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

Arc copper mine is located about 55 km northwest of Birjand city in South Khorasan Province. The rock units at this area include thin to medium-bedded flysch sandstones in red and gray colors with Eocene age. Copper mineralization occurred in the upper part of bleached gray sandstones in a lenticular shape. There are at least two revitalization beds. Each of the horizons consists of three zones: Red Zone, Bleached Zone, and Mineralized Zone.The mineraliztion zone has occurred within the bleached and reductant zone. The texture in this deposit is replacement and scattered grains. The presence of framboidal pyrites in the ore horizons and the intactness of cellular structures replaced by sulfides indicate that this deposit was formed during the early stages of diagenesis prior to deep burial. Based on lithology (host rock from sandstone greywacke to litharnite), mineralogy of mineral (chalcocite, covelite), structure and texture, stratigraphy and factors controlling mineralization (presence of traces and remains of plants as the main factor regenerative environment, appropriate permeability of the host rock) suggest that this deposit is the similar to Red Bed type sedimentary copper deposits.

Granite rocks are widely used in many construction fields and investigate about preexistent or induced microcracks in them had been the subject of many researches. Since the rock thermal properties is affected by thermal properties of all constituent minerals of the rock, in the microscopic thin sections study, assembled effect of them is showed as microcrack creation. In this study, microcrack induction was performed in three coarse-grained granite samples using heat in the furnace and then shock with cold water. Microcracks in fresh and shocked samples at 250, 450, 650, and 850 Cᵒ was investigated using macroscopic core samples, thin sections, SEM images and crack density measurements in three spatial directions perpendicular on each other. Examination of microscopic sections showed that grain in the same size and variety of boundaries cause the microcrack network not to expand. Myrmikite texture accelerates the development of transgranular microcracks. Some minerals such as mica and amphibole have a specific effect on how cracks develop so they are the beginning or ending of microcracks. Examination of microscopic thin sections showed that different type of microcracks in different samples develop in a different way, which is also affected by the absolute age of the rock. Plagioclase has the least and orthoclase has the most number of microcracks. In 250 and 450 Cᵒ thermal shocks, development of microcracks is also affected by porosity.

Fadiheh copper-gold prospect area in northwest of Torbat-e Heydariyeh in Khorasan Razavi Province is located in the central part of the Khaf-Kashmar-Bardaskan magmatic belt. This area includes outcrops of Eocene volcanic-pyroclastic units with felsicintermediate nature. The lavas are andesite and latite, and pyroclastic units include rhyodacitic tuff, andesitic lithic tuff and ignimbrite. Intrusive rocks consist of hornblende monzogranite, synogranite, pyroxene diorite porphyry and quartz monzonite porphyry. Mineralization has structural control and formed as vein-veinlets in accordance with the main trend of NW-SE and NE-SW faults in the region. Mineralization veins have generally N45 ° -75 ° E and N15 ° -30 ° W trending, 2 to 25 m length and 0.2 to 2 m width. The most important veins in the area include quartz + specularite ± pyrite and quartz + specularite ± chalcopyrite. The host rocks are pyroxene diorite porphyry, quartz monzonite porphyry and hornblende monzogranit. The structure and texture of mineralization includes vein-veinlet, open space filling, breccia, secondary replacement, colloform and disseminated. The alteration associated with veins are silicification and chloritization. The propylitic, silicification, chloritization and argillic alteration zones are observed within host rocks and other units in the area. Primary mineralization are specularite, chalcopyrite, pyrite and galena and secondary minerals are malachite, chalcocite, covellite, goethite, hematite, limonite, azurite and chrysocolla. Maximum of geochemical anomalies in veins are up to 5% Cu, up to 3% Pb, 50 g/t Ag, 100 g /t As and up to 791 ppb Au. The geological setting, lithology, mineralogy of mineralized veins, structure and texture, extent and type of alteration zones show that the mineralization in Fadiheh prospect area is iron-oxide copper-gold (IOCG) type.

