مجله بلور شناسی و کانی شناسی ایران
سال بیستم شماره 3 (پیاپی 49، پاییز 1391)

Recognition of heavy minerals in Oman continental shelf sediments and their application for interpretation of sediments sourc rock is the purpose of this study. Seven core samples of sea sediment and three surface samples from tidal flat area have been examined. Heavy minerals are dense grains, wich are found not only in rocks, but also in different types of sand and sediments. Separation of heavy minerals was conducted by heavy liquid of bromoform. Separated heavy minerals were studied by using binocular microscope and SEM equipped with EDS analyser. Various heavy minerals of zircon, garnet, tourmaline, routil, barite, apatite, hornblende, iliminite and magnetite were recognized in studied sediment. The high abundance of zircon, apatite and tourmaline in sediments indicates the felsic rocks as origin. Hornblende was eroded from ophiolitie in ubducted zones. The quartz–toleitic rocks are likely to be the main source for sediments, which are common in back arc zone of Makran subduction.

The S-type granitoid batholith of Shir-Kuh, which is part of central Iran Zone, is located in SW of Yazd and consists of three main granodioritic, monzogranitic and leucogranitic units. The systematic changes in the composition of plagioclase reveal that the granodiorite have been a calcic core plagioclase-rich magma, the monzogranites is a differentiated melt, and the leucogranite is a late residual melt. Totally, all biotites have high AlVI (3.2 to 6.2 apfu) which is characteristic of peraluminous granites. The high almandine component of garnet is similar to those in other peraluminous plutons and, in particular, to the magmatic garnets. Muscovite appears as both primary and secondary-looking grains. Monazite occurs as two types of chemically crystals: monazite and brabantite [CaTh (PO4)2]. The observed homogeneous grains of Th and U poor monazite and tiny microcrystals of brabantite inside the apatite indicate dissolution of apatite during anatexis of sedimentary-metamorphic rocks. Little hematite (less than 10%) composition, which included within restitic biotite ± silimanite assemblages consistent with the idea that the Shir-Kuh granite is generated from the sedimentary source materials contained graphite. Considering the mineral assemblages, presented in the batholith, the fact that some biotites may represent restite and the mean temperature of 820°C is in agreement with the saturation thermometry; such liquids may have formed at a temperature 750 to 850°C by dehydration melting of biotite.

Chromite is one of the important mineral in all lithologies of the Dehsheikh ultramafic complex (South of Baft, Kerman Province) with different shapes and abundances. In the Dehsheikh harzburgites, this mineral present with two distinct generations. The first generation is refractory with variable Cr# values (between 46.2 to 60%) and contains low Al2O3 content (between 21 to 44.4 wt%). The second generation, as interstitial phase, is more Cr depleted and enriched in Al2O3 than the first one. Chemical composition of chromites from the Dehsheikh lherzolites is more similar to the second-type chromites of the Dehsheikh harzburgites. In the Dehsheikh irregular dunites, there are different shapes of chromites. The first group is chemically similar to those of the Dehsheikh chromitites, while the composition of second group is close to the harzburgitic refractory chromites. Cr-spinel in the Dehsheikh chromitties is characterized by high Cr# values (between 69 to 79) and in genetic diagram shows boninitic affinity. In TiO2 vs. Al2 O3 wt% discrimination diagram, the Dehsheikh chromites plot in suprasubduction zone field. Olivine-spinel geothermometry calculations on the Dehsheikh peridotites indicate subsolidus equilibrium temperatures (930 to 1080°C) for these rocks, while oxygen fugacity estimations yield values varing from +1.53 for the Dehsheikh lherzolites to +3.94 for irregular dunites. These values can be found in suprasubduction zone settings. In general, a suprasubduction zone with aqueous fluids derived from subducted oceanic slab is responsible for the formation of the Dehsheikh depleted peridotites and associated chromitites.

The Shanderman metamorphic complex, located in the west of Gilan Province and southwest of Bandar-e-Anzali, is composed of a variety of metamorphic rocks (including slate, schist, calk-schist, marble, serpentinite, metagabbro and eclogite). Based on petrologic studies, protoliths of these rocks have had ultramafic, gabbro-gabbro noritic and pelitic composition. Mineralogically, the metapelitic rocks contain biotite, chlorite, muscovite, andalusite and metabasitic rocks contain amphibole, garnet, olivine, pyroxene and serpentine. Predominant texture of the rocks is porphyrolepidoblastic or nematoblastic. Zr/Y ratio of these rocks, which is less than 3, shows that they are similar to oceanic island arc rocks. Negative anomalies of Ti, P, and K and positive anomaly of Pb (appeared in spider diagrams) are evidences for their relation to crustal assimilated subduction zones. Distribution pattern of trace elements such Th, Hf, La, and U in the studied metapelites indicates a transition from passive margin towards island arc. The characteristics of the studied assemblage show that it was developed in an oceanic passive margin and then evolved within subduction zone.

