JOURNAL OF SCIENCE (UNIVERSITY OF TEHRAN) (JSUT)
Year:2007 | Volume:33 | Issue:1 (SECTION: GEOLOGY)|Papers Count:12

The Boroujerd granitoid massif is as a small portion of Sanandaj-Sirjanzone. It is elongated and parallel the prevailing schistose it in the metamorphic rocks by the trend of NW-SE and consist of quartz diorites, granodiorites, monzogranites and sphene granite. Granodiorites are the most dominant rocks. Petrological, mineralogical, field and geochemical investigations suggest that the Boroujerd granitoid is similarto those of the high-K calc-alkaline series, metaluminousto weakly peraluminous, and displays features typical of I-type granites. Low Al2O3/(FeO+MgO + TiO2) and (Na2O + K2O) / (FeO+ MgO + TiO2) ratios, and the trace and rareearth elements patterns suggest that these rocks formed along a destructive plate margin and were derived from a lower crustal source. This granitoid magma involves partial melting of lower crustal protoliths and frac-tional crystallization of the melts in higher crustal levels can generate the whole spectrum of rock types represent in the Boroujerd massif. Mantle-derived basaltic magmas emplaced into the lower crust are the most likely heat sources for partial melting.

Many special core analyses, including capillary pressure, relative permeability, and water flooding efficiency are affected by the wettability of the core. In order to achieve reliable results, experiment must be performed on preserved or aged sample. Considering the importance of wettability factor in special core analysis data and their fundamental roles in reservoir studies, the present work was defined to search for wettability characterization of some Iranian carbonate formations. Samples were carefully cleaned and aged at reservoir temperature in order to prepare the restored conditions. Experiments were run at 90°C with crude oil and formation water. A period of 40 days was allowed for aging with crude oil. Petrophysical properties of each sample were measured using both thin section and core flooding techniques. The lithology of the samples consists of both dolomite and limestone. The qualitative evaluation of carbonate samples using relative permeability curves showed that there was a discrepancy between the result from the role of end-points and those from the role of cross over saturation. The cross over saturations in relative permeability tests at reservoir temperature showed that samples were oil wet. The Amott and USBM tests have been run on samples in a combination procedure. The capillary pressure curves obtained by the centrifuge method were used in order to calculate the USBM wettability index. Quantitative results by the Amott method showed that most carbonate samples had intermediate wettability characteristics, but the results from combined Amott-USBM testing indicated that system is mostly oil-wet. Centrifuge experiments also produced capillary pressure curves that were used to evaluate the wettability are according to the method of U.S. Bureau of Mines.

The study area, in the eastern mountains of Esfahan city is located about 1 kilometer of Esfahan-Naeen road at the latitude of 32°, 28' N and longitude of 51°, 47' E. The thickness of the Lower Cretaceous sequences is 196.6 meters and consists mainly of siliciclastic and carbonate rocks. The lower boundary of these deposits with the Jurassic Shales is in the form of angular unconformity. Based on petrographic studies four distinctive types of dolomites in the Lower Cretaceous successions have been recognizes. These are as follows: type-I – very fine to finely crystalline (planar-subhedral) dolomite, type-II - fine to medium crystalline (idiotopic-por-phyrotopic) dolomite, type-III - medium crystalline (euhedral) dolomite and type-IV - medium to coar-sely crystalline (euhedral) dolomite. The early dia-genetic processes generated dolomites type-I and other types are related to burial diagenesis. The type-II formed by replacement, type-III formed by re-placement/recrystalization and type-IV is pore filling dolomite. Geochemical (elemental) studies such as high Sr and Na indicate that dolomitization process-ses occurred in the limestone with original aragonite mineralogy. The source of magnesium for different types of dolomite is: seawater (for type-I) and for other types could be connate water, clay minerals of the Jurassic shales locating under the Lower Creta-ceous sequences.

