with pelagic sediments (Fig. 5). The younger, unmetamorphosed e-Babak and Balvard–Baft ophiolites along the southern periphery Khoy ophiolite complex is composed of mantle peridotite, layered of the Central Iranian block and bending north into it (Fig. 2); (c) gabbro, diabasic dike swarm and a huge pile of phyric to aphyric Late Cretaceous–Early Paleocene Sabzevar–Torbat-e-Heydarieh pillowed to massive basalts (Fig. 5). ophiolites (Sabzevar–Torat belt in Fig. 2) of NE Iran; (d) Early to The western metamorphic unit consists of low-grade metamor- Late Cretaceous Birjand–Nehbandan–Tchehel–Kureh ophiolites phic rocks of unknown origin and age. This unit may represent an (Birjand–Nehbanden belt in Fig. 2) in eastern Iran between the eastern extension of the Permian and older Puturge–Bitlis meta- Lut and Afghan blocks; and (e) Late Jurassic–Cretaceous Makran morphic rocks of eastern Turkey (Khalatbari-Jafari et al., 2003). ophiolites of SE Iran including Kahnuj ophiolites. Some of these The Maku ophiolite is the NW continuation of the Khoy ophio- may have originated as conterminous basins or forearcs, for exam- lite (Fig. 4). Cadomian metamorphic rocks outcrop NE and SE of the ple the Zagros belts with Makran; inner Zagros belt and Sabzevar– Maku ophiolite. Ankaramitic pillow lavas and basaltic to dacitic Torbat; Sabzevar–Torbat with Birjand–Nehbandan; and Makran calc-alkaline lavas are common in the ophiolite near Siah-Chesh- with Birjand–Nehbandan, but more work will be needed to address meh (Figs. 4 and 5). Maku ophiolite pillow lavas are overlain by such questions. Field relationships, age and geochemical data for Late Cretaceous pelagic sediments and then turbiditic sediments each ophiolitic belt are summarized in Tables 1 and 2. Even though of Late Cretaceous–Early Paleocene age. Thick pelagic limestone there are some Paleogene ophiolites, in the following all are called layers are stratigraphically interleaved with pillow lavas Mesozoic ophiolites for brevity. (Fig. 6A), showing that volcanic and non-volcanic episodes alter- nated during basin evolution. Basaltic calc-alkaline/OIB-type sills and dikes crosscut the overlying turbidites. 3. Field and structural characteristics of Iranian Mesozoic ophiolites 3.1.2. Late Cretaceous Iraqi–Iranian (Kurdistan) Zagros ophiolites The Zagros Orogen along the Iran–Iraq border is marked by Below we describe the field and structural characteristics of the ophiolite massifs distributed along the MZT near Mawat, Hasanbag 5 belts of Mesozoic ophiolites in Iran. (Iraq) and Kurdistan (Iran). These ophiolites define a belt from Ker- manshah along the Iran–Iraq border and then into Turkey (Fig. 3). This ophiolite belt is not well studied but what we know about it is 3.1. Zagros outer belt ophiolites summarized in Table 1. The ophiolite belt is thought to link Late Cretaceous Zagros and Khoy–Maku ophiolites. The ophiolites in Zagros outer belt ophiolites (ZOB) is by far the longest of the five Iraq are juxtaposed with Balambo Cretaceous carbonate platform belts, stretching 1200 km from NW to SE Iran. This belt includes and deep-water radiolarite Qulqula Group rocks (Triassic–Creta- five main occurences, from NW to SE: Khoy–Maku ophiolites, ceous). Suturing was followed by deposition of the Tanjero flysch Iraqi–Iranian Zagros ophiolites (Kurdistan ophiolites), Kerman- in Maastrichtian time. Late Cretaceous Iraqi ophiolites (with SSZ shah, Neyriz and Haji Abad (Fig. 2). These slices are separated by signature) are associated with the Albian–Cenomanian Hassanbag the Main Zagros Thrust (MZT) from the Zagros Fold-Thrust Belt Arc complex (Ali et al., 2012). to the SW, except the Khoy–Maku ophiolites of NW Iran. A sum- The Hassanbag Late Cretaceous igneous complex (Fig. 3) con- mary of Zagros ophiolites was recently provided by Shafaii sists predominantly of calc-alkaline basaltic andesites to andesites Moghadam and Stern (2011). We briefly discuss these ophiolites intruded by microgabbro and diorite dikes (Ali et al., 2012). Ali below. et al. (2012) considered that subduction of Neotethys seafloor 34 Table 1 Summary of Iranian Mesozoic inner and outer Zagros ophiolitic belt characteristics.
Ophiolite, size Size Mantle lithology Crustal Crust/ Radiometric Type of Age of Lava Temporal Cpx TiO 2 Mafic/felsic Cr# spinel Associated Crustal Ophiolite Proposed References lithology mantle ages overlying sediments geochemistry changes in lavas lavas metamorphic sequence classification tectonic ratio sediments of lavas (wt.%) rocks thickness setting
Khoy-Maku ophiolites 40002 km Mantle Gabbro, pillow 4/1 73–101 K–Ar Pelagic Late OIB, E- MORB MORB to Low in Mafic>>felsic 0.2 (low Micaschist, >5000 m MORB-type Mid- This study, lherzolite, to massive on gabbro- limestones, Cretaceous to with rare N- SSZ-type gabbros Cr#) and phyllite, (with trace oceanic Khalatbari- harzburgite, lavas, cold plagioclase radiolarites, Early MORB, IAT lavas but high 0.3–0.6 amphibolite, of temporal ridge, Back- Jafari et al. with minor breccia, turbidites Paleocene and calc- in E- (high Cr#) gneiss plume-type) arc basin (2003, 2004), chromitite pyroclastic and alkaline MORB- to early Monsef et al. rocks pyroclastic OIB lavas stage of (2010) and rocks infant arc Rezai et al. (2010) 2 Iraqi-Iranian Kurdistan 1000 km Serpentinized Ultramafic 2/1 106–92 Ma Pelagic Late MORB and ? – Mafic 0.5–0.8; Sanandaj-Sirjan 1000– SSZ-type Late Ali et al. (2012), ophiolites 250 km harzburgite, cumulates, (Ar-Ar) limestones- Cretaceous SSZ type- lavas>felsic 0.4–0.8 metamorphic 1200 m Cretaceous Aswad et al. along the MZT dunite, gabbros– radiolarites lavas & lavas in Penjwin rocks SSZ type (2011), Allahy- chromitite, (Late diorites, dike gabbros ari et al. (2014), Cretaceous SSZ complex, Saccani et al. type) pillow lava (2014) and Rahimzadeh ..Mgaa,RJ tr ora fAinErhSine 0 21)31–59 (2015) 100 Sciences Earth Asian of Journal / Stern R.J. Moghadam, H.S. (unpublished data) Eocene ophiolite Cumulate – 37–42 Ma Silicic ooze, – E-MORB to P- E-& P- 0.8–1.3 – 0.5–0.7 Turbiditic >2000 m Intra- Eocene lherzolite, radiolarites MORB- MORBs in in phyllites (SSNZ) oceanic intra- gabbro, pillow lavas toward the east and northeast during Early Cretaceous time was responsible for development of the Hasanbag ophiolite-arc com- plex (106–92 Ma). The Penjween ophiolite (Fig. 3) includes mantle harzburgites and dunites grading upward into ultramafic cumu- References Shafaii Moghadam and Stern (2011) Shafaii Moghadam and Stern (2011) and Shafaii Moghadam et al. (2013) lates-layered (low-Ti) gabbros and diabasic sheeted dike complex (Ali et al., 2012). The Iranian Kurdistan ophiolites occur along the MZT, between the Avroman–Bisotun limestones and Sanandaj–Sir- Proposed tectonic setting short-lived backarc short-lived backarc jan metamorphic rocks/Eocene ophiolites and include depleted harzburgites and fragmented gabbros/lavas. Ophiolite classification 3.1.3. Eocene Hasanbag (Kurdistan)–Kermanshah ophiolites Rare Eocene ophiolites occur along the Iran–Iraq border, from Kermanshah (Iran) to Hasanbag (Iraq; Table 1. These are the Crustal sequence thickness – SSZ-type Forearc or >2300 m SSZ-related Forearc or Walash–Kermanshah volcano-sedimentary unit in Fig. 3 and are related to intra-oceanic subduction within Neotethys, similar to volcanic-arc type ophiolites (e.g., Dilek and Furnes, 2011, 2014). During intraoceanic subduction in Eocene and Oligocene time, metamorphic rocks amphibolite amphibolite the island-arc complex (or arc-type ophiolite) formed the Eocene–Oligocene Walash–Naopurdan magmatic group which subsequently accreted to the Arabian margin (Ali et al., 2013). A 0.4 Minor 0.5–0.9 Minor Cr# spinel Associated similar Eocene ophiolite also occurs in Kermanshah and Iranian Kurdistan. The Iranian Kurdistan ophiolites crop out in a tectonic window within turbiditic phyllites of the Sanandaj–Sirjan zone (SSNZ) and include from bottom to top: (1) ultramafic cumulate, Mafic/felsic lavas (3) a gabbroic–dioritic sequence with granitic dikes, (4) both P- 2 to E-MORB-like pillowed and calc-alkaline lavas unit with micro- gabbroic dikes. in lavas (wt.%) 0.2–0.9 Felsic > mafic Cpx TiO In the Kermanshah region, Paleocene-Eocene turbidites and Eocene calc-alkaline pillow lavas stratigraphically cover the Late Cretaceous ophiolite. Eocene pillow lavas differ from Late Creta- – 0.1–1.4 Felsic >>mafic MORB/ IAT to boninite/ calc- alkaline Temporal changes of lavas ceous pillows by being intercalated with green shale and sand- stone turbidites. Dike swarms, including early basaltic and diabasic dikes and late dacitic–rhyolitic to microdioritic dikes (usu- IAT and calc- alkaline IAT, calc- alkaline and boninite with minoir N- and E-MORB Lava geochemistry ally <0.5 m, locally >1 m wide), are present near Kherran and Sar- takht villages and show Eocene U–Pb zircon ages (Shafaii Moghadam et al., unpublished data), interpreted to have formed during extension associated with intraoceanic magmatism. Coniacian- Maastrichtian Turonian– Maastrichtian Age of sediments Whitechurch et al. (2013) suggested that the Eocene ophiolitic rocks (pillow lavas, gabbros and dikes) were intruded into the Late Cretaceous Kermanshah ophiolite close to the ocean–continent limestones, pyroclastic rocks Pelagic limestones, radiolarite, pyroclastic rocks Type of overlying sediments transition. They considered this as an Eocene arc, constructed in a Paleocene back-arc basin along the Eurasian continental margin. 3.1.4. Mesozoic Kermanshah ophiolite gabbro(K – Ar); 103.2 ± 2.4 U–Pb) Radiometric ages The Kermanshah ophiolite, despite being one of the largest of all Iranian ophiolites (exposed over 2400 km2), has not been studied 3/1 –1/3 94–72, Pelagic Crust/ mantle ratio in detail. Kermanshah ophiolites are complex and include rem- nants of Late Permian–Triassic continental rifting (passive margin ophiolite of Dilek and Furnes, 2011), Late Cretaceous SSZ ophiolites and a Paleocene–Eocene intra-oceanic subduction system (Eocene Volcanic rocks with pyroclastic edifices Pillowed to massive lavas, basaltic– andesitic– dacitic sills in pyroclastic rocks lithology ophiolite). This ophiolite trends NW–SE and is distributed in two regions separated by SNSZ metamorphic rocks: in the NW, near Kamyaran, and in the SE, between Harsin and Sahneh. The ophio- lites between Harsin and Sahneh are Triassic to Early Cretaceous Harzburgite with diabasic dikes and gabbro intrusions Lherzolite, harzburgite with diabasic dikes and gabbroic pockets remnants of continental rifting and subsequent oceanic accretion 2 at a mid-oceanic ridge (Saccani et al., 2013). The ophiolite is bor- 2 dered to the NE by SSNZ metamorphic rocks and to the SW by 500 km the Bisotun limestone, a 3 km thick Late Triassic to Late Creta- ceous (Cenomanian) carbonate sequence, as well as by Triassic to ) Cretaceous Kermanshah radiolarites and then by Zagros Fold- Thrust Belt (ZFTB) sedimentary rocks. The Kermanshah ophiolite was thrust over the Bisotun limestone during Maastrichtian–Palae- continued ( ocene time, evidenced by ophiolitic clasts in the Maastrichtian– Shahr-e-Babak ophiolite Balvard-Baft ophiolite 800 km Ophiolite, size Size Mantle lithology Crustal Palaeocene Amiran Conglomerate Formation of the ZFTB (Braud, Table 1 1987). 36 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 o o o o o o o o o o o Alps10 E J 20 E 30 E 40 E 50 E 60 E 70 E 80 E 90 E 100 E 40 N Budapest J Ligurian Zagreb Tethyan ophiolites EURASIA Tethyan Suture Zones J Black Sea Caucasus J=Mostly Jurassic Samarkand Pontides Tarim Basin K=Mostly Cretaceous J Ankara o Kohistan 30 N Taurides Bitlis-Zagros Suture ZoneCaspian Mediterranean Sea K Sea Lhasa K K K K Tehran J Troodos Sabzevar Baghdad K Yarlung-Zangbo Suture Zone Nain Birjand K K Muslim Bagh Delhi Neyriz ARABIA o Persian Gulf K INDIA 20 N Haji-Abad J Bela AFRICA Red Sea Makran Indian Ocean K Semail ? Fig. 1. Distribution of Tethyan ophiolitic rocks in Alpine–Himalayan orogenic belt (modified from Dilek and Flower, 2003). We can subdivide the Kermanshah and neigboring Iraqi Zagros The Late Cretaceous Neyriz ophiolite is composed of mantle and ophiolites (Ali et al., 2012, 2013) into three subgroups: (1) Triassic crustal units capped by Cenomanian–Turonian to Early Santonian to Cretaceous oceanic lithosphere (passive margin ophiolite) pelagic anhydritic limestones of the Tarbour Formation. The ophi- including OIB-type and E- to N-MORB-type gabbros and metagabb- olite was thrust over the Pichakun and mélange sheets in Turonian ros, dikes (and a fragmented sheeted dike complex) and lavas asso- to Maastrichtian time (e.g., Alavi, 1994; Babaei et al., 2006), expos- ciated with fertile meta-lherzolites. This lithosphere may mark a ing and allowing erosion of the ophiolite and accumulation of such rifted continental margin developed during early Neotethys open- clasts in Late Cretaceous–Paleocene conglomerates (Lanphere and ing (Saccani et al., 2013). (2) Late Cretaceous oceanic lithosphere Pamic, 1983). composed of SSZ-type gabbros and cumulates (including trocto- The mantle sequence contains depleted to impregnated harz- lites) within mantle harzburgites, SSZ-harzburgites and IAT to burgites, layered leucogabbro, olivine-bearing melanogabbro and calc-alkaline lavas, representing early arc magmatism (Shafaii pyroxenite cumulate sills and lenses (Fig. 6C) with screens of resid- Moghadam and Stern, 2011); and (3) Paleocene–Eocene ophiolites ual dunite, podiform chromitite, pyroxenitic sills/dikes, pegmatite with calc-alkaline to E-MORB and P-MORB-like pillow lavas, felsic– gabbros, gabbroic dikes/sills, isotropic melano- to leuco-gabbros mafic dike swarms and plutonic rocks, denoting mature intraoce- and diabasic–basaltic–andesitic dikes (Fig. 7A). The Neyriz ophio- anic arc magmatism (Azizi et al., 2011). lite crustal sequence is best represented by 700–900 m thick The Kermanshah Late Cretaceous ophiolite near Kamyaran com- faulted sheeted dike complex and pillowed to massive lavas asso- prises mantle and crustal rock sequences. The crustal sequence ciated with chert and Late Cretaceous pelagic limestone. (>3000 m thick) is characterized by well-developed pillow lavas. It is difficult to distiguish Late Cretaceous lavas (pillow and/or mas- 3.1.6. Haji Abad (Esfandagheh) ophiolite sive-type) from Eocene ones in the field. We distinguished Globo- The Late Cretaceous Haji Abad (Esfandagheh) ophiolites and truncara bearing-Late Cretaceous pelagic limestones between associated arc-related rocks in southern Iran cover 2000 km2 some calc-alkaline pillow lavas that were previously thought to near the MZT fault (Fig. 2). The Haji Abad ophiolite is in tectonic be