جستجوی مقالات مرتبط با کلیدواژه « sabzevar zone » در نشریات گروه « زمین شناسی »

The Zangalou mine area, a part of NW Bardaskan magmatic assemblage, located south of Sabzevar and northwest of Bardaskan cities in Khorasan Razavi province. The rock units of the area are dominated by sedimentary and volcanic racks (andesite, trachyandesite, latite and andesitic tuff). The dominant minerals are plagioclase, hornblende, pyroxene and alkali feldspar locally affected by argillic and propylitic alterations and the main textures are porphyritic, glomeroporphyritic, amygdaloidal and fine grain. The rocks under study formed in continental volcanic arc related to subduction zone, are calcalkaline in nature, metaluminous in composition and classified as shoshoite series. LREE and LILE enrichment compared to HREE and HFSE of the investigated rocks indicate their magma generation in subduction setting. Both Zr/Ba and Sm/Yb ratios point to lithospheric mantle origin and the rare or the absence of garnet in the origin respectively. The parent magma formed from partial melting of an enriched phlogopite spinel lherzolite. The geochemical properties of Zangalou share many signatures with those of the volacic rocks distributed in other parts of NW Bardaskan volcanic assemblage indicate high similarity in geochemical signatures of volcanic rocks. Studying geochemistry of volcanic rocks in these areas indicates formation of these rocks in a subduction setting.

The Cheshmeh Zagh area is located on Khorasan Razavi Province, the southern parts of the Sabzevar zone, which is one of the most important metallogeny zones of Iran. Lithologically, the area includes a variety of Late Cretaceous volcanic rocks (dacite to basalt), intrusions (gabbro to synogranite), Oligo-Miocene sedimentary rocks, and Quaternary sediments. Alteration zones of propylitic, chloritization, and epidotization well developed but the main mineralization zones can be seen in the form of two lens-shaped zones which are surrounded by argillic and silicification-sericitization alterations. Hypogene minerals include pyrite, chalcopyrite, and magnetite; while secondary minerals contain malachite, covellite, and iron oxides. The maximum content of the main elements in the main mineralization zones includes 1.5% Cu, 2230 ppb Au, 40 ppm Mo, 363 ppm Pb, and 738 ppm of Zn. Factors, such as the tectonic setting of the Sabzevar zone, the presence of a large number of Cu-Mn and deposits in relation to the submarine volcanic activities in the region, and the accompanying mineralization with dacitic volcanic rocks containing specific alterations in the Cheshmeh Zagh area, all indicate a probablity of the Bimodal Felsic-type (Kuroko) volcanic massive sulfide origin for these deposits. The Sabzevar structural zone has a great potential for exploration of this type of deposit, which should be taken into consideration.

The Sharifabad-Bardeskan copper mineralization is located in northeast of Bardeskan and south section of Sabzevar Zone. Mineralization occurs as vein in the pyroxene andesite, tuff, sandstone and conglomerate of Eocene age, which bearing local sericite - carbonate and silicic alterations and regional propylitic alteration. Mineralization occurs as open space filling, disseminated, veinlets and consists of chalcocite pyrite, chalcopyrite, malachite, azurite with calcite and quartz as gangue minerals. Fluid inclusion studies in calcite show the evidence of mixing trend during the ore formation occurred at a wide range of temperature 200to 437 °C and varying salinity between 0.1 to 9.2 wt.% NaCl equivalent. The stable isotope composition of δ34S fall in a range of -23 to -24.3‰ could be considered as biogenetic sulfur from bacterial sulfate reduction. The δ13C values of calcite vary between -3.4 to -24.5‰ suggest a major contribution of marine carbonates associated igneous carbonates. Copper and sulfide rich hydrothermal fluid has flowed upward through the local faults and permeable interbeds within the Eocene volcanic sequence and formed the mineralized veins. Based on the mineralization, alteration, fluid inclusion and stable isotopes, Sharifabad mineralization is similar to those manto type deposits in Chile.

The Baharieh copper deposit with an approximately tonnage 1 million tons of copper ore, is located in the Khorasan Razavi Province and 30 km of northeastern of the Kashmar. Based on subdivision structural geology of the Iran, the deposit is situated in the Sabzevar zone and Taknar complex. The mineralization as stratabound nature in an ore-horizon with an approximately length of 200 m and E-W trending occurs in middle Eocene andesitic to rhyolitic-tuff. Chalcopyrite and pyrite are the main sulfide minerals which accompanies with accessory minerals such as bornite, galena, sphalerite, covelline, chalcocite, malachite and hematite. Based on evidence of the electron probe micro analysis (EPMA) detected the maximum gold and silver contents 0.21 and 0.1 ppm in chalcopyrite, respectively and the maximum silver content is 0.14 ppm in galena. According to mineral chemistry studies, pyrite of the Baharieh deposit obtained the average ratio Co/Ni=2.71, which can be indicate its hydrothermal source. According to the results of the geo-thermometry of the Sb/Bi ratio in the galena and geochemistry of sphalerite (high concentration of Cd with an average value of 9220 ppm and low Zn/Cd=67.54) physico-chemical and thermodynamic conditions of the ore-bearing fluid in the Baharieh deposit has been concordant with average-temperature hydrothermal-magmatic deposits. The variation ranges of δ34S isotopic in the chalcopyrite and pyrite samples are varies between -7.3 to 0.5 ‰.

