جستجوی مقالات مرتبط با کلیدواژه "کوارتز" در نشریات گروه "زمین شناسی"

Masteroon area is located in the northeast of Azna city, in the Sanandaj-Sirjan zone. The rocks units include a relatively uniform sequence of slate and phyllite with a granodiorite intrusive mass that includes pegmatitic complex. The most important minerals include quartz, alkaline feldspar, plagioclase, tourmaline and muscovite. Quartz is high pure and does not have any other elements. EPMA shows the albite-type feldspar with a lesser extent than orthose-type with a less than 550⁰C crystallization temperature. This can be due to the result of below the freezing of the feldspars composition during the cooling of the mass. The available tourmalines are of schorl and alkaline type with a deficiency in the X position, and their numerous and abundant presence, automorphism and absence of chemical zoning, indicate that tourmalines are magmatic. Muscovites are present in two forms: coarse-grained in pegmatites and fine-grained in joints and cracks, and the coarse-grains does not stretch to phengite.

In this study, the trace element composition of various types of granitoids (I-type, S-type, and plagiogranites) at different geological settings was measured using the LA-ICP-MS method, and their distribution was investigated. The amounts of elements Al, Ti, Fe, Mn, Na, K, P, Li, Rb, Be, Sr, Ga, Ge, and Sn in quartz were determined to be above the detection limit. The resulting data indicate that despite variations in age and formation settings, the content and distribution of trace elements in quartz crystals of granitoids are influenced by the type and nature of granitic magma. The S-type granitoids have quartz crystals with the highest abundance of sum trace elements (710-1111 ppm), followed by I-type granitoids (287-438 ppm) and plagiogranites (201-116 ppm). Among the trace elements present in quartz, aluminum (ppm 18-216) exhibits the highest abundances, followed by titanium (ppm 44-183) and lithium (ppm 5-80), entering the crystal lattice with relatively high concentrations. The Aluminum Saturation Index (ASI) is the most significant factor in the distribution of Al in quartz crystals, and the Al content increases with an increase in the Ge/Ti differentiation coefficient. The concentration distribution and variation trends relative to the differentiation ratio of elements Ga, Ge, Li, and Rb in quartz crystals are similar to aluminum. The abundance of Ti decreases with increasing the Ge/Ti, and the distribution of this element in quartz crystals is dependent not only on the nature and composition of the parent magma but also on the ambient temperature-pressure conditions. Thermometric calculations using the Titan Q method (Ti in quartz) indicate that the crystallization temperature of quartz in S-type granitoids (average 776 °C) is higher than in I-type granitoids (average 707 °C) and plagiogranites (average 683 °C). Due to their very low concentrations and the influence of other factors such as involved fluids or very fine inclusions, other trace elements in quartz crystals exhibit irregular distributions.

Andarian area is located north of Tabriz city, north west Iran, and tectonically is a part of Ahar-Arasbaran magmatic belt. Geology of the area includes Miocene shallow pluton, Cretaceous flysch-type sediments, metamorphic rocks )hornfels and skarn( and volcanic rocks. Mineralization occurred in two stages: primary and secondary. The primary ore minerals include Au, pyrite and stibnite. Malachite, azurite and iron-hydroxides are the main minerals of the secondary phase. Two phases of liquid-rich and gas-rich inclusions are the most common type of inclusions. The average formation temperature of quartz-gold vein deposit is 237°C with low salinity (with an average of 8.7 wt% NaCl equivalent). The pressure of entrapment for fluid inclusions is between 26 to 51 bars, which is equal to the depth of 270-550 m. Based on fluid inclusions studies, the gold bearing quartz veins formed in epithermal condition.

Considering the high resistance of quartz against stress and alteration, this mineral was chosen for Geothermobarometry in Almogholagh intrusive masses. To determine the temperature and pressure of crystallization of quartz, the amount of Ti contained in the quartz was measured by Electron Microprobe –Analyzer method and then, the pressure and temperature of crystallization of analyzed points were calculated. The growth and crystallization temperature range of quartz was determined using the P-T diagrams were drawn and contoured. The results show that the negative effects of stress and active fluids on the calculated crystallization temperature can be reduced by contouring. Moreover, in this study, it was found that quartz crystals of intermediate-to-basic rocks and the acidic rocks have been crystallized in a temperature range of 683 to 757 °C and 667 to 741 °C respectively. The examination of fluid inclusions in quartz veins by heating and freezing stage microscope showed that silicic veins in intrusive masses and in the immediate adjacent rock have been formed at temperatures between 134 to 255 °C.

