RESEARCH JOURNAL OF UNIVERSITY OF ISFAHAN "SCIENCE"
Year:2000 | Volume:13 | Issue:1|Papers Count:19

Mineralogy and microscopic structure of pelecypode shell walls are important for nomenclature and systematics. Each of bivalve families has special structure. In this research, a genus of Spondylidae with more than 190 species was strudied. the studied bivalves are rested on collection of Mine School of paris, Malacology laboratory of Natural Musium of paris, plus a collection of bivalves from Khark island, Persian Gulf and Qum Formation.It is proved that, relative thickness and arrangement of layers differ from species to species in this genus. The kind of mineraloagic composition is used as a factor in identifying ecologic conditions.

To investigate the effect of water content on the mechanical behavior of fine-grained sedimentary rocks three different types of shales; clayshale, mudshale and mudstone,from different locations were studied. The samples were tested at different water content conditions ranging from oven-dried to saturated condition. Preparing samples of standard size for testing was a troublesome task. Many samples break during coring, cutting, grinding and storing because of disintegration of these rocks when subjected to change in water content. This nondurable behavior of these rocks is responsible for numerous slope instability problems, underground excavation problems and embankment failures.Water content has been demonstrated to have a marked influence on the strength and deformation properties. The uniaxial compressive strength and modulus of elasticity decrease significantly as the water content increases. The results show a reduction of more than 90% in uniaxial compressive strength from oven-dried to saturated condition. This strength reduction due to moisture content for the rocks studied is significantly higher than the values reported by other researchers. A general equation was developed for this type of fine-grained sedimentary rocks that may be used for predicting uniaxial compressive strength from the available information on water content.The modulus of elasticity was found to be influenced by anisotropy, but the most significant influence, regarding reduction of the modulus of elasticity, was the change from dry to saturated condition. Test results show a significant reduction in the static modulus of elasticity from oven-dried condition to saturated condition. The results of these tests show an average reduction in modulus of elasticity, from that in dry state, of about 84% for the shales studied.

Brachiopod fauna of "Cephalopod Bed" in Shotori Range (east of Tabas) have been studied. The Cephalopod Bed Consists of red oolitic limestone, siltstone, shale and sandstone. Due to its morphology and color, it is known as a key bed in the area.The Cephalopod Bed in 3 areas (Howz -e-Dorah Nias, Hurmok and Pusha ) have been studied. These sections show large differences in thickness and lithology. The thin sections of the succession indicated that the studied strata was deposited in a shallow and high energitic environment. The paleogeoghraphic evidence and the Late Devonian fauna indicates a similar condition in Alborz and in a large scale similar to China, Gahzaghestan and most parts of Europe.18 genera and 16 species have been introduced herein. From the fauna, genus Warrenella is reported for the first time from Iran. 7 of the genera are reported for the first time from the studied area. These are: Megalopterorhynchus, Warren Ella, Productella, Cleiothyridina, Tenticospirifer, Spinatrypa and Ptychomaletoechia. The brachiopod fauna revealed a Middle Frasnian to Late Famennian age for the strata.

Hassan Robat granitoidic mass is situated 38km west of Meimeh, west part of Isfahan-Tehran road. This mass is along Sanandaj-Sirjan Zone and it was intruded in limestones and dolo mites of Upper Triassic and Rhaeto-Liasic shales, emplacement of Hasan Robat granitiodic mass among these formation, were led to produce shistosity, slaty, phyllity and recrystallization textures, so that, we can distinguish Pelitic Hornfels facies. By using of Tuttle & Bown (1958) diagram, show that the range of pressure, temprature at the time of emplacement was P=1.5-4 kbar , T=700-750°c . Composition of this mass is equivalent Monzogranite-Alkali feldspar granite with red to brown biotite and muscovite minerals and Aplite granite. In granitoidic mass is observed two kinds of enclaves: enclaves suromicaceous (symbole of assimilation pelitic metamorphic rocks by plutonic mass) and enclaves rich of fine grain green biotilte (It is in relationship with fast solid margin and they are compositionally petrography Biotite Alkali- feldspar granite.Considering of the variety diagrams, general samples are Calc-alkaline trend and per aluminous. The type of Hasan Robar granitoid mass is S-Type and it could be assaigned to orogenic granites and in relationship with post orogenic granitoids process By field evidences, the mass is related to post of late Cimmerian orogenia

