نشریه پترولوژی
پیاپی 38 (تابستان 1398)

The intrusive body of the Ay-Qaleh-Si is located between the West Azarbaijan and Kurdistan provinces at the intersection of the Urumieh–Dokhtar volcanic belt (UDVB) and the Sandaj-Sirjan metamorphic belt of NW Iran. The lithology of this intrusive body consists of Muscovite granite, which intruded Eocene sedimentary units. Mineral chemical studies of these rocks show that plagioclases are albite-oligoclase in composition and garnets have are almandine-spessartine composition and have been formed in pressure less than 5 kbar. The geochemical investigations of the whole rock indicate that the magma of these rocks has peraluminous and high-K calc-alkaline affinity. The multi-element spider diagrams normalized to chondrite, primitive mantle, upper crust and lower crust indicate the proximity of the samples to the composition of the upper crust. Also, based on different tectonomagmatic diagrams, these rocks are located in the syn-collision and post orogenic environments. The origin of the studied rocks is from flesic pelites and has a clay-poor and plagioclase-rich source. In general, it can be said that the Ay-Qaleh-Si intrusive body have been emplaced after the continental-continental collision, Probably formed from the melting of continental crustal metamorphic rocks in a collision environment.

Muteh gold mining district is located 60 km southwest of Delijan in the central part of the Sanandaj-Sirjan zone (SSZ). It consists of two main ore deposits, including the Chah Khatoon and Senjedeh open pits, and several smaller occurrences. Rock units exposing in the area underwent greenschist to lower amphibolite metamorphism. They consist of NW-SE trending deformed and metamorphosed volcano-sedimentary and acidic volcanic rocks. The gold mineralization in the study area occurred as quartz- sulfide veins and veinlets along N40W tending, NE dipping normal faults in metarhyolite host rock. Geochemical behavior of gold and associated elements in mineralized and altered samples indicates that among the major elements, S, Si and among the trace elements Ag, Te, Th, Bi, Ba increasing with the concentration of gold. The concentration of REE and the spider diagram of the samples from altered and mineralized zone and comparison with unmineralized sample indicate a general increasing enrichment for the all REE especially in LREE in the altered and mineralized zone. LREE enrichment in gold mineralization samples indicates the effect of hydrothermal reduced fluids enriched in sulfur, silica and CO2 on concentration of volatile and mobile elements (LREE) during active tectonic of the region. The negative correlation between gold and HREE elements is probably due to the fluoride fluids that washed and carried these elements.

The Gol-e-Gohar anomaly#3 of Sirjan was initially formed by synchronous submarine basaltic volcanism and sedimentary rocks (basalt, shale, carbonates, sandstone, marl, chert-iron hydroxide-oxides) during Neoproterozoic (Ediacaran) and subsequently metamorphosed to greenschist facies during Cimmerian orogeny. The anomly contains 643 million tonnes iron ore with an average grade of 52.70% Fe, 0.76% S and 0.11% P and is enclosed by alternation of quartzite, sericite schist, chlorite schist, talc schist, biotite schist, actinolite schist. Magnetite occurs as massive, banded, cataclastic and disseminated ore and is associated with pyrite, minor chalcopyrite and bornite. Pyrite occurs as, layered, banded, folded and cataclastic and minor within the magnetite crystals. Minor minerals are tourmaline, apatite, zircon and garnet. Geochemical data demonstrate that enrichment of Cu, Pb,Co, Sn, As and Sb in magnetite ore is 2-10 times higher than the crustal abundance. The enrichment of Cu, Mo, Pb, Zn, Cr, Ni, Co, As and Sb in sulfide minerals is 3-67 magnitudes higher than the crustal abundance. The alternation of different schist bands with banded magnetite-pyrite ores, the presence of dropstones and Al-Fe-Mn, V-Ti and V/Ti-Ni/Ti diagrams indicate that the iron mineralization in anomaly#3 is similar to the Ediacaran-type banded iron formation.

The Rangraz copper deposit is located in 18 km of northern Saveh which is in the central part of the Uromieh–Dokhtar magmatic arc. The host rocks are mainly volcanics and volcaniclastics of Eocene which altered and mineralized by intruding the quartz monzodiorite intrusion and andesitic-basaltic dikes in them. Hydrothermal alterations are propylitic, sericitization, silicification, and the chlorite-clay minerals-quartz assemblage. The principal hypogene ore minerals include pyrite, chalcopyrite, bornite, specular hematite, and magnetite. The Rangraz quartz monzodiorite composes of plagioclase, K-feldspar, quartz, fine grain biotite and amphibole shows granular to porphyritic textures. These rocks are commonly metaluminous and calc-alkaline. The high CaO (2.61 to 5.81) and Na2O (6.90 to 7.78) and low K2O(0.04 to 0.38), Fe2O3 (2.60 to 4.58), and MgO(1.22 to 2.81) contents can be caused by the extensive propylitic alteration in intrusion rocks of the study area. According to the tectonic setting discrimination diagrams, and trace and rare earth elements distribution patterns, depletion of Ti, P and LREE enrichment are the subduction at active continental margin tectonic characteristics. Significant negative Eu anomalies and relative depletion in Sr indicate the presence of plagioclase as a stable phase at magmatic source. The result of petrogenetic studies represent that crystal fractionation, and magma mixing were the most dominant processes controlling magmatic evolution.

Extensive sedimentary- igneous rock associations of Paleozoic age crop out in southwest of Julfa (northwest of Iran). Geochemically, the igneous rocks display various basic to acidic compositions. The basic rocks occur as several lava flows intercalated with Devonian siliciclastic units. Also, the acidic igneous rocks consist of rhyolitic lavas and associated pyroclastics (tuffs and ignimbrites). Based on zircon U-Pb dating, the acidic volcanics represent the age of 297±4 Ma (Carboniferous- Permian boundary). The Devonian basic volcanics are chemically sodic alkaline and characterized by fractionated rare earth element (REE) patterns (LaN/YbN=5.2-17). Furthermore, trace element chemistry of Devonian volcanics implies their formation in within-plate and non-subduction zone environment in accord with Devonian magmatism in other parts of Iran (Alborz and Central Iran). On the other hand, the major and trace element chemistry of acidic volcanics suggests their similarity to A (A2)-type granitoids. Therefore, the Permian acidic magmatism is probably related to an anorogenic (post-collisional) tectonic setting which in this case, the effects of the Hercynian orogeny in northwest of Iran could be assumed.

Chahpalang iron index is located in 90 km northeast of Ardakan city in Yazd province and Central Iran structural Zone. Rock units in the study area consist of meta-volcanics, recrystallized carbonates and schists. Ore body is hosted by meta-volcanics and carbonate rocks. Magnetite (two types), hematite (three types) associated with a few pyrite and secondary minerals of goethite, limonite are as ore minerals. Outcrops of orebody are disseminated, lenses and veins in the host rock. Disseminated, massive, corrosion, brecciated, replacement, network are textures of mineralization and alteration halos are chloritization, epidotization and sillicification. Total iron values vary between 28 and 91% in the samples. Low values of Cr, V and Ni-Co diagram confirm hydrothermal origin of Chahpalang iron index. REE values are between 10 and 110 ppm and distribution pattern diagram of these elements indicate the decreasing trend from LREEs to HREEs, resulting the fractionation of these elements in the hydrothermal process. Negative Ce and positive Eu anomalies and REE calculated ratios show the similarity of Chahpalang iron index with hydrothermal deposits.