مجله علوم دانشگاه تهران
سال سی و ششم شماره 1 (بهار 1389)

Underground structures, depending on their geometrical shape, depth of replacement and different geotechnical and seismic parameters, behave in different manners when earthquake occurs. The buried structures faced significant damages in recent large earthquakes. Buried tunnels with circular cross section, such as urban undergrounds are very popular in transportation engineering. Such these tunnels are usually constructed, using Tunnel Boring Machine (TBM). The seismic behavior of such buried structures during operation is of importance. When designing such structure under earthquake conditions, seismic parameters and physical and mechanical properties if soil play important role. The response of a lining of buried circular tunnel against the earthquake is a function of the compressibility and flexibility ratios of the structure, the in-situ overburden pressure and at-rest coefficient earth pressure, K0, of soil. The trust, bending moment and deformations can be calculated using closed form solution.

n order to determine the source of Pb in a number of Pb–Zn deposits in Iran, Pb isotope ratios of galena in five Pb–Zn deposits with carbonate host rock, located in Central Iran zone and Zagros folded belt, have been measured. Pb isotopic ratios of Kuhe Surmeh deposit from Zagros folded belt, in northeastern of Arabian plate, has the least ratios of 206Pb/204Pb (18.062) and 208Pb/204Pb (38.230). Considering Pb model age (585 Ma) and high values of 207Pb/206Pb (0.8683) and 208Pb/206Pb (2.117) and thus significant contribution of original basement rocks in providing Pb for these deposits, it can be inferred that lead and other metals were derived from the Iranian basement that was metamorphosed and consolidated in late Precambrian.

The Khabr- Marvast Tectonized Ophiolite is part of the internal Iranian group of Ophiolites. This Ophiolitic association crops out in the South-Western edge of the Central Iran Microcontinent, in the middle part of the Nain-Baft ophiolite belt. The mantle sequence comprised of serpentinite and serpentinized harzburgite. The crustal sequence consist of isotropic gabbro, diabasic sheeted dike complex, trondjhemite, which intruded by Isolated diabasic dikes and pegmatite gabbro. The extrusive sequence made of pillow lava, basaltic- andesitic sheet flows and hyaloclastic breccias.The multi- elements plots normalized to primitive mantle, show that most of rock types display enrichments in the LILE and depletion in the HFSE, notably Nb. These geochemical features are comparable to those of subduction-related magmatism patterns.

The siliciclastic Kashafrud Formation (Middle Jurassic) of the Kope-Dagh Basin rests unconformably on Triassic volcanogenic sedimentary rocks (Sina Formation), and nonconformably on older ultramabasic intrusive rocks in study area. This formation is disconformably overlain by marine carbonates of the Mozduran Formation (Oxfordian-Kimmeridgian). Based on field and laboratories studies, 3 facies association (12 lithofacies) have been identifies which were deposited in a fluvio-deltaic and turbities environments. The sandstones are mostly lithicarkose and feldespatic litharenite, rich in sedimentary and volcanic rock fragments. The main identified cements are Fe-oxide, carbonates (calcite, dolomite, siderite and ankerite), silica, clay minerals (kaolinte, illite, serecite and mostly cholorite), pyrite and rarely barite. Therefore cementation and compaction (mechanical and chemical) could be two factors to reduce the porosities in this formation. Based on petrological and geochemical studies, we interpreted the diagenetic history for the Kashafrud sandstones, which consists of early, deep burial and late stages.

The Gol-Gohar Fe ore deposit is located at 55 Km SW Sirjan of Sanandaj-Sirjan structural zone. The host rock for ore deposit is Paleozoic Gol-Gohar metamorphic complex which consists of amphibolite, mica-schist, marble and graphite-schist. Serpentine, talc and clinochlore are only visible in the peripherals of deposit and occur as phases filling magnetite grains or as band and irregular mixtures with ore. It is reasonable to assume that any attempt to evaluate the formation of these mineral phases will help understand the genesis and evolution of Fe ore. Field studies, petrography and chemistry of serpentine, talc and clinochlore minerals indicate that these minerals were formed during three stages. In the high temperature stage (> 550°C), olivine formed. This was followed by the metasomatic stage, in which temperature and XCO2 dropped to < 250°C and >0.5, respectively.