The Bolboli2 copper ore deposit is located about 110 km southwest of Kerman and lies in the Dehaj-Sarduieh metallogenic belt (Kerman Cenozoic Mamatic Arc, KCMA). This ore deposit is hosted by the Eocene extrusive igneous rocks (tuff, agglomerate, andesite, and dacite) and the Oligo-Miocene intrusive igneous body (granodiorite). These rocks are host the propylitic, phyllic, and silicic alteration zones (product of the mineralization fluids). Hypogene mineralization was dominant and occurs mainly as stockwork vein-veinlets and disseminate (chalcopyrite, pyrite, and magnetite). This mineralization is overprinted by supergene assemblages such as hematite, goethite, malachite, and azurite at superficial part of ore deposit. The hypogene minerals show generally vein-veinlet, stockwork, brecciated, granular, and crustiform textures. Microthermometric studies in quartz crystals cogenetic with the ore minerals reveal 4 types (1) L-V, (2) L-V-S, (3) V-L, and (4) V fluid inclusion. Study of fluid inclusions display a Th range of 190-427ºC. The L-V-S fluid inclusions were homogenized with halite disappearance with the Ts(NaCl) ranging from  213ºC to 425ºC which corresponds with salinities within the range of 32-50 wt% NaCl equivalent. The liquid-rich 2-phase inclusions (L-V) show salinities within the range of 0.6-10 wt% NaCl equivalent. Based on microthermometric data, boiling, mixing, and simple cooling of the ore-bearing fluids were the essential mechanisms in deposition and evolution of this ore deposit. The ore-forming fluids were probably of magmatic and mixed magmatic-meteoric sources. The geological setting, structural and textural aspects, alteration and mineralization of mineral assemblages, as well as microthermometric data show that the Bolboli2 ores can be categorized as porphyry copper-type ore deposit.

In this research relationships between petrological properties and physical and mechanical characteristics have been investigated in three different granitoid rocks' texture. According to field investigations granitoid with coarse, medium and fine texture from three regions respectively Golpaigan (Hasn Robat), Aligudarz (Pir Tak) and Borujerd (Tavan Dasht) were selected and sampled. Laboratory studies on these samples and their thin sections determined mineralogical and petrological composition. According to standard testes some of the physical properties such as porosity and density, and some of the mechanical properties such as point load strength and uniaxial compressive strength were calculated. Then relationship between physical and mechanical properties with petrological characterizes have been studied. This research showed that in these granitoid rocks the effect of the texture type on physical and mechanical properties is greater than mineralogical composition. Also findings showed that the investigation on petrological properties as primary index for evaluation of physical and mechanical properties of granitoid rocks could be done in further studies.

Important known bauxite deposits in Iran, which occur in the so called Irano-Himalayan belt, are spatially distributed in four regions, namely (1) the northwest of Iran (e.g. Bukan, Shahindezh), (2) the Zagros heights, (3) the Alborz Mountain Range and (4) the central plateau of Iran. They are restricted to Permian, Permo-Triassic, Triassic, Triassic-Jurassic, and Middle Cretaceous (Cenomanian–Turonian) in ages (Abedini & Calagari, 2014).

The Gazanjeh area is located about 25 km southeast of Bukan city, south of West-Azarbaidjan Province, NW Iran. The stratigraphical gap emerged during the Late Permian is manifested by the development of a bauxite horizon in this area. The propose of the present study is to indentify the texture, mineralogical types, controlling factors of distribution and mobilization of major, minor, and trace elements in residual facies, paleo-geographical conditions, sedimentary environment of formation and development of the bauxite deposit in the Gazanjeh area.