Eocene (Fig. 6B). contact with high-pressure blueschists of the Sanandaj–Sirjan zone (SSNZ), dated as 85–95 Ma (Agard et al., 2006). These are products of high P/T metamorphism in a Late Cretaceous subduction chan- 3.1.5. Neyriz ophiolite nel, exhumed in Early Paleogene time (Shafaii Moghadam and In the Neyriz region there are three imbricated sheets, from bot- Stern, 2011). The ophiolitic units including mantle peridotite tom (SW) to top (NE): Pichukan series, mélange units, and ophio- together with gabbroic/anorthositic dikes/sills are metamorphosed lite (Table 1; Fig. 2; Ricou et al., 1977). The Pichakun series is a at the contact with SSNZ metamorphic units. sequence of Late Triassic limestone, Middle Jurassic oolitic lime- Two distinct mafic–ultramafic complexes exist in the Haji Abad/ stone and Lower–Middle Cretaceous conglomeratic limestone, rep- Esfandagheh region; the older Sikhoran complex in the north, with resenting Neo-Tethys pelagic sediments (analogous to the Bisotun Upper Triassic–Cretaceous ages (Ghasemi et al., 2002; Ahmadipour limestone and radiolarites of Kermanshah). The Pichakun series is et al., 2003), and the younger, Late Cretaceous Haji Abad ophiolite wedged between two thrust sheets of sheared mélange (Pamic and in the south near the MZT. The Sikhoran complex comprises, from Adib, 1982; Babaei et al., 2001). Above the Pichukan series, the bottom to top, cumulate dunite–harzburgite and stratiform-like mélange (or passive margin ophiolite) consists of exotic blocks of chromitite, wehrlite and pyroxenite cumulates (Ghasemi et al., Permian–Triassic Megalodon-bearing limestone associated with 2002). The cumulate sequence is overlain by crustal isotropic gab- radiolarites and alkaline (OIB-type) to tholeiitic pillow lavas bros. No volcanic rocks or sheeted dikes are associated with the (Arvin, 1982; Babaei et al., 2006). The upper mélange is tectonically Sikoran complex, so this may be a layered mafic–ultramafic intru- overlain by Late Cretaceous ophiolite slices, and both ophiolite and sion, not an ophiolite. This interpretation is supported by the mélange thrust sheets are transported over Cenomanian–Turonian observation that the Sikhoran complex contains late-stage true shallow water carbonates (Sarvak Formation; Alavi, 1994). The granitic dikes and shows thermal metamorphism at its contact. contact of the lower mélange with the underlying autochthonous This older complex shows faulted/intrusive contacts with marble Sarvak Formation is marked by a mylonitic amphibolite sole and amphibolites of the Sargaz–Abshur complex and is intruded (Babaei et al., 2005). by Late Triassic–Early Jurassic isotropic gabbros (Ghasemi et al., Table 2 Summary of Iranian Mesozoic ophiolites (Birjand–Nehbandan, Sabzevar and Makran) characteristics. Ophiolite Size Mantle Crustal Crust/ Radiometric Type of Age of Lava Temporal Cpx Mafic/felsic Cr# spinel Associated Crustal Ophiolite Proposed References lithology lithology mantle ages overlying sediments geochemistry changes of TiO 2 in lavas metamorphic sequence classification tectonic ratio sediments lavas lavas rocks thickness setting Sabzevar ophiolites 1500–45002 km Harzburgite, Isotropic 2/5 106–107 Ma Pelagic Late IAT, calc- Intercalated? 0.2–0.5 Mafic > felsic 0.1–0.85 Lawsonite- >3000 m Volcanic-arc Above S- This study, lherzolite, gabbro, (metamorphic sediments, Campanian to alkaline and in bearing type dipping Rossetti dunite and cumulate rocks), 78– turbidites, Early boninite with gabbros blueschist, subduction et al. (2010, chromitite gabbro, 100 Ma for with minor Maastrichtian minor OIB granulite, zone, 2013) with dike sheeted dike plagiogranites pyroclastic greenschist forearc complex, rocks and with plagiogranite, amphibolite mature arc pillow lava 2 Oryan-Bardaskan 5000 km Harzburgite, Ultramafic to 3/1 – Pelagic Late Boninite, IAT, ? – Mafic > felsic – – ? Volcanic-arc- Above S- This study ophiolite lherzolite mafic limestones Cretaceous calc-alkaline type dipping with cumulate, subduction diabasic pillow lava zone, 31–59 (2015) 100 Sciences Earth Asian of Journal / Stern R.J. Moghadam, H.S. dikes, forearc chromitite with mature arc 2 Torbat-e-Heydarieh 3000 km Harzburgite, Pillow lava 1/3 97–98 Ma U– Pelagic Late IAT, calc- ? 0.1–0.2 Mafic > felsic 0.1–0.6 Amphibolite, >1000 m SSZ-type Back-arc This study ophiolite dunite and Pb zircon) sediments Cretaceous alkaline with in greenschist basin chromitite minor MORB, gabbros behind the with BABB? Sabzevar diabasic arc? dikes and gabbroic lenses Birjand–Nehbandan > 500 km Harzburgite, Ultramafic to 2/3 87–83 (Rb-Sr), Pelagic Early to Late IAT, calc- Intercalated 0.05– Mafic 0.2–0.5 in Blueschist and >3000 m MORB to SSZ Supra- This study, ophiolites length  100 km dunite, mafic 86–89 U–Pb) limestones, Cretaceous alkalne and MORB and 1.1 lavas > felsic peridotites, eclogite subduction Babazadeh wide chromitite cumulates, on radiolarites, MORB with SSZ-type lavas 0.5 in zone and De with gabbro, metamorphic pyroclastic minor OIB lavas? pillow lavas Wever diabasic– plagiogranite, rocks; 107– rocks and (2004), gabbroic pillowed to 113 gabbro turbidites Zarrinkoub dikes massive lavas et al. (2012), Brocker et al. (2013) and Tirrul et al. (1983) Jurassic to Calc-alkaline, ? – Mafic 0.5–0.8 in Blueschist, ? Accretionary Supra- McCall Makran ophiolite 200 ⁄ 300 km Harzburgite, Cumulate 3/1 120 Ma Pelagic sediments, Early IAT, MORB lavas > felsic ultramafic amphibolite prism-type subduction (1985), dunite ultramafic (gabbro, K-Ar); pyroclastic Paleocene lavas cumulates and Bajgan- zone McCall rocks, 145–111 U– rocks and Durkan (2002) and cumulate Pb; turbidites metamorphic Hunziker gabbros, trondhjemite) rocks et al. isotropic (2011) gabbros, plagiogranite, SDC, pillow 2 lava Kahnuj ophiolite 600 km – Cumulate and 3/1 156 and Pelagic Aptian- VAT and MORB to 0.33– Mafic – Amphibolites; ? SSZ-type Back-arc Kananian isotropic 136 Ma or limestones Cenomanian MORB, SSZ-type? 2.1 lavas > felsic Bajgan- basin et al. gabbros, SDC, 144–139 Ma (BABB) lavas Durkan (2001), pillow lavas, (gabbro); 124– metamorphic Ghazi et al. trondhjemites 146 (Ar-Ar) complex (2004) and diorite Arvin et al. (2001) 37 38 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 Khoy-Maku belt Paleozoic ophiolite belt Khoy 566-595 Ma Sangbast-Shandiz Caspian Sea Fault Khoy Sabzevar-Torbat-e-Heydarieh Rasht Lahijan ophiolite belt Takab 551-572 Ma Binalud Mountains 548-568 Ma Sabzevar NW -SSZ Zanjan 544-551 Ma Soursat 544-599 Ma Tehran Mashhad 34° 540 Ma Kermanshah Torud-Biarjmand 522-566 Ma Fig. 8 Zagros IB Fig. 3 Muteh Birjand- 578-596 Ma Sanandaj-Sirjan Anarak Nehbandan Zagros OB Birjand belt Nain Yazd Block Zagros Fold- TabasSaghand Block Fig. 9 Dehshir Lut Block Zone 525-547 Ma 30° Thrust Belt N Shahr-e-Babak Neyriz Balvard Baft Persian Gulf Haji-Abad Iranshahr Kahnuj Jaz Murian depression Fig. 10 26° Fanuj-Maskutan Gulf of Oman 200km Makran belt 50°E 54° 58° Central Iranian block Late Cretaceous oph. belt Lut-Tabas-Yazd consolidated blocks Early Cretaceous oph. belt Alborz continental block Late Jurassic-K. oph. belt Mesozoic ophiolites Paleozoic ophiolite belt Paleozoic ophiolites Major faults Ediacaran-Cambrian (Cadomian) terranes Fig. 2. Simplified geological map of Iran emphasizing the main ophiolitic belts (thick dashed lines) and places where Cadomian (600–520 Ma) radiometric ages are documented (stars). Numbers show U–Pb zircon ages (the age of Soursat is from Jamshidi Badr et al., 2011; from Khoy is from Azizi et al., 2011; other ages are from Hassanzadeh et al., 2008). 2002). The contact between the older northern ophiolite (Sikhoran) so relationships and overall thickness are not clear. These include and the younger Haji Abad ophiolite to the south is faulted. These >2000 m thick boninites and 1000 m thick E-MORB-type pillow mafic–ultramafic complexes are intruded by Late Triassic–Early lavas (Shafaii Moghadam et al., 2012). Boninitic lavas are overlain Jurassic isotropic gabbros and Cretaceous diabasic dikes by and interbedded with minor IAT lavas. There is also a thick (Ghasemi et al., 2002). sequence of calc-alkaline lavas but thickness is unclear because The Haji Abad ophiolite formed in Late Cretaceous time. The of faulting. ophiolite displays a disrupted pseudostratigraphy comprising from bottom to top: depleted mantle tectonites (harzburgites, impreg- 3.2. Zagros inner belt ophiolites nated harzburgites), ultramafic cumulates (dunite, chromitite, lherzolite, pyroxenite and wehrlite), plagiogranite, and a volcanic Most researchers consider ZIB ophiolites as ophiolitic mélange sequence. The well-developed volcanic complex consists of pillow that marks a Neo-Tethyan oceanic basin between the SNSZ and basalts and massive mafic to felsic lavas and shows faulted con- Lut blocks (e.g., Berberian and King, 1981; Arvin and Robinson, tacts with other units, especially serpentinized peridotite. Lava 1994; Arvin and Shokri, 1997; Glennie, 2000). Other researchers flows are overlain tectonically or stratigraphically by Late Creta- infer that the marks a Campanian back-arc basin (e.g., Stampfli ceous (Cenomanian) pelagic limestone. The volcanic section con- and Borel, 2002; Agard et al., 2006; Shafaii Moghadam et al., sists of three types of pillow lavas that occur in different places, 2009; Mehdipour Ghazi et al., 2012), which was a narrow seaway H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 39 Maku 39˚00´ Khoy-Maku ophiolites TURKEY Khoy Serow 38˚00´ MZT Connecting pathway? Piranshahr-Serow ophiolites Sanandaj-Sirjan Zone 37˚00´ Naqadeh Hassanbag Kermanshah-Kurdistan ophiolites Zagros Fold-ThrustGalalah Belt choman Piranshahr Sardasht Baneh 36˚00´ Mawat IRAN Penjween IRAQ Marivan Sanandaj 35˚00´ border Hamadan Plio-Quaternary volcanic rocks Kamyaran Walash-Kermanshah volcanosedi. unit Paleogene ophiolite Naopurdan volcanosedimentary unit Kermanshah Sahneh Paleogene Late Cretaceous ophiolites Avroman-Bisotun limestones 34˚00´ Triassic-Cretaceous Qulqula-Kermanshah radiolarites Triassic-Cretaceous 50 Km Paleozoic Metamorphic rocks 44˚00´ 45˚00´ 46˚00´ 47˚00´ Fig. 3. Simplified map showing the distribution of the Khoy–Maku and Kermanshah ophiolites with emphasis on the Piranshahr–Serow ophiolites that seem to connect these two belts (Modified after Ali et al., 2013). with discontinuous oceanic crust (Shafaii Moghadam et al., 2009). 2000 m thick and includes a sheeted dike complex and overlying The NE limit of ZIB is buried beneath younger deposits and may lavas (Fig. 7B). The sheeted dike complex contains mafic and felsic link up with Sabzevar ophiolites in NE Iran (Fig. 2). dikes associated with more depleted gabbronoritic dikes showing Below we discuss four large ZIB ophiolites: Nain, Dehshir, mutually intrusive contacts. Pillowed and massive lava flows Shahr-e-Babak, and Balvard–Baft (Fig. 2). overly the sheeted dike complex. Globotruncana-bearing Late Cre- taceous pelagic limestones overlie the pillow lavas and are found 3.2.1. Nain ophiolite as thin screens between pillows. Pelagic limestones are uncon- The Nain ophiolite (Table 1) is dominated by a mantle sequence formably overlain by grey sandy Paleogene limestones with a basal with isolated outliers of crustal rocks. The mantle sequence is conglomerate. mainly moderately depleted harzburgite with minor plagioclase lherzolite formed by impregnation. Pyroxenitic, gabbroic, gabbron- 3.2.2. Dehshir ophiolite oritic and diabasic dikes and sills crosscut the Nain mantle The Dehshir ophiolite (Table 1) consists of excellent crust and sequence (Fig. 7B). The Nain ophiolite crustal sequence is mantle exposures, most recently studied by Shafaii Moghadam 40 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 MAKU Shah Bandalu Dibak 39˚15´ Khan Gol Mazraeh 20 Km Quaternary Ararat & Tendurak basalts Plio-Quaternary Siah- Cheshmeh andesite-dacite 39˚00´ Late Cretaceous-Paleocene ^ turbidites ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ L. Cretaceous-Early ^ ^ ^ ^ Geldgh^ ^ ^ ^ ^ Paleocene pelagic limest. ^ ^ ^ ^ ^ ^ Tectonic melange, turbidite ^ epiclastic rocks with basaltic ^ sill, Late K-Early P. limestones ^ ^ ^ ^ Zurabad ^ ^ Late Cretaceous pelagic ^ ^^ sediments ^ ^ ^ ^ ^ ^ ^ Galavans 38˚45´ ^ ^ ^ ^ ^ ^ ^ Pillow lava, massive lava ^ ^ ^ ^^ ^ ^ ^ ^ ^ ^ . . . . ^ . .. ^ ^ ^ ^ ... . Gabbro, locally layered ^ ^ ^ ^ ^ Dizeh ^Tudan ^ ^ Paleocene Late Cretaceous-Early ^ ^ ^ ^ . ^ ^ Peridotite, serpentinite ^ ...... ^ . . . . ^ ^ . . Firoraq ^ ^ .. ^ ^ . ^ ^^ ^ ^ ^ ^ ^ ^ ^ ^ ^ KHOY ^ ^ ^ ^ ^ ^ Cadomian granite, gneiss ^. . . ^ ^ 38˚30´ . . ^ ^ ^ . . . ^ ^ 566-595 (U-Pb dating) . . ^. ^ . . . . ^ ^ . . . . ^ . . . ^ . . . ^ ^ 550 Ma (U-Pb dating) . . ^ ...... ^ . . . . ^ ^ Metamorphic rocks TURKEY . ^ ^ ^ ^^ Phyllite, schist, gneiss ^^ ^ ^ ^ ^ Ediacaran-Cambrian ^ ^ ^ ^ 44˚15´ 44˚30´ 44˚45´ Fig. 4. Simplified geological map of Khoy–Maku ophiolites (modified after Ghoraishi and Arshadi, 1978 for Khoy and Alavi and Bolourchi, 1975 for Maku 1/250,000 maps). and Stern (2011). The Dehshir ophiolite mantle sequence com- 3.2.4. Balvard–Baft ophiolite prises harzburgite, clinopyroxene-bearing harzburgite, and cumu- The Balvard–Baft ophiolite (Table 1) defines a 5–10 km wide late rocks. The Dehshir ophiolite crustal section (400–500 m WNW-trending belt that extends NW toward Shahr-e-Babak and thick) comprises pillowed basalts, basaltic and basaltic–andesitic SE to the Dare–Pahn and Haji Abad ophiolites. The Balvard–Baft massive flows, and a basaltic–dacitic sheeted dike complex. Plagi- mantle sequence consists of harzburgite, minor lherzolite with dia- ogranite occurs both as dikelets injected into isotropic gabbros and basic dikes and pockets of isotropic and pegmatitic gabbro. Crustal as small plugs emplaced in metamorphosed (lower greenschist units consist of pillow lavas, basaltic–andesitic–dacitic lava flows, facies) pyroclastic rocks. and basaltic–andesitic–dacitic sills in pyroclastic rocks and total >2300 m thick. Pyroclastic rocks rest unconformably on basaltic lava flows (Shafaii Moghadam et al., 2013a). The Balvard–Baft 3.2.3. Shahr-e-Babak ophiolite ophiolite is in fault or unconformable contact with Middle to Late The Shahr-e-babak ophiolite (Table 1) lies 100 km SE of Deh- Eocene sedimentary-volcanic sequences related to the Urumieh– shir and is bounded to the west by the Dehshir–Baft fault, to the Dokhtar arc. SSW by SNSZ metamorphic rocks and to the NNE by the Dehaj– Sarduiyeh magmatic belt, part of the Cenozoic Urumieh–Dokhtar arc. It consists of both mantle and crust sequences. The mantle 3.3. Sabzevar–Torbat-e-Heydarieh ophiolitic belt sequence is dominated by highly serpentinized harzburgites. Iso- tropic