Totmaj volcano-sedimentary rocks, located at southeastern of Kashan, are mainly composed of basaltandesite lava flow and pyroclastic rocks (various types of tuffs and agglomerate) which locally show an alternation with Oligocene fossiliferous shallow marine sedimentary rocks (limestone and sandstone). Based on major and trace elements geochemical data, the Totmaj volcanic rocks are very similar to calc-alkaline lava. They contain high Al2O3 and low Mg#(100 Mg/(Mg+Fe2+).Their Zr/Y ratio is more than 3, typical of continental volcanic arc rocks. In terms of N-MORB normalized trace element patterns, they show enrichment in K and Pb relative to Nb, Rb, P, and Ti, and also have a wide range of Ta/Yb ratios (between 2.3 to 8.9) and limited values for Th/Yb (0.3 to 1.9), characteristic of seduction-related rocks from orogenic belts.Their enrichment of large ion lithophile elements (LILE) and light rare earth elements (LREE) demonstrate that they have been probably originated from partial melting of enriched mantle wedge when it has been encountered with the released fluids from a subducted oceanic crust.

The Lakhshak granitoid intrusion which is located in the northwest of Zahedan is a part of Zahedan- Saravan plutonic belt. This Oligo-Miocene intrusion, intruded as an elongated pluton into the Eocene flysh type meta-sediments that in turn belong to the Sistan suture zone, between Lut and Afghan blocks. The marginal granitoid rocks in the south and southwest of pluton have been plastically deformed during the emplacement of this pluton with approximately 400 m thick and show fabrics such as S-C structures. These rocks display a transition from strongly deformed fabrics at the margin to progressively less deformed fabrics to the center. Moreover, due to high temperature brittfe deformations, igneous primary minerals, such as plagioclase and orthoclase, were broken and filled by some secondary high temperature minerals such as biotite and quartz. Seemingly, some melt was present during these deformations, as indicated by (1) presence of fine grains of quartz, feldspar and biotite aggregates grains in fracture-controlled openings in the primary feldspar crystals, (2) occurrence of quartz and feldspar grains within deformed biotite cleavages, (3) partial plagioclase replacements by quartz and K-feldspar intergrowth, (4) presence of the undeformed granophyric texture in the margin of deformed orthoclase crystals.

Igneous rocks emplacement NE Gazvin is the main objective of this project. The analysis of emplacement mechanism is done using paleostress direct inversion method. More than 209 shear planes, bearing slickenside lineation are measured at 12 different localities. Processing of corrected data and re-cognition of paleostress state, a paleostress trajectory map established. sill mechanism is the best form of igneous emplacement in this area. This is reflected by geometrical shape of paleostress trajectory lines. The emplacement mechanism also is supported by petrological evidences.

There are several methods for zonation of landslide hazard. They can be generally divided into two groups; direct and indirect methods. In this study, we used Artificial Neural Network (ANN) as an indirect method for landslide hazard zonation in Semnan province. A total of 49 landslides or slide zones, that overlaid on the topographical map with the scale of 1:50000, were studied. Maps of factors such as lithology, slope, aspect, land use, buffer of faults, DEM, precipitation were then prepared. The sedata were then normalized, according to the maximum value of each factor. The normalized data was then fed into a multi-layer preceptor with back error propagation algorithm. The network had 3 layers, first layer as input layer, had 7 input elements each of which related to one factor. The second layer as hidden layer had 20 process element. The last layer as output layer consisted of one process elements which have been trained to offer5 level of hazard risk. This structure was found as the best optimized structure through extensive simulations. Our data base consisted of 2016 records. This database was randomly divided into the two separate groups. One as train database consisted of 1626 records which used to train the established ANN. The second group named the testing database consisted of 400 records, which used to test the performance of the ANN. The accuracy of network for predicting landslide hazard was measured about 91.25%. Results reveal that artificial neural network model the landslide hazard zonation better that other approaches.

In the northwest of Khoy in the west Azarbaijan, there are three rocks complexes consist of metamorphic, ophiolite and non metamorphosed rocks. The grade of metamorphism changes from green-schist to upper amphibolite facies. The study of microstructures shows two foliations; S1 and S2. Mylonitic foliation (Sm) was overprinting them. The main direction of foliations is NNW, which have been generated by three deformations events when Arabian plate were collided into Alborz-Azarbaijan block in later Cretaceous or younger.

