GEOSCIENCES
Year:2007 | Volume:16 | Issue:62|Papers Count:21

Jajarm bauxite deposit (north east of Iran) is the largest bauxite deposit in Iran which is located as a stratiform ore body between Elika and Shemshak formations. From the bottom to top of the profile, this deposit is consists of lower kaolinite, shaly and hard bauxite, and upper kaolinite, respectively. In this study rare earth elements of the hard and shaly bauxite sections of the deposit are investigated by use of the results of 22 chemical analyses. Correlation coefficient between rare earth elements and other elements demonstrate that clay minerals and also some minerals such as Churchite, Loparite, Xenotime, Rhabdophane, Monazite, Florencite, Anatase and Euxenite are the likelihood REE bearing minerals in Jajarm bauxite deposit. In Jajarm deposit toward the carbonate footwall of the profile the concentration of rare earth elements increases, thus from this point of view, this deposit is similar to karstic types. Increase of concentration of the REE at lower part of the profile is not same for all of the rare earth elements and it is as the result of the ionic potential of each of them and also it may be related to the type of the REE bearing minerals. So with increase of the ionic potential of the elements their concentration at lower Part of the profile decreases. Due to the accompaniment of HREE with zircon and clay minerals, these elements have leached at the same amount from hard to shaly bauxite. As the result of the two different valences of Ce & Eu, these elements show different trends from other rare earth elements in chondrite normalized patterns and also as the concentration at lower part of the deposit. This anomalous manner is more obvious for Ce, so this element show positive anomaly and more enrichment in hard bauxite section in comparison with other LREE. In contrast with the hard bauxite, the negative anomaly and less enrichment of Ce can be seen in shaly bauxite. The variation of Eu is less than Ce and it is almost limited to relative negative anomaly of Eu in hard bauxite section.

NW-SE trending Dehnow anticline located between Hendurabi and Razak lineaments and in hanging wall of Mountain Front Fault (MFF), has prominent characteristics such as existence of thrust faults on either limb, box shape at depth and occurrence of two minor anticlines in en-echelon array. In this paper, structural geometry of the anticline and the effect of subsurface-transverse lineaments on its geometry are presented using field data, satellite images and available seismic reflection sections. Fold style of the anticline is affected by Salt Hormuz series, as a regional detachment layer. The fault detachment fold style of the anticline has been analyzed using seismic sections and structural data. The effects of regional deep-seated transverse structures such as Hendurabi and Razak Lineaments on structural geometry of the anticline were also investigated. Accordingly, a NW-SE trending subsurface transverse-shear zone was inferred in region. This shear zone caused development of en-echelon array set of fractures and folds in the interior of the anticline and counterclockwise rotation of its axis. It is suggested that this transverse-shear zone is the southern continuation of Sabzpoushan transverse fault zone. NE-SW trending Hendurabi lineament which was conformed to have a sinsteral fault zone causes clockwise rotation of the anticline axis. No structural evidence son the effect of the Razak lineament has been recognized in Dehnow anticline.

Three tridactyl footprints were found on bedding planes of rippled fine grain sandstone layers of the Shemshak Formation, in Harzavil village, western Alborz, Gilan province, north Iran. Footprints are in the form of concave epirelief and convex hyporelief. Only the middle footprint is completely preserved (85 mm length and 72 mm width). The first and last footprints are approximately the same size (78 mm). Based on ichnological factors, it seems that footprints have been made by two or several bipedal dinosaurs that moved in the same direction.

Knowledge of the petrographic and physical characteristics of a coal has a broad application in processing of coal. Petrographic data are fundamental to the understanding of the behavior of coals during mining, washing, blending and coking. The visible bands in coals called lithotypes consist of four main groups namely, vitrain, kelarin, durain and fusain. The main lithotypes of coals are macerales that can be identified based on their texture and the degree of relative reflectance. In this research, coals from five different mines (i.e., Hashoni, Hamkar, Komsar, Eastern Darbid Khoon and main Pabedena) from Kerman area were studied by the reflected microscope. The samples of these mines were taken from the feed to the Zarand coal preparation plant sent by the mines in question. After the preparation of polished samples, the amount of coal macerals for each mine was determined. The results revealed that Eastern Darbid Khoon mine had the highest level of vitranite and the lowestamount of fusinite that render the best coking properties for this type of coal. From the coking properties aspects, main Pabedenamine showed the poorest quality.

