Introduction

Extensive middle Eocene to recent alkaline and calc-alkaline magmatic rocks, mainly volcanic and unrelated to subduction processes, are present in Iran between Arabia and Eurasia. The origin of these rocks is related to shortening and thickening processes of the continental crust. Major fault systems such as the Doruneh fault zone have played an important role in the generation and emplacement of the magmas (Berberian and King 1981). Magmatism lasted from the middle Eocene (c. 46 Ma) to the Late Oligocene (c. 25 Ma). In the Lut–Sistan region, this magmatism can best be explained by lithospheric removal and asthenospheric upwelling associated with the extensional collapse of the east Iranian ranges (Pang et al. 2013).

Post-kinematic intrusions of Eocene age (47–44 Ma) occur in the western part of the Saghand area (Fig. 1a). Their formation is related to the convergence between Arabian and Eurasian plates and the Cenozoic closure of the Tethys oceanic tract(s) (Ramezani and Tucker 2003). In the Khaf-Kashmar-Bardaskan belt (Fig. 1b), subduction of the Neotethys was followed by collision and post-collision suturing and magmatism, during the Early Tertiary. Significant Eocene plutonism is related to an extensional setting triggered by heating and melt generation in a subduction-modified mantle by upwelling of asthenospheric mantle even far from the Neotethyan subduction zone (Alizadeh et al. 2017).

Fig. 1
figure 1

(a) Simplified geological map of Iran showing the distribution of Eocene magmatic rocks (modified after Shafaii Moghadam et al. 2015), (b) geological and tectonic zones, and simplification of igneous rocks and location of the Aliabad Daman pluton in the Sabzevar Ophiolitic Suture zone (NE Iran). Tectonic zones and location of magmatic rocks redrawn from the geological map of Iran 1:1000000, Geological Survey of Iran (Sahandi and Soheili, 2014)

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A magmatic flare-up occurred during the Late Paleocene-Eocene in the Urumieh-Dokhtar belt and the Alborz Mountains, central Iran. This flare-up was accompanied by normal faulting (Verdel et al. 2011). Whole rock geochemical and geochronological data suggest that this flare-up was extension related and the resulting melts show typical characteristics of continental arc magmas, whereas the Oligocene basalts, which were erupted after the flare-up, are more consistent with derivation from the asthenospheric mantle (Verdel et al. 2011).

The Doruneh fault (Fig. 1b) is a major transcurrent fault, extending c. 900 km from western Afghanistan to West-Central Iran. It is also a key structure in the Arabia–Eurasia collisional zone, bounding the northern margin of the central Iranian microcontinent (CIM) block. Javadi et al. (2013) report an Eocene (c. 56 Ma) initiation age and a slip rate of about 5.2–5.5 mm year−1 of the fault, which accompanied the 35° anticlockwise rotation of the CIM. The Doruneh fault operated as a major zone of residual stress transfer and accommodation in Central Iran. The tectonic evolution of the fault was modulated by convergent plate boundary dynamics (Tadayon et al. 2017). By combining the structural, stratigraphic, and thermochronological dataset, a tectono-stratigraphic evolutionary model for the Doruneh fault has been proposed (Tadayon et al. 2018). In this model, the Sabzevar back-arc oceanic domain started to form during the upper Cretaceous, and the rotation of the CIM along the Doruneh fault zone is placed within the Paleocene-Eocene epoch (60–40 Ma).

The Sabzevar structural zone (Fig. 1) hosts numerous post-ophiolite middle Eocene volcanic rocks. Some of these rocks emplaced along major faults, such as the Sabzevar, Mayamey and Doruneh faults at the southern Sabzevar zone (Fig. 1b). Middle Eocene igneous rocks in the Sabzevar zone can be divided into two main groups, (1) adakitic rocks with ages of c. 47 Ma (Alaminia et al. 2013; Rossetti et al. 2014; Jamshidi et al. 2015b; Shafaii Moghadam et al., 2016; Jamshidi et al. 2018), and (2) igneous rocks without adakitic affinities and ages of c. 40 Ma (Shafaii Moghadam et al. 2015; Alizadeh et al. 2017; Almasi et al. 2019; this study).

The Aliabad-Daman pluton (Fig. 2) is located along the Doruneh fault zone at the southern edge of the Sabzevar structural zone, 25 km northwest of Rashtkhar and 10 km from Aliabad-Daman, northeast Iran. So far, no geochronological studies have yet been performed on this pluton. In the geological map of Dolatabad and Torbat-e-Heydarieh, this pluton has been mapped as a post middle Jurassic granite (Kholghi Khosraghi 1996a, b). Here, we present petrographic, whole rock geochemical, and zircon U-Pb ages for the Aliabad-Daman pluton. On the basis of the new results in combination with previous studies, an explanation of how various tectonic processes controlled the injection of the granitic melts in the Eocene is given.

