Iranian Journal of Crystallography and Mineralogy
Year:2012 | Volume:19 | Issue:4|Papers Count:19

Quartz-monzonitic porphyry stock at Kighal is located about 12 km north of Varzeghan, East Azarbaidjan Province, NW Iran. It has intruded older volcanic units during magmatic activities of Pyrenean orogenic phase and produced Cu-Mo mineralization and hydrothermal alteration zones in the region. The stock was intruded by numerous cross-cutting dikes mainly of dioritic to quartz-dioritic compositions. The hydro-fracturing brought about permeable zones within the stock and surrounding rocks facilitating the circulation of hydrothermal fluids that led to the development of potassic, phyllic, argillic, advanced argillic and propylitic alteration zones within the area. The general pattern of REE spider diagrams of different alteration zones show distinct negative trend from LREE toward HREE. In potassic and phyllic zones, REEs display depletion because of high activity of sulfate complexes, low pH and high ratio of water/rock during alteration, but in argillic zone, besides LREE depletion, HREEs display enrichment, which can be referred to their absorption by clay minerals and low activity of sulfate complexes within fluids responsible for argillic alteration. In propylitic zone, HREEs were immobile but LREEs display enrichment relative to nearly fresh sample. In leached zone, depletion of LREEs and MREEs is conspicuously higher than HREEs. Eu/Eu* ratio in nearly fresh and altered samples is<1 but Ce/Ce* ratio is>1. On this basis, relatively negative anomaly of Eu can be produced by fractional differentiation of ca-rich plagioclase from parental magma or their absence within the magma-source materials. The highest value of Eu/Eu* ratio belongs to the leached zone which is likely due to the dominance of oxidizing condition and immobility of this element. In argillic zone, this ratio is similar to nearly fresh sample and in potassic and phyllic zones is higher than fresh sample, probably because of concentration and precipitation of this element by hydrothermal oxides and sulfides.

Microscopical studies were carried out, in addition to physico-chemical and mineralogical analysis, in order to evaluate the effect of parent material and weathering on soil genesis in forest regions of Lahijan. Two representative soil pedons in mountain landform developed on granite and andesitic basalt located about 8 km southeast of Lahijan were selected and sampling were taken from each horizon by Kubiena boxes or clod. Mineral and their weathering were studied by a polarized microscope under plain and cross light and comparison was made with total elemental analysis by XRF and X-ray analysis (XRD). All evidences showed that there is a close structural relationship between the host mineral and the weathering products. Microscopic observation of soils and weathered rock derived from granite showed evidence of the alteration of feldspars to sericite and chlorite under hydrothermal condition and clay minerals under soil condition. In soils and weathered rock derived from andesitic basalt, alteration of plagioclase (labradorite) and olivine to chlorite and clay minerals as well as pyroxene to amphibole were dominant process. Moreover, higher depth of soil under andesitic basalt with comparison to granite was the morphological evidence of intense weathering effects of humid condition in the study area for different minerals.

The Upper Jurassic (Kimmiridgian-Tithonian) Mozduran Formation in the Kopet-Dagh basin is mainly composed of limestone and dolomite with minor amounts of silisiclastic and evaporaite sediments. The purpose of this study is to identify and differentiate dolomite types in this formation, north of Chenaran. Based on petrographic studies, two types of dolomitization (fabric selective and pervasive) have occurred. More detail studies of the pervasive dolomite led to recognition of three different dolomite types including: fine to medium crystal, coarse crystal and cement. Elemental and stable isotope analysis indicated that the Mozduran dolomites were subjected to a complex diagenetic history. The calculated temperature for dolomitization of DP1, DP2 and DP3 dolomites are 58oC, 64oC and 80oC respectively.

Band-e-Ziarat ophiolitic complex is located approximately about 45 Km south of Kahnuj, Kerman Province. The complex is a horst structure at the western boundary of the Jaz Murian depression, southern Lut block and southeastern Sanandaj-Sirjan zone. It bounded to the east and to the west by two major north-south trending fault zones of Jiroft and Sabzevaran. The complex is mainly composed of low- and high level gabbroic sequences, diabasic dikes with lesser amounts of basaltic lavas and the intrusive sodic plagiogranites. The ultramafic rocks are rare and only, found near the fault zones, without any distinct stratigraphic position. Petrological and geochemical investigations along with K-Ar dating on ophiolitic rocks indicate that these rocks crystallized from Ti-rich tholeiitic melts during fractional crystallization at the Late Cretaceous time in Neotethyan oceanic basin.