The Masjeddaghi area, located in the Jolfa 1/100000 geological map sheet, is a part of West Alborz zone - Azarbaijan. The oldest rock unit outcropped belongs to the Eocene flysh, widely distributed in the southern and north eastern part of the area.The other outcrops are mainly volcanic rock complex of andesite and trachyandesite affected by quartz monzonite intrusives and produced phyllic and carbonate phyllic alteration. The mineralization in volcanic complex is mainly silicic and barite veins. SEM and mineralography studies indicate the occurrence of sulphide mineralization especially Cu, Pb, and Zn sulphides. In addition, various pyrites occur as primary and secondary minerals. The galena and sphalerite mineralization can be observed in the main vein but not in the altrated area. SEM study indicates absence of gold in sulphide minerals. On the other hand fluid inclusionstudies show slow temperature gold formation (120 - 150°C) and very low salinity which specify probably that the gold is not carried along with chloridric complex in this stage. Evidences like parageneses, elements, gangue and alteration around silicified veins all indicate the presence of a polymetal gold - copper vein ore deposit of epithermal origin with high sulphide values.

Due to the topography and geological situation, East Azarbaijan province has massive deposits of ornamental and construction stones. As the province is located on "the hot spring marble and travertine belt of Iran" due to past activity of Sahand and Sabalan volcanoes, ornamental stones of this region are famous worldwide and have desirable quality. In this article, geological conditions and formation of travertine deposits of Iran has been studied, followed by an investigation on the physical and chemical specifications of ornamental travert, ine of Azarshahr. In addition, results of laboratory studies and chemical analyses are presented and discussed in different tables.

The Sardasht and Shayoun area in the north of Dezful embayment structure and on the southwest of Zagros structural belt is affected by shear zone pattern of Balarud. This watershed occupies an area of about 1042 km2 and encompasses parts of Dez, Shirinab and Sardashat watersheds. The purpose of this investigation is the assessment of structural factors (specifically fractures) on sandstone permeability and spring occurrence in the study area. In this investigation, geology and structural geology including folding, faulting and fracture studies were carried out. For fracture examination, joint data collections from eleven stations were analyzed and the collected data taken into account to prepare the structural map of the area. The iso-density fracture map indicates more permeable zones. It is also evident from the map that springs are mostly occurring in dense fracture zones of the area. The position of the springs, their structural and qualitative characteristics were assessed, and found that springs with more discharge, showed more temperature fluctuation in wet and dry seasons.

In this study, sediments of the Qom Formation were investigated from the two stratigraphical sections in the northeast (Attari section) and southeast (Garmab section) of Semnan. The Attari section that consists mainly of limestone. Sandy limestone, sandstone, calcareous shale and marl has a thickness measured 280 meters. In this section, the Qom Formation lies nonconformably on basic subvolcanic rocks and is disconformably overlain by the Upper Red Formation. Garmab section, with 97.5 m thick is composed of limestone and lies disconformably between Tuff at the base and Upper Red Formations at the top. The study of 167 samples taken from the studied sections led to the identification of 31 genera and 36 species of benthonic foraminifera, I genus and species of planktonic foraminifera, 3 genera and species of red algae and 2 genera and species of bryozoa. Among them, benthonic foraminifera have more variety and abundance. So the benthonic foraminifcra from the measured sections are used to determine the age of success ions and justify their correlation. Based on the identified foraminifera, the Attari section is comparable to biozonation introduced by Adams & Bourgeois (1967). It is analogous to Bore/is melo group-Meandropsina iranica Assemblage Zone (I). According to the distribution of the index foraminifera. The age of sediments belonging to studied formation in Attari section is Burdigalian. The age of sedimcnts of the Qom Formation in Garmab section based on the occurrence of Triloculina tricarinata, Triloculina trigonllla and Globigerinoides triloba is probably Aquitanian.

Young volcanic domes and other associated sub-volcanic bodies of Baladeh (Central Alborz) have reached the surface passing through Shemshak Formation (Jurassic). Most of acidic domes and bodies (dacite, rhyolite, and rhyo-dacite) have extruded relatively cold and possess some surficial features. Petrological, textural, and geochemical similarities all over the surface of these domes indicate that they have an endogenous history. According to modern geodynamic models, all of these volcanic rocks are derived from one feeding dike (along Haraz River) which has been dissected after passing the brittle-ductile boundary. Some of the pieces of dikes can be traced in the 2nd and 3rd locations (east of Ba ladeh village and south of Valashid village). Convergent (collision or post-orogenic) condition is the best scenario for tectonic setting of these bodies based on geochemical data. In addition to partial melting, some other processes such as crustal contamination, gas transfer and to some extent alteration were effective genetic processes. LILE and LREE enrichment patterns indicate low degree of partial melting or end products of fractional crystallization and some crustal contamination (Ba enrichment).

