مجله زمین ساخت
پیاپی 2 (تابستان 1394)

Abstract NW-SE trending Sarvejahan granite with Precambrian age in about 15 Km2 areas has intruded in Precambrian Kahar Formation with an obvious contact aureole in the Soltanyeh Mountains in SE Zanjan. The Sarvejahan granite has exposed at the hanging wall, SW side of the moderately dipping Soltanyeh reverse fault. Deformation fabrics in granite demonstrate a ductile mylonitization indicating deformation in a ductile shear zone at appropriate deep situation in the crust. Structural study of mylonitic fabrics in granite indicates a shallowly to moderately plunging stretching lineation and moderately to shallowly-dipping foliation in a dome geometry. The Soltanieh reverse fault has transported and elevated the granite over the Karaj Formation with Eocene age. Considerable wide fault zone containing advance alterations indicate the role of Soltanyeh fault during alteration and exposition of the Sarvejahan granite at surface. Structure and fabric study in the Kahar Formation and metamorphic rocks in contact aureole in addition to ductile fabrics of the Sarvejahan granite indicate that the Soltanyeh fault has played main role after Eocene during collision event and exposition processes.

Zagros Fold-Trust belt with 2000 km length and it’s hydrocarbon reservoirs is the richest fold-trust belt in the world. Marun Oilfield is one of the biggest reservoir in south-west of Iran and north-east of Ahwaz city also in north Dezful embayment. Asmari Formation is the most important reservoir in Marun oilfield. Nowadays, knowledge about state, magnitude and in-situ stress direction in different studies of Oil and gas reservoir like geology, drilling and petroleum engineering is cleared. Study of in-situ stress in hydrocarbon reservoirs is divided to some part like state of stress, magnitude and the direction of stress tensors from each other. One of the advantages of stress study in hydrocarbon reservoir is usage these results in reservoir geomechanics that could solves some problems like wellbore instability during drilling, choosing safe trajectory, casing failure, different methods of reservoir stimulation, have an important role. This research was paid to review and determination of in-situ stress direction in Asmari reservoir formation in Marun Oilfield. For Analysis of in-situ stress direction, the result of image logs is the best way to use and so 19 wells became candidate. Also on this research, because of the importance on most of reservoir geomechanics applications, minimum horizontal stress direction was in focus. Finally, because of structural complexity and stress concentration in the ends of Marun structure, it determined that in-situ stress direction was changed but in other places has the strike of NW-SE. If both the north and north-east and centre fractures are associated with folding and bending seen, based on maps along fracture zones located on the southern limb of the layer at wells No. 181, 341, 322 and 278 in the eastern cape of along the dominant fracture orientation E130N, except those marked the longitudinal tensile fractures.

Abstract Shekarab Fault system is located at north of Birjand city include fault scarps parallel to the main fault. For investigate the directionofmigration, fourcross-sections perpendicular to the fault has done. In all thesesections, by moving from north to south, the older lithological units are trusted over younger ones. Unitswith lowresistanceincludingshaleandmarl are locatedinthe southern part, andunits with high resistancesuch aslimestoneand sandstone are locatedin the north side of Shekarab fault. In various sections, by moving from north to south, an increase in the slope of the fault scarp is noticed. This cases and presence of new Qanat inside south of fault and sinstral movement in stream and cutting and tilting in Quaternary sediments indicate the growthand lateral migration in Shekarab faultscarps is from northto south. In four sections, espaces bettwin scarps in shale and marl are less than  sandstone and crystalline limestone. In analyzing sections, the estimation distance -27 meters- from the last scarp can be introduced as the later activity candidate.

Abstract Adjacent to the northern margin of the Taknar wedge, south of the Sabzevar zone, and along to the Kuh Sorkh Mountain, there are huge conglomeratic blocks have been attributed to Oligocene. These blocks were dispersed onto the sedimentary beds with almost same age and material. Based on the Kadkan geological quadrangle map, a pronouncedunconformity was considered between these litho-stratigraphical units. The extensive field excursions as well as satellite image studies led us to have a different idea regarding the relationship between the two mentioned units.  The evidences such as a clear and extensive detachment zone between the units, several overturned to recumbent folds with vergences toward northeast, a number of northeast and southwest dip-slip thrusts, a pervasive shear lineament, and a tectonic window in the southwest of Kadkan, however, totally represent a huge thrust-nappe system along the Kuh Sorkh Mountain.  Indeed, the thrust-nappe system described here is composed of a huge north- to northeast-verging recumbent fold, which its southwestern limb moved probably a few hundred meters upon the northeastern limb. Accordingly, the huge dispersed conglomeratic blocks are the remnants of the resistant part of the southwestern allochthonous fold’s limb.We call these remnants as the Kadkan klippe assemblage.The existence of such a thrust-nappe system could represent a considerable shortening perpendicular to the Kuh Sorkh strike after the Oligocene time.  This reality could also document the notable distribution of strain around the Sangerd fault.

The primarystructuresofgranitic body canrecording flow patternbefore completely coolling. Through theconstruction study of primery structurecan be realized partly howevolutionmagmaduringascent andthe events thatoccur  durring emplacment it. This study  introduce the way for determine of magma flow from primary structure.one ofthe useful primarystructuresingraniteispreferredorientation ofthe uhedral minerals of  potassium feldspar.With using the  Preferredorientationof K-feldspar thestrainellipsein threeexposuresdetermined from asoftwareSPO  and Then integrated them with softwareEllipsoid  and obtained Strainellipsoid. However,inthree different areasofthesouthern partofthe Alvandbatholite strainellipsoid shapeis obtained.due tothe Strain ellipsoid shapeofthemagma flow patternin the southof Alvand is non-uniformdivergent flow.In this typeofflowpattern ,magma intruded fromanarrow pipeintoa wide area, and its ascent slowly. Thistype offlow patternis made upinthe igneous body that have syntectonic emplacement

Abstract In this study, fracture systems of Akhlamad area was drawn using remote sensing methods and satellite data processing. Then their fractal pattern examined. Based on the regional fault related morphologies, different techniques were utilized to detect fault lines and fractures. To study the region, data of SPOT5, LandsatETM+ and ASTER were used. The resulting image of Landsat ETM+ merged with Panchromatic band for increasing the spatial resolution. Then the data were analyzed for detection of tectonic lineaments, lithological interruption and displacements due to faulting in ER-Mapper, ENVI and ArcGIS softwares. Also, Sunshading method was used on the DEM for detecting roughness caused by faults. Finally, the structural map of region was constructed using the fractures detected by the above mentioned techniques. Then, the fractal pattern of the structural fracture zone have done by Box-counting algorithm. For this purpose, the study area is divided into 94 separate areas and each area was analyzed separately. Based on the results, the fractal dimension is more in the direction NS, NNW-SSE and EW. Because the D value increases in these directions that has reached to 1.6. In other words, the directions have been developed further during the structural transformation. Given the certainty of these three direction, reactivation this area undertaken along these three.