gabbros as small lenses cut by plagiogranitic veins are com- The Sabzevar–Tobat-e-Heydarieh ophiolite belt (STOB) is situ- mon within the mantle sequence. The volcanic sequence is ated in NE Iran (Fig. 2) where it trends E–W for over 400 km. STOB composed of basalt, andesite, dacite and rhyolite associated with is bordered to the north by the major Sangbast–Shandiz strike-slip pyroclastic rocks. The lavas are either massive flows or associated fault delimiting the Binalud Mountains. To the south, the STOB is with pyroclastic rocks and interbedded with Coniacian–Maastrich- bounded by the major Dorouneh sinistral strike-slip fault (Fig. 8) tian pelagic sediments (Fig. 6D). Massive and pillowed lavas overlie delimiting the Lut Block. STOB comprises three main alignments the interbedded volcanic sequence. Shallow dioritic–granitic plu- (Fig. 8), separated by the Paleocene–Eocene Oryan sedimentary tons and trachytic dikes intrude the massive lavas. basin: (1) ophiolites NNW of Sabzevar (the Sabzevar ophiolite); H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 41 Khoy ophiolite Radiolarite-tuff-breccia Ankaramitic breccias & lavas Pillow lava Maku ophiolite Turbidites Maku-Mazraeh section Siah-Cheshmeh section Epiclastic breccias & tuffs Late Cretaceous Pelagic limestones OIB-type basalts pelagic sediments Epiclastic rocks Volcanic breccia Basaltic sill Basaltic calc-alkaline Basaltic sill/dike fragments Massive basaltic sheet flows OIB-type Epiclastic rocks Pillow lava sequence Pillow lava sequence Tuff-breccia Hyaloclastic rocks (Ankaramitic) Diabasic dike Basaltic sill 500 m Crustal gabbros 500 m Radiolarite/tuff Gabbroic lens + Turbidite-sandstone + Pelagic limestone Ultramafic-mafic cumulates . .. Diabasic dike Late Cretaceous Khoy ophiolites Supra-ophiolitic series .. + Mantle lherzolite + 1km Mantle lherzolite-harzburgite . + . + Gabbroic- ...... Gabbroic-pyroxenitic dike pyroxenitic dike Gabbroic lens Gabbroic lens Wehrlitic intrusion (Modified after Poor Mohsen et al., 2010) (Modified after Khalatbari Jafary et al., 2003) Fig. 5. Simplified stratigraphic columns diplaying idealized internal lithologic succesions in the Late Cretaceous–Early Paleocene Khoy (A) and Maku ophiolites (B), (modified after Khalatbari-Jafari et al., 2003 for Khoy and Poor Mohsen et al., 2010 for Maku ophiolites). (2) ophiolites SSW of Sabzevar (the Oryan–Bardaskan ophiolites); within the sheeted dike complex; and (5) pillowed and massive and (3) ophiolites north of Torbat-e-Heydarieh. These ophiolites basalts. Shojaat et al. (2003) recognized three chemical varieties are overlain by Upper Cretaceous to Paleocene extrusive rocks, of mafic rocks: (1) N-MORB basalt and gabbro; (2) E-MORB basalts associated with volcanoclastic sediments, pelagic limestones and and (3) arc basalts. Baroz and Macaudiere (1984) distinguished radiolarian cherts. To the NNE, the Sabzevar ophiolite is associated four lithostratigraphic units overlying the ophiolite, from Campa- with mainly mafic protoliths metamorphosed to lawsonite-bearing nian to Paleocene, including alkaline to calc-alkaline pillow lavas, blueschist (lawsonite, epidote, albite, crossite, phengite, garnet), litharenites, breccias and agglomerates with pelagic sediments. granulite and greenschist (Rossetti et al., 2010; Omrani et al., The lavas grade upwards into turbiditic sandstone/breccias and 2013). The Paleocene-Eocene sedimentary basin separating the pyroclastic deposits containing OIB-type basaltic fragments. Late three ophiolitic alignments is composed of transgressive flysch Cretaceous to Paleocene pelagic limestone is interlayered with atop the ophiolite with arc volcanic remnants. We briefly discuss these turbidites. Pelagic sediments also stratigraphically cover the three ophiolite remnants below, which are summarized in the pillow lava sequence (Fig. 7C). The geodynamic reconstruction Table 2. of Shojaat et al. (2003) included: (1) generation of back-arc basin oceanic crust in middle Late Cretaceous time; (2) deposition 3.3.1. Sabzevar ophiolite of the volcano-sedimentary series, fed from a Late Cretaceous– Ophiolites NNW of Sabzevar define a belt about 150 km long Paleocene arc; and (3) collision of the arc with the Lut block. and 10–30 km wide along the northern margin of the Lut Block. This ophiolite is part of a northern branch of Neotethys known as 3.3.2. Oryan–Bardaskan ophiolite the Sabzevar Ocean that opened and closed during the Late Creta- The Oryan–Bardaskan ophiolite (Fig. 8) is mostly composed of ceous (Lensch et al., 1980; Sengor, 1990). volcanic rocks, although mantle peridotites with crosscutting dia- Harzburgite, lherzolite, dunite and chromitite are the major basic dikes, chromitites and gabbros are also common. Ultramafic components of the Sabzevar mantle sequence. Large chromitite cumulates including plagioclase- and amphibole-bearing lherzo- deposits occur in the Gaft and Forumad regions (Shafaii lites and harzburgites are abundant, grading upward into coarse- Moghadam et al., 2013b). Dunite occurs as lenses/layers or irregu- grained cumulate gabbros. The ophiolite is crosscut and covered lar sill-like intrusions within harzburgites (Fig. 6E). Wehrlitic by younger, Eocene plutonic and volcanic rocks, which show (rarely gabbroic) sills and dikes in the Gaft region crosscut all units faulted contacts with the Cadomian(?) Taknar basement (Fig. 8). including chromitite, dunite and harzburgite (Shafaii Moghadam There are no detailed studies on this STOB segment. The sedimen- et al., 2013b). tological and paleogeographical features of Mesozoic and Cenozoic Sabzevar crustal rocks are divided into five subunits: (1) isotro- strata of the Oryan basin are considered as a series of gravitational pic gabbro lenses; (2) cumulate gabbro/gabbronorite/leucogabbro nappes (Lindenberg et al., 1983). Oryan–Bardaskan ophiolitic (with minor diorite) with local layering associated with minor mélange is interpreted as tectonic breccia at the base of the oldest ultramafic cumulates in Soleimanieh, Tabas and Baghjar; (3) a nappes. Volcano-pelagic series of the Oryan zone include Cenoma- highly fragmented and sheared sheeted dike complex, but clearly nian to Maastrichtian pelagic sediments interbedded with pyro- with dike-into-dike relationships, with early basaltic to andesitic clastic and andesitic to dacitic lavas (Lindenberg et al., 1983). basaltic dikes and late dacitic dikes; (4) plagiogranite lenses. These This sequence grades upward into shallow water sediments of are often found within cumulate gabbro associated with abundant Maastrichtian to Paleocene age (Lindenberg et al., 1983). These crosscutting micro-dioritic to dacitic dikes and as small pockets strata are overlain by Early Eocene to early Middle Eocene Oryan 42 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 Fig. 6. Field photographs of Outer Zagros ophiolites including Khoy–Maku ophiolites. A – The stratigraphic position of pelagic limestones between thick volcanic sequences of the Maku ophiolites. B – Pillow lavas near Kherran village (Kermanshah ophiolite). C – Layered leucogabbro, olivine-bearing melanogabbro and pyroxenite cumulate sills within Neyriz mantle sequence. D – Late Cretaceous pelagic limestones interbedded with pyroclastic rocks in Shahr-e-Babak ophiolite. E – Discordant dunites within mantle Opx-rich harzburgites in Shareh region (Sabzevar ophiolites). F – The faulted contact between Bajgan metamorphic complex and Sorkhan–Rudan ultramafic rocks within the outer Makran ophiolites. marine sediments (lower and middle Oryan sediments). Lower and to Cheshmeshir and beyond (Fig. 8). This is the largest unstudied middle Oryan sediments include marine conglomerates, turbiditic ophiolite in Iran. sediments, reefoid limestones, marls and Nummulitic limestones (Lindenberg et al., 1983). These sediments are overlain stratigraph- ically by late Middle Eocene upper Oryan series of continental 3.4. Birjand–Nehbandan (Eastern Iranian) ophiolitic belt affinity. These relationships indicate that the STOB seaway was open until upper Middle Eocene time. Another belt of Cretaceous ophiolites is found in eastern Iran, adjacent to the western margin of the Afghan block (Shafaii Moghadam and Stern, 2014; see Fig. 1). The N–S trending Sistan 3.3.3. Torbat-e-Heydarieh ophiolite suture demarcates the boundary between the Lut (eastern segment This ophiolite lies N of Torbat-e-Heydarieh and constitutes the of the central Iranian micro-continent) and the Afghan continental southeastern STOB covering an area 60 km long and 50 km wide blocks (Table 2). The main ophiolites from north to south include (Fig. 8). It is mostly composed of mantle peridotite, especially the Birjand ophiolite, the Nehbandan ophiolite complex (Delavari Opx-rich harzburgite with minor dunite and chromitite. Diaba- et al., 2009; Saccani et al., 2010) and the Tchehel Kureh ophiolite sic–gabroic–pyroxenitic and plagiogranitic dikes crosscut the man- (Fig. 9). Generation and emplacement of these ophiolites reflect tle sequence. Abundant massive and pillowed basalts are the consumption of the Sistan arm of Neotethys with subduction metamorphosed to greenschist to lower amphibolite facies. Late polarity to the east, beneath the Afghan block, and the subsequent Cretaceous pelagic sediments associated with pyroclastic rocks collision between the Lut and Afghan continental blocks (e.g., are interlayered with and conformably overly the lavas. The ophi- Tirrul et al., 1983). Radiolarites of the Ratuk complex in the Sistan olite is unconformably overlain by Paleocene-Eocene conglomerate Suture Zone are characterized by two faunal assemblages of Early and sandstone. Aptian and middle Late Albian ages (Babazadeh and De Wever, There is also a long arcuate belt of ophiolites and ophiolitic 2004). Deep-water sedimentation continued until Early Eocene mélange that stretches for 150 km from east of Torbat westwards time (Saccani et al., 2010). Tirrul et al. (1983) suggested that H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 43 (A) Neyriz ophiolite Tarbor Formation (C) Sabzevar ophiolite Unconformity Pliocene conglomerates ^ pillow lava ^^^^^ Miocene red-type sandstones Late K pelagic limestone Marls & limestones ^ ^ ^ ^ sheeted dike complex massive lava ^ ^ Eocene volcanic rocks & wehrlite, pyroxenite, coarse-grained gabbro + + pyroclastic rocks gabbro cumulates + + + + + _ + plagiogranite _ _ _ _ _ _ _ _ _ ______Paleocene to Eocene tectonic melange Dacitic-rhyolitic dome gabbroic-diabasic dike/sill impregnated peridotite with Eocene red-type conglomerates + + + + + + + Arc lavas and sediments + + + isotropic gabbro- + Turbiditic sequence with intercalation of + leucogabro Late Cretaceous-Early Paleocene? + pelagic limestone pelagic limestone & OIB pillow fragments (Late K-early Paleocene?) ^ ^ ^ ^ ^ ^ ^ ^ harzburgite ^ ^ ^ ^ ^ ^ chromitite pod ^ OIB-type pillow lava ^ ^ + ^ ^ ^ ^ ^ ^ + ^ Late Cretaceous pelagic limestone + pegmatite gabbro ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ Calc-alkaline to IAT pillow lava residual dunite + ^^^ ^ ^ ^ ^ ^ ^ ^ + ^ + + + Plagiogranite + + Sheeted dike complex + + + = = = = = + = = = = = + = Layered ultramafic-mafic tectonic contact 500 m = = Plagiogranitic lens = = == = = = = = + = cumulates ======amphibolitic sole = = = = = CRUSTAL SEQUENCE CRUSTAL = = = = = Dacitic/diabasic dike + + (B) Nain ophiolite + Plagiogranite dikelet + + + diabasic sill + neritic limestone + + + Diabasic dike Gabbroic dike swarm + chert .. ++ pelagic limestone . . . . + . . . . Isotrope gabbro/diorite pillow lava Late Cretaceous ophiolites ... . Sheeted dike complex ++ +++ ^^^ ^ +++ ^ ^^^ ^ massive lava Podiform chromitite amphibole gabbro +++ ^ ^ plagiogranite + Discordant dunite lens/dike diabasic dike + + + + + + 3 km + + + isotropic gabbro- + + . + coarse-grained + . . . . gabbronorite Melt conduits/concordant + + . . ... sulfide-bearing .. . .. deep seated intrusives + ...... Opx layering gabbro . . melt impregnation ..... + .. MANTLE SEQUENCE Diabasic-pegmatite gabbro ... + + . to pyroxenitic dike + .. chromite pod + Mantle lherzolite, harzburgite + + gabbroic-pyroxenitic + + depleted harzburgite & dunite + + dike + + + + pegmatite gabbro pyroxenitic sill + + + + Retrograded granulite + Lawsonite-blueschist, + + + ^ ^ ^^^ + + ^ ^ ^ ^ ^ Melt segregations + + epidote amphibolite tectonic contact 500 m Tonalitic to trondhjemitic lenses garnet amphibolite U-Pb dating= 105-107 Ma (Rossetti et al., 2010) (not sole) Fig. 7. Simplified stratigraphic columns displaying idealized internal lithologic succesions in a typical Outer Zagros (A) and Inner Zagros ophiolites (B) (Neriz and Nain ophiolites). (C) Idealized lithological succesions in the Sabzevar Late Cretaceous ophiolites. Gaft Joghatay ^ ^ Sabzevar ophiolite ^ ^ ^ Late Cretaceous-Early Paleocene Late Cretaceous- ^ ^ ^ + ^ ^ + + + + ^ ^ ^ ^ ophiolite Eocene arc ^ 30 km ^ ^ ^ ^ ^ ^ ^ ^ Forumad ^ ^ ^ ^ ^ ^ ^ ^ ^ Pelagic sediments Dacitic dome (adakite) ^ ^ ^ ^ ^ ^ ^ Soltanabad ^ ^^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ~ ~ ~ ~ Lava flow, pillow lava ^ Basaltic-andesitic ~~~ ~ ~ ^^ ^ ~ ~ ^ ~ ^ tectonic melange -dacitic lavas, breccia ^ + + + ^ 36°15΄ ^ + + + + ^ + + + ^ + + + + + + Cumulate gabbro + Diorite-granodiorite Baghjar Garmab Serpentinite, peridotite Precambrian (Lut basement) Sabzevar Meta-rhyolite; schist Neyshabour ~ ~ Metamorphic rocks (HP) ~~ Taknar Formation Paybaz + + P ^ + ^ + 36°00΄ + + + +^ + + + + a +^ + + + + + Ghasem abad ^ + ^ + ^ ^ ^^ + + + + + l + ^ + ^ + + e + + ^ Banghan + + ^ + ^ Torbat-e-Heydarieh ophiolite + + + + + + + + ^ Hamireh + o ^ + + ^ + + ^ + + ^ c ^ + + ^ + e ^ ne ^ -E Derakht-e-Senjad Oryan oc + 35°45΄ en + e + S + e + Fariman dimentary Kadkan + Dehnow Robat-e-Sang + + + + Qale Now + + + ^ + ^ + + + ^ + + ^ + Raush + + ^ ^ 35°30΄ ^ + + + ^ ^ ^ ^ + ^ + ^ ^ ^ ^ ^ ^ Cheshmeshir ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ ^^ ^ ^ ^ ^ ^ ^ ^ ^ + + ^ ^ + ^ ^ + ^ + ^ ^ ^ ^ + + + ^ + ^ ^ ^ ^ + ^ ^ + Abbasabad ^ ^ + + + ^ ^ + ^ ^ + + + + + + + + + + + + + + + ^ Oryan-Bardaskan ophiolite + + + + + + + ^ ^ + + ^ ^ + + ^ + ^ Torbat-e-Heydarieh ^ ^ ^ + ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ Azghand ^ ^ ^ ^ Dorouneh Fault Uchpalang ^ ^ ^^ ^ ^ ^ ^ ^ ^ ^ ^ ^ 35°15΄ ^ Bardaskan ^ ^ ^ Kashmar ^ ^ ^ Lut Blo ^ c ^ k ^ ΄ ΄ ΄ ΄ ΄ ΄ ^ 58°45 59°45 59°15 58°15 57°15 57°45 Fig. 8. Geological map of the Sabzevar–Torbat-e-Heydarieh region, north of the Dorouneh Fault, with emphasis on the distribution of ophiolitic and arc-related rocks. isolated Turonian (90 Ma) limestone blocks represent Birjand– was reported for epidote–amphibolite facies rocks (Fotoohi Rad Nehbandan