RESEARCH JOURNAL OF UNIVERSITY OF ISFAHAN "SCIENCE"
Year:2008 | Volume:34 | Issue:5 (GEOLOGY)|Papers Count:17

Considerable part of the Central Iran is made by deserts and arid regions; therefore the Central Iran contains the lowest water content in the land of Iran. Because of the water deficiency and hard weather conditions, the indigenous people of arid regions have selected the springs and water found areas for living.But most of these areas are locations of deep strike sleep faults, shear zones, and thrusts, because these structures are able in lead and chanellizing the ground waters. Living of the people in faulted areas presents many hazards that are earthquake, asbestos minerals in ophiolite melanges, radioactive-toxic and heavy metal elements mineralization, and Radon and CO2 releasing. These hazards are obvious in Central Iran and attention to them is highly necessary in development of the old cities and villages and establishing the new cities.

In order to study of sequence stratigraphy of the Qom Formation in southwest of Qom and northwest of Aran, a stratigraphy section in Shourab area was selected. The sediments (Kuh-e-Bichareh) of this section with 631 m thickness overlies the Lower Red Formation and underlies the Upper Red Formation. The studied section is situated at the type area of the Qom Formation, and mainly consists of limestone, sandy limestone, argillaceous limestone, sandstone, shale, marl and gypsum. All members of the Qom Formation, except the unnamed member exist in the examined section. A total 185 samples including 70 soft and 115 hard was collected. Based on the index foraminifera the suggested age of the Qom Formation in Kuh-e- Bichareh.section is Aquitanian to Burdigalian. The microfacies studies were led to recognition four facies belts including tidal flat, lagoon, barrier and open marine. According to field & laboratory studies 6 sequences and 7 sequence boundries introduced which 2 sequence boundries are comparable with world sea level changes and other probably are related to tectonic in the studied area.

The Asmari Formation with a thickness of 294m located at the north of Mokhtar Anticline 5 km northwest Yasuj. This formation was studied from biostratigrarphy, microfacies and sedimentary environment point of view. Study of benthic foraminifera led to recognition of 31 genera and 20 species.Based on the distribution of foraminifera, three assemblage zones were identified. The Late Oligocene (Chattian) - Early Miocene (Aquitanian-Burdigalian) is suggested for the Asmari Formation at the study area. Based on laboratory studies, 9 microfacies related to 3 subenvironments (lagoon, bar and open marine) were identified. This study revealed that, the Asmari Formation deposited on an homoclinal epicontinental carbonate ramp.

Analytical results of 29 groundwater samples are used to evaluate the quality of groundwater in the Salmas area, Northwest of Iran.Based on the analytical results, groundwater quality in the Salmas area is generally fresh and varies from hard to very hard. The dominant hydrochemical facies of groundwater in study area is Mg, Ca -HCO3. Alkali earths (Ca2+, Mg2+) and weak acids (CO2-3, HCO-3) are slightly dominating over alkalis (Na+, K+) and strong acids (SO2-4, Cl-). Consideration of rocks composition in the north part of the study area shows that evaporation formation (limestone, marl, shale and intercalated with gypsum and salt) caused increased Na+, cl- concentrations and salinity of the ground water The results of calculation saturation index show that the saturation index for carbonate minerals is positive and for sulfate minerals, CO2 and H2 gases is negative. According to the parameters and international standards, except groundwater of north part of the study area almost all of groundwater in the study area is suitable for drinking and agricultural purposes.

