فهرست مطالب فاطمه نجمی

Bahariyeh deposit is located in the central segment of the Khaf-Kashmar-Bardaskan magmatic belt (KKBMB), NE Iran. This belt is dominated by plutons of Kashmar batholith and associated volcanic rocks along the northern side of the Dorouneh Fault and is one of the most important metallogenic provinces in Iran. Based on geochemical data carried out for the purpose of the present study, the expansion of Cu and other metals mineralization is determined, and on the basis of investigation of trace and rare earth elements behavior, the genetic-lithological relationship of the intrusive rocks is determined in the North of Bahariyeh region.

Method of study:

 About 80 thin sections of intrusive rocks were prepared and 10 least altered 10 samples were selected and analyzed by X-ray fluorescence (XRF; PHILIPS PW 1480) at the Analytical Laboratory of the Kansaran Binaloud Institute of Mashhad, Iran. Also, 10 samples were selected for geochemical analysis by (ICP-OES) at the Zarazma Mineral Studies Co., Mashhad, Iran. Regional Geology Based on field observations a 1:10,000 geological map prepared from the study area, the existing rock outcrops mainly include an alternative of pyroclastic units, Eocene-Oligocene lavas, as well as subvolcanic and intrusive rocks. Field observations show the North of Bahariyeh area is composed of dacite-rhyodacite and andesite volcanic units, and has been intruded by granodiorite, quartz monzonite, monzodiorite-diorite porphyry. These acidic-intermediate intrusive masses have a granular texture and are mainly porphyroid, which have been affected by propylitic, siliceous, argillic, and sericitic alterations. Copper mineralization is observed in the form of veins in different parts of the region, the thickness of these veins varies from about 5 mm to more than 10 cm. Two types of vein-veinlets can be distinguished in the mineralization zone of North of Bahariyeh: 1) vein-veinlets containing quartz + chalcopyrite + specularite + pyrite; 2) specularite-rich veins. Petrography Granodiorite: Granodiorite shows a coarse-grained granular texture with graphic and myrmekitic intergrowths. The main minerals consist of plagioclase, K-feldspar (orthoclase), quartz, hornblende, and opaque minerals. The euhedral-subhedral plagioclase and K-feldspar phenocrysts have been altered to sericite, clay minerals, epidote, and chlorite.Monzodiorite porphyry: This unit has porphyritic and glomeroporphyritic textures with medium-grained groundmass. The monzodiorite porphyry contains up to 45-50 vol.% phenocrysts, consisting of plagioclase (15–20 vol.%), K-feldspar (10–15 vol.%), hornblende (5–7 vol.%), clinopyroxene (5–8 vol.%), and biotite (2–5 vol.%). The same minerals are also present in groundmass. Hornblende and biotite are replaced by chlorite in some places. Also, some plagioclase and feldspar phenocrysts have been altered to sericite, chlorite, and epidote.Quartz monzonite porphyry: The quartz monzonite porphyry has a porphyritic texture (0.1–0.2 mm) with a fine-grained groundmass and normally contains 40–45 vol.% phenocrysts that are 0.1–4 mm in diameter. It is mainly composed of plagioclase (30-35 vol.%), K-feldspar (25-30 vol.%), quartz (15–20 vol.%), and hornblende (5-10 vol.%). The same minerals are also present in groundmass.Diorite porphyry: This unit has porphyritic and glomeroporphyritic textures, with medium-grained groundmass with phenocrysts 0.1–5 mm across, and 40-50 vol.% phenocrysts including 25-30 vol.% plagioclase and 15-20 vol.% clinopyroxene and hornblende with minor biotite and alkali feldspar. The same minerals are also present in groundmass. Its accessory minerals are quartz, zircon, and magnetite (2–3 vol.% and 0.5 mm).

North of Bahariyeh provides important insights for reconstructing the Middle Eocene tectono-magmatic evolution of the NE of Iran. Significant outcomes of this work are:The intrusive sequence in the North of Bahariyeh is inferred as monzodiorite porphyry, diorite porphyry, quartz monzonite, and granodiorite of middle Eocene. and all intrusive rocks belong to I-type metaluminous-peraluminous granites. Major and trace element geochemistry indicate the acidic-intermediate intrusive rocks in the North of Bahariyeh were likely generated by partial melting from the subcontinental lithospheric mantle affected by both slab-derived fluids and lower continental crustal components.The enrichment of LILE (Ba, K, and Cs), depletion of HFSE (Nb, Ti), and the enrichment of LREE relative to HREE indicate crustal contamination and formation of the source magmas in a subduction environment zone by low degrees of partial melting. Trace element geochemistry confirms the evolution of dioritic rocks by a partial melting process (1-5%). Geochemical results, combined with regional geological data, demonstrate a shallow mantle with a clear subduction imprint (metasomatized mantle wedge melts). The post-collisional transtensional tectonic regime favored magma genesis with decompression melting and magma rise through the well-developed fault system and the subvolcanic and intrusive units in the North of Bahariyeh area form the active continental margin-related subduction zone.Overall, the data of the rare earth elements of acidic-intermediate units in the area of study shows that the rocks under investigation were originated by partial melting of enriched mantle under the influence of the fluids released from the subduction blade and then under the contamination of the crust.