Barandagh quadrangle (1:50000), a part of Tarom-Hashtjin polymetallic district, is located in NE of Zanjan and SE of Ardabil. The results of preliminary regional geochemical explorations have led to the discovery of anomalous areas for a varietyof elements. The anomalies were verified by studies on heavy minerals in stream sediments and mineralized and altered samples taken from the surface outcrops. The identified heavy minerals are hematite, goethite, pyrite, barite, limonite, native copper, native zinc, native lead, malachite, molybdenite, micaceous hematite, limonite, cerussite, galena, smithsonite, marcasite, chrysocolla, rutile, zircon, pyroxene, amphibole, and apatite. The identified heavy metallic minerals are principally affiliated with zones of widespread alterations and dispersed veinlet-type mineralization. Chemical analysis of some litho geochemical samples from the anomalous areas shows noticeable assays for elements such as Ba, Zn, Cu, Sr, Mo, and Be. The majority of anomalous areas are intimately associated with alteration zones in the region. Based on field evidence and mineralogical studies, the alterations are categorized into two discrete types, (1) acid-sulfate alterations (e.g., silisified, alunitized, advanced argillic, phyllic, and propylitic) which are related to shear zones and (2) alterations developedin neutral pH conditions (e.g., argillic, calc-silicate-bearing, and zeolitized) cropped out along the margin of Ghezel-Ozanriver. Combination of the overall obtained data from chemical analyses, study of the heavy minerals, petrography of mineralized and altered samples, and field relations led to identification often anomalous spots that some, in south and along the margin of the Ghezel-Ozan River, have more potential for ore deposits. The comparison of final anomaly map with the map of fault density depicts that there exists a good correlation between them that may indicate that the fault and shear zones have played a crucial role in creation of these anomalies. Finally the overall results obtained from geochemical investigations in Barandagh show that the identified anomalies belong chiefly to elements such as Sn, Sb, As, Ag, W, Au, Bi, and Pb that can be used as tracer for exploration of epithermal gold and silver and of polymetal (Au, Ag, Cu, Pb, Zn) deposits.

Maharlu basin with an area of 4274 km2 is located in Fars province. The Precambrian Hormoz series and the Quaternary unitsare the oldest and youngest rocks in the basin, respectively. Spans of outcropped rocks, covering from the Cretaceous to Quaternary, are carbonate sediments of deep to shallow marine facies. These sedimentary sequences include large and small stratigraphic gaps in the form of disconformity and sometimes nonconformity. More than 50% of the basin area is covered by the Quaternary sediments. The region is mainly composed of sedimentary deposits. Six factors of rock unit weathering: rock resistance, weathering condition, fissure and joints, slope, climatic conditions and vegetation covering are the main factors for estimation the sensitiveness of geological formation to weathering resulted from laboratory and field tests. 12 formations Cropped out in the basin. To evaluate erodibility, BLM method is used to measure the weathering sensitivity of soft geological formations. The acquired data and the formations with their sensitivity to weathering arecombined into GSl and finally the map of sensitivity of different geological formations to weathering of Maharlu basin was prepared. The data resulted from laboratory and field tests indicate that Asmari-Jahrum formation and the Quaternary alluvial fanpossess lesser sensitivity and higher resistance to erosion and Hormoz series, Pabdeh-Gurpi formation, Razak formation and Aghajari formation are critical to weathering. Bakhtyari formation, Bangestan formation, Tarbur formation, Sachoun formation, and young and old Quaternary deposits can be placed in group of moderate to weathering.

The Dareh Zanjir zinc mine is located at about 25 km south - east of Yazd city and 2 km south - west of Taft town. The aim of this research is to characterize leach ability of ore minerals. The results of XRD analysis and microscopic investigation of representative sample and calcined and residue obtained from acidic and alkaline leaching confirmed the presence of dolomite, calcite, smithsonite, cerrussite, hemimorphite, franklinite and willmite. Chemical analysis indicated that zinc grade was about 14 percent that present in the form of smithsonite, hemimorphite, willmite and franklinite. These minerals were solublein dilute and warm sulfuric acid (except franklinite) and produced zinc sulphate solution. Dissoloution of zinc silicate minerals in sulfuric acid produce silica gel causing problems of decreasing of zinc recovery and filtration rate. Therefore, after the leaching process, the elimination of silica gel should be considered.

