---

Neogene high silica adakitic domes of south Quchan, cropped out in the northern part of the Quchan-Esfarayen Cenozoic magmatic arc (north of Sabzevar ophiolitic and metamorphic belt). In this volcanic belt, magmatic activities has been started since Eocene (about 40 Ma ago) and continued to Plio-Pleistocene (about 2 Ma ago). The ages of volcanic rocks range from Eocene to Plio-Pleistocene from south (in adjacent to the Sabzevar ophiolitic belt) to north (in south of Quchan) respectively. Northern part of this high silica adakitic arc is composed of pyroclastic units and several domes contain trachyandesites, trachytes, dacites and rhyodacites (2-12 Ma ago) which are usually overlain an olivine basaltic- basaltic basement of Eocene to Lower Miocene(19-20 Ma ago). Existence of Eocene volcanic enclaves and gneissic, siltstone, marl and pellitic enclaves, appearance and disappearance of some mineral phases, corrosions and chemical disequilibriums of some phenocrysts and sieve textures are some evidences of magmatic contamination. ⁸⁷Sr/⁸⁶Sr ratio ranges from 0.7041 to 0.7057 confirms this contamination. A clear positive anomaly in LREE and LILE and a negative anomaly in HREE found in the rocks of Neogene domes. Negative anomalies in HFSE (e.g. P, Nb, Ti) which is the indicator of arc settings, also found in these rocks. Calc-alkaline nature, continental arc subduction setting, presence of an eclogitic or garnet-amphibolitic source rock (resulted from metamorphism of Sabzevar subducted oceanic crust as a source of magma generation), high silica adakitic nature of magmatism (HAS) and the role of fractional crystallization, assimilation and magmatic contamination in the genesis and evolution of magma in these domes, indicated by the geochemical evidences. These adakitic magmas were the latest melts resulted from partial melting of young and hot Sabzevar Neotethyan subducted oceanic crust and its overlaying mantle wedge, which have been emplaced and manifested in the form of subvolcanic adakitic domes.

---

Khanlogh magnetite-apatite deposit is located in northwest of Neyshabour. This area is situated in Binaloud structural zone and east of Tertiary Quchan-Sabzevar magmatic arc. Geology of the area is dacitic volcanic rock intruded by Oligocene subvolcanic rocks with composition of quartz monzodiorite and granodiorite. Miocene sedimentary rocks trusted on them. The magmatism in the area shows characteristics of I-type granitoids and related to subduction zone. Mineralization occurred in the form of vein and veinlet that is hosted by subvolcanic rocks. Veinlet, brecciate, massive, open space filling, and needle-like structures and textures is observed. Magnetite (low Ti, V, and S) and hydroxyl apatite associated with calcite, epidote, quartz, pyroxene, and chlorite are the most important minerals at deposit accompanied by minor pyrite and chalcopyrite. Hematite and malachite are the main secondary minerals. The main alterations of this deposit are propylitic, carbonate, silicification, and argillic where propylitic and carbonate alteration zones are most abundant than other alterations. Tectonic setting, host rock, mineralogy, alteration, and structure and texture studies indicate the Khanlogh deposit has the most similarity with the Kiruna type deposits.      

---

Jalambadan mineralization is located in northwest of Sabzevar, Khorasan Razavi Province, and in the southwestern Quchan-Sabzevar magmatic arc. Geology of the area consists of Eocene andesitic to trachyandesitic volcanic rocks, which are intruded by monzodioritic to dioritic subvolcanic units. Mineralization occurs in intrusive rocks and surrounded volcanic units as disseminated. Pyrite is the main primary mineral and malachite, hematite, goethite, and limonite are the secondary minerals. Well alteration developed in this area and the mineralogy of them consist of quartz, sericite, kaolinite, chlorite, epidote, and calcite. Gold anomaly is between 0.018 to up to 2 ppm and copper content is maximum 509 ppm, especially at eastern half of the area. Monzodioritic to dioritic intrusive rocks had major role in mineralization. The texture of intrusions is porphyry and plagioclase, pyroxene, and hornblende are the common minerals. Geochemically, the intrusions are calc-alkaline I-type granitoids, which are formed in subduction zone from partial melting (7 to 15%) of spinel lherzolite. Based on tectonic setting, geology, type and development of alteration and mineralization, and geochemical anomaly, Jalmbadan occurrence is porphyry Au±Cu mineralization.
 

---

Quchan- Esfarayen magmatic belt (north of Sabzevar) include Neogene adakitic domes with andesite to rhyolite in composition which is cut by Jurasic sedimentary rocks, Eocene volcano-sedimentary rocks, Miocene sedimentary rocks and even occasionally Peliocene conglomerate. The main minerals of these rocks are plagioclase and amphibole with various textures such as felsitic porphyry, microlitic porphyry, glomero porphyry, sieve and flow textures. The calc-alkaline and metaluminous to peraluminous nature, enrichment in large ion lithophile elements (LILEs) and light rare earth elements (LREE) and depletion in heavy rare earth elements (HREE) in primitive mantle and chondrite normalized spider diagrams, along with high contents of Na₂O, Al₂O₃, Sr, high ratio of Sr/Y and low ratio of K₂O/Na₂O and depletion in HFSEs in these rocks are characteristics of the young arc volcanics. Furthermore, these rocks display initial ⁸⁷Sr/⁸⁶Sr ratios of 0.70390 to 0.70562 and εNd(t) values of -0.86 to +4.98 respectively, which show that they are originated from partial melting of oceanic slab with crustal  contamination. Emplacement age of these rocks into the quchan-Esfarayen magmatic belt obtained with U–Pb dating on separated zircons of 17.83±0.24 to 8.50±0.34 Ma. The results show that parental magma of the rocks generated by partial melting of a garnet-amphibolitic to eclogitic subducted Sabzevar Neo-Thethyan oceanic slab underneath the Binaloud continental lithospher. Presence of continental metamorphic and sedimentary xenoliths, corrosion and chemical disequilibrium of the phenocrysts and their sieve textures in plagioclase along with Sr-Nd isotopic ratios in these rocks indicate the operation of differentiation crystallization, assimilation and crustal contamination (AFC) in the genesis and evolution of igneous rocks of this belt.