cover. et al., 2009). These high-pressure metamorphic rocks are uncon- Subduction-related blueschists and eclogites associated within formably overlain by Maastrichtian Rudist-bearing limestones Birjand ophiolites give Early to Late Cretaceous radiometric ages (Tirrul et al., 1983). (Fotoohi Rad et al., 2005; Brocker et al., 2010; Brocker et al., Birjand ophiolites are divided into Neh and Ratuk complexes 2013). P–T estimates for eclogite and blueschist indicate ca. 1.5– and Sefidabeh sedimentary basin deposits (Tirrul et al., 1983) 2.4 GPa and ca. 450–650 °C, whereas ca. 0.5–0.7 GPa, 520–590 °C (Fig. 9). The Neh and Ratuk complexes, which represent an accre- 44 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 59o E 60o 61o Birjand ophiolite AFGHAN BLOCK ++ Paleogene-Neogene + volcanic rocks + T + Paleogene Birjand h + flysch deposits + ophiolite e o Late Cretaceous 33 flysch deposits Birjand Early-Late K limestone -radiolarite S 500 m Pillowed/massive lavas IAT/E-MORB i s t E-MORB/IAT type a gabbroic dike/lens n Diabasic dike Mantle tectonite 32 o Podiform chromitite S u t u Nehbandan r Nehbandan ophiolite e Bandan Mine SSZ-like sequence (Saccani et al., 2010) o Gabbro 31 Gabbronorite Pyroxenite LUT BLOCK Olivine websterite Z Mantle tectonite o n e N A Tertiary sedimentary T 500 m 50 km N rocks A S IR NI A MORB-like sequence (Saccani et al., 2010) H G Pelagic limestone F 30o N A Massive basalt Nosrat Abad Pillow lava Plagiogranite High-level gabbro Tchehel Kureh PAKISTAN Cumulate gabbro ophiolite 500 m Foliated gabbro Dunite Troctolite Gabbro alluvium Troctolite Dolerite volcanic rocks intrusive rocks Eocene-Pliocene Mantle tectonite sedimentary rocks (Senomanian-Eocene) Sefidabeh volcanic rocks (Maastrichtian-Paleocene) Basin deposits Tertiary sedimentary marls and turbidites rocks phyllites Neh and Ratuk Complexes (Senonian-Eocene) Mafic-ultramafic rocks basement rocks (Pre-Late Cretaceous) Fig. 9. Sketch of the Sistan suture zone and its ophiolites. The main ophiolites are, from north to south, the Birjand ophiolite, Nehbandan ophiolite and the Tchehel Kureh ophiolite. The left side lithological sections are pseudo-stratigraphic columns of the Birjand and Nehbandan ophiolites. Two main kinds of tectonically distinct ophiolite sequences in the Nehbandan complex (i.e., MORB and IAT-like) are from Saccani et al., 2010. tionary prism and a forearc basin respectively, are subdivided into: the Nehbandan ophiolites, although IAT massive lavas are common. (1) ophiolites with early Aptian to middle Late Albian and Cenoma- Troctolites, olivine gabbros and leucogabbros are also common nian to Maastrichtian pelagic sediments; (2) Late Cretaceous– (Zarrinkoub et al., 2012). Pelagic sediments associated with pyro- Eocene phyllites; and (3) Late Cretaceous–Early Eocene unmeta- clastic rocks cover the Birjand ophiolite volcanic sequence (Fig. 9). morphosed marine clastic sediments including sandstone and mar- The Nehbandan ophiolites comprise a mantle sequence (harz- ly turbidite (Fig. 10). Detritus includes fragments of ophiolitic burgite-Cpx bearing harzburgite and depleted harzburgite) with chert, basalt and gabbro. Sedimentary fill of the Sefidabeh basin two different crustal units including (Saccani et al., 2010) (Fig. 9) includes Cenomanian to Eocene clastic deposits with (Fig. 10): (1) MOR-type ultramafic cumulates (dunite–wehrlite– deep-marine carbonates and calc-alkaline lavas (Tirrul et al., troctolite), cumulate gabbros, high-level gabbros with plagiogran- 1983; Camp and Griffis, 1982). itic dikes and basalts and (2) SSZ-type ultramafic cumulates (web- Cpx-bearing harzburgite, harzburgite, dunite and (podiform) sterite and pyroxenite), gabbronorites and gabbos, without chromitite lenses are common in the Birjand mantle sequence volcanic rocks. (Fig. 9). Crustal rocks include massive to pillowed lavas with MORB On the basis of mantle tectonite chemistry, Saccani et al. (2010) and OIB affinities respectively (Zarrinkoub et al., 2012) similar to suggested that Nehbandan MOR-like tectonites were generated at H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 45 57˚E Kahnuj ophiolite 28˚N 63˚E Sorkhband & Rudan Saravan 28˚N complexes Accretionary Prism Jaz Murian Depression Minab FM 2 3 Rameshk 4 1 Fanuj Zendan Fault 26˚N 26˚N Makran Accretionary Prism 57˚E Pakistan 63˚E Gulf of Oman 100 Km Present vector of 150 km the subducting plate Main Makran Accretionary Prism Metamorphic complex (Cenozoic) Upper Miocene-Pliocene neritic Deyadar high pressure metamorphic rocks & coastal sediments (blueschists) Lower-Upper Miocene neritic sediments Bajgan-Durkan complex (Jurassic, upper Paleozoic Upper Oligocene-Lower Miocene flysch turbidites carbonates of shelf facies over Lower Paleozoic? Lower Eocene-Lower Oligocene flysch turbidites metamorphic rocks) Ophiolites Saravan Accretionary Prism (Cenozoic) Band-e-Zeyarat/Dare Anar complex Shah Kuh granodiorite intrusions (Oligocene) (Lower Cretaceous-Lower Paleocene) Ganj complex (Cretaceous) Lower Eocene-Lower Oligocene flysch turbidites Rameshk-Mokhtarabad complex (Lower Cretaceous-Lower Paleocene) Inner Makran Ophiolite Belt Coloured melange complex (Outer Makran Ophiolite Belt) (Jurassic-Lower Paleocene) FM Fanuj-Maskutan complex Fig. 10. Simplified geological map showing the geotectonic zones in the Makran region of southern Iran (modified after McCall, 1983, 1997). Numbers show the reconstructed sequences in Fig. 13. a mid-ocean ridge and that the mantle tectonites with SSZ-like which may be a sediment-filled Mesozoic back-arc basin (McCall affinities formed above an east-dipping subduction system that and Kidd, 1982; McCall, 1997; Glennie et al., 1990) or an intra- nucleated after spreading stopped. arc basin (Shahabpour, 2010); and (3) Cenozoic volcanic and plu- tonic rocks of andesitic to rhyolitic composition which reflect arc magmatism related to the Makran subduction system. Below we 3.5. Makran ophiolites (SE Iran) including Kahnuj ophiolites divide ophiolites in the region into two parts: (1) Makran ophio- lites including Jurassic–Early Paleocene Rameshk–Mokhtarabad The Iranian Makran is an accretionary prism developed above a and colored mélange complexes; and (2) Kahnuj ophiolite, which North-dipping subduction zone subducting Indian Ocean crust is the NW continuation of the Inner Makran ophiolite belt. (Siddiqui et al., 2012). The Makran accretionary prism extends for 450 km, from SE Iran to SW Pakistan. Makran comprises a 3.5.1. Makran ophiolites region about 200 km wide in SE Iran (Fig. 10) between the Jaz Murian depression and the Gulf of Oman. In the north, in the Cha- According to McCall (1983) and McCall and Kidd (1982), the Makran region can be divided into 8 geotectonic provinces, for gai and Ras Koh mountain ranges, there are rock sequences that represent the associated magmatic arc (Siddiqui et al., 2012). the most part presented from N to S (Fig. 11): There are three important zones in Iranian Makran, from S to N: (1) the Makran accretionary prism which continues to form as a 3.5.1.1. Jaz Murian depression (4 in Fig. 11). This is a Late Pliocene result of subducting the Indian plate and the sediments on it epeirogenic depression elongated about 300 km long East–West. beneath the central Iranian block; (2) the Jaz Murian depression, This region is defined by Quaternary sediments, which are 46 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 1 2 Southern Makran Bajgan-Durkan block U. Pliocene- Oligocene Pleistocene Continental fanglonerates Neritic clastic sediments Kahnuj ophiolite Lower Pliocene Neritic clastic sediments Eocene Pelagic limestone Lower Paleocene Pillow lava Platform limestones Thick flysch sequence highly deformed with Miocene large included raft of Sheeted dike complex Jurassic, Permian, (K-Ar=91.6-65.4 Ma, WR) Carboniferous platform Oligocene Thick flysch sequence limestones Albian-Aptian Plagiogranite Diabasic/amphibole (K-Ar=118.2 Ma, WR) gabbroic dike Eocene Thick flysch sequence (K-Ar=136.6 Ma; Amp) Gabbroic agmatite Paleocene Granitic dike (K-Ar= 121.4 Ma, Chl) Colored melange (ophiolite) Metamorphic rocks (K-Ar= 88.6 Ma, Chl) (127.6 Ma, Chl) layered ultramafic, basement of the (89.4 Ma, Orth) microcontinental block radiolarite, globotruncana (92.6 Ma, Orth) Uralitized gabbro-diorite limestone Lower Paleozoic Cretaceous Outer Makran Ophiolitic Belt trondhjemite Cretaceous Mylonitic gabbro/amphibolite (K-Ar=80.3 Ma, Feld) (K-Ar=139.4 Ma, Amp) 3 4 (142.2 Ma Amp) Inner Makran Ophiolitic Belt Southern edge of Jaz Murian depression Isotropic gabbro (K-Ar=517 Ma, Plag) Oligocene 168 Ma, Plag Neritic clastic sediments Neritic clastic sediments 213.6 Ma, Amp & shallow water limestones Eocene & shallow water limestones Layered gabbro Eocene (K-Ar=519 Ma, Plag) 438 Ma, Plag Lower Paleocene Deep water pelagic limestones & 140.7 Ma, Amp radiolarites 144.4 Ma, Amp Pillow lavas 156.5 Ma, Amp Metamorphic rocks of the Deyader complex, (schists, 1 km quartzites, marbles), including Sheeted dike complex patches of blueschists which may represent Cretaceous subduction & metamorphism Modified after Kananian et al., 2001 Layered ultramafic-mafic rocks gabbros, trondhjemites lower Paleozoic/Pre-Cambrian? Late Jurassic-Cretaceous Fig. 11. Generalized stratigraphic columns showing the reconstructed internal sequences in the Makran (modified after McCall, 1997) and Kahnuj ophiolites (modified after Kananian et al., 2001). The K–Ar ages in the Kahnuj ophiolite are shown for clarity. Analyzed phase for K–Ar are plagioclase (Plag); amphibole (Amph); chlorite (Chl); orthoclase (Orth), feldspar (Feld) and whole rock (WR). underlain by Eocene shallow water limestones and metamorphic carbonates, sandstones and argillic rocks with interbedded lavas rocks (column 4 in Fig. 11). The Deyadar complex (Figs. 10 and and small mafic intrusions (Kananian et al., 2001). Pillow lavas, 11 (4)) is composed of metamorphic rocks including blueschists cherts, lapilli tuffs and minor mafic–ultramafic intrusions are also and is interpreted as a site of Mesozoic subduction (McCall, 1997). common (McCall, 2002). The Bajgan–Durkan complex is consid- ered as a narrow continental block, which could be the SE contin- 3.5.1.2. Inner Makran ophiolite belt (3 on Fig. 11). There are three uation of the Sanandaj–Sirjan zone (McCall and Kidd, 1982; McCall, distinct ophiolites in this belt (Fig. 11; McCall and Kidd, 1982) 2002). comprising from W to E: (a) Band-e-Zeyarat/Dare Anar complex, an Early Cretaceous to Early Paleocene tholeiitic suite consisting 3.5.1.4. Colored mélange zone (outer Makran ophiolite belt). This of cumulate gabbro overlain by high-level isotropic gabbro, tron- mélange is located south of the Bajgan–Durkan complex (Sorkh- dhjemite, diabasic sheeted dike complex, pillow lava and pelagic band and Rudan complexes in Fig. 11) and consists of serpentinites, sediments; (b) Cretaceous Ganj complex, which is a calc-alkaline mafic–ultramafic rocks, pillow lavas, pelagic limestones, radiola- sequence thrust on top of tholeiitic suite ophiolites, and (c) rites and distal turbidites with minor outcrops of andesites, rhyo- Rameshk–Mokhtarabad complex, which is an Early Cretaceous– lites, andesitic tuffs, and Lower Cretaceous reefal limestones. This Early Paleocene ophiolite consisting of fragmented ultramafic– mélange is suggested to have formed in the trench of a North-dip- mafic cumulates, high level gabbro, trondhjemite, sheeted dike ping subduction zone by scraping off fragments of the downgoing complex, pillow lava and pelgic sediments. plate during Late Cretaceous to Early Paleocene time (McCall and Kidd, 1982; McCall, 2002), thus it represents the northernmost part 3.5.1.3. Bajgan–Durkan complex. This zone is up to 40 km wide and of the Makran accretionary prism, which continues to grow today. consists of Early Paleozoic metamorphic rocks of the Bajgan com- The four southernmost Makran zones reflect southwards plex overlain by mainly Mesozoic shelf carbonates of the Durkan growth of the Makran Accretionary Prism during Cenozoic time complex. The Bajgan complex includes amphibolites, marble, and include lower Eocene to Pliocene sequences of calcareous calc-silicate rocks, and schists with abundant meta-volcanic rocks and turbiditic flysch, evaporites, reefal limestone, gypsiferous and mafic to felsic intrusive rocks. Eastward, the Bajgan complex is mudstone, deltaic sandstone and estuarine conglomerate. overlain by shelf limestones of the Durkan complex (McCall and The ophiolites to the north and south of the Bajgan-Durkan Kidd, 1982). The Durkan complex also has tectonic windows of complex are considered by McCall (1997) to respresent two dis- Carboniferous, Permian and Jurassic shelf limestones (Fig. 11). tinct oceanic basins. The Inner Makran ophiolites to the north com- The Durkan complex is mainly composed of Mesozoic shelf prise the Band-e-Zeyarat/Dare Anar, Ganj and Rameshk/ H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 47 Mokhtarabad (McCall 1985) complexes, formed as a deep basin 4. Age constraints of Iranian ophiolites associated with radiolarites and pelagic limestones interbedded with ophiolitic basalts. The Ganj ophiolite complex exposes an In this section we synthesize age information for Iranian ophio- intermediate to felsic sheeted dike complex and calc-alkaline lites, using both biostratigraphic ages (based on microfossils) and basaltic–andesitic (pillow) lavas. Turbiditic sediments intercalated radiometric ages (such as K–Ar, Ar–Ar and U–Pb ages) from Iranian with lavas show Campanian to Maastrichtian ages (McCall, 2002). Mesozoic ophiolites. Our synthesis is graphically presented in Eocene–Oligocene sediments lie unconformably on the Ganj com- Fig. 12. plex. The Band-e-Zeyarat complex exposes layered ultramafic– mafic rocks and trondhjemite below Dare–Anar sheeted dikes 4.1. Zagros outer belt ophiolites and pillow lavas. The Rameshk complex exposes layered ultra- mafic–mafic rocks including harzburgite, troctolite, anorthosite, Age constraints for outer Zagros ophiolites (including Khoy– gabbro, leucogabbro, diorite and tonalite/trondhjemite overlain Maku) are summarized in Table 1 and Fig. 12. Based on K–Ar ages, by Mokhtarabad complex rocks, a sequence of pillow lavas with Khalatbari-Jafari et al. (2003, 2004) distinguished two ophiolitic interbedded Late Jurassic to Early Paleocene radiolarites and Globo- complexes in the Khoy region; (1) older ophiolites composed of truncana-bearing Santonian–Maastrichtian limestones (McCall, huge slices of metamorphic rocks (amphibolites, gneisses and 2003). mica-schists) and harzburgitic to lherzolitic tectonites; and (2) Ophiolites