Fault migration, an important phenomenon in fault-zones, is neither fully investigated nor defined comprehensively. In this paper, based on observations on Ardekul active fault zone (Eastern Iran), an evolutionary path is considered for strike-slip fault zone. According to this evolutionary path four stages; namely embryonic, youth, maturity and declining have been recognized. This evolutionary path may be generalized over different scales of brittle deformation. The proposed evolutionary path makes the fault migration clear. A case study of Ardekul fault zone is chosen for applying defined fault zone evolution and fault migration. Based on the results, fault migration can be divided into two grades; first, the prior and second, the posterior fault migration. Details of prior migration are distinguished including time of occurrence, stages, types, scales and mechanisms of migration, effective factors on migration and its characteristic features. The posterior migration can be studied from the viewpoint of prior migration. Moreover, the fault migration can be comprehensively classified into two topics; production-oriented fault migration and development-oriented fault migration. Some clay cake experiments are also designed to show the prior and posterior fault migrations.

Millimetric, lens like and flat cake like monazite nodules are found within the Upper Triassic sedimentary rocks in Marvastin the south of Yazd. Monazite is one of the several rare earth phosphate minerals. Marvast monazite has a chemical formula of (Ce, La, Nd, Eu) P04. The size of grains changes from 0.1 to 2mm and the grains with a diameter of 0.3-0.8 mm are often prevail. Monazite nodules are gray and greenish-gray in color and often formed in earthy aggregates. Monazite has a numerous inclusions of light minerals (such as quartz, calcite and ...) and is enriched in Light and Middle Rare Earth Elements (LREE & MREE). Marvast monazite is completely different from igneous type Monazites. The nodules are formed during diagenesis of the Upper Triassic- Lower Jurassic sedimentary sequences and exposed in the shales. These nodules are potentially useful means for dating the diagenetic duration of the Upper Triassic sedimentary rocks.

The type section of the Gurpi Formation which is located in Anbar-e-Sefid Valley near to Lali town is about 182 mthick and consists of calcareous shales and black shales. The formation lies by an erosional disconformity on Ilam Formation and turns gradually to the purple shales of the overlying Pabdeh Formation. The Gurpi Formation was dated the late Campanianto late Paleocene based on the presence of foraminifer species Globotruncana calcarata and dinocyst species Odontochitina porifera in the lowermost parts and foraminifer species Morozovella velascoensis in the uppermost parts of the section. The Cretaceous I Tertiary boundary (KTB) is located some 57 meters below the Gurpi and Pabdeh contact within the blackshales of the Gurpi Formation. In order to study paleoproductivity of the Gurpi Formation, the authors examined many different factors includingchangesin ratio of Peridinioid to Gonyaulacoid (P/G) dinotlagellate cysts.Peridinioid dinocysts are stenotopic forms and usuallyused for this purpose but one has to determine whether their absence in sediments is because of original absence during depositional period or because of bad preservation and destruction after their production and during depositional period. Thus factors related to state of preservation of the organic matters including "lability" and ratio of structureless organic matter (SOM) to marine palynomorphs were calculated for the samples throughout the stratigraphic column. In addition four different indices were also calculated for pale productivity condition including ratio of Peridinioid to  Gonyaulacoid (P/G) dinocysts, ratio of dinocysts indices for outer neritic to those of inner neritic, ratio of terrestrial to marine elements (T/M), and ratio of planktonic to benthonic foraminifera. Based on the se factors three biofacies and two subfacies were recognized and differentiated. Facies (I) is marked by the low state of preservation of organic residue, low lability and a relatively high ratio of SOM to marine elements. The ratio of Planktonic to benthonic (P/B) is relatively high, abundance of deep-water benthonic foraminifera and dinocysts indices for outer neritics such as Impagidinium. Absence of peridinioids is more probably because of their bad state of preservation. In biofacies II preservation of organic matter is much better (higher lability, and low ratio of SOM to marine palynomorphs). Altogether production of organic matter is much higher in this facies. In biofacies III presence of cold-water foraminifera and dinoflagellate cysts indicate presence of cold-water currents at the beginning of Paleocene. Presence of phosphates and glauconites and abundance of ecological generalist foraminifera indicate that the absence of the Peridinioid dinocysts is related to reduction in temperature and lack of suitable condition for their propagation.

The drainage basin of Mahabad Dam has been exposed to severe erosion as a result of land use change. In this basin sediment yield takes place in only two measuring stations; therefore, it is often difficult in smaller basins to locate erodible areas and to plan land use and conservation. To do this, one way is to categorize areas with different erosion susceptibility basedon certain parameters used in this study. These parameters are slope, altitude, rock erodibility, land use, precipitation and concentration time. The distribution maps prepared on each of these parameters and their overlaps have shown that areas with more severe slopes and higher rock erodibility are categorized as highly susceptible to erosion. However, in areas with resistant rocks, change of land use has been the determining factor. Land use is the only. parameter modified by man, and it is the only one which can be quickly and effectively changed. Hence, it seems that the upstream areas of basins with low concentration time, severe slope, high erodibility, and high precipitation, yet with forest and pasturing coverage, are in greater need of preventative measures.