The Meiduk porphyry copper deposit is located in the northwest of Dehaj- Sarduieh volcano- sedimentary complex in Kerman (southeast of Urumieh- Dokhtar volcano-plutonic belt) and about 42 Km northeast of the Shahr-Babak. The Meiduk porphyry stock with an age 12.5 Ma intruted into Eocene volcanic rocks with andesite, andesitic-basalt and dacite composition (Razak complex). Petrographic studies indicate that this deposit consists mainly of diorite, q-diorite and granodiorit rocks. Mineralogically, Meiduk porphyry rocks contain plagioclase, K-feldespar amphibole, biotite and quartz. Sericite, cholerite, epidote and magnetite are secondry phases. Geochemically, the Meiduk porphyry rocks are alkali and alkali- calcic, meta to peralumine and I-type granitoids. Tectonic studies indicate that the Meiduk porphyry were emplaced at active continental margine. Tectonic characteristics also indicate that, after the collision of the Arabian and Iranian plates, the Meiduk porphyry was emplaced during a late orogenic stage of arc development (compressional tectonic regimes) in a post-collisional tectonic setting at the end of magmatism related to Neo-Tethyan subduction system.

The Galand-rud coal mine is one of the coal producing areas of central Alborz coal basin which is located in Mazandran Province. Based on mineralogical and geochemical studies pyrite is the main sulfide mineral in the mine. Based on correlation matrix, cluster analysis and principle component analysis (PCA), SiO2, Al2O3, Na2O, K2O and TiO2 are associated with alluminosilicate minerals, CaO, MgO and MnO with carbonate minerals (calcite and dolomite) and Fe2O3 and SO3 with pyrite. Ambiguous correlation between P2O5 and other major oxides and also the presence of apatite in Galand-rud coals indicate two sources for P2O5. A negative correlation between SiO2, Al2O3, Na2O, K2O, TiO2 and Cl indicate organic origin of Cl. Also, V and Rb originate from alluminosilicate minerals, Ni, Cu, Co, Cr, Pb, Ce, Y and Zn from sulfide minerals and Ba, Sr from carbonate and phosphate –bearing minerals. Galand-rud coals enriched in most of trace elements respect to China and America coals and Clark coals, whereas, exhaustion in Cl and Nb.

Gushk chromite mine is one of the largest and the most important chromite mines in Iran that is located in southwest of Kerman Province, 5 km north of Baft city. In this open pit active mine, about 60 tons of chromite is extracted per day. The studied chromitites are podiform type and form discontinuous layers or lenses surrounded by completely serpentinized dunites. The chromites with average Cr2O3 = 62.8% and Cr# = 0.83 are classified as Cr rich chromitites or as the first grade type chromites in the world. Cr# and Mg# values indicate that the studied chromitites have been crystallized from boninitic magmas, probably in suprasubduction zone setting in a back-arc basin environment. It seems that the Baft chromitite ores have initially been formed in a primary ophiolitic complex within dunitic envelopes. In the next stage, due to serpentinization of the peridotites and ascending of the resulted serpentinite, the studied deposits have been emplaced along the shear zones of the Baft ophiolitic melange en route to the surface.

The study area is located in the central part of the Siahrood geological map, Kharvanagh of Ahar town, in the East Azerbaijan Province. The volcanic rocks of the Kharvanagh area include trachybasalt, trachy-andesi-basalt and trachy-andesite. The main minerals in the rocks are plagioclase, pyroxene, olivine and hornblende and the main textures are microlitic-porphyry. At the contact between the volcanic rocks and Miocene sandstones, epidote and calcite are formed due to thermal effect. Based on the geochemical data of major and trace elements, these rocks belong to High K alkaline to shoshonitic magmatic series. The absence of distinct Eu anomaly and relatively enrichment in LILE (Ba, Rb, and K) and LREE in these rocks indicate a back arc tectonic setting. Also enrichment of incompatible elements can be related to mantle metasomatism or contamination by continental crust. The chemistry of back arc rocks is relatively complicated and the geochemical features depend on the degrees of partial melting, heterogeneity in the sources mantle, etc. Considering the geological features and the Miocene age of the rocks, it can be concluded that the parental magma belongs to extensional basins magmatism, which produced from partial melting of the garnet lherzolite mantle.