to the south of the Bajgan–Durkan zone are tectoni- younger (Late Cretaceous) unmetamorphosed ophiolite. Khoy lay- cally fragmented (colored mélange zone and/or outer Makran ered gabbros yield plagioclase K–Ar ages of 100.7 ± 6.0 and ophiolites), consisting of a jumble of large blocks, mainly of ultra- 72.6 ± 5.0 Ma (Khalatbari-Jafari et al., 2003). Limestone beds and mafic–mafic plutonic rocks and mafic lavas as well as pelagic sed- screens between pillow lavas yield Turonian to Santonian–Campa- iments. The outer Makran ophiolites include two relatively intact nian microfauna (Khalatbari-Jafari et al., 2003). Volcano-sedimen- ophiolites, the Sorkhband and Rudan complexes (McCall, 1985), tary rocks in the upper member of the supra-ophiolitic turbidites which are 17 km long and 9 km wide, composed mainly of dunite, contain Late Cretaceous–Early Paleocene microfossils (Fig. 12B). harzburgite and stratiform-type chromitite with pyroxenite/wehr- Recently Azizi et al. (2011) reported U–Pb zircon ages of 566– lite sill-like intrusions Figs. 6F) and minor isotropic to coarse- 596 Ma for eastern metamorphic complex gneissic granite and grained gabbros at the top of the sequence. This complex shows 550 Ma for amphibolite. This shows that the K–Ar ages of faulted contact with Bajgan–Durkan metamorphic rocks (Fig. 6F). Khalatbari-Jafari et al. (2003, 2004) are reset. We suggest that Biomicrites intercalated with outer Makran ophiolite pillow lavas the Khoy eastern metamorphic complex is Cadomian crust of the are dominated by Campanian–Maastrichtian microfaunas, Central Iranian block margin, not part of a Mesozoic meta- although there are also Cenomanian, Turonian, Coniacian and San- ophiolite. tonian microfossils (McCall, 2002). Radiolarites associated with pil- Ar–Ar dating results on dioritic dike/volcanic rocks from the low lavas and pelagic limestones range from Pliensbachian Hassanbag ophiolites (Iraqi Zagros) (Ali et al., 2012) give Albian– (Jurassic) to Coniacian. Cenomanian (106–92 Ma) ages. These mid-Cretaceous ages over- lap some Khoy younger ophiolite ages and also a zircon U–Pb age 3.5.2. Kahnuj ophiolites on the Kermanshah ophiolite (98 Ma Ma; Shafaii Moghadam The Kahnuj ophiolite covers more than 600 km2 in NW Makran et al., unpublished data). Ar–Ar ages on Haji Abad blueschists show and is the northwestern continuation of the Inner Makran ophio- that these were metamorphosed 95–85 Ma (Agard et al., 2006). lites (Figs. 2 and 10). McCall (1985) divided the Kahnuj ophiolites The need for careful U–Pb zircon geochronology on outer Zagros into (1) the plutonic Band-e-Zeyarat complex comprising layered ophiolites is demonstrated by the fact that pelagic sediments cov- and non-layered gabbroic cumulates, trondhjemites and a transi- ering the ophiolites give slightly older ages; 99–97 Ma. In con- tion zone including sheeted dike complex, and (2) the Dare Anar trast, some ophiolites along the Iran–Iraq border have Eocene (42 volcanic sequence including basaltic to andesitic pillowed and and 37 Ma) U–Pb zircon ages (Shafaii Moghadam et al., unpub- massive lavas, associated with pelagic sediments. The Kahnuj ophi- lished data; Rahimzadeh, pers. comm.). Felsic dikes from Triassic olite is separated from the Ganj complex to the east by the Jiroft passive margin-type Kermanshah ophiolites yield U–Pb zircon fault. To the west, the Kahnuj ophiolite is separated from the Baj- age of 220 Ma (with abundant inherited ages at 800 and gan metamorphic complex by the Sabzevarn fault. Outer Makran 2200 Ma) (Shafaii Moghadam et al., unpublished data). ophiolites are present to the west and south of the Bajgan complex (Fig. 10), made of basaltic pillow lavas and pelagic pink limestones (Kananian et al., 2001). Kananian et al. (2001) distinguished 6 mag- 4.2. Zagros inner belt ophiolites matic units in the Kahnuj ophiolites, from bottom to top, including (Fig. 11): (1) a thick, layered gabbroic unit of banded troctolite, U–Pb zircon TIMS ages are 103–101 Ma for Nain and 101– olivine gabbro, gabbronorite, leucogabbro and anorthosite with 99 Ma for Dehshir ophiolites (Fig. 12A) (Shafaii Moghadam et al., minor wehrlitic intrusions. This unit makes 40% of the whole Kah- 2013c), apparently older than outer Zagros ophiolites and more nuj ophiolite; (2) isotropic and uralitized gabbros, overlying the consistent with biostratigraphic ages of overlying sedimentary layered gabbros. (3) highly deformed fine-grained amphibolite sequences, which range from Cenomanian to Maastrichtian. Gab- and mylonitic gabbro; (4) an agmatite unit in which the gab- bro and plagiogranite from the Balvard–Baft ophiolites have con- broic/diabasic rocks at the base of the sheeted dike complex are cordant ages of 103.2 ± 2.4 Ma, but most grains are inherited fragmented and float in a whitish trondhjemitic matrix. These four Early Palaeozoic (Ordovician) xenocrysts (Shafaii Moghadam units combined are equivalent to the Band-e-Zeyarat complex of et al., unpublished data). McCall (2002, 2003); (5) a sheeted dike complex mainly made of north–south striking diabasic dikes (65° dip to the E) that occupy 4.3. Sabzevar–Torbat-e-Heydarieh ophiolitic belt about 2–2.5 km2 (Arvin et al., 2001), and (6) an extrusive unit (Dare Anar complex) mainly made of basaltic pillow lavas and associated Zircon and titanite U–Pb geochronology on felsic segregations pelagic sediments. Pillow lavas of the Dare Anar complex are in STOB mafic granulites yield ages of 107.4 ± 2.4 and intruded by numerous diabasic and gabbroic dikes as well as 105.9 ± 2.3 Ma (Albian), respectively (Fig. 12A; Rossetti et al., feldspathic wehrlitic and trondhjemitic dikes. 2010). A SHRIMP U–Pb zircon age of 99.32 ± 0.72 Ma is interpreted 48 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 A) Mesozoic Sabzevar, Outer and Inner Belts Zagros Ophiolites 30 Ma Outer Zagros Ophiolites Inner Zagros Ophiolites + plagiogranite Eocene + 50 Ma Eocene ophiolite Pelagic sediments Paleocene & turbidites 70 Ma TIMS + plagiogranite Late Cretaceous diabasic dike + + + TIMS + + + + + + 90 Ma Plagiogranite + + + SHRIMP + gabbro + plagiogranite + + + + high-P blueschists Plagiogranite + + + + gabbro-plagiogranite plagiogranite + + + plagiogranite Albian dioritic dike, 110 Ma Felsic segregations Legend in metamorphic rocks volcanic rock diorite-gabbro Early Cretaceous + K-Ar ages + U-Pb zircon + Ar-Ar ages 130 Ma Biostratigraphical ages Nain Dehshir Neyriz- Haji Abad Sabzevar- Torbat Hasanbag- Kermanshah Balvard-Baft B) Mesozoic Makran, Khoy-Maku and Birjand Ophiolites 50 Ma Limestones Supra-ophiolitic from Ganj complex turbidites Volcano-sedimentary Early Paleogene Pelagic limestones rocks Pillow lava Turbidites Pelagic limestone K-Ar (plag) + high-P blueschists 70 Ma & eclogites Rb-Sr Late Cretaceous limestone Mokhtarabad Mokhtarabad Radiolarites interbedded ~ with pillow lavas Pillow lava + U-Pb zircon + + ophiolite 100 Ma K-Ar, granites eclogite & acidic rocks + K-Ar, dike + granitic dike granitic + Gabbro + Leucogabbro + + Band-e-Zeyarat K-Ar (plag) Early Cretaceous + + gabbro + Radiolarites 130 Ma K-Ar, gabbro + Ganj complex + + Gabbroic rocks U-Pb + + + K-Ar, amph. + + trondhjemite + Late Jurassic + 160 Ma Mokhtarabad Band-e-Zeyarat radiolarites gabbros, Ar-Ar Kahnuj Nehbandan Birjand- Khoy-Maku Inner Makran Outer Makran Fig. 12. Simplified chart showing the ages of magmatic and sedimentary sequences of the Mesozoic ophiolites. Ar–Ar age data on the Hasanbag ophiolites (Iraq) from Ali et al. (2012); K–Ar ages on the Kermanshah ophiolite from Delaloye and Desmons (1980); U–Pb zircon ages on the Kermanshah Late Cretaceous and Eocene ophiolites are from Shafaii Moghadam et al. (unpublished data); Ar–Ar ages on Neyriz plagiogranites are from Lanphere and Pamic (1983) and on Neyriz gabbros from (Babaei et al., 2006). Ages of high-pressure metamorphic rocks of the Haji Abad ophiolite is from Agard et al. (2006). K–Ar ages of inner belt Zagros ophiolites are from Shafaii Moghadam et al. (2009) and U–Pb zircon ages of the Nain and Dehshir ophiolites are from Shafaii Moghadam et al. (2013c). U–Pb zircon data on felsic segregations of the Sabzevar ophiolite metamorphic rocks are from Rossetti et al. (2010), SHRIMP and TIMS U–Pb zircon ages of Sabzevar plagiogranites are from Shafaii Moghadam et al. (2014). U–Pb zircon ages of Birjand gabbroic rocks are from Zarrinkoub et al. (2012) and on the Birjand high pressure and felsic rocks from Brocker et al. (2010, 2013); K–Ar ages of Khoy–Maku magmatic rocks are from Khalatbari-Jafari et al. (2003, 2004), K–Ar ages of Inner Makran ophiolites are from McCall (1985); U–Pb zircon ages of Inner Makran magmatic rocks are from Hunziker et al. (2011), K–Ar ages on Kahnuj ophiolites are from Hassanipak et al. (1996) and Ar–Ar ages are from Ghazi et al. (2004). as when Sabzevar ophiolite magmas crystallized (Fig. 12A) (Shafaii Cenomanian–Maastrichtian (97.0 ± 0.2 Ma; 92.8 ± 1.3 Ma) to Moghadam et al., 2014). SHRIMP and TIMS U–Pb zircon dating Oligo-Miocene (29.8 ± 0.2 Ma) time (Shafaii Moghadam et al., reveals an age of 96.7 ± 2.1 and 98.3 ± 0.16 Ma for the formation unpublished data; Alaminia et al., 2013). Although younger tec- of the Torbat ophiolite (Shafaii Moghadam et al., 2014). Our U– tonic phases have influenced the Sabzevar region, intrusive con- Pb zircon dating and microfossil results (A. Taheri; personal com- tacts between the old granitic–dioritic plutons (e.g. Arghash and munication) show that the Torbat-e-Heydarieh (SE part of STOB) Ali-Abad plutons) show no major tectonic phases since Late Creta- and Sabzevar ophiolites (NW part of the STOB) are the same age. ceous time that could be the force for displacing a single coherent The paleontological ages vary from Campanian to Maastrichtian slab of Sabzevar oceanic lithosphere. These ages are similar to in the Sabzevar and Torbat-e-Heydarieh. Volcano-pelagic series those obtained from the inner Zagros ophiolites, but clearly a lot of the Oryan zone also include Cenomanian to Maastrichtian pela- more work is needed before we understand when this ophiolite gic sediments that are interbedded with pyroclastic and andesitic belt formed. to dacitic lavas. TIMS U–Pb zircon ages of STOB plagiogranites yields ages that variy from 99.92 ± 0.12 to 77.82 ± 0.28 Ma, compa- 4.4. Birjand–Nehbandan (Eastern Iranian) ophiolitic belt rable with U–Pb zircon ages on the Arghash–Ali Abad plutonic rocks (between Sabzevar ophiolite in the north and Cheshmeshir Brocker et al. (2013) obtained Rb–Sr isochron ages of ca. ophiolite in the south). Arghash pluons were emplaced from 87–83 Ma for high pressure metamorphic rocks from the H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 49 Birjand–Nehbandan. SHRIMP U–Pb zircon dating of metafelsic affinities (Poor Mohsen et al., 2010). Mostly OIB-type (but some rocks and eclogites also gave ages of ca. 86–89 Ma (Fig. 12B). Based calc-alkaline) basaltic dikes and sills crosscut the Maku pillow lava on these data, they concluded that Late Cretaceous subduction and sequences. Basaltic calc-alkaline/OIB-type sills and dikes also collision formed the Sistan Suture. However these ages are signif- crosscut the overlying turbidites. Basaltic fragments within the icantly younger than those reported for the crystallization of Birj- turbidites show mostly calc-alkaline characteristics but OIB-type and ophiolite gabbroic rocks by Zarrinkoub et al. (2012) (ca. 113– fragments also are common (Fig. 14A). Compared to the Khoy ophi- 107 Ma; LA-ICP-MS technique) which agree with biostratigraphic olite, the Maku ophiolite is mostly characterized by OIB-type alka- ages on the pelagic limestones (Tirrul et al., 1983)(Fig. 12B) but line lavas with more calc-alkaline lava fragments as breccias. are younger than Early Aptian–middle Late Albian ages for radiol- Zagros outer belt ophiolitic basalts have E-MORB and rarely N- arites (Babazadeh and De Wever, 2004; Babazade, 2007). MORB geochemical signatures (Khalatbari-Jafari et al., 2003, 2004) (Fig. 14A). Khoy pillow lavas and most basaltic fragments in turbi- 4.5. Makran ophiolites dites have low Th/Yb for a give Nb/Yb, similar to E-MORB and/or T- MORB (Fig. 14A). Such lavas may have formed by partial melting of There is limited geochronological data for Makran ophiolites. plume-contaminated depleted mantle beneath an oceanic spread- Associated pelagic sediments contain Jurassic to Early Paleocene ing center (Khalatbari-Jafari et al., 2006) or from subontinental microfauna in the inner Makran ophiolites (McCall, 1997). Ganj lithospheric mantle. The exceptions are some basaltic fragments complex gabbroic rocks yield Aptian–Albian K–Ar ages whereas within the turbidites with calc-alkaline characteristics and lower dikes have Cenomanian ages (McCall, 1985). K–Ar dating of Ti and Nb abundances. Some lavas have higher Th and lower Nb Band-e-Zeyarat gabbros yields an age of 120 Ma (McCall, 1985). and Ti contents (Fig. 14A), resembling SSZ lavas. Most Kermanshah U–Pb zircon ages of trondhjemite and granitic dikes from the lavas have calc-alkaline signatures and plot in the Oman V1 lava Rameshk ophiolite are 145 and 111 Ma, respectively (Hunziker field on Ti vs. V diagram (Fig. 14B). Island-arc tholeiitic lavas are et al., 2011). Biomicrite intercalated with outer Makran ophiolite minor components. The Harsin–Sahneh ophiolitic associated dikes pillow lavas are dominated by Campanian–Maastrichtian microfa- that intrude harzburgites or gabbros are thought to have a back-arc unas, although there are also Cenomanian, Turonian, Coniacian and basin basalt (BABB) signature (Whitechurch et al., 2013). Haji Abad Santonian microfossils (McCall, 2002). The radiolarites associated ophiolite lavas can be divided into E-MORB-like (or OIB-like), calc- with pillow lavas and pelagic limestones range from Pliensbachian alkaline and boninitic pillow lavas (Shafaii Moghadam et al., 2012). (Jurassic) to Coniacian (Fig. 12B). Haji Abad E-MORB-like lavas are enriched in Nb–Ti and may have Pelagic limestones in the Dare Anar complex of the Kahnuj formed during subduction initiation (Shafaii Moghadam and Stern, ophiolite contain microfaunas of Aptian–Cenomanian age (Arvin 2011) from a mantle source uncontaminated by slab-derived flu- et al., 2001). Most K–Ar ages from gabbros and dikes of the Kahnuj ids. Haji Abad boninitic lavas resemble Oman V2 lavas and Izu– ophiolite range between 156 and 136 Ma or 144–139 Ma Bonin–Mariana (IBM) boninites. Most Neyriz ophiolite lavas are (Kananian et al., 2001). K–Ar ages for amphibole from dioritic rocks slightly depleted in Nb and enriched in Th but some of them are are 125 Ma, while younger ages of 93–89 Ma are from