Fig. 2
figure 2

Geological map of the Aliabad Daman granite area,Sabzevar zone, NE- Iran and sampling locality, redrawn from regional geological map of Dolatabad and Torbat-e-Heydarieh 1:100000, Geological Survey of Iran (Kholghi Khosraghi 1996a, b)

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Geological setting

The Sabzevar zone is located at the northern margin of the central Iranian microcontinent (Takin 1972), northeast Iran. This zone extends east–west and is separated to the north by the Maymey and Joveyn faults from the Alborz-Binalood and Kopet Dagh mountains of the Turan plate, and to the south by the Doruneh fault from the Lut block (Fig. 1).

The occurrence of early Cretaceous deep marine sediments, ophiolites and mélange complexes led to a model that three inner Mesozoic Oceans surrounded the central Iranian microcontinent (CIM) block. (1) Sabzevar Ocean, that was located in the north of the CIM, and separated the CIM from the Turan and Kopeh Dagh plates. (2) Sistan Ocean, that was located in the east of the CIM, and separated the CIM from the Farah and Helmand blocks in Afghanistan. (3) Baft-Nain Ocean that was located in the west–southwest of the CIM, and separated the CIM from the Sanandaj–Sirjan zone and Afro-Arabian plate (e.g., Sengör et al. 1988; Sengör 1990; McCall 1997; Shojaat et al. 2003; Baroz et al. 1984; Arvin and Robinson 1994; Agard et al. 2011). Some authors assume that the Baft-Nain Ocean was connected to the Sistan basin (Saccani et al. 2010; Agard et al. 2011; Bonnet et al. 2020).

The basement of the Sabzevar zone is composed of Late Neoproterozoic to Early Cambrian (Cadomian) magmatic rocks. Outcrops of these rocks can be found in the Taknar-Bornaward and Fariman regions (Fig. 1b). Based on the Kashmar geological map, the Cadomian basement of the Sabzevar zone in Doruneh and Kashmar regions consists of brecciaed metarhyolite (Taheri and Shamanian 2001). The Arghash dioritic pluton with a U–Pb zircon age of 554 ± 6 Ma is reported from the Sabzevar zone (Alaminia et al. 2013). Based on inherited zircon record, it was suggested that 10–20 vol.% of the middle Eocene Kashmar granitoid (Fig. 1) has been formed from the Cadomian lower crust (Shafaii Moghadam et al. 2015). The age of the Taknar and Bornaward granitoid complex (Fig. 1) is Late-Neoproterozoic (570–530 Ma) (Monazzami Bagherzadeh et al. 2015; Shafaii Moghadam et al. 2017). Detail geochronological data show that the plutonic rocks of the Taknar zone in the Kaboodan area mainly formed during the late Neoproterozoic (550–530 Ma, (Mazhari et al. 2019).

Upper Cretaceous igneous rocks in the Sabzevar zone can be divided into two main groups, (i) ophiolitic igneous rocks and (ii) the non-ophiolitic, subduction-related igneous rocks. The ophiolitic igneous rocks are NW-SE orientated and are mostly found along faults (Fig. 1b). The Sabzevar ophiolite originated from a tholeiitic magma source in an intra-oceanic island arc/supra-subduction zone setting (Rahmani et al. 2017). The non-ophiolitic, subduction-related igneous rocks in the Sabzevar zone are exposed as both intrusive and extrusive rocks. These rocks crop out mostly southwest and south of Sabzevar (Fig. 1b). The non-ophiolitic rocks formed during upper Cretaceous time between c. 101–75 Ma. In the Arghash region, I-type granitoids with ages of c. 93 Ma originated in an island-arc or back-arc basin setting (Alaminia et al. 2013). A series of shallow mafic to felsic rocks that are intrusive and extrusive with ages of 101–75 Ma have been formed in a supra-subduction system (Kazemi et al. 2019). In the Kaboodan region, there are extrusive and intrusive rocks with ages between 99 and 75 Ma (Mazhari et al. 2019).