The Precambrian Takab complex consists of various metamorphic rocks including metabasites, metaultramafic rocks, calc-silicates and marbles which are metamorphosed under green schist to granulite facies. The pick metamorphic rocks are retrogressively metamorphosed during crustal exhumation related to pressure and temperature decreasing as well as H2O-rich fluid infiltrations. Retrograde metamorphism of the Ol-bearing marbles caused their transformation from granulite to amphibolite facies. Some mineralogical and textural evidence of retrograde metamorphism in the Takab dolomitic marbles are (a) appearance of low temperature and H2O-bearing phases such as tremolite, clinonochlore, (±) titanite and (±)epidote, (b) formation of tremolite+dolomite assemblages as pseudomorph after olivine and (c) titanite corona around ilmenite. The temperature and pressure of retrograde metamorphism are calculated by using mineral chemistry of the retrograde phases and the equilibria reactions at 650±25oC and 6.5±0.5kbar, respectively. The estimated temperatures and pressures are consistent with the amphibolites facies. Due to lack of appropriate chemical composition, retrograde tremolite is the stable phase of Takab dolomitic marbles at the amphibolite facies. Retrograde clinochlore is appeared in the dolomitic marbles having Al2O3 impurities at the high temperature amphibolite facies.

The Homond Cu-Au porphyry prospecting area is located southwest of Birjand. Subvolcanic monzonitic to dioritic rocks are highly altered. The main alteration zones are: quartz-sericite-calcite-pyrite, propylitic and carbonate. The content of major, trace and rare earth elements (REE) of the rocks changes due to alteration. The changes are less in some such as TiO2, MnO, P2O5, Nb, Gd, Y, Eu and higher in SiO2, K2O, Na2O, CaO, Al2O3, MgO, TFeO, Ba, Sr, Rb, Zr, Hf and most of REE. The chemical and mineralogical composition of the rock, type and intensity of the alteration control the changes. Quartz-sericite-calcite-pyrite alteration made the following changes in monzonite and diorite. The content of SiO2 and Al2O3 has increased and the amount of K2O, Na2O, TFeO and MgO are decreased. The changes in CaO content are being control by the amount of calcite. REE elements are usually lowered. Rb show different behavior in different intensity. Ba, Sr and Zr are highly depleted. With increasing the intensity of alteration, the content of Hf has depleted in monzonite and enriched in diorite. In propylitic alteration zone, the amount of SiO2, K2O and TFeO are decreased in both monzonite and diorite. The content of Al2O3 and Na2O are decreased and CaO and MgO are increased in monzonite but in diorite are vice versa. REE elements are enriched in monzonite and depleted in diorite. Rb shows different behavior with different intensity of alteration. Ba, Sr and Zr are highly depleted. Hf shows enrichment both in monzonite and diorite. The chemical composition of mozonitic rocks within carbonate zone show depletion in SiO2, K2O, Na2O, MgO, TFeO, Rb, Sr, Ba, Zr and Hf and increase in CaO and Al2O3. REE elements are slightly decreased. Chemical composition of the rocks changes with alteration, therefore classification of the igneous rocks based on their chemical composition, rock series, Al-index (Shand) and REE pattern, can be affected. Finding the source of igneous rocks, based on Rb-Sr in altered rock, can be misleading. Therefore, it is important to select the right rock for studying the petrognesis and radiogenic isotopes in altered areas.

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 is 1.08×10-12-7.3×10-15. 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.