With respect to the vast area of Iran and extensive mineral potential zones (existence of Urumiyeh–Dokhtar volcanic belt) and the need for identifying and management of these deposits implies the use of GIS. Using GIS not only organizes the information related to mineral exploration but also has the ability to produce and integrate information layers in different models with more precision and speed and supports spatial decision makings. In this article mineral potential map of Now Chun porphyry copper prospect has been produced in detailed stage. Main steps of mineral potential mapping include: identify mineralization recognition criteria, information preparation and structuring, weighting and producing criteria maps, Integration of criteria maps and results evaluation. Used layers in this study include rock type, fault, alteration, mineralization indicators, anomaly zone of Chargeability and Apparent resistivity and metal factor, anomaly of Copper and Molybdenum and Cu-Mo additive indexes.

Pre-researches evidences including isotopic and fluid inclusion thermometry results at the1/50000 sketch map of Mianeh area located in east Azerbaijan, indicate to Cenozoic post magmatism activities given rise to facing adularia facies as initial alteration sequences related to gold mineralization processes may be hosted by Paleogene pyroclastics and rhyolithic tuffs constraining number of quartz pyrite occurrences belong to Neogene epithermal systems. According to Queensland exploration results, the evolution of textural zoning associate with gold bearing vein systems is in close spatial relationships with quartzitic appearances and siliceous alteration developments at the most surfaces of the prospect area. So, in this paper, a new fractal approaching to analysis of nonlinear distribution of silica variations (glassy types, microcrystalline, crystalline, etc) were applied to revealing textural patterns and prognosis of gold mineralization stages within the west Mianeh indices as known epithermal prospects.

Nankai Trough basin is an active convergent margin at south-east of Japan. Its sediments are mainly composed of sand, silt and clay together with authigenic calcite cement. Biological reactions have been realized by microorganisms and the organic materials derived to the mixture of methane and CO2. These changes occurred by bacteria and archaea under anaerobic conditions. Anaerobic oxidation of methane (AOM) have been occurred by sulfate reducing bacteria (SRB) and methane oxidizing bacteria in lower depths, which caused increasing of alkalinity in pore water leading to deposition of authigenic calcite. The existence of biofilm in thin sections indicates microbial growth in sediments. Formation of authigenic calcite is due to activity of particular bacteria such as calcinogenic bacteria, which is simultaneously accompanied with anaerobic oxidation of methane and sulfate reduction. Physiological processes and special structure of the bacteria influence on morphology and mineralogy of produced carbonate minerals.

Only a few studies have been carried out on the relationship between geomorphic surfaces, isotope geochemistry of pedogenic carbonates and paleoecological changes in Iranian arid lands. The aims of this study were to investigate the pedogenic development of geomorphic surfaces in eastern Isfahan and to understand the ecologicological and climatic conditions during evolution of these surfaces. Three pedons on geomorphic surfaces of an alluvial fan were selected and studied. Paleovegetation of the study area was identified using signals from carbon isotopes in pedogenic carbonates. The results indicate that the expansion of C4 plants occurred during periods with low? 18O (Glacial periods). It seems that a decrease in atmospheric carbon dioxide concentration during glacial periods was a primary factor responsible for the expansion of C4 plants, landscape stability and pedogenic development of soils in this region.

In this research 2 new lithostratigraphic units based on studying of 8 stratigraphic sections which outcrops with a considerable thickness in high Zagros (Semirom-Ardal) is introduced. The clastic-carbonate sediments (unit stratigraphic 1) is 314 m in thickness at its type section (station 7). The lower contact of this unit is conformable with the underlying Amiran Formation but its upper contact is unconformable with the red colore clastic sediments (unit stratigraphic 2).The red colore clastic sediments (unit stratigraphic 2) is 220 m in thickness at its type section(station 5). The lithostratigraphic 2 overlies the clastic-carbonate sediments (unit stratigraphic 1) or Gurpi Formation by an unconformity boundary but its upper contact is conformable with the Tarbur Formation. The type sections of both lithostratigraphic units are selected according to the maximum thickness and completed successions in Semirom area (stations 7 and 5, respectively).

