Iranian Journal of Geology
Year:2011 | Volume:5 | Issue:19|Papers Count:9

The study area is a part of the Sanandaj- Sirjan metamorphic belt. Hamadan metamorphic rocks can be divided into three groups: regional metamorphic rocks, contact metamorphic rocks and migmatites. Garnet crystals are usually common in all of the metamorphic rocks (except slate and phyllite) and in the igneous rocks (i.e. aplite, pegmatite and monzogranite). They fall in pyralspite group and are rich in almandine. Some of these garnets illustrate zoning which can be divided into three groups: evident zoning, hidden zoning and mixed zoning. Origin of observed garnet crystals is metamorphic and igneous. Garnet crystals in the regional metamorphic rocks, contact metamorphic rocks, mesosome and melanosome of migmatites and garnet monzogranites have metamorphic origin. These crystals in the garnet aplites and garnet pegmatites have igneous origin.

There are many alluvial fans with different morphology formed around uplifting Danekhoshk anticline south of the city of Sarpole Zahab in Kermanshah Province in the Zagros Folded Belt. The purpose of this research is to evaluate the morphometric characteristics of alluvial fans such as area (FA), topographic slope (SF), length of fan base (BF), width/length ratio (W/L), fan radius (R), and sweep angle (SA), and their relationships with structural dip of anticline limb (DAL), basin area (AB) and basin topographic slope (BS). Danekhoshk anticline was subdivided into 8 tectonic zones based on dip of strata on limbs. Then, mean of mentioned parameters were calculated in each zone. Result of this study reveals that rate of SA, R, W/L, BF, SF and FA increases as dip of anticline limb increases. Nonetheless, correlation coefficient between dip of strata on limbs and SA as well as BF is higher than other parameters. There is positive relation between topographic slope of basins (SB) and all parameters of SA, R, W/L, BF, SF and FA with low correlation coefficient (less than 60%). Data analysis represents that basin area (BA) doesn’t have considerable effect on SA, R, W/L, BF and FA parameters. There is a negative relation between basin area and slope of fan (SF) with a correlation coefficient of 78%. Overall, this research shows morphology of alluvial fans specially sweep angle and length of fan base are entirely affected by tectonic setting of Danekhosh Anticline.

The Upper Cenomanian–Lower Turonian deposits of Hamam-Qal’eh section (east Kopeh- Dagh) were studied based on foraminifera from biostratigraphic point of view. Based on the standard biozonation, three biozones for Upper Cenomanian–Lower Turonian deposits were differentiated in a 1m interval sampling (R. cushmani, W. archaeocretacea, H.helvetica). Whiteinela archaeocretacea zone was divided into three subzones. This recorded zonation confirms that the sedimentation was continuous at the Cenomanian-Turonian boundary.

The Asmari Formation in the Kupal Oil Field is composed of fossiliferous limestone, dolomitic limestone, argillaceous limestone, sandstone and shale. It is the major reservoir rock of Iran in several oil fields of the Zagros. The age of Asmari Formation in this oil field is Oligo-Miocene (Chattian–Burdigalian). In this research, depositional environments and sequence stratigraphy of this time interval are studied in 3 subsurface sections using cores, thin sections and cuttings. Based on this study, 9 carbonate microfacies and 2 siliciclastic lithofacies are recognized. These sediments are deposited in a homoclinal ramp including inner ramp (A1-A7), mid ramp (A8) and outer ramp (shale and A9) sub-environments. Rapid changes of deep marine facies to lagoonal and/or tidal flat/sabkha conditions, suggest a restricted sedimentary basin. Based on microfacies analysis, stacking pattern and sequence boundaries, 4 third- order depositional sequences have been recognized. The interpreted sea level curve can relatively be correlated with global sea level changes and the differences are related to local and regional structural events.

In the Kalaybar Hasht-Sar area, in the western part of secondary Palaeo-Tethys suture zone (NW Iran), gabbro intrusion, which is older than Paleocene in age, has cropped out. This gabbro is shoshonitic in composition with has arc type geochemical composition. The rocks show high K2O concentration and enrichment of Rb, Ba, U, Th and Pb and depletion of Ta, Nb, Ti also Hf, Zr on primitive mantle-normalized spider diagrams. The parental magma of gabbro is formed by low partial melting rate (less than 10%) of spinel-garnet lherzolite. According to trace elemental ratios, the gabbro was derived from a source strongly modified by subducted slab fluids. Then crustal contamination caused the LILE enrichment in the magma. Considering accompany of the rocks with Palaeo-Tethys suture zone suit, it seems that gabbro was formed due to subduction of this oceanic crust. Metasomatism above subduction zone is an important process that produced heterogeneous mantle and thus changes in geochemical ratios of the magma.

Most of the previous studies on the relative sea level changes of the Caspian Sea have been carried out on the foreshore sediments, which are mostly affected from the land processes, such as human activities. In this paper, relative sea level changes of this basin is investigated based on the sedimentological characteristics of 7 cores collected from the offshore parts. This is for minimizing the effects of the land processes on the analysis of the relative sea level changes. This study mainly focuses on the magnetic susceptibility (MS), as a significant factor in the study of relative sea level changes of the offshore deposits. Magnetic susceptibility of studying successions is investigated by comparison of their MS value to the mean MS value in the marine sediments. The positive values of the MS indicate the abundance of detrital grains in the sediments, whereas the negative values indicate the low sediment influx to the basin. Results from this study shows that the MS value of the studying sediments depends on the amount of detrital grains derived from the land. Due to the high influx of the detrital material to the offshore setting during the relative sea level fall, the high and low values of the MS in the sediments are related to the relative sea level fall and relative sea level rise periods respectively.

Amphibolites and epidote amphibolites are the main exposures of metabasites in south of Salmas area. Mineral chemistry of these two rock groups is different, and shows differences in the P-T conditions during prograde metamorphism. Study of amphibole chemistry show increases of tschermakite and crossite end members in amphiboles from epidote amphibolites toward amphiboles within the amphibolite samples, while increasing of the edenite content during transformation from epidote amphibolite to amphibolite is negligible. On the basis of mineral chemistry, rising of temperature was more effective than rising of pressure in transformation of epidote amphibolites to amphibolites in the studied samples. According to geothermobarometeric studies, epidote amphibolites and amphibolites were metamorphosed at 500±20oC, 2-5 (commonly less than 5) Kbar and 600±20oC, 6-8 Kbar conditions, respectively.

Misho Heights are located at northwest of Iran, Eastern Azerbaijan province and south of Marand town. They are a result of positive flower structure, and their central part is limited by North Misho Fault and South Misho Fault. North Misho Fault has three segments which their azimuths vary between 109o and 120o. Multiple stress inversion techniques are carried out to study the stress state(s) around the North Misho Fault. Two tectonic episodes are recognized: (i) Pliocene extensional stress regime; (ii) Modern compressional stress regime. In general, compressional and extensional stress regimes are produced strike-slip faults, and caused transtensional and transpressional deformations.