The Sabzevar zone hosts abundant early to middle Eocene (57–45 Ma) adakitic intrusions, mainly of extrusive nature (Fig. 1b). This magmatism occurred during the collision between the central Iranian microcontinent (CIM) block and the Turan block between c. 57 and 45 Ma. A suite of felsic magmatic rocks with zircon U-Pb ages of c. 58 Ma crop out in the Soltanabad area of the Sabzevar zone (Rossetti et al. 2014). Adakitic igneous bodies of andesite, dacite and fine-grained granite with ages of c. 55 Ma occur in the Arghash region (Alaminia et al. 2013). Adakitic intermediate to felsic mainly extrusive and minor intrusive rocks with zircon U–Pb and mica Ar–Ar ages of 47–45 Ma are found northwest of Sabzevar (Shafaii Moghadam et al. 2014; Shafaii Moghadama et al. 2016). Numerous middle Eocene (c. 45 Ma) extrusive intermediate to felsic rocks intruded into the Sabzevar ophiolitic belt northwest of Sabzevar (Jamshidi et al. 2018). Post-ophiolitic high-silica adakitic rocks with emplacement ages of c. 48 Ma and dacite/rhyolite composition outcrop in the ophiolitic complex of the Sabzevar zone (Jamshidi et al. 2015b).

In addition, several intrusive rocks without adakitic affinities and of middle Eocene and Bartonian age (c. 40 Ma) intruded into the Sabzevar zone along the major Doruneh fault zone. So far, some researchers (Shafaii Moghadam et al. 2015; Alizadeh et al. 2017; Almasi et al. 2019) have studied three similar plutons along the Doruneh fault zone from the Sabzevar zone and the Lut block. The Aliabad-Daman pluton occurs along the Doruneh fault zone, 10 km north of Aliabad Daman, 12 km northeast of Sangan, 25 km northwest of Rashtkhar and the southern edge of the Sabzevar structural zone (Fig. 2). This pluton consists of alkali feldspar granite, syenogranite, and monzogranite. The Aliabad-Daman pluton intruded into the Shemshak Formation containing Jurassic sandstone, siltstone, shale, and claystone, and the Nayband Formation containing Triassic sandstone and shale. The concentration of Eocene magmatic rocks along the Doruneh fault zone shows that this major fault zone, with a length of 900 km, exerted an important role in the emplacement of the Eocene magmatism on the southern edge of the Sabzevar structural zone (Fig. 1).

Field relations and petrography

Rocks of the Aliabad Daman pluton (Figs. 1, 2) have a massive structure, a leucocratic appearance and a color index of 5–15. (Fig. 3a–d). The pluton has fault-bounded contacts with Jurassic shales of the Shemshak Formation (Fig. 3 e). The pluton consists of syenogranites, alkali feldspar granites, and monzogranites with mainly granular (Fig. 3f) and minor granophyric textures (Fig. 3d). Syenogranites form the main volume (~50%) of the pluton and are composed of 30–50 vol.% quartz, 20–40 vol.% alkali feldspar, 5–15 vol.% plagioclase and accessory minerals of biotite, titanite, apatite and zircon. Alkali feldspar granites make up about 30% of the volume of the Aliabad Daman pluton. Mineral constituents are alkali feldspar 40–50 vol.%, quartz 20–30 vol.%, plagioclase 5–10 vol.%, and apatite, titanite, and zircon occur as accessory mineral phases. Monzogranites make up a smaller volume of the pluton with a mineral assemblage of 25–30 vol.% quartz, 25–30 vol.% plagioclase, 20–30 vol.% alkali feldspar, 5–10 vol.% biotite, and accessory minerals including titanite, apatite, and zircon.

Fig. 3
figure 3

a Field photographic view of the Aliabad Daman granite. b, c, d Field photograph from contact between Jurassic shale of the Shemshak Formation and the Aliabad Daman granite. e Polarized microscopic image showing granular texture, quartz, K-feldspar, plagioclase, Biotite and zircon in the Aliabad Daman granite. f Polarized microscopic image showing granophyric texture in the Aliabad Daman igneous body. Abbreviation symbols (Whitney and Evans 2010); Pl = plagioclase, Kfs = K-feldspar, Qz = quartz, Bt = biotite, Zrn = zircon

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Analytical methods

Fifty-five samples from the Aliabad Daman granite with the least signs of alteration were selected for analyses. Thin sections were prepared from all samples and studied under an optical polarized microscope (Zeiss-Axioskop 40 POL) at the Department of Geology, Bu-Ali Sina University, Hamedan, Iran. Fifteen fresh samples were selected for whole rock geochemical analyses. For this purpose, eight samples were sent to the Geological Survey and Mineral Exploration of Iran and seven samples to the Zarazma Mineral Studies Company, Iran. Major elements were analyzed by Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and trace elements by Inductively Coupled Plasma-Mass Spectroscopy (ICP-MS).