In this research, Biostratigraphy and depositional environment of the Asmari Formation in south flank of Khaviz anticline was studied. The thickness of Asmari Formation in this section is 283m that consists of alternating thin, medium and thick bed to massive Limestones. Study of benthic foraminifera led to recognition of 28 genera and 25 species. According to the vertical distribution of foraminifera, four assemblage zones were identified. Based on vertical distribution of the identified foraminifera and assemblage zones, the age of Asmari Formation in the studied section is Oligocene (Ruplian- Chattian)- Early Miocene (Aquitanian-Burdigalian). Based on field and laboratory research, 10 microfacies in the Asmari Formation were recognized. These microfacies have been deposited in three major depositional environments including shallower part of the open marine, barrier and lagoon. As a result a homoclinal ramp is suggested for deposition of the Asmari Foamation.

Structural Fracture Map of Taknar Zone in Central Iran has been drawn using 6 applied remote sensing methods, based on local morphological and structural characteristics. In this paper detected fractures were classified to 6 main directions after studying their distribution in the related diagram. Then rose diagrams of the fractures were drawn for 5 different regions of the zone, for studying distribution of each group of the 6 fracture sets. Most of the fractures and variety of them were concentrated in the central and southern part of the zone. In the next part of the study, Length values (L) of the fractures were calculated and classified in 3 main classes. It was found that the number of each fracture set decreases exponentially by increasing the length values. Calculating Spacing (S) values of each fracture set and comparing them with the number of fractures showed similar

Kerman Cenozoic magmatic arc has gone through a different tectonic and magmatic evolution from that of central and northwestern parts of the Urumieh-Dokhtar volcanic belt and has particularly been influenced by the subduction of Neo-Tethys oceanic crust to the east of Nain-Baft transform fault beneath the rotating central Iran micro-continent and its surrounding circum ocean. The arc magmatic activities started from early Eocene with extensive volcanism of Bahr Asemen and Razak complexes which are characterized by silica-satureated magmas with ranges mafic to felsic compositions without feldspathoides, calc-alkaline and locally tholeiitic-like affinity, low enrichment in LILE, weak to moderately REE fractionation (La/Yb<20), non-radiogenic Sr isotopic ratios (0.7041-0.7049), and high? Nd (6-2.3).

Celestite mineralization has more than 60 Km outcrop at Bangestan anticline, Northwest Behbahan, Ahwaz. The structure and form of mineralization occur as stratiform, following the lower massive limestones and upper shaly limestones of the Asmari Formation. Pseudomorphism of sucrosic celestites with gypsum, anhydrite and calcite inclusions is an indication of Sr2+ substitution for Ca2+ in calcium sulfates and calcium carbonates. The late diagenetic and epigenetic effects on the celestite mineralization is shown by the zebra and vein-type celestite, the mosaic crystals with 1200 angles, the fine-grained euhedral celestite into the coarse-grained anhedral celestite and the spary calcite and celestite, cross cutting the first generation celestite. The Sr/Ba ratio of the celestite is 7500 times greater than sea water. A strong positive correlation exists between SrO and SO3 (0.998). Trace element data are compatible with these late diagenetic effects.

Uniaxial compressive strength is one of the most important parameters that are used in rock engineering plans. Since, standard samples are needed for conducting of uniaxial compressive test and obtaining of standard samples from week and layered rocks is hard and sometimes impossible, recently indirect methods for estimation of UCS are in attention. Using of Punch test results is one of these methods that has introduced recently. In this study many different tests conducted to obtaining of uniaxial compressive strength, block punch index, point load index, velocity of compressive wave and the physical properties of 63 different rock types. In plus, for the first time cylindrical punch test is used. By analyzing of results of the tests the accuracy of different methods for predicting of UCS is investigated. These analyses are performed once for all rock types and once for three separate rock groups.