The composition of Kuh-e- Barandeh volcanic dome is andesite, dacitic andesite and dacite of calc-alkaline affinity. A prominent feature of this dome is the presence of various types of enclaves with different composition, shape and size. Detailed field and laboratory investigation proved that they are of xenolith and autolith types. The xenoliths are of pelitic and basic protoliths. Xenoliths show two distinct metamorphic events: (1) Regional dynamomorphic event justified by clear preferred orientation and foliation. (2) Thermal metamorphism producing andalusite, sillimanite, cordierite and spinel at the expense of former minerals like biotite, muscovite etc in pelitic rock and green hornblend at the expense of brown hornblend in basic rock. T. P measurement shows that these xenoliths have suffered a range of T.P 768- 830 mC and 5-7 Kb) during regional metamorphism and a retrograde contact metamorphism (747- 821 mC and 3.6-6.7 Kb).

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.

In southeast of Bardsir (Kerman Province), there is a volcanic complex belongs to Uromieh-Dokhtar volcanic belt.This complex mainly contains basaltic-andesite and basalt lava flows with the Eocene age, alternative with pyroclastic rocks. Petrographic evidences include zoning, sieve texture and rounded crystal in plagioclase and pyroxene phenocrysts disequilibrium conditions between crystals and host melts during crystalization. Geochemical characteristics indicate that these rocks belong to calcalkaline domain. The highly enrichment of LREE compared to HREE, high contents of LILE relative to HFSE and significant anomalies of Nb, Ti and P suggest a subduction-related volcanism. These features indicate that these rocks have probably been generated in an enriched mantle with a low degree of partial melting in a subduction zone. Mineralogical, textural and geochemical investigations on volcanic successtions in this area show that systematic chemical changes have been occurred in shallow magma chamber and these changes have been affected on mineralogy, texture and chemistry of related lava flows.

Broujerd granitoid complex is one of the large intrusive complexes in structural zone of Sanandaj-Sirjan and petrologicaly they are composed of granodiorite and quartzdiorite and which are accompanied by monzogranite stocks. Study of Broujerd granitoid complex replacement mechanism (west of Iran) has been done with the use of anisotropic magnetic susceptibility technique (AMS) on the basis of results obtained from analysis of 290 samples collected from 96 stations from the main petrologic units. The results show that this complex is part of paramagnetic granitoids and rate of magnetic susceptibility anisotropy is reduced from quartz diorite to monzogranite unit. Elliptical magnetic form is in half of the linear stations and in rest of plane stations. Magnetic fabrics show that replacement of Broujerd granitic complex has been done as sill and structural setting of granitic complex in Broujerd is extensional shear fractures which are product of transpression tectonic regime.

The study area is located in the east of Ahar town in Eastern Azerbaijan Province and is part of the Ahar-Arasbaran Cenozoic magmatic belt of NW Iran. The geological units of the Eocene age are volcanic rocks with andesite, latite - andesite and basaltic andesite composition.Khankandi and Useflu Oligocene intrusive bodies intruded in the volcanic rocks and caused widespread alteration and copper and gold mineralization. The intrusive bodies include I type granite, grano-diorite, quartz monzonite, monzonite-monzodiorite and gabbro. Granite, granodiorite and quartz monzonite belong to calk-alkaline series, while monzonite- monzodiorite and gabbro belong to alkaline series. They are related to continental margin tectonic regime and generated at post collisional tectonic settings. Alkaline basic rocks postdate calk-alkaline acidic rocks and are barren. The low sulfidation epithermal Au veins occurred in the Eocene volcanic rocks and Useflu quartz monzonitic body. Also Au-bearing quartz veinlets with relatively widespread alteration zone occurred at the eastern side of the Useflu intrusive body. Argillic and sericitic alteration accompanied the Au mineralizations. Pyrite, sphalerite, galena, chalcopyrite and bornite are the common ore minerals and occurred as disseminated and open space fillings. Stockwork and disseminated Cu mineralization occurred in the quartz monzonitic rocks at the SW side of Khankandi intrusive body. Pyrite, chalcopyrite, bornite with minor amounts of magnetite are the common ore minerals. Phyllic - pottasic alterations accompanied the Cu mineralization. Similar mineralizations of Cu occurred in other parts of the area (for example around the Useflu) in quartz monzonitic rocks which are accompanied by magnetite- mafic (amphibole and biotite) mineral veinlets.