The Baghuo gold mine (Kuhzar) is located about 100 km S-SE of Damghan. The area is part of Torud- Chahshirin volcano- plutonic belt. The hosts of quartz – tourmaline veins are mainly granite, granodiorite and volcanic rocks such as andesite and dacite.  Mineralization occurs as a copper- gold bearing silica vein. Quartz, pyrite, chalcopyrite, gold, hematite, malachite, azurite, covellite and Fe- hydroxides ore are main constituents of mineralized veins. Gold grains with <50 µm in diameter commonly occurr within quartz grains. Based on petrography studies, six types of fluid inclusions in quartz were distinguished: (1) monophase liquid inclusions; (2) monophase vapor inclusions (3) two- phase inclusions of liquid-rich; (4) two- phase inclusions of vapor-rich; (5) three- phase halite-bearing inclusions; (6) poly-phase inclusions. Fluid inclusion studies show homogenization temperatures ranging from 250 to 400 °C with salinities from 4 to 30 wt% equivalent NaCl. Data shows that the evolution of mineralizing fluid occurred at a depth of more than 600 m below the surface and pressure about 100 bar. Evidences suggest that Baghu area mineralization may have occurred at the epithermal condition related to a porphyry system.

Gazu prospect area is located about 65Km southeast of Tabas in the southern part of Shotori range. Sub -volcanic intermediate intrusive rocks (Upper Cretaceous?), monzonitic to dioritic in composition, intruded into carbonate rocks of Shotori Formation (Triassic) which are the main source for copper mineralization in Gazu district. Alteration zones associated within the intrusive are: Quartz- sericite± pyrite (main type), silicified- sericite, propylitic, silicified- propylitic and strong silicification. The carbonate unit is silicified, near some intrusive rocks, and in some area Skarns were formed. Mineralization occurs mainly as stockwork and disseminated with minor breccia. Veinlet’s type is: Quartz, pyrite, quartz- pyrite, quartz-carbonate-sulfide, carbonate-sulfide and sulfide. The density of quartz-sulfide veinlet with sulfide minerals is about 40 per m2, in some places. An extensive gossan zone is formed due to oxidation of sulfides appeared in intrusive rocks and carbonate unit that due to oxidation of sulfide minerals. The geochemistry of stream sediments are as follow: Cu = 36-1200 (ppm), Pb = 36-125(ppm), Zn = 62- 738 (ppm). Rock chip geochemistry is: Cu = 100-20000 (ppm), Pb = 10-400 (ppm), Zn = 50- 3000 (ppm). High content Cu and Zn are associated with quartz- sericite± pyrite and strong silicification. The evidence shows that the Gazu is porphyry copper and related skarn type system.

Trace elements distribution in granitic quartz is highly sensitive to differentiation processes. Abundance of Ti, Ge, Al and Li in primary quartz of Naqadeh granitoids have been studied by Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). Trace elements ratio in quartz exhibits completely different trends in two different Naqadeh granitoid units (more mafic granitoids (MMG) and monzogranites). The variation of Ti/Ge within of quartz in MMG prevents magmatic differentiation as a major role in the evolution of this unit; and Li variation has been produced by different values of amphibole co-crystallization. In other hand, Ti/Ge and Li trends in monzogranites shows important role of magmatic differentiation in their formation. Various Al concentrations between MMG and monzogranites can be ascribed to other factors such as Aluminum Saturation Index.