Preparation processes of zircons for U–Pb dating, such as crushing, sieving, heavy liquid and magnetic separation, hand picking under a binocular microscope, mounting on epoxy resin, and polishing were carried out at the Department of Geology, Bu-Ali Sina University, Hamedan, Iran. Forty zircon grains, 100–300 μm in size, were separated from sample TP4990 (syenogranite), and TP1011 (alkali feldspar granite). Polished grains were studied by cathodoluminescence (CL) using a scanning electron microscopy (JEOL JSM-6510LV) equipped with cathodoluminescence system (GATAN MiniCL) at Nagoya University, Japan. Forty spots from 30 zircons of sample TP4990 and 23 spots from 19 zircons of sample TP1011 were analyzed by LA-ICP-MS (Agilent 7700x) connected with a laser ablation system (NWR213 Electro Scientific Industries) at Nagoya University (Japan). ISOPLOT v. 4.15 software (Ludwig, 2012) was used for U-Pb data evaluation.

Results

Zircon U–Pb ages

Cathodoluminescence (CL) images (Fig. 4a, b) show that the zircon grains have short to medium prismatic euhedral to subhedral shape and magmatic oscillatory textures. The U–Pb data are listed in Table 1, and the concordia diagrams are plotted in Figs. 5 and 6.

Fig. 4
figure 4

a Cathodoluminescence (CL) images of the zircon grains of sample TP4940 (Syenogranite). b Cathodoluminescence (CL) images of the zircon grains of the sample TP1011 (Alkali feldspar granite) with positions of the ablation

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Table 1 U-Pb isotopic data for zircon crystal determined by LA-ICP-MS in plutonic rocks of the Aliabad Daman granite, Sabzevar zone, NE Iran
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Fig. 5
figure 5

Zircon U–Pb Concordia diagram and weighted mean ages and 2 sigma error for the sample TP4940 (Syenogranite)

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Fig. 6
figure 6

Zircon U–Pb Concordia diagrams and Weighted mean ages and 2 sigma error for the sample TP1011 (Alkali feldspar granite), (b) the Age-Gaussian deconvolution diagram display two dominant age populations with peak ages of 41.3 Ma and 44.7 Ma

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Sample TP4990 (syenogranite)

Th/U ratios in the zircon grains from sample TP4990 vary between 0.32 and 2.21 with a mean value of 0.73 (Table 1). This is consistent with a magmatic origin of the grains (e.g., Xiang et al. 2011; Kirkland et al. 2015; Yakymchuk et al. 2018). Forty spots from 30 zircon grains of this sample cluster on the concordia at 39.98 ± 0.39 Ma (2σ error), MSWD = 2.6 (Fig. 5a), with a weighted mean 206Pb/238U age of 40.01 ± 0.33 Ma (2σ error), MSWD = 2.5 (Fig. 5b). Interior and outer parts of most grains yield the same ages. Cores of three zircon grains yield slightly older ages of 48.5, 73.8 and 52.0 Ma (Table 1).

Sample TP1011 (alkali feldspar granite)

Twenty-three spots from 19 zircon grains were analyzed from alkali feldspar granite sample TP1011 and the U–Pb zircon analyses listed in Table 1. Nineteen zircon grains from this sample give a range of ages from c. 40 to 47 Ma. A discordia line through these fractions yields a lower intercept age of 41.1 ± 1.8 Ma (Fig. 6a). From the Gaussian deconvolution diagram two dominant age populations with peak ages of 41.3 Ma and 44.7 Ma are obtained (Fig. 6b). This can be taken as evidence of differences in the formation ages of the igneous rocks.

Nine spots from zircon grains of the alkali feldspar granite sample TP1011 yield a concordia (Terra-Wasserburg) age of 41.91 ± 0.92 Ma, MSWD = 0.88 (Fig. 6c), with a weighted mean 206Pb/238U age of 41.54 ± 0.87 Ma (2σ error) and an MSWD value of 3.9 (Fig. 6d). Ten spots from this sample yield a discordia (Terra-Wasserburg) age of 45.1 ± 1.5 Ma, MSWD = 0.73 (Fig. 6e), with a weighted mean 206Pb/238U age of 44.97 ± 0.84 Ma (2σ error), MSWD = 2.5 (Fig. 6f). Three spots yield an upper intercept age of c. 776 Ma due to presence of old inherited zircon components in the respective grains (Table 1).

