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Cenozoic adakitic rocks of the northern part of the Central Iran Structural Zone (CISZ) are among the notable geological features of the terrains in northeast Iran, so a comprehensive comparison of several of these adakitic sequences is presented. This lithogeochemical analysis is constrained to examining adakitic magmatism of the three magmatic belts within the CISZ, which from southeast to northeast and from oldest to youngest are as follows: (a) south of Shahrood‐Damghan, (b) north‐northwest of Sabzevar‐Neyshabour, and (c) south of Qouchan and west of Esfarayen. Radiogenic isotope analysis using Rb–Sr and Sm–Nd methods show that the adakitic rocks associated with Qouchan‐Esfarayen magmatism have 0.512581 to 0.51288 initial 143Nd/144Nd and 0.703903 to 0.705627 initial 87Sr/86Sr, with εNd −0.86 to 4.98. Adakitic rocks in south to southeast Shahrood have 0.512775 to 0.512893 initial 143Nd/144Nd and 0.703746 to 0.705314 initial 87Sr/88Sr, with εNd 3.69 to 6.0, and adakites emplaced into the Sabzevar ophiolite have 0.512846 to 0.512911 initial 143Nd/144Nd and 0.70379 to 0.705019 initial 87Sr/86Sr contents with εNd of 5.26 to 6.54. Isotopic initial ratios of Nd and Sr support an origin involving partial melting of the subducting oceanic lithosphere of the northern branch of Neo‐Tethys and the associated suprasubduction mantle wedge in producing these adakitic rocks. [ABSTRACT FROM AUTHOR]

Some high silica adakitic domes with rhyolite, dacite, trachy-dacite, trachy-andesite and andesite compositions belonging to upper Eocene-Pliocene, trending W-NW, intruded in to the Cretaceous-Paleocene ophiolitic complex, the Eocene volcano-sedimentary series and in some cases the Oligocene-Miocene sedimentary rocks, and enclose some fragments of these rocks as xenoliths. The most abundant minerals in these rocks are plagioclase and amphibole with various textures such as felsitic porphyric, microlitic porphyric, sieve, flow and glomeroporphyric. The presence of large volumes of detritic fragments of these adakitic domes in the Pliocene conglomerates and their absence in the Miocene detritus indicate uplifting and exposing of the studied domes in the earth surface in the Miocene-Pliocene interval. The parent magma of these rocks has calc-alkaline and per-aluminous nature which is characteristics of the arc volcanics. These rocks fall into the field of high-silica adakites (HAS) in classification diagrams. Enrichment in light rare earth elements (LREEs) and large ion lithophile elements (LILEs) and depletion in heavy rare earth elements (HREEs) are obvious in their MORB, primitive mantle and chondrite normalized spider diagrams. Strong depletion in HFSEs including Nb, Ti and P which is signature of arc volcanic, can be observed in these rocks. According to the petrogenetic diagrams, the parental magma of the rocks studied generated by partial melting of an eclogitic-garnet amphibolitic source derived from metamorphism of the Sabzevar Neotethyan subducted oceanic slab underneath the southern edge of the eastern Alborz zone. Also, the magma has been subjected to assimilation, fractional crystallization (AFC) and crustal contamination during ascend to higher levels and emplacement into the ophiolitic belt. The presence of the xenoliths, corrosion and chemical disequilibrium of the phenocrysts and their sieve textures and (Sr87/Sr86) i ≈ 0.7045 in these rocks support the occurrence of these processes. [ABSTRACT FROM AUTHOR]

The Darreh Bagh granitoid pluton (DGP), with middle Jurassic age (178 Ma), located in the northwest of Aligudarz city. The pluton is mainly granodioritic composition which emplaced in metapelitic rocks of Sanandaj-Sirjan structural zone. For the first time, the emplacement mechanism of this pluton, investigated by anisotropy of magnetic susceptibility (AMS) method. Based on the present investigations, the mean magnetic susceptibility, in terms of µSI for the studied rock groups are as follow: granodiorites (257), leucogranites (47), high tourmaline leucogranites (148), low tourmaline leucogranites (48), migmatites (437), surmicaceous enclaves (386). Considering the obtained values, the felsic part of the DGP belongs to the paramagnetic granitoids (500>km>0 in µSI) (equal to ilmenite series or S-type). Based on the magnetic parameters and their interpretations it is possible to divide DGP into the A and B domains and A1, A2 subdomains. The magnetic lineations in the subdomains oriented to the north. Whereas in the middle part of the pluton (B domain) it oriented dominantly to the east and southeast. Based on distribution patterns of magnetic lineations these domains were emplaced with a short delay compared to each other. Meanwhile, A domain was emplaced prior to B domain. With attention to distribution patterns of magnetic lineations and foliations, the principles of interpretation of magnetic parameters and regional geological characteristics, the Darreh Bagh granitoid pluton was emplaced in the form of a relatively large sill in a dextral shear zone (related to a transpression regime). [ABSTRACT FROM AUTHOR]

Zafarghand granitoid pluton with approximately 80 Km in the extent with early to middle Miocene age cropped out in 35 Km of SE Ardestan. The pluton composed mainly of gabbro to tonalite and intruded in the Eocene volcanic and volcanosedimentary rocks of Uroumieh-Dokhtar structural zone. For the first time, variations of anisotropy of magnetic susceptibility in Zafarghand granitoid pluton have been investigated by using anisotropy of magnetic susceptibility (AMS) method. Based on obtained data, the measured mean magnetic susceptibility values (Km in µSI) of the different rock groups of Zafarghand pluton are as follows: gabbros (32536), diorites (23768), granodiorites (18436), granites (8068) and tonalites (68). Therefore, the Km values decrease from grabbros and diorites to granodiorites, granites and tonalites. Gabbros and tonalites have the highest and the lowest Km values, respectively. The measured Km values indicate that, the studied granitoid belongs to ferromagnetic type (according to magnetite series and I-type granitoids). [ABSTRACT FROM AUTHOR]