The Sar-cheshmeh porphyry Cu-Mo deposit is located in the south of Uromieh Dokhtar Volcanic belt (65 km southwest of Kerman City). The Eocene andesites are the predominant host rocks of the ore deposit. These rocks are characterized by gray color and porphyry texture. Plagioclase (oligoclase-andesine), hornblende, biotite (phlogopite), and minor quartz are the major minerals and Zircon and apatite are the magmatic accessory minerals of these rocks. The studied andesites have experienced hydrothermal alteration.Propylitic alreation is identified by crystallization of albite and replacement of plagioclase and K-feldspar by albite, and it is also characterized by epidote (pistashite), calcite, chlorite (clino chi ore) and sulfide. Pervasive sericitization was the last hydrothermal stage leading to crystallization of sericite, quartz and sulphide. Hornblende is almost totally replaced by biotite and chlorite, and early biotite shows partial or total chloritization. Two generations of quartz, magmatic and hydrothermal are common. Furthermore, the widespread occurrence of opaque minerals (pyrite, chalcopyrite, chalcocite) in this zone is notable. Clay minerals (Ilite, Kaolinite, Muscovite, Dickite) are the major mineral assemblage of argillic zone. Pyrite is the predominant disseminated sulfide in all alteration lithologies. Biotite from the propylitic and phyllie alteration zones possesses higher Al2O3 Sio2, and FeO concentrations than magmatic one. This phenomenon is similar to that recorded for biotite of other porphyry Cu deposits Throughout the woeld. The mineral assemblages of the alteration zones along with different chemical composition of biotite, clearly point to the various physico - chemical condition governing the hydrothermal alteration processes.

The Boroujerd granitoid similar to most of the granitoids in world has one foliation that is parallel to country rocks. Microscopic characters show that this foliation is not magmatic but occurred to solid-deformation in high temperature. S-C structures and shear banded together improved catac1astic in outcrop show that the motion of shear zones continues to reduce temperature and brittle deformations over than ductile deformation. Faults are the most important macroscopic structures in area, so these cause different metamorphic facies in two sides of pluton and cause to asymmetry in metamorphic areola. These structures have three trends, one set similar to Zagros trend that mine veins and aplites occurred in this trend. Second set is almost perpendicular to Zagros trend that mine veins and the some of the basic and intermediate dykes occurred in this trend. The third set with southern-northern trend which isn't widespread in the studied area.The large folding is another important macroscopic structures that the variety of schistose pole in different points in area imply that these are numerous. At least three deformation phases or different folding and planed structures S1, S2, S3 occurred that the second deformation is the major episode in the area.

A total of 329 samples from the IIam Formation of the type section and Male-kuh well no. I were paleontologicaly investigated to revise the biostratigraphical zonation and determine the paleodepth of this formation.11 genera and 16 species of planktonic foraminifera and oligosteginids were recorded, which permit the recognition of 3 biostratigraphic zones: Zone 1 (Dicarinella asymetrica zone) suggests Late Santonian. Zone 2 (Globotruncanita elevate zone) confirms Early Campanian. Zone 3 (Globotruncana ventricosa zone) indicates Middle Campanian. Study of morphotype groups of planktonic foraminifera shows that deposition of the Ilam Formation mostly took place in a relatively deep marine condition (more than 100 m).

N-W Ardestan travertines are located south of Milajerd village and north-east of Esfahan city. The region belongs to Uromia-Dokhtar belt zone. Morphologic evidences imply that the travel1ines are Fissure- Ridge type and are related to the Quaternary age. Petrology and geochemistry evidences indicate that most of these resources are thermogenic.Fabric and texture characteristic of these sediments emphasize the active presence of microorganisms and biological activities with travertine sedimentation simultaneously. The presence of lamination in travertine is due to alternative seasonally/daily growth. Most of these sediments are seen on/in the 1 to 2 kilometers of the active fault zones. With regard to the process of these faults, the generating agent of travertines is the local tension in fault regions. The geological evidences shows that these rocks occurred in a high geogradiant environment and due to the tectomagmatic activities circulation of magmatic and meteorite waters in depth and represented on surface by the faults and fractures in the form of hot springs causing the formations of travertines in springs and large faults trends.