In this study, a profle perpendicular to the strike of bauxitic layers was selected and 16 systematic and

representative samples with varying intervals (80-150 cm) were collected. Laboratory works began with preparation of thin and /or polished sections from all 16 samples and their examination under microscope. For the identification of mineralogical phases in the bauxites, 8 samples from a selective section were chosen for X-ray diffraction (XRD) analyses.  XRD analyses were carried out using diffractometer model D-5000 SIEMENS in Geological Survey of Iran (Tehran). The chemical compositions of the bauxites (#16) were determined at the Kansaran Binaloud Company, Tehran, Iran. The values of major and minor elements were determined by X-ray fluorescence (XRF). Rare Trace element contents were determined by inductively coupled plasma mass spectrometry (ICP-MS). Loss on ignition (LOI) was determined by weight loss of 1 g sample after heating at 1000 °C for 60 min.

Since the rocks are fine-grained, identifcation of minerals in the bauxite ores under a microscope was not possible.Terefore, petrographic examinations were principally focused on textural features of the ores. Considering the mode of distribution of texture-forming components and matrix, various kinds of textures such as pelitomorphic, microgranular, ooidic, pisoidic, macro-pisodic, spastoidic, colloform, nodular, pseudo-breccia, breccia, and clastic identified within the ores. These textures show allogenic origin for deposit (Bardossy, 1982). The pelitomorphic and colloformic textures imply an indirect bauxitization and weak draining processes during the evolution of this deposit. The development of hematitic nodules in the ores can be attributed to factors such as variation in water activity in pedogenic environments and/or climatic fluctuations (Mongelli, 2002). The XRD analyses show that the minerals including diaspore, hematite, pyrophyllite, chlorite, chamosite, rutile, anatase, and muscovite-illite are the main mineral phase of the phreatic.Trivariate plot of SiO2-(Al2O3+TiO2)-Fe2O3 (Balsubramaniam et al., 1984) denotes that three distinct mineralogical types can be differentiated within the horizon, namely (1) laterite, (2) ferruginous laterite, and (3) siliceous bauxite. Also, plotting the Kanigorgeh data on trivariate diagram SiO2-Al2O3-Fe2O3 (Schellmann, 1982) attests to the formation of the above ores under moderate to intense lateritization conditions. Trivariate plot of SiO2-Al2O3-Fe2O3 (Meshram & Randive, 2011) reveal that deferritization-ferritization mechanisms and destruction of kaolinite were the most important processes involving during development of ores in this deposit. Comparison of the range of stability fields of major constituent minerals of the bauxite ores with the pH and Eh variations of natural environments (Temur & Kansun, 2006) show that this deposit formed two facies, (1) oxidant-basic and (2) reduction-acidic. Geochemical investigations indicate that the degree of concentration of elements such as V, Zr, Co, Cu, Ga, Hf, Mo, Sc, U, and Zn in oxidant-basic facies and concentration of elements such as Ba, Cr, Ni, Pb, Rb, Sr, and Th in reduction-acidic facies is great. Difference in concentration of elements in these two facies can be associated with occurrence of processes such as adsoption by clays, scavening by hematite and manganese oxides, lateritization intensity, function of carbonates bedrock as geochemical barrier, and chemistry of meteoritic waters (Braun et al., 1990; Mordberg, 1996; Schwertmann & Pfab, 1996; Marques et al., 2004; Fernandez-Caliani & Cantano, 2010; Ndjigui et al., 2013; Abedini & Calagari, 2014).

In the present study, erodibility of various deposits of Sefidrud Delta was evaluated based on effective engineering geological factors. First of all, the study area was studied geology and sedimentology point of view and various deposits were identified in this area. Then the engineering geological characteristics of deposits were determined based on existing geotechnical data, field investigation and performance of 32 dynamic cone penetrometer test (DCP). Finally, by development a simple and precise method, the erodibility of various deposits was evaluated based on texture and shear strength factors. The results show that the erodibility of deposits has a close relationship to the sedimentological characteristics and erodibility could be analyzed regarding the geological history of deposits. According to the results of this research, natural levee deposits have highest erodibility and in other hand old deltaic deposits have lowest erodibility in Sefidrud Delta area. Such researches have a main role in sustainable development of the study area.