Phosphatic depositions are necessary for the living organisms and for the industrial activities. Most of the phosphatic depositions can be found within sedimentary rocks. Lots of Late Devonian phosphatic horizons were reported from the sedimentary facies of Iran and Arminia. A sea level transgression of Late Devonian platform covered most parts of Iran, from Alborz in the north to the Zagros sedimentary basin at the northern part of Bandarabbas. Late Devonian facies mainly composed of limestone, marly limestone, shale and sandstone in Iran.Phosphatic horizons were found throughout the most Upper Devonian sections in Kerman. With regard to the importance of this element, four Upper Devonian sections were sampled and studied in detail. Percentage of phosphate in 24 rock samples and 10 brachiopod fossils were measured. Phosphatic horizons are found within the limestone, shale and sandstone facies. The highest percentage of phosphate was recorded within limestone beds at Hutk and Zangu sections. Rate of phosphate in the other rocks were low.Phosphatic layers in this region were deposited in a sea platform type. Upper Devonian fish and brachiopods are the main Sorce for the phosphatic depositions.With regard to the characteristics of the phosphate horizons, their mining is not economical at present.

Kuh-e-Zar is a valuable mineralized complex which is located 100 km to SSE of Damghan. It consists of intrusive, extrusive, pyroclastic rocks and also gold bearing Quaternary deposits. The general structural trend of the area is NE-SW. The oldest out-crops of the area are related to late Eocene and the latest magmatic activity phases to Miocene - Pliocene ages. The Ores are conbain valuable amounts of gold and turquoise. Ancient works on gold bearing deposits and veins, recent works on turquoise and numerous chemical analysis results, and field study considerations, confirm the idea of volubility of the area. Concentration of gold within tourmaline bearing quartz veins and Quaternary sediments is clear. Turquoise as veins and veinlets and thin films could be seen in the igneous rocks of the area.

The Sungun copper deposit situated 100 km northeast of Tabrize, is a reservoir of skarn-porphyric copper and molybdenium, and reconnaissance to detailed explorations are achieved on it. In this paper distribution of kinds of alteration zones have been investigated and mapped in this ore deposit. The rock units of the area comprise a complex intrusion of felsic composition in adjacent to Upper Cretaceous limestone.Alteration zones of potasic, phillic and propyllitic are found in the area.Propyllitic alteration is found in the north and south of the exploration network. In the west side of the exploration network the alteration zones are not limited to propyllitic zone and have been cut with a fault. Zonality of mineralization is as follow: mineral assemblage of pyrite + chalcopyrite + molybdenite are located in central and deep parts of deposit, while pyrite + chalcopyrite are situated around and top parts of deposit, and finally pyrite and some chalcopyrite are covering these assemblages.

Three types of pyroclastic deposits - Fall, Flow, and Surge - are present around Damavand volcanic cone. Only pyroclastic Flow deposits are under research in this paper. Pyroclastic flow deposits of Damavand Volcano are categorized in three types: Pumice Flow deposits, Scoria Flow deposits and Ash and Block Flow deposits one of which is related to one of the three later eruption phase of Damavand volcano.

Pateyar antimony ore deposit is located 13 km northeast of Anarak. From geological aspect the ore deposit is part of the upper Anarak metamorphic cover ling Chah - Gorbeh and Morghab complexes.These rocks have Late Proterozoic age. The ore deposit is composed of metamorphic, igneous and sedimentary rocks.This area is tectonically very active. The antimony minerals associated with quartz (as a gaunge), are concentrated as vein in fault contact zones.Arsenic, gold, Silver, copper and molybdenum are associated with antimony study in this paper.A high correlation is observed between antimony and arsenic elements. Based on geochemical studies and fabric evidences, pateyar antimony deposit is formed in two stages. At first stage, ore minerals associated with detrital sediments is precipitated and in the second stage, mobile elements from country rock during metamorphic activities are concentrated in faults and open spaces and is enriched by ore minerals.