Sorkheh Dizaj apatite-iron oxide deposit is located in southeast of Zanjan, within the Tarom subzone of Western Alborz - Azarbaijan structural zone. The oldest units in the area are Eocene trachyte, trachyandesite, olivine basalt and volcanoclastic brecciated tuff and lapilli tuff intruded by a quartz-monzonite, monzonite and granite subvolcanic pluton of Late Eocene -Early Oligocene age. The subvolcanic plutonic rocks show characteristics of I-type granites and the magmatism shows orogenic characteristics related to magmatic arcs. Mineralization in the area occurred in the form of vein that is located in the host subvolcanic pluton. Furthermore, mineralization in the volcanic rocks occurs as veins similar to those in the subvolcanic rock mineralization, but less abundant. Geometry of the ore bodies is of vein type and their textures are stock work, massive, banded, brecciate and vein-veinlet. Magnetite (low Ti) and apatite are the most important minerals at Sorkheh Dizaj deposit accompanied by minor sulfide minerals such as chalcopyrite, bornite and pyrite. The supergene minerals like chalcocite, malachite, azurite, covellite, hematite and goethite have been formed due to weathering and supergene processes. The main alterations of this deposit are K-feldspar metasomatism, actinolitization, argillic, sericitization, silicification, tourmalinization, and chlorite-epidotic where silicification and argillic alterations are more abundant than other alterations. The most important characteristics of the Sorkheh Dizaj apatite - iron oxide deposit (including tectonic setting, host rock, mineralogy, hydrothermal alteration, structure and texture) indicate magmatic Fe-P-REE rich fluids source for the mineralization. Comparison of the Sorkheh Dizaj deposit with various types of iron mineralization in the world suggests that the deposit shows the most similarity with the Kiruna type Iron Oxide-Apatite (IOA) deposits.

Razak and Mishan Formations (Early to Middle Mioceneage) in Polkavar and Zanjiran areas located in south and southwest of Fars Province in the Zagros foldbelt. Major minerals are illite/muscovite, chlorite, calcite, quartz and minor minerals are albite, and palygorskite. Analyses of whole rock chemistry show high amounts of CaO, MgO and low SiO2, Al2O3, Fe2O3, K2O, Na2O contents compared to NASC (North American Shale Composits), PAAS (Post Arcean Austeralian Shale), and UC (Upper Crust). The pattern of chondrite/NASC-normalized rare earth elements of samples indicates enrichments of LREE related to HREE with no anomaly of Eu. Samples have high La/Sc, Ba/Sc, Ba/Co ratios and low Th/Sc, Th/Cr, La/Cr ratios, which gives indications of felsic origin with some contribution of basic rocks. The TiO2/Al2O3 plot could be further evidences of granite/rhyolite+basalt original rocks. The low intense of weathering of source rocks was evaluated by low CIA, low CIW and high contents of Sr and Ca. Low CEC of these samples show illite, chlorite, and palygorskite and very low amount or absences of vermiculite and montmorilonite. Atterberg limitations are low to intermediate between 10-16. Final conclusion of these investigation indicate the potential usage of these sediments for brick, tile ceramic and earthenwares.

Basaltic lavas have been reported at the base of the Shemshak Formation in some areas of the Alborz zone. However, detail observations of geological outcrops in different areas in eastern Alborz show that these rocks in most aereas around Shahrood (e.g. Gheshlagh in Khosh Yeilagh area) and Damghan (e.g. Tazare, Talo and Kalate Rodbar) are intrusive as sill, dike and small stocks and in few areas of Damghan (e.g. Cheshmeh Ali and Toyedarvar) and Semnan (e.g. Shahmirzad) are basaltic flows. High contents of Ti and P and alkaline nature of parental magma, supported by presence of apatite, primary and secondary sphenes and phlogopite in these rocks. Identification diagrams of magmatic series and tectonic setting discrimination diagrams have been proved an alkaline nature and intracontinental setting for these rocks. Enrichment in LREE and highly incompatible elements and depletion in HREE are obvious in chondrite and primitive mantle normalized spider diagrams. Parallel trends in patterns of REE variations, Pb-positive anomaly associated with patterns of compatible versus incompatible elements variation diagrams, indicating an unique source for these igneous rocks and the main role of fractional crystallization in the evolution of magma, although, minor amounts of assimilation and contamination of magma by crustal rocks occurred too. Geochemical investigations indicate that this alkaline magma has been formed by low degrees partial melting (10-15%) of an enriched subcontinental lithospheric garnet-lerhzolitic mantle in an extensional intracontinental environment. This environment was an extensional proto-backarc basin located on the passive continental margin of Alborz during Late Triassic-Early Jurassic time.

