Geochemical description and sulfur isotope data for Shahrak intrusive body and related Fe‐mineralization (east Takab), northwest Iran

Abstract

The Shahrak intrusive body (SIB) occurs at the intersection of the Urumieh-Dokhtar Volcanic Belt and the Sanandaj-Sirjan metamorphic belt in northwest Iran. This intrusive body consists of granodiorite, monzonite, monzodiorite, and monzogabbro, that intruded Oligo-Miocene sedimentary units and Cretaceous and Precambrian metamorphic rocks. Iron mineralization has occurred as magnetite skarn with hematite and pyrite in calcareous units at the contact with the SIB. The Rb-Sr age dating shows that the age of the SIB is about 24.9 Ma (Chattian). Whole rock geochemical studies indicate that the magma has calc-alkaline to high-K calc-alkaline affinities and is metaluminous. The multi-elements spider diagrams normalized to chondrite and primitive mantle show significant enrichment of light rare earth element against heavy rare earth element and depletion of Ti, P, Ta, and Nb, indicating characteristic features of the volcanic arc rocks in a subduction setting. Furthermore, the various types of tectonomagmatic diagrams show that these rocks are generated in an active continental margin. The parental magma of the rocks probably originated from an enriched mantle on the basis of the geochemistry of the REE elements. The average Sr isotopic composition of the SIB is 87 Sr/ 86 Sr(i) = 0.706. Therefore, the parent magma of the SIB may be the result of partial melting of enriched mantle or subducted slab contaminated with the continental crust. The sulfur isotope composition of pyrite grains (ave., +5.29 ‰) in the Korkora-1 iron deposit indicates that the sulfides are formed from magma or due to in situ dissolution and leaching of igneous sources. Dehydration melting of the subducted part of oceanic crust has likely produced the fluids that are necessary for melting of the mantle wedge to produce mafic-intermediate melts. The generated melts penetrated into the crust, and during their ascent they underwent a little crustal contamination and eventually were emplaced as intrusive bodies comprising gabbrodiorite to granodiorite.

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

“…From the Mesozoic, the TRC became the upper plate of the Neo‐Tethys subduction system and was affected by multiple episodes of arc magmatism (e.g., Hassanzadeh et al., 2008). 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).…”

“…40 Ar-39 Ar ages are from, (2) Daliran et al (2013), (3) Gilg et al (2006), and (6) Mehrabi et al (1999); K-Ar ages are from (6) Mehrabi et al (1999); Rb-Sr ages are from Sepahi et al, 2020; Zircon U-Pb ages are from (2) Daliran et al (2013), (4) Hassanzadeh et al (2008), (5) Heidari (2013), and (7) Shafaii Moghadam et al (2016). (8)Sepahi et al, 2020, (9) Honarmand et al, 2018, (10) Shafaii Moghadam et al (2017, and (11)Azizi et al (2021). Abbreviations: Am, Amirabad Fault; An, Angouran Fault; Ch, Chahartagh Fault; Kk, Kaka Fault; Lk, Lalekan Fault; Ma, Mahneshan Fault; Qu, Qozlu Fault; Qa, Qarenaz Fault; Ag, Angouran Mine Fault; Sh, Shahrak Fault; Sl, Sheikhlar Fault; Ts, Takht-e Soleyman Fault; Al-i, Almalou granite (∼25 Ma); and Sh-i, Shahrak intrusive body (∼25 Ma, but possibly assembled during earlier intrusions).…”

Post‐collisional alkaline lamprophyre magmatism in northern Iran: Implications from whole‐rock geochemistry and mineral compositions

“…The Iranian crust is composed of tectonic blocks that were involved in the closure of Prototethys, Paleotethys and Neotethys ocean basins during the northward convergence of Gondwana with Eurasia (Omrani et al, 2013a,b, 2017; Sepahi et al, 2020; Stampfli & Borel, 2002). In Iran, the Paleotethys suture zone is located along the Alborz Mountain range (e.g., Omrani et al, 2013b; Şengör, 1992; Zanchetta et al, 2009).…”

The age and geochemistry of the Bardkish syenite, northwest Iran: Syenite formation during Neo‐Tethyan subduction

“…It is separated from the ZFTB by the Main Zagros Thrust (MZT) in the southwest, and is bordered by the UDMA in the northeast. It consists mostly of complexly deformed and metamorphosed Mesozoic basement intruded by numerous deformed and un‐deformed Mesozoic plutons and widespread Mesozoic volcanic rocks (Mohajjel, Fergusson, & Sahandi, 2003; Sepahi, Ghoreishvandi, Maanijou, Maruoka, & Vahidpour, 2020). The ZFTB, a 150–250 km wide zone between the MZT to the northeast and the Mountain Front Fault to the southwest, consists of thick (13–14 km) folded shelf deposits of late Paleozoic to early Cenozoic age (James & Wynd, 1965).…”

“…Subsequent folding and thrusting were related to the ongoing collision between the Arabian plate and central Iran, starting along the MZT in the in the Late Cretaceous–Early Tertiary (e.g. Sepahi et al, 2020).…”