Some iron-rich samples from the Famennian strata of Iran and Morocco were collected. The samples were subjected to the neutron activation analysis (NAA) in order to get some information about the geochemical changes after their deposition. The collected samples consist of noduls and remains of brachiopods, goniatites and gastropods from the top of Khoshyeilagh Formation at the Meyghan area in Iran and the top of H-member of Bou Tserfine section in Morocco. Comparison was made between data obtained from the neutron activation analysis (NAA) of the collected samples. Based on this comparison, a broad similarity has been found between the Famennian deposits of Iran and Morroco with respect to their chemical component and trace elements (titanium dioxide and lutetium). There is also a similarity between the shape, general structure and age of crystals in the studied samples of the two countries. Habit of the iron crystals in the samples indicate that iron contents have been preliminarily deposited as crystal of pyrite, which ultimately changed into hematite. This is very likely to be due to the fact that the depositional environment had first been deep and poorly-oxygenated and then changed to a shallow and well oxygenated environment due to uplifting.

In the Baba Ali magnetite skarn deposit, the main load of magnetite ore body lies between the dioritic and quartz syenitic rocks of the batholith hosted mainly by meta-dioritic rocks. Petrographically from SE towards NW, eight zones with distinct mineral assemblage can be recognized. The geochemical distribution pattern of elements across the Baba Ali skarn zones is governed by the distribution pattern of the prograde and retrograde mineral assemblages. The presence of andradite, salite, actinolite, epidote, sphene and idocrase as the calc-silicate minerals, and the absence of minerals like tremolite, forsterite, phlogopite, talc, and humite  and also  minerals of manganoan skarns  in these skarn zoning allow the grouping of the Baba Ali skarn deposit as a calcic Fe-skarn deposit. The EPMa compositions of pyroxene and garnet also are consistent with the Fe-skarn deposits. The average S content in the Baba Ali ore body is < 1.5 %. The low content of sulfide in the Baba Ali allots Island Arc type calcic Fe skarn characteristics to this deposit. The high ratio of exsoskarn by endoskarn (Extensive exsoskarn facies) indicates a shallow depth” hypabyssal “(< 5 km) for formation of the Baba Ali skarn. EPMa analysis of magnetite from the Baba Ali deposit show a rather pure magnetite phase, devoid of impurities such as Mg, Mn, Zn, Ni, Ti, V, and Cr. The absence of these impurities indicates a low temperature for formation of magnetite. Replacement of the hydrothermal (retrograde) minerals by magnetite also shows a low temperature within the green schist facies conditions for magnetite mineralisation. Replacement of the prograde assemblage i.e. garnet and pyroxene which formed in the 500 –550°C range by hydrothermal minerals along with magnetite indicates that magnetite mineralisation occurred at relatively lower temperature. The inferred temperature of Fe mineralisation at the Baba Ali deposit is  in the range of 350 –400°C.

Reshadat Oilfield is an anticline with an approximately North- South trend. The Upper Sarvak Formation is a potential reservoir in this area. Mishrif Reservoir in this field has been divided into five zones. Zone A, (the uppermost) is recognized as the best reservoir zone. Diagenetic processes including (dissolution, dolomitization and fracturing) Improved reservoir qualities. As a result of diagenetic process (dissolution), stratighraphic trap (diagenetic) has been created, and zones A and B are shaped into pinch out trap. Weathering dramatically improves the reservoir permeability and thus controls the extent of this diagenetic trap. Investigation shows that local unconformity in the southern flank of Reshadat oilfield, created the highest reservoir zones in this part. Consequently; reservoir quality of zones C and D have been improved.The inversion of the seismic data to acoustic impedance has allowed for better definition of the main litho logical units. The inverted impedance clearly highlights facies and porosity variations within Mishrif interval which not apparent on seismic data. Depth conversion has been performed and accurately ties the interpreted horizons to the available well data. The combination of seismic interpretation and seismic inversion has improved our understanding and definition of the Mishrif  reservoir. Applying reasonable cutoffs for porosity and permeability, reveals valuable zones (A&B) in this portion of the field.These zones are located in west and northwest of Reshadat Oil Field. The study shows that thickness of valuable zones are increasing towards the west and the northwest and decreasing in the center and south of the field.