Chehrabad Cu deposit is located in the Zanjan province and in the northwest corner of Central Iran. Rock units exposed in this area belong to the Cenozoic era (especially Miocene period) and include the Lower Red Formation, Qom Formation, Upper Red Formation and Quaternary deposits. In the study area, the Upper Red Formation which hosts the mineralization consists of alternating beds of marl, siltstone, oxidized red sandstone and light gray sandstone. Mineralization has occurred within the gray sandstones of bleached zone containing organic materials. In Chehrabad, copper deposit mineralization has been recognized in five horizons. Each horizon is composed of three zones including reduced zone with mineralization, bleached zone and oxidized red zone. The dominant texture in the Chehrabad Cu deposit is replacement texture which is accompanied with other textures such as disseminated, solution seams, lens like and interparticle cement texture. Lithology (sandstone host rock), sulfide mineralogy (e.g. pyrite, chalcocite, bornite and chalcopyrite), structure and texture, stratigraphy as well as factors controlling the mineralization (presence of plant remains performing as environment reductant and also the permeability in the host rock) suggest that this deposit is similar to the red-bed type sedimentary Cu deposits which is formed during the early to late diagenesis.

Upper parts of Elika carbonate Formation belonging to middle Triassic in central part of structural- sedimentary zone of Alborz in East of Mazandaran province (Savadkuh, Khatirkuh and Kiasar regions) are hosted some of important F-Pb-Ba ore deposits contain of PachiMiana, SheshRudbar, Era(Alikola) and Kamarposht. Based on of field observations in study, main localization of ore bodies within carbonate rocks are as acrostic, irregular, and discordant respect to bedding that are displayed in fractures and/or karstic cavities in the form of vein, lenses and bodies. Mineralogy in studied ore deposits generally is simple and mainly composed of galena, barite, fluorite, calcite and minor sphalerite. Macroscopic and microscopic observations are shown variety of syngenetic and epigenetic structures and textures. Disseminate, stylolite and micro-veinlet textures of galena and calcite with or without other mainly minerals are recognized as syn-genetic textures respect to host rocks. Epigenetic structures and textures as open space filling type such as vein-veinlet, zebra, lamination, primary replacement and colloform are dominant textures of high-grade ores that formed main and economic zones of ore body concentration in deposits. Existence of secondary textures such as curvature and wind in triangle cleavage of coarse-grained galenas and also replacement of galena by cerussite and covellite show deformation and supergene oxidation after the main stage of mineralization. Based on current research, mineralization in F-Ba-Pb ore deposits of central Mazandaran is formed and evolved at two steps (1) primary or syn-diagenetic, and (2) main or epigenetic. According to structural signatures of ore body appearance in deposits environment and also textural evidences in macroscopic and microscopic scales, the main and economic stage of mineralization in studied ore deposits is introduced as epigenetic.

Evaporite minerals form when evaporation is more than precipitation. One of the most important evaporate minerals are calcium sulfate, that have extensive distribution in geologic time. Sedimentary and diagenetic processes, operating within different environments such as shallow margins to deep water, have an important role in the formation of these minerals. Due to the presence of anhydrite as a cement, as well as distributeon of this mineral in sedimentary facies of the Asmari Formation in Mansouri oil field, this mineral can affect on the reservoir quality in the studied reservoir. In this study, the fabric of anhydrite in production zones in the Mansouri oil field has been investhigated. Microscopic studies led to the identification of 11 microfacies that are formed from sabkha to open marine enviroment. Note that the textures of anhydrite is partly related to sabkha and lagoon environments (felted fabric and  acicular crystals) and partly are related to diagenetic processes operated in shallow to deep burial (coarse crystals of  anhydrite with cleavage) in grain-supported facies. Other anhydrite textures indentified in the Asmari Formation include layers, poikilotopik, pore ​​filling and inclusive, nodular, nodular - burial, scattered and fracture filling.