The Bidvaz Watershed is located east of Esfarayen in northern Khorasan Province. Bidvaz is the major river in this watershed with two tributaries (Darparchin and Sorkh-Ghaleh). These rivers have gravelly beds with braided patterns. For analysis of sedimentary link and recognition of fining factors, surface samples from channels have been collected from Bidvaz and its tributaries. Grain size analysis shows that the sedimentary link does not show a uniform trend, especially about in two tributaries and have broken in two pointes along the river. Sedimentary link shows a relatively uniform trend in the Bidvaz River which is the longest one in this basin. It is shown that the (1) sudden changes in slope gradient, and (2) tributaries entrance with high course of sediment yield are the main factors that change the sedimentary link. Analysis of sedimentary link, grains size variations and textural parameters (sorting, skewness and kurtosis) show that the "selective transport" is the most important process that controls the downstream fining in grain size. Because of the abundance of grains with diameter larger than 16 mm, it can be concluded that selective sorting depends on the grain size increased in upper parts of each subtrend. We hope that the results of this research can be used in similar basin to predict erosion.

In order to determine changes across the K/T boundary and to detect for aminiferal biozones a well preserved section of the Gurpi Formation in north of Kabirkuh, southwest of Iran was investigated. Maastrichtian biozones of Caron (1985) were all recorded. Moreover, Li & Keller's (1988a) CF 1 to CF4 zones were also recorded. Paleocene layers were divided into two biozones; Parasubbonna pseudobulloides and Parvularugoglobigerina eugu-bina zones based on Toumarkine & Lutherbakher (1985). As the index species for uppermost Maas-trichtian and lower Danian biozones were recorded the sedimentation across the KTB seems to be continuous though research to locate zone PO is still continued. Statistical studies of foraminifera show that 2/3 of the species extinct below and at the KTB and 1/3 remain in the lower Danian. The extinct fauna are of large size and omamented while the survivors are of small size and without omament-ation and cosmopolitan. This indicates that the extinction model was similar to that of type section.

The Asmari Formation (Oilgocene-Miocene), in the Ahwaz Oilfield, consists of sandstone, limestone, sandy limestone, dolomitic limestone and marl; the Ahwaz Sandstone Member can be identified within the Asmari Formation of this oilfield. Seven boreholes namely Az 11, Az 19, Az 20, Az 43, Az 45, Az 65, and Az 85, are selected in which to study temporal and facies relationship, rock accumulation rate, stratigraphic continuity/fault, and stratigraphic range of various microfossils of the Asmari Formation. Plotting stratigraphic data of other boreholes against that of Az 65, as the Standard Reference Section (SRS), it is obvious that basal and upper parts of the SRS are missing from other stratigraphic sections. Application of the Graphic Correlation Method also indicates the rate of rock accumulation has been slower in Az 11 and Az 45 compared to that of the SRS. In Az 19, the Line of Correlation (LOC) occurs in a channel testifying to complete stratigraphic range of microfossils in the Composite Standard Reference Section (CSRS).

The studied deposit is the main bauxite ore deposit in Iran, which is now being exploited. Main horizons of the Jajann bauxite deposit, which has been developed on the karst topography of the Elika formation, are composed of diaspore, silica, iron and titanium oxides. This deposit English Abstracts of Farsi Papers indicates marine regression and domination of the equatorial continental climate in this time. The most important textures in the hard bauxite horizon are micritic, pseudo-porphyric, oolitic, pisolitic and microclastic. Major diagenetic features are pisolite, oolites and some diasporic cement in microfractures. Some epigenetic processes such as decertification and resilicification have subsequently altered bauxiute ores. In many samples, presence of eroded and rounded intraclasts is indication of reworking. Seemingly, under warm climatic conditions, dominated in the early late Triassic time, weathering products of melaphyers (the early bauxite), after short-distance transportation, trapped in the karst topography on the Elika formation. Finally, bauxitization processes had completed in these karst features, which were under active circulation.