Aliabad-Daman granitoid body with NW-SE trend is located in northeastern of the Rashtkhar city (about 15 km) with an area of approximately 10 km2. This body with probably age of middle Jurassic is located above Darouneh fault and is part of Sabzevar zone. This pluton consists of alkali feldspar granite, syenogranite and monzogranite. In the discriminant diagrams of micas, biotites plot in the field of syderophyllite and are generated from the crystallization of magma. The plagioclase is in the field of albite to oligoclase and orthoclase resemble to anortoclase due to its micro-perthitic occurrence. Chlorite located in the field of repidolite and brensovigite which indicate its iron-rich composition. Based on petrographic and geochemiscal studies Aliabad- Daman granitic pluton resemble with A2-type granites with slightly peraluminous nature. Negative Ba, Nb, Ti, Sr and P anomalies in discrimination tectonic setting diagrams indicate that they are generated in a volcanic arc setting. Extensional environment in a continental arc has provided conditions for generation of these granitic rocks.

The study area is located at 220 km southwest of Mashhad and 80 km south of Neyshabur and is situated between 58° 40' 30" to 58° 43' 30" E longitudes and 35° 47' 30" to 35° 52' 00" N latitudes. The study area is part of Sabzevar zone. The lithology of the area consists mainly of volcanic rocks with trachyte, trachy andesite, and basaltic trachy andesite composition and in some parts has been subjected to argillic, carbonate and propylitic alteratins. The dominent phenocrysts in these rocks are plagioclase, alkali feldespar, opacitized hornblende and pyroxene. The main texture in these rocks is porphyritic with fine and medium grain matrix. These rocks have calc-alkaline nature and show enrichment in LILE (except for Ba) and depletion of HFSE. The enrichment of LREEs relative to HREEs indicates that the parental magma formed in a subduction zone, which is well manifested by the volcanic rocks of Golcheshmeh area. Tectonic setting diagrams and geochemical properties of volcanic rocks of the study area suggest an active continental margin setting. The low ratios of (La/Yb)N (5.3 to 9.3) and (Ce/Yb)N (4.2 to 7) point to low degree partial melting at shallow depths and low garnet in the source magma. The source magma formed by 2 to 5% partial melting of a spinel-garnet lherzolite source (low garnet) accompanied by crustal contamination.

Cheshmeh Gaz (Nasim) copper deposit is located in northwest of Bardaskan, Khorasan Razavi province. Geology of the area is consist of andesite, basalt, nummulitic limestone, and marl with gypsum intercalations Eocene in age, Pliocene conglomerate, and Quaternary sediments. Mineralization has been formed in andesites and contact between andesitic units and limestone as stratabound with disseminated, veinlets, and open space filling textures. Orebody consist of primary minerals such as chalcocite, native copper, and pyrite and secondary minerals including malachite, covellite, azurite, and goethite. Based on microscopic studies and XRD analysis, mineralogy of alteration zones is chlorite, calcite, zeolite (natrolite, thomsonite, and analcime), quartz, and minor epidote. Considerable anomaly of Cu (up to 3.36%) is present in the area. The hosted volcanic rocks are calc-alkaline type and are formed in subduction zone volcanic arc. Host rock type and geochemical features, alteration, structure and texture of mineralization, and ore types in Cheshmeh Gaz deposit are similar to Manto-type deposits and epigenetic-diagenetic model is suggested for formation of it.

Namen pluton is located in the SW of Sabzevar Zone and is composed of three different phases include two granitoid units and a basic phase. Namen syeno-granites (SG unit) are high temperature magmas enriched in HFSE such as Ga, Nb, Ta and Zr; and classified as aluminous A-type granitoids. This magmatic phase has been generated by partial melting of felsic rocks. The main phase of Namen pluton (BG unit) contains assemblage of various granitoids (granodiorite, quartz monzodiorite, quartz diorite). This phase shows I-type granitoid characteristics and has been yielded by amphibolite melting in the lower crust. Mafic rocks consist of hornblende gabbros which have cumulative texture of amphibole and plagioclase. There are diffused and circular patches of magnetite ore in some sections of gabbroic occurrences. Magnetite-hosted hornblende gabbros (MHB) are enriched of V, Cr, Co, Cu, Zn and Ca and depleted from incompatible elements of LILE and HFSE relative to other gabbros (HB). The separation of volatile phases during the gabbroic magma evolution has led to the segregation of primary magma. Finally, the F- P and H2O-S enriched parts of this fractionated magma have formed HB and MHB rocks, respectively.