potassic similar to early arc tholeiites of the IBM forearc (Fig. 14A). The Ker- granites (Kananian et al., 2001). K–Ar (Hassanipak et al., 1996) manshah Triassic–Cretaceous lavas and gabbros related to the pas- and Ar–Ar (Ghazi et al., 2004) ages of amphibole separates from sive margin-type ophiolites have OIB- and E-MORB-like signatures Band-e-Zeyarat high-level gabbros range from 124 ± 4 to (Fig. 14A) suggesting origin from low-degree partial melting of 146 ± 2 Ma and 142.9 ± 3.5 to 140.7 ± 2.2 Ma respectively. plume-contaminated mantle (Saccani et al., 2013). However the lavas and gabbros from Kurdistan Eocene ophiolites have E-MORB and P-MORB geochemical signatures and are geochemically similar 5. Summary of compositional variations in Iranian Mesozoic to Khoy-Maku lavas (Saccani et al., 2014). ophiolites 5.2. Zagros inner belt ophiolites In this section we synthesize geochemical information for Ira- nian Mesozoic ophiolites. The datasets we integrate in this section Most inner Zagros peridotite spinel Cr#s are like those of SSZ are whole rock trace element data and chemical composition of peridotites (Cr# > 40) except some plagioclase-bearing (impreg- indicator minerals especially Cr# (=100 atomic Cr/Cr + Al) spinel nated) lherzolites from the Nain and Dehshir ophiolites in peridotite. Tables 1 and 2 also summarize the most important (Fig. 13B). The SSZ signature increases from Nain toward the Bal- compositional features of these ophiolites. vard–Baft ophiolites. Nearly all inner Zagros ophiolitic lavas have calc-alkaline and island-arc tholeiitic signatures (IAT) and MORB 5.1. Khoy–Maku and Zagros outer belt ophiolites rocks are rare (Shafaii Moghadam and Stern, 2011). The SSZ signa- ture is conspicuous in Th/Yb vs. Nb/Yb diagram; nearly all mag- Khoy ophiolite mantle peridotites are mostly fertile lherzolites matic rocks are characterized by high Th/Yb, similar to Oman V2 with low Cr# spinels (Cr# 16–21; Monsef et al., 2010) similar to lavas and IBM boninites and forearc basalts (Fig. 14C). The SSZ sig- those of abyssal peridotites (Fig. 13A), although some high Cr# spi- nature of the inner Zagros ophiolites is stronger than in outer nels (31–60; Monsef et al., 2010) plot in the compositional range Zagros ophiolites. This may reflect proximity to the magmatic between abyssal and SSZ peridotites (Monsef et al., 2010). Maku arc, with higher sediment melt/fluid input into the mantle wedge peridotites have Al-rich spinels (Cr# 19) resembling those of abys- source of inner Zagros ophiolite lavas. sal peridotites (Rezai et al., 2010). The Zagros ophiolites including Late Cretaceous Kermanshah, Neyriz and Haji-Abad ophiolites have 5.3. Sabzevar–Torbat-e-Heydarieh ophiolitic belt spinels like those of forearc peridotites (Fig. 13A). Basaltic fragments in basal breccias of the Khoy supra-ophiolite Our geochemical data indicates that nearly all STOB lavas have turbidites show T-MORB to calc-alkaline geochemical affinities SSZ geochemical signatures and that MORB-type lavas are absent whereas pillow lavas (in the upper parts of the turbidite section) (Shafaii Moghadam et al., 2014). Mantle rocks also show SSZ signa- show IAT to calc-alkaline characteristics (Khalatbari-Jafari et al., tures, as shown by spinel and pyroxene compositions. Sabzevar 2003, 2004). Maku ophiolite basalts include massive to pillowed peridotite (Sabzevar, Forumad and Gaft) spinels have elevated lavas with calc-alkaline and/or OIB-type alkaline geochemical Cr# (>40). The exceptions are impregnated peridotites in the 50 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 100 100 AB Boninite Boninite Penjwin oph. Abyssal Abyssal peridotite peridotite 50 50 Forearc peridotite Forearc peridotite Cr# (100Cr/Cr+Al) Cr# (100Cr/Cr+Al) Back-arc peridotite Back-arc peridotite Khoy ophiolite Oman Kurdistan ophiolite Nain ophiolite Kermanshah late K oph. Dehshir ophiolite Maku oph. Neyriz ophiolite Shahr-e-Babak oph. Haji-Abad ophiolite Balvard-Baft ophiolite 0 0 100 50 0 100 50 0 Mg# (100Mg/Mg+Fe) Mg# (100Mg/Mg+Fe) 100 100 CD Boninite Boninite Abyssal Abyssal peridotite peridotite 50 50 Forearc peridotite Forearc peridotite Cr# (100Cr/Cr+Al) Cr# (100Cr/Cr+Al) Back-arc peridotite Back-arc peridotite Sabzevar ophiolite Makran ophiolite (Rudan) Torbat-e-Heydarieh oph. Birjand-Nehbandan oph. 0 0 100 50 0 100 50 0 Mg# (100Mg/Mg+Fe) Mg# (100Mg/Mg+Fe) Fig. 13. Composition of peridotite spinels in Iranian Mesozoic ophiolites. Data on the Haji Abad peridotite spinels from Shafaii Moghadam et al. (2012b) and on the Kermanshah, Neyriz, Nain, Shahr-e-Babak, Sabzevar and Torbat-e-Heydarieh ophiolites from Shafaii Moghadam et al. (unpublished data). Data on the Dehshir peridotite spinels from Shafaii Moghadam et al. (2010), on Baft ophiolites from Shafaii Moghadam et al. (2013a). Data from Shafaii Moghadam et al. (unpublished data) on the Birjand peridotites and from Saccani et al. (2010) for the Nehbandan ophiolites. Data from Khalatbari-Jafari et al. (2006) and Monsef et al. (2010) on the Khoy peridotites; data on the Maku peridotites from Rezai et al. (2010). central Sabzevar belt that were generated due to percolation of ophiolite (Alabaster et al., 1982). The occurrence of these types of MORB-type melts (Fig. 13C). Torbat-e-Heydarieh peridotite spinels lavas may be the result of late-stage off-axis magmatism fed by are mostly Al-rich with low Cr# similar to back-arc basin and/or melts from an asthenospheric window formed by slab break-off, abyssal peridotites (Fig. 13C). shortly after ophiolite emplacement (Shervais, 2001). Whole rock major and trace element data from the Sabzevar We do not have any isotopic age, mineral chemical or geochem- ophiolite indicate that most lavas have IAT and calc-alkaline ical data for the Oryan–Bardaskan and Neyshabour ophiolites, nor affinities (Fig. 14E and F). MORB lavas are rare. All of the gabbroic are there any paleontological ages. rocks (orthopyroxene + clinopyroxene + plagioclase ± olivine ± Most Torbat-e-Heydarieh magmatic rocks have IAT affinity, but amphibole cumulates) and some late plagiogranitic dikes and MORB-type lavas are also common. In Th/Yb vs. Nb/Yb and V vs. Ti intrusions have boninitic affinities. OIB-type (alkaline) lavas occur diagrams, the Torbat lavas can be subdivided into two types; (1) both as fragments within agglomerates and breccias of Late Creta- samples with higher Th/Yb but lower Ti content resembling arc ceous–Paleocene age (Baroz and Macaudiere, 1984) and in a pillow tholeiites and Oman V2 lavas and (2) samples with lower Th/Yb lava sequence near the Baghjar–Aliak villages. These agglomerates but higher Ti content, similar to MORB (Fig. 14E and F). and pillow lavas are respectively interbedded with or are overlain by Late Cretaceous pink limestone. These late OIB-type lavas are 5.4. Birjand–Nehbandan (Eastern Iranian) ophiolitic belt similar to Late Cretaceous OIB-type dikes intruding ophiolites in the Tauride belt of Turkey (Çelik and Delaloye, 2003; Parlak The tectonic affinities of Nehbandhan and Birjand ophiolitic et al., 2006) and Late Cretaceous Salahi volcanics of the Oman crustal rocks differ. Lavas with SSZ affinities dominate the Birjand H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 51 ophiolite whereas Nehbandan lavas show N-MORB and E-MORB ophiolites (Siddiqui et al. 2012). The oldest rock unit in the Ras characteristics. Peridotites show the opposite: Birjand peridotites Koh arc is the Jurassic Ras Koh accretionary complex. Late Creta- are mostly MORB-like whereas Nehbandan mantle tectonites exhi- ceous volcanic rocks of the Ras Koh magmatic belt show IAT signa- bit both MORB-like and SSZ-affinities (Delavari et al., 2009). Neh- tures suggesting that this was an intraoceanic arc. Ras Koh arc is bandan MORB-type mantle rocks include Cpx-rich harzburgites part of the magmatic arc stretching from Zagros to Waziristan with low Cr# (15–21) spinels whereas more depleted peridotites (Siddiqui et al., 2012). have higher Cr# spinels (33.5–37) and Birjand ophiolite mantle Jurassic ophiolites may also exist in NW Iran. Ophiolites along peridotites contain mostly MORB-like spinels (Fig. 14D). Nehban- the Ankara–Erzincan (NE Turkey)–Sevan (Armenia) suture zone dan ophiolite basalts comprise both enriched (E-MORB) and (at the boundary with NW Iran), including Refahiye, Sahvelet, depleted (N-MORB) varieties (Saccani et al., 2010). MORB-like mas- Karadag, Kirdag (Turkey) and Sevan, Stepanavan, Vedi and Amasia sive lavas and OIB-like pillow lavas are subordinate (Zarrinkoub (Armenia), have Lower–Middle Jurassic to Early Cretaceous Ar–Ar et al., 2012). MORB and OIB samples may represent magmas gen- ages of ca. 176–169, 170–150 and 117 Ma (e.g., Çelik et al., 2011; erated in an oceanic island (Zarrinkoub et al., 2012). Other Nehban- Galoyan et al., 2009; Rolland et al., 2009a, 2010; Hassig et al., dan samples including lavas, diabasic dikes within mantle sections 2013). Because the K–Ar ages of Khalatbari-Jafari et al. (2003, and gabbroic rocks have high Th/Yb and low Nb/Yb ratios resem- 2004) are ambiguous, we are unsure about the presence or absence bling SSZ lavas (Fig. 14G). of Jurassic ophiolites in NW Iran and U–Pb zircon ages are needed More attention is needed to highlight the spatial and temporal to resolve this issue. Lesser Caucasus ophiolites include lavas and relationships between E-MORB and N-MORB lavas and SSZ-type gabbros with MORB, OIB and arc signatures (e.g., Galoyan et al., sections in the Birjand and Nehbandan ophiolites. This will allow 2009; Rolland et al., 2009b; Hassig et al., 2013). OIB magmatism us to better understand if the enriched lavas are part of the ophio- (ca. 117 Ma) is younger than MORB-type magmatism (170– lite or formed later, perhaps accompanying ophiolite emplacement. 150 Ma) and OIB lavas erupted on the top of ophiolites. Early Cre- taceous OIB seems to have issued from a mantle plume source 5.5. Makran ophiolites prior to Late Cretaceous (Coniacian–Santonian) ophiolite obduc- tion (Rolland et al., 2009b; Hassig et al., 2013). There are no geochemical data for outer Makran ophiolites, except some spinel compositions from Rudan and Sorkhband ultra- 6.1.2. Comparison with Late Cretaceous ophiolites mafic rocks. These data show that peridotite spinels are SSZ-like Most Iranian Neotethyan ophiolites have Late Cretaceous ages. while chromitites have high Cr# resembling those of boninites Brocker et al. (2013) recently documented the importance of Late (Fig. 13D). Ghazi et al. (2004) concluded from REE and trace ele- Cretaceous subduction processes for the geodynamic evolution of ment patterns that Band-e-Zeyarat gabbros and trondhjemites the Birjand ophiolite, although gabbro crystallization agess are as and Dare Anar complex lavas are E-MORB. T-MORB-like and old as late Early Cretaceous. Late Cretaceous Tethyan ophiolites back-arc basin basalt-like geochemical affinities are inferred for south of the Tauride platform of Turkey and the Central Iranian Dare Anar lavas and Band-e-Zeyarat gabbros (Arvin et al., 2001; Block were emplaced onto the northern edge of Arabia, including Arvin et al., 2005), who inferred a SSZ environment for Kahnuj Troodos (Cyprus), Kizildag (Turkey), Baer-Bassit (Syria) and Zagros ophiolite formation. (Dilek and Thy, 2009). All these Late Cretaceous Neotethyan ophi- Band-e-Zeyarat gabbros (both deep cumulates and high-level olites are about the same age; 90–94 Ma for Troodos plagiogranite isotropic gabbros) are characterized by high Th/Yb and low Nb/ (U–Pb zircon; Mukasa and Ludden, 1987); 95 Ma for Oman plagi- Yb similar to IAT, except for two samples that plot near E-MORB ogranite (U–Pb zircon; Hacker et al., 1996); 91–92 Ma for Kizildag (Fig. 14G). Based on the geochemistry of Band-e-Zeyarat gabbroic plagiogranite (U–Pb zircon; Dilek and Thy, 2009); 92–93 Ma for 40 39 rocks, a mid-oceanic ridge environment is suggested for formation Outer belt Neyriz hornblende gabbros ( Ar– Ar; Babaei et al., of the Kahnuj ophiolite (Arvin et al., 2005). Geochemical data for 2006); 103–99 Ma for Inner belt plagiogranites and diorites (U– Kahnuj and Ganj ophiolite lavas mostly show MORB signatures, Pb zircon; Shafaii Moghadam et al., 2013c); and 100–78 Ma for similar to Oman V1 lavas, although some have higher Th/Yb, sim- Sabzevar–Torbat plagiogranites and 101–77 Ma on Khoy gabbros ilar to IAT. The relationship between lavas and gabbros with higher (Khalatbari-Jafari et al., 2006). These ages differ from those of Mak- and lower Th/Yb is not clear and we do not yet understand if there ran (U–Pb zircon; 145–111 Ma)–Kahnuj (Ar–Ar; 143–141 Ma) and are anysystematic chemotemporal changes in Kahnuj ophiolite Birjand (U–Pb zircon on felsic rocks; 89–86 Ma and on gabbros; lavas. 113–107 Ma) ophiolites. Late Cretaceous Neotethyan ophiolites of Troodos and Oman are better studied than any ophiolite in Iran and provide very useful 6. Discussion perspectives. The Troodos ophiolite crustal sequence contains lower pillow lavas with IAT signature while upper lavas are bonin- Below we discuss three aspects of Iranian Mesozoic ophiolites: itic (Thy and Xenophontos, 1991; Dilek and Thy, 2009; Osozawa (1) how similar and different these are to other Tethyan ophiolites et al., 2012). Kizildag ophiolite (Turkey) shows geochemical evolu- of similar age; (2) their petrological diversity; and (3) what they tion from MORB to boninite (Bagci et al., 2008; Dilek and Thy, tell us about the tectonic evolution of the region. 