Kuh-Rakhneh  district is located in the southwest of Qaleh Zari mine in Birjand city and in the central part of Lut block. The geology of the area includes the alternation of volcanic rocks with dacite to andesite composition and subvolcanic units involving granodiorite porphyry, tonalite porphyry, pyroxene diorite porphyry, diorite porphyry, and quartz diorite porphyry that have penetrated them. The alteration zones in the study area include propylitic-chlorite, sericite, argillic, silicification, and carbonate that silicification and argillic alterations are closely related to the mineralization process. Mineralization has occurred in the form of three main veins (A, B, and C) with a southeast-northwest trend within fault zones in andesitic and diorite rocks. Primary ores include pyrite, chalcopyrite, and secondary ores include bornite, chalcocite, covellite, and malachite. Mineralization in these veins is also created in the form of veins, masses, replacement, and breccia.The chemical composition of these I-type subvolcanic intrusions are between predominantly metaaluminous to slightly peraluminous with calc-alkaline characteristics. Also, negative Eu anomalies and a ratio of less than one (Eu/Eu*=0.54-0.96) indicate the presence of plagioclase in the origin of magma. The low amount ​​of Nb and Ti in these units reveals formation at tectonic setting associated with the subduction zone in the active continental margin. Based on geochemical analysis, trace and rare earth elements, the magma source that forms these subvolcanic units had been generated from  1 to 5% partial melting of garnet spinel lherzolite in the enriched mantle and at the depth of about 65 to 67 km.

The Golcheshmeh copper deposit is located in the north-easth of Iran (south of Neyshabour) at the margin of Sabzevar Structural Zone. Based on geological and labratory studies, the outcroped rocks consist of Eocene volcanic rocks such as andesite, basaltic- andesite and basalt, that associated with the sedimentary and volcanosedimentry rocks including limestone, tuff and breccia. The alteration is hosted andesitic layers that includes carbonatization, propylitic and less argilic and sericitic. The carbonatization zone is the most important alteration zone in this area. Mineralization mainly occurs in Eocene or younger volcanic rocks as vein- veinlets, amygdaloidal fillings and some replacement and disseminated styles. According to the minerallographic studies, the main ores containing copper are divided into oxide and sulfide types. Mineralization mainly consists of oxide phases and can be seen as contamination of surface fractures and pores or voids filling in host rocks. The main oxide minerals are malachite, azurite and chrysocolla and sulfide minerals are chalcocite, covellite, with minor chalcopyrite, bornite, digenit and also native copper. Chalcocite is the most abundant sulfide ore in this area. There are probably two generations: The first generation is a primary ore that was formed directly in joints, cracks, and fractures from the ore-containing solution and currently is replaced covellites, and the second generation is chalcocite that was probably formed from the conversion of bornite and chalcopyrite through substitution and under supergene conditions. In most cases, the observed intergrowth between copper ores suggests the multi-stage mineralization in this region. Geochemical studies based on minor and trace elements obtained from this research indicate that the igneous rocks in this region were characterized by the calc-alkaline basalt characteristics and in terms of tectonic setting, could be attributed to subduction zone-related continental arc magmatism. In addition, based on the results of the analyses of trace and rare earth elements, the high amount of Nb (more than 16 ppm), Rb-rich, (Zr / Nb)N (less than 2 and between 0.7 to 0.46), could be an indication of contamination of magma with continental crust. The absence of Eu anomaly suggests a broadly defined melting conditions at oxidation state. On the basis of this study and with respect to some evidences such as tectonic setting, host rock types, structure and texture of ore body, mineral paragenesis, shape of the ore body and associated elements, this area is comparabale to a Manto type deposit located in Chile regardless of some differences. Thus, it is suggested that the Golcheshmeh copper mine classified a Cu- Manto type deposit.