The Late Cretaceous volcano-sedimentary sequences that bear Cu (Zn) mineralization compose of four units (Unit1, Unit2, Unit3, and Unit 4). The copper (Zn) mineralization on the unit 2 occurred in two distinct horizons. The host rock includes olivine basalt flow and tuffaceous silty sandstone. In this deposit, mineralization occurred in three different facies (stringer zone, massive ore facies and bedded ore facies). The Nudeh deposit has a strongly horizontal geochemical zonation from Massive ore facies to bedded facies (decreasing of ore grade and Cu:Zn ratios, increasing of Ba:Zn ratios, and increasing of Fe and Mn) and vertical zonation, specially within massive ore facies (upward increasing of Cu:Fe and Cu:Ti ratios, and decreasing of Cu:Zn ratio). The lithogeochemica studies show that maximum copper grade in massive ore facies is about 11.2%, which is decreased to the bedded ore facies. This grade in the bedded ore facies changes from 4 to 5 percent. The base metal overall grade (Cu/Zn+Pb) of the Nudeh deposit in massive ore facies is more than the stringer zone and bedded ore facies. Some parameters such as changing in hydrothermal and sedimentary components ratio, variation of temperature, Eh and pH, the role of refinement process in massive ore facies and dominants of sedimentary conditions in bedded ore facies, control this geochemical zonation of the Nudeh deposit.

Copper mineralization in Nudeh Cu deposit and Frezy, Garab, Kalateh lala (Nieran) and Chun occurrences, located in southwest of Sabzevarhosted by a Upper Cretaceous volcano-sedimentary sequence formed in a rift environment. The main is host rock of the Nudeh Cu sulfide deposit includes alkali olivine basalt flow and subordinate tuffaceous silty sandstone. Host rock of the Ferizy and Garab occurrences is andesite flow. The rock forming mineral of Kalateh lala (Nieran) and Chun occurrences is tuffaceous silty sandstone. Sulfide mineralization in the Nudeh deposit and occurrences within an Upper Cretaceous volcano-sedimentary sequence occurs as sheet-like &tabular shape within three ore horizons. Based on nature of sulfide mineralization, mineralogy and textures of sulfideminerals, the Nudeh deposit can be divided into three different ore facies. Based on their situation towards the vent of mineralizing fluid, these facies include: A) Vein-veinlets facies (Stringer zone) includes sulfide veins and silica that form as a scissors of host rocks under the massive ore facies. Vein-veinlets and replacement textures formed main features of this facies. B) Massive ore facies that forms the thicker part of generally massive higher grade ores in west of the deposit and includes sulfide mineralization with heterogeneous nature and stratabound, limited in the alkali olivine basalt flow. C) Bedded ore facies which is thinner than the massive ore facies and is characterized by layered and banded apparent and low grade ore. The rock forming mineral of this facies is tuffaceous silty sandstone. This facies occurs as laminated and banded sulfides contemporaneous with the host rocks layering ateastern part of the deposit. Mineralogy of Nudeh deposit includes chalcopyrite, pyrite, bornite, sphalerite, boulangerite and magnetite wall rock alterations are dominated by silicification, chloritization, sericitization and epidotization. The most important characteristics of mineralization at the Nudeh deposit such as tectonic setting, host rocks, mineralogy, metal content as well as wall rock alterations, show similarities with volcanogenic massive sulfide (VMS) deposits. Accordingly, Nudeh Cu deposit is regarded as a Besshi - or pelitic mafic VMS deposit.

The Arghash gold prospect occurs in the northeastern of Central Iranian domain. It is located in Sabzevar zone, north of Darouneh fault. The exposed rocks in the study area consist of volcanic rocks (andesite and dacite), plutonic rocks mostly diorite, quartz diorite, quartz monzodiorite, granodiorite and granite with minor sedimentary rocks (limestone, sandstone and conglomerate). We focus on a suite of hbl-bearing granitoid rocks consisting of diorite, quartz diorite, quartz monzodiorite and granodiorite. The rocks are metaluminous, medium K, calc-alkaline belonging to Magnetite-series granitoids (I-type). They are related to small numbers of iron bodies and veins. They show low TiO2, P2O5, Nb, La, Zr. Initial 87Sr/86Sr ratios and initial εNd are 0.703755 and +4.74, respectively. U/Pb zircon dating of this suite, using laser inductively coupled plasma mass spectrometry (LA-ICP-MS) yielded mean age of 92.8 ± 0.9 Ma (Turonian). Their chemical compositions as well as initial isotope ratios of 87Sr/87Sr strongly suggest that the original magma formed in a depleted mantle in the subduction zone in Sabzevar Paleoocean.