2009). Chemostratigraphy for Oman lavas shows that these lavas change from MORB-like (Geotimes or V1 unit) upwards into 6.1. Comparison with other Mesozoic Tethyan ophiolites depleted IAT and boninitic (Lasail and V2 unit) (Alabaster et al., 1982; Ernewein et al., 1988). Our compiled data indicates that 6.1.1. Comparison with Jurassic ophiolites most Iranian ophiolites are similar to other Late Cretaceous Teth- There is the puzzle of the Jurassic ophiolites of Iran, what do yan ophiolites in terms of age and geochemical signatures, these indicate? Jurassic–Cretaceous ophiolites are distributed in although OIB-like lavas are more abundant in Iran than elsewhere. SE Iran and SW Pakistan, north of the Makran subduction zone. They include Kahnuj and inner and outer Makran ophiolites, an 6.1.3. Importance of Eocene ophiolites ophiolite belt that continues eastward into S–SW Pakistan (Baluch- Eocene and younger ophiolites exist in Indonesia (Ishikawa istan) Jurassic–Cretaceous ophiolites, including Muslim Bagh et al., 2007; Kaneko et al., 2007), Philippines (Yumul, 2007), Taiwan (Khan et al. 2007), Bela (Zaigham and Mallick, 2000) and Ras Koh (Jahn, 1986), Japan (Hirano et al., 2003) and also in Chile (Veloso 52 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 et al., 2005; Anma et al., 2006) but are rare in the Tethyan realm of types) but all are related to the opening and closure of Neotethys SW Asia. Occurrence of dike swarms (with Eocene U–Pb age) and (Furnes et al., 2014 and references therein). They are principally SSZ-type lavas in Kermanshah and Kurdistan show that the south- of two ages; an older group around 170–140 Ma (Betic, Chenaillet, ern Neotethyan Ocean was open and magmatism was active until Zermatt-Saas, External and Internal Ligurides, Calabrian, Corsica, at least Late Eocene and may reflect a phase of back-arc rifting. Cer- Mirdita, Pindos, Eldivan, Refahiye, Sevan, Makran, Muslim Bagh, tainly more work is needed to understand the significance of Saga, Sangsang) and a younger group around 125–90 Ma (Troodos, Eocene ophiolitic suites in Iran. Kizildag, Oman, Outer and Inner Zagros belts, Birjand–Nehbandan, Sabzevar–Torbat-e-Heydarieh, Muslim Bagh, Waziristan, plus most 6.2. Petrological diversity of Iranian Mesozoic ophiolites of the examples of the Yarlung–Zangbo Suture Zone) (Furnes et al., 2014). The older group dominates in Europe and the younger group Mesozoic ophiolites in the Alpine–Zagros–Himalayan belt have dominates in Asia. The various types of Neotethys ophiolites and different origins (continental margin, mid-ocean ridge, and SSZ how Iranian ophiolites relate to these are discussed further below. 100 600 ABKermanshah Late K. ophiolite IAT Eocene Kurdistan oph. (S et al.) Haji-abad ophiolite MORB 10 Neyriz ophiolite Boninite Oman V1 lavas 400 OIB volcanic arc array 1 Oman V2 lavas OIB E-MORB 200 0.1 Khoy supra-ophiolitic rocks MORB-OIB array Khalatbary jafari et al., 2006 N-MORB Maku ophiolite (PoorMohsen et al.,) Khoy volcanic rocks 2010 Khalatbary jafari et al., 2006 0.01 0 0.1 1 10 100 0 5 10 15 20 25 30 100 600 CDIAT te 10 IBM forearc lavas MORB Bonini 400 OIB volcanic arc array 1 Oman V2 lavas OIB 200 E-MORB 0.1 OIB array MORB- Nain ophiolite Balvard-Baft ophiolite N-MORB Dehshir ophiolite Shahr-e-Babak ophiolite 0.01 0 0.1 1 10 100 0 5 10 15 20 25 30 Th/Yb Sabzevar ophiolites EFV (ppm) IAT Torbat-e-Heydarieh ophiolite MORB 10 Boninite 400 OIB volcanic arc array OIB 1 Oman V2 lavas 200 E-MORB 0.1 MORB-OIB array N-MORB 0.01 0 0.1 1 10 100 0 5 10 15 20 25 30 100 600 GH Ganj lavas (Shaker Ardakani et al., 2009) IAT Nehbandan ophiolite (Saccani et al.,) Kahnuj lavas (Arvin et al., 2001) 2010 MORB 10 Boninite 400 OIB volcanic arc array OIB 1 Oman V2 lavas 200 E-MORB Kahnuj gabbros 0.1 Ghazi et al., 2004 MORB-OIBBirjand array ophiolite (this study) Kahnuj lavas N-MORB Ghazi et al., 2004 Birjand ophiolite (Z. et al.,) 0.01 0 0.1 1 10 100 0 5 10 15 20 25 30 Nb/Yb Ti (ppm)/1000 Fig. 14. Trace element compositional variations (Th/Yb vs. Nb/Yb and Ti vs. V) of Iran Mesozoic ophiolitic magmatic rocks. Th/Yb vs. Nb/Yb diagram modified after Pearce (2008) and Ti vs. V diagram modified after Shervais (1982). Data for the Haji Abad ophiolites are from Shafaii Moghadam et al. (2012b) and for the Kermanshah, Neyriz, Nain, Shahr-e-Babak and Torbat-e-Heydarieh ophiolites are from Shafaii Moghadam et al. (unpublished data). Data for the Dehshir ophiolites are from Shafaii Moghadam et al. (2010), for Baft ophiolites from Shafaii Moghadam et al. (2013a) and for Sabzevar ophiolites from Shafaii Moghadam et al., (2014). Data on the Birjand ophiolites from Shafaii Moghadam et al. (unpublished data) and Zarrinkoub et al. (2012); data on the Nehbandan ophiolites from Saccani et al. (2010). Data on the Khoy ophiolite from Khalatbari- Jafari et al. (2006) and on the Maku ophiolite from Poor Mohsen et al. (2010). Data on the Kahnuj ophiolite lavas from Arvin et al. (2001); data on the Kahnuj gabbros and lavas from Ghazi et al. (2004) and data on the Ganj complex from Shaker Ardakani et al. (2009). H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 53 6.2.1. Passive continental margin-type ophiolites 6.2.5. Volcanic arc-type ophiolites This type of ophiolite is related to early rifting of northern Volcanic arc-type ophiolites typically have longer lifespans than Gondwana during Late Permian–Triassic time to open Neotethys. other ophiolite types, sometimes >20–30 Ma (Dilek and Furnes, These ophiolites have Triassic-Jurassic (to early Cretaceous) ages 2011). Many more U–Pb zircon ages are needed for Iranian ophio- and fragments of this activity are found in Kurdistan, Kermanshah lites, but available data indicate that most were magmatically (Bisotun limestone and Kermanshah radiolarite), Neyriz (the active for less than 10 Ma, except the Sabzevar–Torbat-e-Heyda- mélange associated with Pichakun complex) and Oman (Hawasina rieh ophiolites with >20 Ma life. The presence of the intra-oceanic complex) (Table 1). Our U–Pb dating from Kermanshah plagiogra- felsic arc within the Sabzevar basin with ages similar to Sabzevar nites reveals an age of 222.1 ± 3.8 Ma for the extension of Tethyan plagiogranites (98 Ma) is another line of evidence showing that Ocean (unpublished data). Igneous rocks in these ophiolites have the Sabzevar ophiolites resemble volcanic-arc type ophiolites of OIB (alkaline) and E-MORB signatures (with Nb–Ta and without Dilek and Furnes (2011). Kurdistan Eocene ophiolites have also vol- Th enrichment) and are often associated with fertile lherzolite, per- canic-arc type ophiolite characteristics. haps subcontinental mantle. This led Sacanni et al. (2013) to con- sider a passive margion origin for the Triassic–Jurassic 6.2.6. Accretionary prism-type ophiolites Kermanshah ophiolites. However, a subcontinental origin for these Although the Makran ophiolites (including Kahnuj) have both fertile meta-lherzolites is not well explained, as spinel Cr# from MORB- and SSZ-type magmatic rocks and their tectono-magmatic these lherzolites is not so low (25–29). Alpine subcontinental setting is similar to that of back-arc basins, the presence of huge lherzolite is characterized by spinel with very low Cr# (<10), masses of turbidites with oceanic lithosphere slices and the pres- high-Al Opx, and high Al, high Na Cpx, as well as association with ence of blueschists confirm that these ophiolites are similar to garnet-spinel pyroxenite (e.g., Ishiwatari, 1985; Muntener et al., accretionary prism-type ophiolites of Dilek and Furnes (2011). 2010). Garnet pyroxenite is missing from Kermanshah Triassic From geochemistry, it seems thatthe Makran ophiolites were ophiolites. derived from a mix of MORB and SSZ-type sources. An accretionary prism scenario is also pertinent for Birjand–Nehbandan ophiolites 6.2.2. MORB-type ophiolites in eastern Iran. Ophiolites with only MORB-type igneous rocks are rare because they form on the downgoing oceanic plate, which is hard to obduct. Such ophiolites are also rare in Iran. The best example is the Late 6.3. Tectonic evolution of Iranian Mesozoic ophiolites Cretaceous Khoy–Maku ophiolite, which has E-MORB, N-MORB and OIB-type igneous rocks (Fig. 14). These igneous rocks generally Iranian Neotethyan ophiolites are part of the Maghrebian– lack Nb–Ta depletions. However even in this ophiolite the MORBs Alpine–Himalayan belt (referred to as the Alpides), which extends grade upward into calc-alkaline and arc tholeiites and/or late SSZ- from Morocco in the west, through the European Alps, the Anato- type dikes crosscut the early MORB sequences. This shows a tran- lides, Zagros, Makran, and the Himalayas in the east, defining an sition from a MORB-type setting to supra-subduction zone mag- orogenic belt 9000 km long (Furnes et al., 2014). This orogenic matism during Late Cretaceoues–Early Paleocene time. The belt approximates the location of the Neotethys seaway. Neotethys Nehbandan (and some Birjand) rocks in the Birjand–Nehbandan began with Permian rifting of the northern margin of Gondwana, ophiolitic belt also show MORB signatures but the occurrence of from which Cimmerian fragments drifted north and collided with SSZ-type lavas and peridotites and exhumed eclogites and blues- Eurasia to close Paleo-Tethys in Triassic time. Below we describe chists indicate a supra-subduction zone setting for these ophio- briefly the tectonic scenarios in which Iranian Mesozoic ophiolites lites. It seems that early eruption of MORB- (N-MORB & E-MORB) formed. and OIB-like lavas (ca.113–107 Ma) was followed by Late Creta- ceous (ca. 100–80 Ma) intraoceanic subduction and eruption of 6.3.1. Zagros ophiolites SSZ-related lavas, gabbros and depleted mantle harzburgites. This There is broad agreement that Zagros ophiolites reflect the geo- is analoguous to the chemostratigraphy identified for ‘‘subduc- logic evolution of Neo-Tethys, from rifting to closure. Evidences for tion-initiation rule ophiolites’’ by Whattam and Stern (2011). Permo-Triassic rifted margins include the presence of OIB-type gabbros and lavas; turbidites, deepwater radiolarites and platform 6.2.3. Plume-type ophiolites carbonates along with plume-related alkaline lavas within Ker- The Maku ophiolite in NW Iran is characterized by OIB-type and manshah radiolarites, Bisotun–Avroman limestones (Kerman- ankaramitic pillow lavas and OIB-like dikes that are similar to shah–Hasanbag), and Pichakun series (Neyriz). These Permo- plume-type ophiolites of Dilek and Furnes (2011), although Triassic volcano-sedimentary sequences correlate with the Hawa- MORB-like and SSZ-like lavas are also common in the Khoy sina complex of Oman. ophiolites. Late Cretaceous events to form Zagros ophiolites (ZOB and ZIB) are controversial. According to some geologists, Neo-Tethyan oce- 6.2.4. Supra-subduction zone-type ophiolites anic lithosphere was consumed in a NE-dipping subduction zone Most Iranian ophiolitic rocks – from mantle peridotites to over- beneath the Sananadaj–Sirjan zone (SNSZ) margin during Early lying lavas – have geochemical signatures resembling magmas and Jurassic time (Dercourt et al., 1986; Saccani et al., 2013). In this residues generated over subduction zones, including arcs, backarc model, the Neyriz and other ZOB ophiolites are fragments of basins and forearcs. SSZ magmatism was very common in forming Neo-Tethyan MORB oceanic lithosphere. The Kermanshah ophio- both outer and inner Zagros ophiolite belts. Mantle peridotites of lite has been described as a piece of Tethyan oceanic lithosphere these have spinels mostly with Cr#>40. Most magmatic rocks from scraped off during NE-directed subduction underneath the Iranian these ophiolites have Nb–Ta depletion and Th (and LILEs) enrich- block in Early Cretaceous time (e.g., Agard et al., 2005). An intra- ment, consistent with magmatism above a convergent margin. oceanic arc origin has been suggested for the Eocene Kermanshah Most Sabzevar ophiolitic magmatic rocks are also SSZ-type, and Iranian–Iraqian Kurdistan ophiolites by Ghazi and Hassanipak with Nb–Ta depletion (Fig. 14). This is also true for Torbat-e-Hey- (2000), Desmons and Beccaluva (1983) and Whitechurch et al. darieh lavas, which were also influenced by slab-derived compo- (2013). Our field, geochronological and geochemical data also con- nents, testified by higher Th/Yb ratios, but peridotite spinels have firm that a younger intraoceanic arc or Eocene volcanic-arc type lower Cr#, similar to back-arc basin peridotite spinels. ophiolite is present in the Kermanshah–Kurdistan area (Fig 15). 54 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 ZOB ophiolites are distributed between older rocks of the SSNZ and Shafaii Moghadam and Stern (2011) (Fig. 15). In this model, the Main Zagros Thrust (MZT) fault. Late Cretaceous Zagros ophiolites along with Troodos and Oman ZIB ophiolites have been described as originating from a Neo- ophiolites constitute a long, broad, and continuous tract of oceanic Tethyan oceanic branch between the SSNZ and the Lut block lithosphere created at about the same time when subduction (e.g., Berberian and King, 1981; Arvin and Robinson, 1994; Arvin began along the southern margin of Eurasia. This subduction initi- and Shokri, 1997). In many interpretations the Nain-Baft ophiolite ation event was accompanied by extension and infant arc igneous belt represents a suture on the site of small Mesozoic ocean basin activity, which initially occurred via seafloor spreading to form a (e.g., Stampfli and Borel, 2002; Agard et al., 2006; Shafaii broad ophiolitic forearc. This model infers that ZIB and ZOB were Moghadam et al., 2009) surrounded by Cadomian microcontinents. once part of a single ophiolitic forearc. Separate inner and outer However, evidence in support of this hypothesis, including evi- Zagros ophiolite belts formed later, when the forearc slab was dence of rifted margins such as turbidites, deep water radiolarites uplifted in Paleocene-Eocene time by exhumation of the partially and platform carbonates along with rift-related alkaline lavas is subducted SSNZ, leading to erosion that separated ZIB and ZOB missing. Some geologists prefer a model whereby the IB marks outcrops. the position of a Campanian back-arc basin (e.g., Stampfli and This model is supported by strong SSZ affinities of most Zagros Borel, 2002; Agard et al., 2006; Shafaii Moghadam et al., 2009). ophiolite igneous rocks, especially for the most diagnostic litholo- Such a back-arc basin could also have been a narrow seaway with gies of mantle harzburgite, diabase dikes, and lavas, and by the discountinous oceanic crust (Shafaii Moghadam et al., 2009). observation that early MORB-like lavas in some of these ophiolites The other model for the genesis of Zagros ophiolites is the sub- are succeeded by more arc-like lavas, a chemotemporal evolution duction initiation/infant-arc model, first applied to Zagros by expected for subduction-initiation ophiolites (Whattam and Passive margin-type ophiolite exhumed sub-continental mantle GONDWANA Carbonate platform OIB basalts SSE NNW SSE OIB-type gabbros & dikes NNW Arabia Cimmeria Arabia Cimmeria Asthenosphere Lithosphere Plume-type components (A) Continental rifting, Neotethys opening and OIB-type magmatism (Late Permian-early Triassic) lherzolite exhumed sub-continental mantle N- & E-MORB magmatism SSE gabbro & dike seamount (OIB) NNW Cimmeria Arabia Neotethyan lithosphere Late Triassic-Cretaceous Bisotun limestones; Kermanshah radiolarites & Pichakun series (Neyriz) associated with Triassic OIB-type magmatism (B) Neotethys accretion, mid-oceanic-ridge N-MORB magmatism (Late Triassic) SSZ-type ophiolites IB OB Spreading (proto-forearc) (C) Intraoceanic subduction Iran Arabia initiation (Late Cretaceous) Residual depleted (SSZ) harzburgite Eocene ophiolites Eocene Kermanshah-Kurdistan Urumieh-Dokhtar magmatic arc & Iraq