Whole rock geochemistry

The results of whole rock geochemical analyses from the Aliabad Daman pluton are presented in Table 2. The rocks are commonly granitic in composition with minor variation in major elements. Silica content ranges from 75.40–77.00 wt.%., Al2O3 from 11.38–12.80 wt.%, CaO from 0.25–0.90 wt.%, K2O from 3.60–4.97 wt.%, Na2O from 2.80–3.99 wt.%, Fe2O3T from 1.01–2.47 wt.%), MgO from 0.08–0.20 wt.%, and LOI from 0.38–2.77 wt.%. In the Harker variation diagrams (Fig. 7), the samples display decreasing Al2O3, CaO, Fe2O3, Sr, Ba, Zr, Ce, Y, Yb, increasing Na2O, and increasing then decreasing K2O concentrations with increasing silica.

Table 2 Major and trace element concentrations of the Aliabad Daman granite, Sabzevar zone, NE Iran
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Fig. 7
figure 7

Selected Harker variation diagrams for samples of the Aliabad Daman granite

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In the REE-chondrite-normalized diagram (Fig. 8a), the samples are characterized by variable fractionation between light and heavy REE (LaN/YbN = 11–22) and negative Eu anomalies (Eu/Eu* = 0.1–0.4). In the primitive mantle-normalized multi-elements diagram (Fig. 8b), the samples display negative Ba, Nb, Sr, P, Zr, and Ti anomalies, relative depletion of heavy REE and enrichment of large ion lithophile elements (LILE).

Fig. 8
figure 8

a Chondrite normalized REE pattern for representative samples from Alabad Daman granite. b Primitive mantle normalized multi-elements pattern for representative samples from Alabad Daman granite. The normalized values of REE are from (Boynton 1984), the normalizing values of the multi-elements are from (Sun and McDonough 1989)

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In the total alkali versus silica (TAS) diagram from Middlemost (1994), all samples from Aliabad Daman pluton plot in the granite field (Fig. 9a). In the A/NK (molar Al2O3/Na2O + K2O) vs. A/CNK (molar Al2O3/CaO + Na2O + K2O) diagram all samples display metaluminous to peraluminous affinity (Fig. 9b). As shown in Fig. 9a and b, the samples have geochemical characteristic similar to those of felsic rock types from the Kashmar pluton (Shafaii Moghadam et al. 2015) and to those of the Nay pluton (Almasi et al. 2019) along the Doruneh fault zone. According to the K2O–SiO2 diagram of Peccerillo and Taylor (1976), the samples belong to the high-K calc-alkaline series (Fig. 9c). In the AFM triangular diagram (Fig. 9d), the granitic rocks show calc-alkaline nature.

Fig. 9
figure 9

a Total alkalis versus SiO2 diagram for classification of the Aliabad Daman rocks (after Middlemost 1994). Compositional field for the Bartonian (~40 Ma) felsic rocks in the Sabzevar zone (yellow and red dashed line) and source rock of the Late-Neoproterozoic Taknar and Bornaward Granitoid Complex (BGC) (green square) respectively are from (Almasi et al. 2019; Shafaii Moghadam et al. 2015; Monazzami Bagherzadeh et al. 2015). b A/NK (molar Al2O3/Na2O + K2O) vs. A/CNK (molar Al2O3/CaO + Na2O + K2O) diagram. c K2O–SiO2 diagram. d AFM diagram. A (Na2O + K2O), F (FeO + Fe2O3), M (MgO) (Irvine and Baragar 1971) diagram

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Samples from the Aliabad Daman pluton have low Sr/Y, according to the definition of Defant and Drummond (1990), but they do not have similar geochemical characteristics to adakites. In the Rb against Y + Nb diagram (Pearce et al. 1984), samples from the Aliabad Daman pluton, similar to samples from other Bartonian plutons of the Iranian structural zones plot in the volcanic arc granite (VAG) field (Fig. 10a). In the Th/Yb versus Nb/Yb diagram (Pearce 2008), the samples plot in the field of Archean crust (A) close to the data for the late-Neoproterozoic Taknar (Bornaward) granitoid complex (BGC) (Fig. 10b).