Content of iron cations in three biotite specimens of true trioctahedral mica were determined by Mossbauer spectroscopy, electron microprobe and wet-chemistry methods. International certified reference materials were analyzed simultaneously with micas to evaluate the accuracy of the wet-chemistry method. High precision Mossbauer spectroscopic Fe3+/Fe2+ ratios coupled with the electron microprobe iron determinations were compared with the wetchemical data. Comparisons of data show that in wet-chemistry method powdered micas dissolve more readily during acid attack than the granular micas and thus yield higher precision and accuracy.

In the present study, the phase transition of clinoptilolite, 16 (Na, K)6 [Al6Si30O72]. 20H2O, to barium zeolites, has been investigated in the alkaline hydrothermal conditions, at the presence of the barium bearing solutions, and the high temperature. Firstly, the primary sample collected from Aftar area, west of Semnan. Secondly, powdered and examined without purification. Clinoptilolite, as a natural zeolite, transformed to edingtonite, BaAl2Si3O10.4H2O, and harmotome, BaAl2 Si6O16.6H2O, as the barium zeolites, in the influence of alkaline solutions, and the hydrothermal circumstances, arranged by the hydrothermal autoclaves. Finally, the processed products evaluated by the X-Ray graphs and SEM images.

In southwest of Birjand, the Tertiary igneous rocks have oxposed in Cretaceous flysch type deposits. These bodies are made of micro quartzmonzodiorite, trachyandesite, andesite and dacite. The main texture in these rocks is porphyry. Their phenocrysts are plagioclase, hornblende and biotite. Plagioclases contain zoning. Pyroxene, quartz and opaque minerals are in groundmass. Often, hornblendes have burned rims. These rocks have calcalkaline nature and have formed in an active continental margin. These rocks enriched in LREE and LILE and depleted in HREE. However, negative Nb anomalies as well as enrichment in LILE implied in generation of these rocks by a low grade partial melting of an enriched mantle in a subduction zone or subducted oceanic slab that during ascend to higher level of crust, undergone crustal contamination.

The Kuh-e-Sefid and Banari phosphate horizons in Zagros Simply fold belt occurred in Pabdeh Formation. At this regard several samples collected from two phosphate horizons, for ICP-MS analyses. The result of ICP-MS analyses show that major oxides in two horizons are CaO>SiO2>Al2O3>Fe2O3>P2O5 respectively that the values of P2O5 in the Banari and Kuh-e-Sefid horizons is low and about 1.95 and 2.1% respectively. The REE concentration in the Kuhe-Sefid phosphate horizons is high but in the Bnari Phosphate horizon is low. Shale normalizes-REE patterns show negative Ce anomaly and MREE enrichment. Negative Ce anomaly is very similar to marine seawater pattern. MREEs enrichments relative to Fe complexes, when this complex located in the redox conditions, are entered into the micro-environments, therefore they cause the enrichment of MREE elements. The Ce negative anomaly and MREE enrichment suggested that rare earth elements derived from seawater.

Paleosols provide invaluable paleoclimatic data especially in arid regions. Buried paleosols are found in central Iran. Givdary alluvial fan, south of Rafsanjan, was selected for paleosols study. Soil moisture and temperature regimes of the area are aridic and mesic, respectively. Based on paleosols' identification criteria, four paleosol layers at the depths of 15, 20, 45, and 50 m from the surface were identified in the Canyon of Givdary River. Palygorskite, illite, smectite, chlorite, and kaolinite clay minerals identified using XRD analyses. Palygorskite was not found in paleosol 4 which is attributed to higher moisture at the time of soil formation that prevented palygorskite formation, or caused transformation of palygorskite to smectite. Electrical conductivity content of 60 dS/m in paleosol 3, together with 5% gypsum content and high amount of palygorskite found during SEM observations showed that the climate at the formation time of this soil was more arid than other studied paleosols. Micro morphological observations demonstrated the role of gravel content on pore spaces percentage.

K1-x (NH4) xH2PO4 mixed crystals were grown by the low temperature solution growth method. [100] and [101] faces growth rates were investigated using an in-situ optical method. It was found that the growth rate of K1-x (NH4) xH2PO4 with x=0.1 and 0.9 along [101] is faster than that along [100]. FTIR spectra of the mixed crystals with selected composition values confirmed the presence of both salts in the grown crystals.