Zagros intraoceanic arc (D) Intraoceanic arc (Kermanshah-Kurdistan) Iran & Urumieh-Dokhtar magmatic arc Arabia Early Paleocene-Late Eocene Fig. 15. Schematic model for the formation and evolution of Zagros Mesozoic (and Cenozoic) ophiolites. (A) Early phases of Neotethys opening with eruption of early OIB-type (plume-related) lavas and gabbros in Late Permian-early Triassic (modified after Saccani et al., 2013). (B) Neotethys accretion, mid-oceanic-ridge N-MORB magmatism in Late Triassic (modified after Saccani et al., 2013). (C) Intraoceanic subduction initiation in Late Cretaceous and formation of proto-forearc and OB and IB ophiolites. (D) Intraoceanic arc formation within Kermanshah–Kurdistan (Eocene ophiolites) and development of active continental arc magmatism (Urumieh–Dokhtar magmatic belt) over the Iranian block. H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 55 Stern, 2011). The forearc/subduction inititiation model for Zagros associated with an ocean basin that opened between the Lut Block ophiolites is most consistent with diagnostic lithologies, boninite to the south and the Turan block to the north beginning no later and harzburgite. A similar model has been applied to the Troodos than mid-Cretaceous time. Intraoceanic subduction began before and Semail ophiolites, by Whattam and Stern (2011), Pearce and Albian time, testified by the age of felsic segregations in Sabzevar Robinson (2010) and Osozawa et al. (2012). The geochemical data high-P metamorphic rocks (Fig. 16A). Subduction polarity was we have summarized for both Late Cretaceous belts of Zagros southwards, beneath the Lut block. Intraoceanic subduction was ophiolites, plus the observation that some ZIB ophiolites are responsible for generating SSZ-related magmas within the Sabze- conformably overlain by arc-derived pyroclastic rocks compels us var oceanic lithosphere and formation of an arc between the Sab- to conclude that both ZOB and ZIB formed over a nascent zevar ophiolite in the north and Cheshmeshir–Torbat-e- subduction zone. This model predicts that ZIB and ZOB formed at Heydarieh ophiolites in the south during Late Cretaceous time. In the same time, a prediction that needs to be tested with U–Pb zir- this model, the Torbat-e-Heydarieh ophiolite formed as a back- con geochronology. If confirmed, the excellent exposures of ophio- arc basin. Evidence for oceanic lithosphere behind the mature lites in the Troodos–Zagros–Semail ophiolite belt make it an and felsic arc comes from Oryan ophiolites. Clearly, the remarkable excellent natural laboratory for reconstructing how new subduc- expanse of STOB ophiolites invites more work. tion zones form. 6.3.4. Birjand–Nehbandan ophiolites 6.3.2. Khoy–Maku ophiolites Birjand–Nehbandan ophiolites define the Sistan suture between The age and thus tectonic evolution of the Khoy–Maku ophio- the Lut and Afghan continental blocks and their emplacement lites are controversial. As previously discussed, we consider that reflects the consumption of the 110 Ma Sistan Ocean followed the older (eastern) metamorphic complex is part of the Central Ira- by collision of the Lut and Afghan continental blocks. Early workers nian block margin, not a Mesozoic ophiolite. Microfossils show thought subduction polarity was toward the east, beneath the Santonian–Campanian to Early Paleocene ages for the young Khoy Afghan block (e.g., Camp and Griffis, 1982; Tirrul et al., 1983). More ophiolites, somewhat younger than crystallization ages of the OB recently, because of abundant Eocene–Oligocene calc-alkaline to and IB Zagros ophiolites, so the relationship of the Khoy–Maku shoshonitic volcanic rocks in the Lut block, Pang et al. (2013) con- ophiolite to Zagros ophiolites is not clear. One key concerns the cluded that subduction polarity was toward the west, beneath the relationship of the Khoy–Maku ophiolite to the poorly known ophi- Lut block. Other models propose involve westward subduction olite belt that trends North–South through Kurdistan along the beneath the Lut block (Zarrinkoub et al., 2012) and eastward Iran–Iraq border north from Kermanshah to Khoy–Maku. The intra-oceanic subduction (Saccani et al., 2010). Ocean closure occu- Khoy–Maku ophiolites could represent a Late Cretaceous back- red either in Middle Eocene (Camp and Griffis, 1982; Tirrul et al., arc basin behind the Zagros ophiolites. This hypothesis is sup- 1983) or Late Cretaceous (Zarrinkoub et al., 2012; Angiboust ported by the occurence of E- to T-MORB pillow lavas in the et al., 2013). Dating of metamorphic rocks indicates Late Creta- Khoy–Maku ophiolite, which are crosscut by SSZ-type dikes and ceous (83–87 Ma) subduction. Ophiolite emplacement occured in overlain by turbidites with SSZ-type clasts. These lavas are geo- Late Cretaceous time. Rb–Sr dating of high pressure metamorphic chemically similar to Eocene Kermanshah–Kurdistan ophiolites. rocks yields ca. 84–87 Ma ages, reflecting Late Cretaceous meta- More studies and especially U–Pb zircon dating is needed for these morphism associated with subduction of the Sistan Ocean. massifs as well as more studies of the ophiolites between the Khoy We have considered all the geochronological and geochemical and Kermanshah regions. characteristics of the Birjand–Nehbandan ophiolites to present a geodynamic model (Fig. 16B and C). In this model, Sistan Ocean 6.3.3. Sabzevar–Torbat-e-Heydarieh ophiolites opening was accompanied by early eruption of N-MORB-, E- There are four key questions concerning Sabzevar–Tobat-e- MORB-, and OIB-like lavas as well as 113–107 Ma MORB-type Heydarieh ophiolite belt (STOB); (1) is there any relationship gabbros (Zarrinkoub et al. 2012)(Fig. 16B and C). Early Cretaceous between the Zagros ophiolites (especially IB) and STOB? (2) What opening is further indicated by occurrence of gabbroic rocks and tectonic environment did these ophiolites form in? (3) What is the Aptian–Albian pelagic sediments (Babazadeh and De Wever, age variation within STOB? (4) Did the various fragments of STOB 2004; Babazadeh, 2007). The Late Cretaceous was the time of intra- oceanic lithosphere form about where they are today or are they oceanic subduction near the Lut block, with eruption of SSZ-related far-traveled nappes? Our review provides some insights for the lavas, associated with gabbros and depleted mantle harzburgites. first three but not the last question. This interpretation agrees with ages obtained from high-P rocks Regarding the first question; it may be that STOB connects with in the region (Brocker et al., 2013). Late Cretaceous pelagic sedi- ZIB. Inspection of Fig. 2 shows a similarity of trends between Nain ments further demonstrate that the Sistan Ocean was open. ophiolite and STOB, but the intervening region is buried beneath Toward the latest Cretaceous to Middle Paleocene time (ca. 70– younger volcanics and sedimentsAeromagnetic and gravity sur- 60 Ma), the continental arc started to develop, accompanied by for- veys could help answer this question. There is similarity between mation of calc-alkaline magmatic rocks as well as adakites and A- the ZIB and STOB ophiolites but ZOB ophiolites may be slightly type granites (Pang et al., 2013). One interpretation is that the Sis- older (ca. 103–99 Ma) than STOB (ca. 99–78 Ma). tan Ocean closed in Late Paleocene time, accompanied by post-col- Regarding the second question, nearly all STOB lavas have SSZ lisional magmatism in response to the convective removal of the geochemical signatures (Shafaii Moghadam et al., 2014). Mantle lithosphere and resultant asthenospheric upwelling during rocks also show SSZ signatures, as shown by spinel and pyroxene Eocene–Oligocene extensional collapse of the east Iranian orogen compositions. The STOB basin was somehow related to a conver- (Pang et al., 2013). The presence of Late Cretaceous–Early Eocene gent margin, perhaps forming as a back-arc basin behind the unmetamorphosed marine clastic sediments including sandstone Zagros convergent margin. and marly turbidite suggests that the Sistan Ocean was open as late Regarding the third question, ophiolitic magmatism continued as Early Eocene time. for 30 Ma, an unusually long life for an ophiolite. This suggests that STOB may be a volcanic arc ophiolite (Dilek and Furnes, 2011). 6.3.5. Makran ophiolites Taking into account all the geochemical, geochronological and We have more work to do in order to understand the formation paleontologic evidence that we have for the STOB, we conclude and evolution of Makran ophiolites. It seems that ocean accretion that the Sabzevar Ocean was an arc-backarc basin complex and generation of MORB lithosphere began in Jurassic time 56 H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 intraoceanic Island arc magmatism N-NE S-SW 100-78 Ma granitoids (97-92 Ma) plagiogranites exhumed high-P metamorphic rocks Oryan-Cheshmeshir ophiolites 107-105 Ma (felsic rocks) Turan block Lut block Sabzevar ophiolites Sabzevar-Torbat-e-Heydarieh ophiolites (A) Intraoceanic subduction and mature arc formation (middle to Late Cretaceous, ~110 Ma). E W MORB-type gabbros (U-Pb=113-107 Ma) sedimentation of Early Cretaceous pelagic sediments N-MORB, E-MORB & OIB Sistan ocean Afghan block Lut block Birjand-Nehbandan ophiolites (B) Ocean accretion & MORB-OIB eruption, (Early Cretaceous, ~120 Ma). E Continental magmatism W sedimentation of Late detrital sediments Sistan ocean Cretaceous pelagic sediments N-MORB, E-MORB & OIB Afghan block Lut block exhumation of high-P rocks Birjand-Nehbandan ophiolites (C) Intraoceanic subduction, exhumation of high-P rocks (Late Cretaceous, ~90 Ma) to continental margin magmatism (Late Cretaceous-Paleocene, 70-60 Ma). Fig. 16. Schematic models for the formation and evolution of the STOB and Birjand–Nehbandan oceanic basins in NE Iran. (A) Intraoceanic subduction in middle Cretaceous and then mature arc formation in Late Cretaceous were responsible for the exhumation of the high-P metamorphic rocks; formation of SSZ-related plagiogranite and other crustal rocks and crystallization of Late Cretaceous granitoid rocks (arc rocks). (B) Oceanic lithosphere accretion and eruption of early lavas with MORB and OIB signatures. Aptian–Albian pelagic sedimentation in this basin was accompanied with plutonism and crystallization of MORB-type gabbros. (C) Intraoceanic subduction and exhumation of high-P rocks occurred during Late Cretaceous (90 Ma), passing into continental margin magmatism during Late Cretaceous to Paleocene (70–60 Ma) (modified after Pang et al., 2013). >170 Ma. This ophiolite belt probably continues east into SW Paki- SSZ-related plutonic rocks. (2) The Bajgan–Durkan zone could be stan (Baluchistan) where there are several Jurassic–Cretaceous a subducted and exhumed accretionary complex, similar to the ophiolites (e.g., Muslim Bagh, Khan et al. 2007; Bela, Zaigham SNSZ. In this model, inner and outer Makran ophiolites formed as and Mallick, 2000; Ras Koh, Siddiqui et al. 2012). Concerning the a once coherent sheet as a result of intraoceanic subduction initia- Bajgan–Durkan zone, we see two competing hypotheses: (1) as tion in Late Jurassic–Early Paleocene time and the two ophiolite proposed by most geologists, this zone could represent a rigid belts formed by uplift and erosion associated with exhumation of block. Following this scenario, a Jurassic back-arc basin formed the Bajgan–Durkan complex. Clearly more work is needed to test behind the Bajgan–Durkan arc. Back-arc basin opening was accom- and refine these models. panied with early MORB magmatism and subsequent SSZ-type Whatever models are developed for the tectonic evolution of lavas during Late Jurassic to Late Paleocene time. This age is Makran ophiolites, they must help explain how these relate to inferred from biostratigraphic ages for the interbedded sediments the ophiolites to the west (Zagros), north (Birjand–Nehbandan), with SSZ-type lavas and/or and geochronological results from east (Baluchistan, Pakistan), and south (Semail, Oman). H.S. Moghadam, R.J. Stern / Journal of Asian Earth Sciences 100 (2015) 31–59 57 7. Conclusions Naopurdan groups) in the Kurdistan region of the Northeast Iraqi Zagros Suture Zone. The Island Arc 22, 104–125. Angiboust, S., Agard, P., De Hoog, J.C.M., Omrani, J., Plunder, A., 2013. Insights on Our main understanding about the evolution of Neotethys deep, accretionary subduction processes from the Sistan ophiolitic ‘‘mélange’’ Ocean in Iran comes from its many Mesozoic and rare Cenozoic (Eastern Iran). Lithos 156–159, 139–158. ophiolites. We have identified five main belts but this should be Anma, R., Armstrong, R., Danhara, T., Orihashi, Y., Iwano, H., 2006. Zircon sensitive high mass-resolution ion microprobe U–Pb and fission-track ages for gabbros modified as we learn more about Iran ophiolites. There are so many and sheeted dykes of the Taitao ophiolite, Southern Chile, and their tectonic ophiolites and so much subsequent deformation, sedimentation, implications. Island Arc 15, 130–142. and volcanism that we cannot yet see clearly which exposures Arvin, M., 1982. Petrology and geochemistry of ophiolites and associated rocks from the Zagros suture, Neyriz, Iran, Ph.D. Thesis. London University, London. are related and which are not. Considering all the field, geochemi- Arvin, M., Robinson, P.T., 1994. The petrogenesis and tectonic setting of lavas from cal and geochronological data on these ophiolites now in hand lets the Baft ophiolitic mélange, southwest of Kerman, Iran. Canad. J. Earth Sci. 31, us conclude that: (1) Most Iranian Mesozoic ophiolites range in age 824–834. Arvin, M., Shokri, E., 1997. Genesis and eruptive environment of basalts from the from Jurassic to Late Cretaceous, but Late Cretaceous–Paleocene Gogher ophiolitic mélange, southwest of Kerman, Iran. Ofioliti 22, 175–182. and even Eocene ophiolitic components are also present; (2) Ira- Arvin, M., Houseinipour, A., Babaei, A.A., Babaie, H.A., 2001. Geochemistry and nian Mesozoic ophiolites are subdivided into passive-type margin, tectonic significance of basalts in the Dare–Anar complex: evidence from the Kahnuj ophiolitic complex, southeastern Iran. J. Sci. I. R. Iran 12 (2), 157–170. SSZ-type, accretionary prism-type, and volcanic-arc type with rare Arvin, M., Babaei, A., Ghadami, G., Dargahi, S., Ardekani, A.S., 2005. The origin of the MORB-type ophiolites; (3) we have much to learn about Triassic, Kahnuj ophiolitic complex, SE of Iran: constraints from whole rock and mineral Jurassic and Early Cretaceous ophiolites of Iran, but these may chemistry of the Bande–Zeyarat gabbroic complex. Ofioliti 30 (1), 1–14. 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