Fig. 10
figure 10

a Rb vs. Y + Nb diagram (Pearce et al. 1984) for samples from Aliabad Daman granite, Compositional field for the Bartonian (~40 Ma) magmatism of the Sabzevar zone, Alborz zone, Lut block, Urumieh-Dokhtar magmatic arc and Sanandaj-Sirjan zone respectively are from Shafaii Moghadam et al. (2015), Verdel et al. (2011), Javidi Moghaddam et al. (2020), Nouri et al. (2019) and Ranin et al. (2010). b Th/Yb vs. Nb/Yb diagram (Pearce et al., 2008) of the Aliabad Daman granitic samples and its source rock (BGC)

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Discussion

Magma source and petrogenesis

Our results such as major-trace elements characteristics and presence of inherited zircon suggest that Aliabad Daman pluton was derived from a continental crustal source with input of mantle material. The Th/Yb versus Nb/Yb diagram (Pearce 2008) shows that the samples from the pluton have chemical properties similar to the Late-Neoproterozoic Taknar and Bornaward Granitoid Complex (BGC) (Fig. 10b). Besides, the geochemical characteristics of the Aliabad Daman pluton are comparable with felsic members of the Eocene Kashmar granitoids (Shafaii Moghadam et al. 2015), and with the Nay intrusive rocks studied by Almasi et al. (2019) (Fig. 9a, b). Sr-Nd isotopic data obtained from samples collected from the Batonin (c. 40 Ma) plutons along the Doruneh fault zone, southern edge of the Sabzevar suture zone, show that two end-members, i.e., an enriched mantle source and a continental crustal source were involved in magma generation (Shafaii Moghadam et al. 2015; Almasi et al. 2019) (Fig. 11).

Fig. 11
figure 11

Initial 143Nd/144Nd vs. (87Sr/86Sr)i for Eocene (~ 40 Ma, Bartonian time) magmatic rocks of the Zabzevar zone along the Doruneh fault zone compared with Eocene (~ 46 Ma, Lutetian time) adakitic rocks and Late-Neoproterozoic Taknar and Bornaward Granitoid Complex (BGC) from Zabzevar zon. Data for Eocene (~ 46 Ma, Lutetian time) adakitic rocks, from Shafaii Moghadam et al., (2016); data for Nay intrusive rocks, from Almasi et al., (2019); data for Kashmar granitoid rocks, from Shafaii Moghadam et al., (2015); data for Taknar and Bornaward Granitoid Complex (BGC), from Monazzami Bagherzadeh et al., (2015)

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The presence of old inherited zircons ages (e.g., 623 Ma) in the Aliabad Daman pluton suggests that melts of the Cadomian crust played a role in the generation of the magma. Also, the presence of old inherited zircons with an age of c. 640 Ma in felsic members of the Kashmar granitoids from the Zabzevar zone (Shafaii Moghadam et al. 2015) support the assimilation of the Cadomian crust during Bartonian magmatism. Hence, it seems that the magmas of the Aliabad Daman pluton were generated by partial melting of material from the continental crust and the lithospheric mantle.

From the Zr/Nb versus Zr diagram (Shen and Pan 2013) and the Dy/Yb versus Dy, La/Yb versus La diagrams (Gao et al. 2007), it can be inferred that partial melting played a more important role than fractional crystallization in the generation of the Aliabad Daman magma (Fig. 12a–c). However, in Harker variation diagrams (Fig. 7), the samples display decreasing Al2O3, CaO, FeO, Sr, Ba, Zr, and Y and increasing Na2O, K2O concentrations with increasing silica. This variation can be ascribed to the fractionation of Ca-rich plagioclase, Fe oxides and zircon during crystallization. Sr, Ba, and Y are compatible in Ca-rich plagioclase; consequently, Sr, Ba, and Y decreased due to fractionation of Ca-rich plagioclase.

Fig. 12
figure 12

a Zr/Nb versus Zr diagram (Shen and Pan 2013), b, c La/Yb versus La and Dy/Yb versus Dy diagrams (Gao et al. 2007) display that partial melting has important role rather than fractional crystallization in Aliabad Daman Granite

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Geodynamic setting and geochronological characteristics

U-Pb zircon ages for Cretaceous and Paleogene extrusive and intrusive rocks of the Sabzevar Ophiolitic Suture Zone (SOSZ) are summarized in Table 3, and the resulting age spectrum is shown in Fig. 13. From the middle Jurassic to early Cretaceous extensional tectonics prevailed in the oceanic realms around the Central Iranian Microcontinent (e.g., Lindenberg et al. 1984; Sengör 1990). The Sabzevar oceanic crust started to form during the early Jurassic and reached its maximum extension during the early Cretaceous (e.g., Stöcklin 1974; Omrani et al. 2018). The presence of continental alkaline basalts, dikes, and sills in the lower members of the Shemshak Formation (e.g., Annells et al. 1975; Ghasemi and Jamshidi 2012) points to the likelihood of extensional tectonics in the early Jurassic time in the Sabzevar zone. The presence of sandstone, siltstone, shale and claystone in the early Jurassic Shemshak Formation (Fig. 2) is further evidence for the existence of an oceanic environment and for extensional tectonics in the Sabzevar zone. Thus, the generation of the Sabzevar ocean as a back–arc domain in the Neotethyan subduction system probably started from middle Jurassic by rifting and sedimentation of clastic sediments (Skemshak Formation) in a continental shallow basin. It was completed by deposition of pelagic limestone associated with volcanic rocks during middle Cretaceous (Aptian) times (c. 115 Ma).

