Petrogenesis and tectonic evolution of metaluminous sub-alkaline granitoids from the Takab Complex, NW Iran

Abstract

The Takab complex is composed of a variety of metamorphic rocks including amphibolites, metapelites, mafic granulites, migmatites and meta-ultramafics, which are intruded by the granitoid. The granitoid magmatic activity occurred in relation to the subduction of the Neo-Tethys oceanic crust beneath the Iranian crust during Tertiary times. The granitoids are mainly granodiorite, quartz monzodiorite, monzonite and quartz diorite. Chemically, the magmatic rocks are characterized by ASI < 1.04, AI < 0.87 and high contents of CaO (up to ∼ 14.5 wt %), which are consistent with the I-type magmatic series. Low FeO t /(FeO t +MgO) values (< 0.75) as well as low Nb, Y and K 2 O contents of the investigated rocks resemble the calc-alkaline series. Low SiO 2 , K 2 O/Na 2 O and Al 2 O 3 accompanied by high CaO and FeO contents indicate melting of metabasites as an appropriate source for the intrusions. Negative Ti and Nb anomalies verify a metaluminous crustal origin for the protoliths of the investigated igneous rocks. These are comparable with compositions of the associated mafic migmatites, in the Takab metamorphic complex, which originated from the partial melting of amphibolites. Therefore, crustal melting and a collision-related origin for the Takab calc-alkaline intrusions are proposed here on the basis of mineralogy and geochemical characteristics. The P-T evolution during magmatic crystallization and subsolidus cooling stages is determined by the study of mineral chemistry of the granodiorite and the quartz diorite. Magmatic crystallization pressure and temperature for the quartz-diorite and the granodiorite are estimated to be P ∼ 7.8 ± 2.5 kbar, T ∼ 760 ± 75 • C and P ∼ 5 ± 1 kbar, T ∼ 700 • C, respectively. Subsolidus conditions are consistent with temperatures of ∼ 620 • C and ∼ 600 • C, and pressures of ∼ 5 kbar and ∼ 3.5 kbar for the quartz-diorite and the granodiorite, respectively.

Low‐Temperature Thermochronologic Response to Magmatic Reheating: Insights From the Takab Metallogenic District of NW Iran, (Arabia‐Eurasia Collision Zone)

“…The Eocene flare up is the most voluminous magmatic event recorded in Iran (e.g., Verdel et al., 2011) and was followed by an Oligocene to possibly early Miocene (∼29–22 Ma) phase of intrusive activity associated with the emplacement of granitoids (mainly granodiorite) and the development of migmatites (Figure 2, Hajialioghli et al., 2011; Honarmand et al., 2018; Moazzen et al., 2013; Sepahi et al., 2020; Shafaii Moghadam et al., 2016, 2017). The geodynamic setting that caused migmatization, however, is not clear and has been linked either to core complex formation during upper plate (intra‐arc) extension (Shafaii Moghadam et al., 2016, 2017; Stockli et al., 2004) or partial melting of a thickened lithosphere during collisional deformation (Hajialioghli et al., 2011; Honarmand et al., 2018). Partial melting may have been facilitated by the occurrence of a lithospheric scale, inherited boundary such as a slab tear that could have focused asthenospheric upwelling (Rabiee et al., 2020, 2022).…”

“…The Oligocene represents a rather enigmatic period in the geological history of the Eurasian upper plate of Iran because the stratigraphic record, which is represented by the LRF, is discontinuous and poorly dated (e.g., Berberian & King, 1981). Available petrological data indicate that during the Oligocene, the metamorphic basement of the TRC was characterized by: (a) formation of localized migmatitic gneisses, (b) emplacement of small size granitoids and fractures/dikes filled by leucosome formed during the partial melting of the crystalline basement, and (c) emplacement of large plutons like the Almalou and Shahrak intrusives, which were previously mapped as Neoproterozoic basement or Triassic/Jurassic granitoids (Babakhani & Ghalamghash, 1998; Hajialioghli et al., 2011; Moazzen et al., 2013; Saki et al., 2012; Shafaii Moghadam et al., 2016, 2017; Figures 2 and 8). The metamorphic conditions that led to migmatization and the development of a leucosome through the melting of metamorphosed middle crust rocks (mostly amphibolites) are estimated to be 750°C–800°C and 5–7.5 kbar, corresponding to 13.5–20 km of depth assuming a density of overlaying rocks of 2.7 g/cm 3 (Shafaii Moghadam et al., 2016).…”

“…The Eocene flare up is the most voluminous magmatic event recorded in Iran (e.g., Verdel et al, 2011) and was followed by an Oligocene to possibly early Miocene (∼29-22 Ma) phase of intrusive activity associated with the emplacement of granitoids (mainly granodiorite) and the development of migmatites (Figure 2, Hajialioghli et al, 2011;Honarmand et al, 2018;Moazzen et al, 2013;Sepahi et al, 2020;Shafaii Moghadam et al, 2016. The geodynamic setting that caused migmatization, however, is not clear and has been linked either to core complex formation during upper plate (intra-arc) extension (Shafaii Moghadam et al, 2016Stockli et al, 2004) or partial melting of a thickened lithosphere during collisional deformation (Hajialioghli et al, 2011;Honarmand et al, 2018). Partial melting may have been facilitated by the occurrence of a lithospheric scale, inherited boundary such as a slab tear that could have focused asthenospheric upwelling (Rabiee et al, 2020(Rabiee et al, , 2022.…”

“…versus erosional unroofing during thrusting and compression (Hajialioghli et al, 2011;Moazzen et al, 2013;Saki et al, 2012). The TRC was also affected by a rather continuous magmatism lasting ∼40 Myr, from the early Eocene to the late Miocene (Figure 2b and references therein), in association with mineralization processes (Table 1 and references therein).…”

The Van Microplate: A New Microcontinent at the Junction of Iran, Turkey, and Armenia

“…We have compiled whole-rock, chemical data on 900 volcanic rocks (Agostini et al, 2007;Jahangiri, 2007;Azizi and Jahangiri, 2008;Haghnazar and Malakotian, 2009;Mazhari et al, 2009Mazhari et al, , 2011Ahmadzadeh et al, 2010;Dilek et al, 2010;Ranin et al, 2010;Aghazadeh et al, 2011;Aghazadeh et al, 2015;Ansari et al, 2011;Dabiri et al, 2011;Hajialioghli et al, 2011;Mahmoudi et al, 2011;Asiabanha and Foden, 2012;Alishah et al, 2013;Ansari, 2013;Castro et al, 2013;Ghaffari et al, 2013;Kheirkhah et al, 2013;Moghadam et al, 2014;Neill et al, 2015;Doroozi et al, 2016;Haghnazar et al, 2016;Moritz et al, 2016;Sahakyan et al, 2017;Taki, 2017;Ashrafi et al, 2018;Haghighi Bardineh et al, 2018;Jafari Sough et al, 2018;Lechmann et al, 2018;Shafaii Moghadam et al, 2018;Zhang et al, 2018;Ghalamghash et al, 2019;Temizel et al, 2019) from Cretaceous to Quaternary magmatism in northwestern Iran, southern Armenia, and eastern Turkey (Supplementary S2). The sample locations and references for each area are shown in Figures 4A-E.…”