JOURNAL OF THE EARTH
Year:2009 | Volume:4 | Issue:3|Papers Count:8

The aeromagnetic data is used in the reduction of poll, the first order derivation in vertical direction and Euler deconvolution, to elucidate the subsurface structures and redefine the structural zoning of Tabas region - eastern Iran. The main objective of this study is to delineate the buried faults and structural setting of the area, and define the main tectonic trends, responsible for the structural features. The present study deals essentially with the application and correlation between geology and aeromagnetometry to establish the structural framework of the area. Two interpreted magnetic basement structural (IMBS) maps are constructed along the two computed interfaces to show the structural setting of study area, including the display of uplifted and subsided blocks in it. Filtering combined with analytical upward continuation on the two assigned interfaces is then conducted. The shallow and deep anomalies can be determined and the structural setting indicated through four model profiles across the area under investigation. The structural elements affecting the basement complex at the two assigned interfaces are delineated and the fault system is statistically analyzed to determine the main structural trends affecting the area. The trend analysis of these structural elements shows that the most abundant trends affecting the area are the NW-SE followed by the NE-SW and then the E-W, considered as the most ancient trend affecting the area under investigation.

Zajkan area with about 40 km 2, is one of Tarom’s prospect areas (located in the geological map of Tarom, 1:100,000 sheet) which has considered for two reasons: 1) similarity to other mineral occurrences in other around prospect and 2) having mineral potential specially for Copper and Gold.Then the alteration survey in this local inplemented base on thin section studies and remote sensing investigations. In this area geochemical and heavy mineral sampling were accomplished with higher congestion (in the more detail scale). After processing and analysis of raw data, fundamental areas correlate to different mineralization (specially Cu and Au) were recognized, and ultimately three prospect areas were introduced to more complementary exploration. In this direction, rock units and ore microscopy studies were controlled by the microscopic examination.

Emaft Fluorite mine is located in 20 km southeast of the pole-sefid area in the Mazandaran Province, its part of fluorite belt in this province, this mine is difference among other mine in this area, because having particular properties. The host of ore is Tizkooh Limestone with lower cretaceous age .The structural condition, comprised a syncline with curving axis that it’s have estimating NE-SW trend .There is a lot of fault in this area that almost mineralized in these faults. Host lithology included Mudstone, Micrite that almost altered to dolomite by effect of Hydrothermal activities near to the mineralization. Field and laboratory investigation indicated that mine have simple Paragenesis and mineralogy .It’s included Fluorite, Calcite, Quartz and a few Barite and Sulfur (0/1%).For achievement to ore fluid characterizes, fluid inclusion studied for 2 two side- polish section on fluorite mineral of Emaft mine .This studies showed rather low Homogenization temperature (with average 158ºc)and average of salinity 13.7%wt equal NaCl. Simple cooling with willing to Boiling and Boiling (low salinity CO2- bearing ) is mechanism of fluorite deposition .The range of density of ore fluid vary 0.9 to 1.1 gr/cm3. Base on evidence of lack of filling degree ,existence of a few sample of vapor-rich phase shows boiling of ore fluid in fault and fracture zones.Base on relation Homogenization temperature- salinity, this ore deposit is one of Mississippi valley type deposits.

For the determine of Jurassic-Cretaceous boundary, a stratigraphic section in northern slopes Central Alborz was studied in southern Chalous (Pol-e-Zoghal section) with a thickness of 2913 meters. In the studied section, Jurassic rocks with a thickness of 657 meters, consist mainly of sandstone, shale, with coal beds (Shemshak Formation) which overlaying by 2256 meters thickness deposits, consist of conglomerates, sandstone, shale of Early Cretaceous (Tizkuh Formation).In the studied section the sequences of Dalichai and Lar formations do not exist. Gap these formations could be the result of emergence of the studied region from water at the end of Early Jurassic, created due to the orogenic movements of Middle Cimmerian (Batonian tectonic). As a result, the Jurassic-Cretaceous boundary in this section is unconformity. Further advance of the sea has occurred during Aptian period when warm climate prevailed in the region and benthic organisms, particularly Orbitolinidae family including Dictyoconus arabicus, Iraqia simplex and Orbitolina discoidea lived in the warm and shallow sea of the period. During Aptian period many volcanic activities have also occurred. Of course, there is a weak possibility that the absence of Neocomian and Barremian deposits have been coincide with Late Cimmerian orogenic movements.On the basis of lithofacies, 12 lithologic units have been distinguished. According to the fromainiforal study, the following biozone of with Early Cretaceous (Aptian) age have been Dictyoconus arabicus-Iraqia simplex Assemblage Zone introduced.

In this paper some geological young features, neotectonical activities and traces of their effects along the Ghom-Zefreh Fault are investigated to find some evidences of qualitative and quantitative rate and type of the tectonical deformations. Investigations imply a strike slip dextral with a reverse component for this fault system. Using the results of calculating some morphotectonical index in combinations with other data types, tectonical activity rate is determined in some selected basins.

Oil companies are trying to increase production rate by improved recovery methods. Typically, oil and gas fields have been penetrated by lots of wells. The seismic inversion method is a powerful technique. This project is about inversion of 3-D seismic data to acoustic impedance in one of the south-west oil field of Iran. In this study we checked other different inversion methods such as sparse spike and model based. We applied model based inversion method in the studied area. The input data includes seismic data, well log data, and structural interpreted data. Knowledge of the seismic wavelet is also necessary. In this study we integrated available information from seismic data, well logs and the knowledge of regional and local geology to produce detailed, spatially consistent, 3-D impedance models. The results of this study reveal that there are several reefal structures in the main reservoirs.

Satellite pictures and aerial photos showed the general figure of the causative fault of Bam earthquake, 2003 Dec. 26, in the southeast of Iran that left about 33000 victims and heavy damages. Three dimensional pictures collected before and after the earthquake by advanced thermal distribution and radiometric reflection, or visible waves and infrared, and other investigations accomplished by compound maps, suggest the development of a new fault due to Bam earthquake. In this paper, the results of field study and mapping of the faults and fractures developed by Bam earthquake are presented. The tensile fractures, created in the new fault zone, define the active in situ stress direction in Bam region as N32E. Combining the findings of present study with what presented by telemetric studies identifies the steep slope of the new fault toward east.

During an occurring earthquake, whatever has make important a soft alluvium layer, is its resonance or amplification. Study losses due to recent earthquakes show how much site response estimation and the hazardous zones assessment is important. In the best status resonance parameters and amplification for the alluvium layer could be determined by analysis of accelerogram records in several sites with different alluvium thickness for one or more earthquakes. In this research according to horizontal to vertical spectral ratios (HVRs) method the range of predominant frequency has been estimated from 1.3 to 9.4Hz and alluvium thickness from 20 to 170 m using data of Iran Strong Motion Network (ISMN) of BHRC what happened from1990 to 2005 in 29 sites located in Gilan province, then Isoperiod and Iso thickness map for Gilan province was shown.