Table 3 Summary of zircon/titanite U-Pb and 40Ar-39Ar age data from the Sabzevar zone, NE Iran
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Fig. 13
figure 13

Spectrogram for zircon/titanite U-Pb and 40Ar-39Ar age data from the Sabzevar Ophiolitic Suture Zone (SOSZ). N: Number of published age data for the samples collected from the SOSZ. Data sources are summarized in the Table 3

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It has been frequently stated that the Sabzevar Ocean was created in the back–arc domain of the Neotethyan ocean during Mesozoic time (e.g., Sengör et al. 1988; Sengör 1990; McCall 1997; Bagheri and Stampfli 2008; Rossetti et al. 2010; Jamshidi et al. 2015a; Shafaii Moghadam et al. 2015, 2016, 2019; Mazhari et al. 2019; Kazemi et al. 2019; Almasi et al. 2019; Rahmani et al. 2020). Numerous investigators argue that the magmatic rocks of the Sabzevar zone such as mantle ophiolite sequence, mafic and ultramafic units of the ophiolite sequence, volcano-sedimentary sequence (pelagic limestone), crustal plutonic rocks and extrusive rocks were generated in a supra-subduction setting (e.g., Khalatbari Jafari et al. 2013a, b; Shafaii Moghadam et al. 2014; Rahmani et al. 2017; Omrani et al. 2018; Omrani 2018; Kazemi et al. 2019). It was also stated that the Sabzevar ophiolites formed as island arc tholeiites (IAT) in an intra-oceanic arc setting and in a supra-subduction system (e.g., Shojaat et al. 2003; Rossetti et al. 2010; Khalatbari Jafari et al. 2013a, b; Shafaii Moghadam et al. 2014; Omrani et al. 2018; Rahmani et al. 2017; Omrani 2018; Kazemi et al. 2019; Rahmani et al. 2020).

U-Pb dating of zircon and titanite from felsic rocks (tonalite / trondhjemite) of the Sabzevar ophiolite indicates a range of ages from 115 to 99 Ma. These rocks coexist with garnet-clinopyroxene residues (granulite) that formed by melting of mafic rocks (Rossetti et al. 2010). C. 93 Ma old I-type granitoids are present in the Arghash region (Alaminia et al. 2013). Petrological and geochronological data on other rock units of the ophiolite sequence from the Sabzevar zone such as plagiogranite, gabbro, tonalite, and diabasic dike within the peridotite members show that they formed during upper Cretaceous time (100–78 Ma) from a depleted mantle source (Shafaii Moghadam et al. 2014, 2019). The formation of basaltic andesites (c. 93 Ma) from the Kabudan area (Mazhari et al. 2019) and granitic rocks (c. 102 Ma) from the southern edge of Sabzevar basin (Kazemi et al. 2019) is related to subduction zone magmatism. Thus, it can be concluded that an intra-oceanic arc setting existed in the Sabzevar structural zone during Albian times. We propose that a supra-subduction system existed in the Sabzevar back-arc basin during lower Cretaceous Aptian time. Also, the southern flank of the Sabzevar oceanic crust started to subduct beneath its northern side at c. 110 Ma (pre-Albian). Based on results reported by Rossetti et al. (2010), Shafaii Moghadam et al. (2014), Kazemi et al. (2019), Mazhari et al. (2019) and Shafaii Moghadam et al. (2019), magmatic activity related to a supra-subduction system continued until the upper Cretaceous (Campanian) (Table 3, Fig. 13).

It was postulated that the Sabzevar ocean closed during the transition from Paleocene to Eocene time (c. 57 Ma, Thanetian) contemporaneous to the suturing between Iran and Arabia (e.g., Davoudzadeh 1972; Lensch et al. 1977; Mazhari et al. 2009; Delaloye and Desmons 1980; 1981; Spies et al. 1983; Baroz et al. 1984; Sengör et al. 1988; Arvin and Robinson 1994; Stampfli and Borel 2002; Shojaat et al. 2003; Omrani et al. 2008; Rossetti et al. 2010; Agard et al. 2011; Jamshidi et al. 2018; Kazemi et al. 2019). As shown in Fig. 14, Eocene magmatic activity of the Sabzevar zone is contemporaneous with magmatic activity in the central Alborz zone (Verdel et al. 2011).