The studied sample presents garnet textural sector-zoning as inclusions in two types in garnet schist from Morlaix, North-West Brittany, France. Crystal size distributions (CSD) of quartz crystals were measured in both types inclusions, in the matrix and strain shadows around garnet porphyroblasts using Back-scatter electron (BSE) images. The CSD plots of quartz crystals show an increase of average in sizes from type 1 inclusion,60μm, to the matrix,116 μm, and strain shadow,248 μm,. These differences could be explained of quartzes size distribution by many processes such as capturing by pophyroblast, crystal face, annealing and grain boundary migration

Kalchoyeh copper deposit is located about 110 km east of Isfahan, in Central Iran, Urumieh- Bazman volcanoplutonic belt. Host rocks of this deposit are Eocene volcanic rocks and tuffs which are pyroxene andesitic lava and sandy and lithic tuffs. Sandy tuffs are the main host rocks of the deposit. Ore mineralization is taken place as veins and veinlets and quartz is the main gangue mineral. Hypogene mineralization includes chalchopyrite, galena and magnetite. Covellite and chalcocite are also found as supergene mineralization. Microthermometric measurements of fluid inclusions in quartz indicate homogenization temperatures between 101 to 312 °C and salinities from 0.7 to 7.3 wt % NaCl equivalent. Boiling occurred in the mineralizing fluids at 400 meter below the paleo- water table. Based on performed studies, Ore fluid was low to medium temperature and low salinity and potential mineralization. In addition ore mineralization in Kalchoye is type of epithermal deposits with low sulfidation.

Dehnow tonalite in west of Mashhad, NE Iran, is one of the oldest pluton in Mashhad Granitoied Complexes. This pluton cut by four systematic fracture sets. Among them, two sets show right lateral strike separation. Set A consists of parallel right lateral strike slip faults with a minor reverse slip component and Set B includes right lateral strike slip faults with a small component of normal slip. Other set is formed between faults in set A. Tonalite is deformed into mylonite in fault cores. Study of microstructures and dynamic recrystallization of quartz grains in these mylonites indicates that the formation of mylonites have taken place under 410-430 (ºC), 42.54 - 59.31(Mpa) differential stress and 21.27-29.65(Mpa) maximum shear stress. The strain rate in this deformation isAWT IMAGE-AWT IMAGE. Field observations and study of microstructures revealed that these fault sets have formed during renewed slip on the earlier formed extensional joints and their asymmetric fringe joints probably during Late Cimmerian orogeny.

Kuh – e- Zar gold deposit located in central part of Khaf – Bardaskan volcano-platonic belt and about 40 km west of Torbat-e-Heydariyeh area in Khorassan-e-Razavi province. The extensive exploration of the last decade done in the above belt has been caused the exploration of several Iron oxide copper – gold deposits, such as Kuh-e-Zar deposit. Several types of Tuff and Acide to intermediate lavas (lover tertiary) are widespread all over in the area. Mineralization appeared in different type such as vein, stockwork and Hydrothermal breccia in strike sleep fault zone which are hidden inside volcano plutonic rocks.The average gold grade is between 3.02 ppm and ore reserve is estimated more than 3 million tons (cut off grade = 0.7 ppm). The copper grade in mineralized zone located in intrusive bodies between 0.3 to 1.1 %. The main mineralized zones are Quartz and specularite (more than 30%). However, the various types of sulfides are very rare on surface. Pure gold can be observed together with Quartz and Specularits. Based on consideration of oxygen stable isotope () in Quartz and siderite as well as sulfur () in chalcopyrite, geochemical investigation and micro thermometric study has caused the gold mineralization through magmatic fluid with low sulfide content and high oxidation state. It is clear that the kuh-e-zar mineralization in case of paragenesis, alteration and dimension has been the only case all over the world. Regarding the lack of recognized and similar sample in the world, this deposit is a new and different variety of Iron Oxide Cu-Au (IOCG) deposit. It is introduced and named as Iron Oxide Gold deposit (IOG) or Specularite rich Gold deposits. This deposit has unusual richness in gold and LREE and is poor in copper.

The study area is located in northern part of metamorphic belt of Sanandaj-Sirjan in east of Hamedan Batolith. This area is mainly composed of regional metamorphic rocks, such as staurolith, andalusite, silimanite and garnet bearing mica schists and slates, with nearly NW-SE trend. The age of these rocks (tectonites) are Pre-jurassic and have experienced two stages of deformation during ductile deformation. The first schistosity (S1) formed at the first phase (D1). The second phase (D2) was formed by sided forces where the most of structures have formed by this force. The fabric elements of second schistosity (S2) and second lineation (L2) formed in this phase. The subfabric elements of quartz, due to its physicochemical characteristic, was producted at this phase. Quartz grains, first and second schistosity and axes of microfolds all have orthorombic symmetry.