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.

Pegmatites and associated granitoids are integral parts of the Alvand plutonic complex in the Sanandaj–Sirjan zone, Iran. Whole rock major- and trace-element lithogeochemistry together with zircon U–Pb geochronology and zircon geochemistry are examined to evaluate the petrogenesis of sapphire-bearing pegmatites and other peraluminous pegmatites in the region. Pegmatites vary in their chemical compositions from mostly peraluminous, high-K calc-alkaline to shoshonitic signatures. A rare variety of extremely peraluminous sapphire-bearing syenitoid pegmatite (Al2O3 > 30 wt %; A/CNK > 2) exists. This silica-undersaturated pegmatite and its sapphire crystals have a primary igneous origin. U–Pb zircon geochronology of three separate samples from this pegmatite indicates the following ages: 168 ± 1 Ma, 166 ± 1 Ma and 164 ± 1 Ma. The zircon grains have notable amounts of Hf (up to 17 200 ppm), U (up to 13 580 ppm), Th (up to 5148 ppm), Y (up to 4764 ppm) and ∑REE (up to 2534 ppm). There is a positive correlation between Hf and Th, Nb and Ta, U and Th, and Y and HREE and a negative correlation between Hf and Y values in the zircons. These zircons exhibit pronounced positive Ce anomalies (Ce/Ce* = 1.15–68.06) and negative Eu anomalies (Eu/Eu* = 0.001–0.56), indicative of the relatively oxidized conditions of the parent magma. Ti-in-zircon thermometry reveals temperatures from as low as ~683 °C up to ~828 °C (average = 755° ± 73 °C). Zircon and monazite saturation equilibria are also consistent with these temperatures. Zircon grains are magmatic (average La < 1.5, (Sm/La)N > 100 and Th/U > 0.7), with chemical characteristics similar to zircons from continental crust.

The Almogholagh–Dehgolan region is in the North Sanandaj–Sirjan zone of NW Iran. The granites of the region are metaluminous and display geochemical and textural characteristics of transitional granites between ferroan (A-type) and I-type granites. In geotectonic discrimination diagrams, the Almogholagh–Dehgolan granites plot mainly in the fields of within-plate granites and volcanic arc granites. With the exception of the Qalaylan granites, parts of other granites resemble A2-type granites. Granites of the Qalaylan intrusive body have petrographic and geochemical features close to I-type granites and are not A-type. Primary mantle and chondrite-normalized spider diagrams show enrichments in light rare earth elements relative to heavy rare earth elements. For an age of 150 Ma, the initial 87Sr/86Sr and 143Nd/144Nd ratios vary from 0.702769 to 0.706545 and from 0.512431 to 0.512558, respectively. Epsilon Nd values vary in a relatively limited range between −0.3 and +2.2, which corresponds to a mixed mantle–crustal source. On the basis of new geochemical and isotopic data, we suggest a geodynamic model involving partial melting of lower crustal rocks with the contribution of mantle magmas in a weakly extensional tectonic setting for the generation of the A-type granites of the region. The occurrence of ferroan (A-type) granites in this region of the Sanandaj–Sirjan zone indicates the existence of a partly extensional tectonic environment in a mainly compressional subduction-related regime in Late Jurassic time.

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