Fig. 14
figure 14

Correlation of the magmatic activities in the Sabzevar ophiolitic suture zone and Alborz zone after closing of the Sabzevar Ocean, from upper Paleocene (~ 57 Ma). (a) Stratigraphy of the Chalus Road area and geochronological results of magmatic activities are from Verdel et al. (2011). (b) Spectrogram of the magmatic activities in the Sabzevar ophiolitic suture zone is taken from Fig. 13

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For a long time period, from upper Cretaceous time (c. 75 Ma, Campanian) to upper Paleocene time (c. 57 Ma, Thanetian) no magmatic activity occurred in the Sabzevar zone (Fig. 13). During this time, closure of the Sabzevar Ocean only occurred by shorting and thickening of oceanic crust and lithospheric mantle. This interval possibility corresponds to the subsidence of intra-oceanic subduction of the Sabzevar basin (c.75 Ma, Campanian) and to the start of collision between the central Iranian microcontinent (CIM) and the Turan block. Tadayon et al. (2018) depict a tectono-stratigraphic evolutionary model of the Doruneh fault region for this time period.

Middle Eocene igneous rocks in the Sabzevar structural suture zone can be divided to two main groups, (i) adakitic igneous rocks of Lutetian (c. 47 Ma) age (Alaminia et al. 2013; Rossetti et al. 2014; Jamshidi et al. 2015b; Shafaii Moghadam et al., 2016; Jamshidi et al. 2018), and (ii) calc-alkaline igneous rocks without adakitic affinities of Bartonin (c. 40 Ma) age (Shafaii Moghadam et al. 2015; Alizadeh et al. 2017; Almasi et al. 2019; this study). From middle Eocene to present time, extensive alkaline and calc-alkaline volcanic rocks, unrelated to subduction zone processes, were formed in respond to shortening and thickening of the central Iran microplate (Berberian and King 1981). This petrogenetic model is compatible with present-day crustal thicknesses and a gravimetric Moho depth of 47 km in the Sabzevar zone reported by Dehghani and Makris (1983), an Eocene initiation age of the Doruneh fault zone (Javadi et al. 2013), and the tectono-stratigraphic evolutionary model for the Doruneh fault region (Tadayon et al. 2017, 2018). Magmatism occurred after the cessation of subduction (c. 57 Ma, Thanetian) by melting of the detached slab of oceanic crust (MORB), and upwelling of the asthenosphere. Therefore, shortening and thickening of the continental crust and the lithospheric mantle, delamination of the lower crust and the lithospheric mantle, and heating by asthenospheric upwelling played important roles in the production of the middle Eocene (c. 45 Ma, Lutetian) and the younger granitoids such as the Aliabad Daman pluton and the initiation of the Doruneh fault zone (Fig. 15).

Fig. 15
figure 15

Schematic model showing the generation of the Aliabad Daman granitic body. Occurrence of post-collision extension, extensional collapse of the Sabzevar ophiolitic suture zone, asthenosphere upwelling, delamination of the lower crust and mantle lithosphere, Doruneh fault zone activities, and generation of the fault related calc-alkaline igneous rocks without adakitic affinities of the Aliabad Daman granite at Middle Eocene, Bartonian time (~ 40 Ma)

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Conclusions

Based on whole rock geochemical data, the Aliabad Daman pluton represents a metaluminous to peraluminous magma body belonging to the high-K calc-alkaline series. Compositional variations of major and trace elements can be mainly related to the partial melting process. The U–Pb dating results show that the magmas crystallized 45–40 Ma ago. Geochemical characteristics, the presence of inherited zircon, and the combination of new results with previous studies suggest that the Aliabad Daman pluton formed by melting of material from the continental crust and the lithospheric mantle.

Middle Eocene igneous rocks in the Sabzevar structural suture zone comprise a group of the adakitic rocks of Lutetian (c. 47 Ma) age and a group of rocks without adakitic affinities of Batonin (c. 40 Ma) age. From upper Cretaceous to upper Paleocene (c. 75 to 57 Ma) no magmatic activity occurred in the Sabzevar zone. During this period, closing events within the Sabzevar Ocean only occurred by shorting and thickening of the oceanic crust and the lithospheric mantle. Delamination of the lower crust and the lithospheric mantle followed by upwelling of hot asthenosphere played an important role in the production of the Aliabad Daman pluton. Tectonic activity along the Doruneh fault zone and the extensional collapse of the crust also contributed to the generation and emplacement of this pluton.