The Sirzar Sb prospecting area is located in northeast of Torbat -e- Jam in Khorasan Razavi Province. Mineralization is found both as vein and replacement within carbonate rock (Permian). Two primary stages of mineralization are: 1) galena ± pyrite ± chalcopyrite ± sphalerite ± sulfosalte ± Cu-Sb sulfides, quartz and barite. 2) Stibnite ± pyrite ± sphalerite ± fuloppite, quartz, barite, dolomite and calcite. Minerals which are formed due to weathering and oxidation include valentinite, bindheimite, covellite, malachite, azurite, anglesite, cerrusite, geothite, hematite and Sb-oxides. Main alteration is: silicification, baritization and dolomitization. SEM analyses of galena revealed high content of Ag, As and Sb and low Bi. This indicates that galena was formed at low temperature. Sulfosalte within galena also contain higher Sb which prove this case. Stibnite also contains some Ag. Fluid inclusion microthermometry on quartz, calcite and barite revealed that the first stage of mineralization were formed between 371-317°C and the second stage associated with quartz, barite, and dolomite were formed between 275-188 °C and associated with calcite is between 197 132°C. Sirzar Sb mineralized area is similar to Xikuangshan mine in China with respect to host rock, mineral paragnesis and type of mineralization. Based on mineral chemistry and fluid inclusion microthermometry, Sirzar is a low temperature epithermal deposit.

The aim of this research was to estimate iron and manganese carbonate values in dolomites using XRD technique. This method is done easily and with less cost than the conventional chemical methods which are used to determine the amount of iron and manganese. For this purpose, total number of 20 samples from four different formations with various ages and locations, including Soltanieh, Sibzar, Shotori and Mozduran Formations, were selected and their iron and manganese contents were measured using atomic absorption spectrophotometery technique. Then all samples were analyzed by XRD. Finally, with drawn cell space values versus amounts of iron and manganese, the graph was obtained and the function of mol% FeCO3 + MnCO3 = 1271.5 d104 – 3667.2 (r2 = 0.897) was obtained from it. This function can be used to estimate iron and manganese carbonate contents in the other unknown dolomite samples which have only been studied using XRD method.

Extensive outcrops of metamorphic rocks is located in east of fariman (gandab) cantain andalusite schiste has been evaluted their potential as mineral deposite in this study. For this purpose, after preliminary studies of petrography and geochemistry, were performed processing tests including gravity and magnetic separation with aim of evaluation ability of production andalusite used in refractories industry. Petrography study includs of thin sections, X-ray diffraction (XRD) and in order of identify the associated elements, chemical analysis of samples taken by XRF. The results show that processing operations using dry high intensity magnetic separation and heavy media method of gravity seperation, product %55 aluminum oxide, %1.5 iron oxide, %42 silicon oxide and less than %0.5 of potassium and sodium oxides, which is comparable to international standards and marketable andalusite

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

East of Shahindezh (south of West Azarbaidjan province), as a part of Irano Himalayan karst bauxite belt, comprises discontinuous layers and lenses of bauxite, laterite, and kaolin within the Ruteh carbonate formation (Middle- Upper Permian). The XRD analyses show that the lateritic ores have rather simple mineralogy, and consist of hematite, boehmite, and kaolinite as major phases accompanied by minor phases such as goethite, montmorillonite, diaspore, illite, chlorite, and rutile. According to petrographical considerations, it can be deduced that the ores have polycyclic nature and their evolution being largely affected by the function of diagenetic and epigenetic processes. Petrographical features along with mineral assemblages reveal that the lateritic ores were deposited almost in a vadose environment. Based on chemistry of major elements, the ores are categorized into three types; (1) bauxitic ferrite, (2) laterite, and (3) ferritic laterite. Distribution pattern of REEs normalized to chondrite displays a low degree of differentiation between LREEs and HREEs and also a weak negative anomaly for Eu during the lateritization processes. These features along with field relations and concentration values of Al, Ti, and Zr indicate a diabasic protolith for the ores. Consideration of Ce and Eu anomalies unveil that the intensity of lateritization is directly related to the pH increase of drained water, Eh variations, and fluctuation of water table. Results from geochemical data have furnished compelling evidence that buffering of underground descending acidic weathering solutions, dissimilaritis in degree of resistance against weathering among primary minerals, discrepancies in degree of stability of complexing legands, and chemical characteristics of elements are four key controlling factors for the distribution and behavior of major, minor, trace, and rare earth elements during lateritization in east of Shahindezh.