The sedimentary deposits of lower Cretaceous in khaseh Tarash area at 50 km northeast of Esfahan with 600m thickness are mainly of terrigenous and carbonate sediments which are orverlaying Jurasic (Lias) sediments after angular - unconformity.After studing microscopical tin section and sedimentary microfacies in general, three types of sedimentary environments of open marine, barrier or bar and lagoon - Tidal flat were distinguished. These rocks were formed in shallow sea water environment of epicontinental platform around continental margins.Vertical changes of microfacies along with depth indicate that, the lower Cretaceous rocks in these areas were formed by upward cycles of deposition in meter scales, which in overall formed a progressive big cycle in million year scale.Apparently, the small cycles were originated from static sea water fluctuations or climatic cycles and bigger scale cycles were formed by techno static rising of sea water which was caused by opening of plate tectonics.

The Carboniferous region of Shahrud Gheshlagh is situated in Ramian Division of Gonbad - Kavous district, between Mazandaran and Semnan Provinces. This region is located 110 Km northeast of Shahrud and 15 Km west of Shahrud - Azad Shahr road.In this region, the sediments of Upper Trias-Lias possess a good extension and thickness; although the diversity and the distribution of plant fossils is fairly abundant, and no precise study has been yet achieved with regarding to their plant fossils.In this paper, 14 genera belonging to the following four phylum are recognized: Cycadophytes (6 genera), Ginkgophytes (2 genera), Phyllicophytes (4 gerera) and Coniferophytes (2 genera).Study of plant fossils of Carboniferous sediments of Shahrud Gheshlagh region, revealed that, the age of these sediments probably relate to the Upper Trias (Retian). This conclusion is based on the presence of Scytophyllum persicum which is characteristic of Upper Trias sediments, as well as, the absence of characteristic fossils of Lias. The flora of this period show more affinity with the plant fossils of North Hemisphere. Moreover, climatic conditions of the time of Carboniferous layer into MIBK under the same experimental conditions as samples.

The fish bearing beds in pabdeh Formation were studied in two sections at High Zagros: Baba Heidar - Feal Abad in Bakhtiari region and iiam at Northwest of Iran.In this research, 25 species of bony fishes (Teleostei, 21 families, 6 orders) were identified. These orders are as follows: Anguilliformes, Clupeiformes, Salmoniformes, Gadiformes, Beryciformes, and Perciformes.Numerous and various fish remains are locally accompanied by other fauna and flora such as: leaves, stems and fruits of Angiosperms (e.g. Nerium, Salix, Acacia, Laurus, Vistis, Quercus, Myrcia, etc.), insects and reptiles (e.g. snakes, and turtles).It can be suggested that the accompanying bony fishes with Angiosperms in some localities indicate the mouth of a river to the sea (Delta) on those locations.Based on associated pelagic formainifers, the age-range of these fish faunas is middle to Late Eocene time, interval in the pabdeh Formation.According to some of the key beds which are rich in plant remains, the palaeoecology of the studied area can be considered a warm to subtropical conditions.These assemblages are very similar to Green River Formation in Michigan, USA, and Mont Bolca of Italy with Eocene age.

Due to the importance of calcareous nannoplankton biostratigraphy in - Mesozoic and Cenozoic strata, the Abderaz formation was E and 36o 10" 40" studied at the type locality.The type section N).This of Abderaz formation is located in kopeh-Dagh area (60o33" 00" formation comprises of shale, marl, grayish or yellowish-white chalky limestone. The Abderaz formation discomformably rest on Aitamir Formation and it is underlined by the Abtalkh Formation.For the first times the calcareous nannofossils of the chalky limestone beds of this formation were studied by using both light and electron microscope. As a result of this study 4 subspecies,66 species,36 genera and 16 families were determined and illustrated. Based on the obtained nannofossils, the sample interval is consistant with CC14-CC17 of Sis Singh (1979) zonation. Therefore the abderaz to the Late Coniacian formations assigned Early Companian.