The late Miocene - Pliocene to Quaternary calc-alkaline volcanic rocks are exposed in Gowriz mountain in southeast of Isfahan. The volcanic rocks comprise basaltic andesites, andesites, dacites lava flows and domes. Geochemical studies show that they are a medium to high K calc-alkaline suite. These rocks belong to Urumieh-Dokhtar magmatic belt of central Iran structural zone. Some of rocks with dacitic and andesitic composition are characterized by disequilibrium phenocrysts assemblages and textures. Plagioclase is the dominant mineral in these volcanic rocks and has large range in composition, this mineral generally display reverse and oscillatory zoning; sieved or dusty texture. Amphibole phenocrysts are classified as calcic amphiboles. Amphibole and biotite phenocrysts have reaction rims indicating disequilibrium crystallization with surrounding magma. Quartz phenocrysts are embayed and a few have augite reaction rims.Clinopyroxenes are augite approaching the diopside composition and Orthopyroxenes are hypersthene to bronzite. The presence of normally and reversely zoned pyroxene in the same sample is another evidence of disequilibrium. These Criteria; support crystallization under disequilibrium condition and magma contaminated with other melt and suggested magma mixing as an important process in the evolution of these rocks.

In the eastern aureole of the Alvand plutonic complex, a band of migmatitic rocks occur which have various structures such as stromatic, ptygmatic, dyctionitic, schollen, surreitic and nebulitic. In this migmatitic complex, separation of melanosome from mesosome is difficult in many cases, so that melanosome has not developed or is very thin. Three types of leucosomes including trondjhemitic, granodioritic and alkali feldspar granitic types occur in migmatites. Field observations and microfabrics show that metamorphic segregation, partial melting and migmatitic injection have been important in migmatization. The partial melting due to ultrametamorphism has been very important. There is also a genetic link between migmatizaton and formation of S-type granites. Major migmatization due to regional metamorphism has been occurred syn-to pre- intrusion of granites, but contact metamorphism has been also occurred later. The partial melting has been precocious and occurred before the complete change of andalusite to sillimanite.Tectonic disturbances and alternation of thin layers of various rocks caused partial melting has been (not pervasive) and therefore separation of mineral zones is selective difficult, in the region.

The submarine volcanic rocks of Totmaj area as a small part of Sahand-Bazman volcanic belt are mainly composed of mafic and intermediate lava flow and pyroclastic rocks which locally show an alternation with Oligocene sedimentary rocks. The volcanic rocks undertaken the hydrothermal alteration during the waning stages of the explosive activity and include secondary minerals such as albite, chlorite, calcite, actinolite, epidote, hematite and quartz.Based on the chemical and mineralogical characteristics, the altered rocks have been divided into four following groups: least altered, chlorite-epidote rich, hematite rich, and epidote rich rocks. Least altered rocks, including basalt, andesite and basaltic andesite, form approximately 10 percent of the area. The chlorite-epidote alteration which is the earliest hydrothermal event, has extensively affected the rocks due to seawater circulation into the heat submarine volcanic rocks. These rocks, compared to least altered rocks, suffered some increase Ti02, Sr, CaO, and Ni in Basalt and Rb, Th, CaO and K20 in andesite.The epidote rich zones have been as a high permeable part of chlorite-epidote rich zones which during interaction with Ca rich fluid have been enriched of epidote and lost some elements such as Fe, Mg, and Na.j The rocks containing hematite, subsequent to chlorite-epidote alteration, have been evolved by high- L.temperature Fe and Mg rich fluid which have been circulated within the chlorite-epidote rich rocks leading to CaO leaching.

The upper Asmari Formation in southeast Laki Mountain comprises of 376 meters of thin, medium and thick beds of limestone interbedding with marly limestone. It is overlies by the Gachsaran formation. Based on field work and laboratory analysis, 13 microfacies related to basin (outer ramp), open marine (middle ramp), bar and lagoon (inner ramp) environments were recognized, as follows: Planktonic foraminifera mudstone wackestone, Bioclast planktonic foraminifera wackestone-packstone, Planktonic foraminifera Heterostegina packstone, Bioclast Miogypsinid corallinacea packstone, Coral and corallinacea floatstone, Rotalia wackestone-packstone, Rotalia miliolid wackestone-packstone, Foraminifera (Rotalia, Meandropsina, Borelis, Archaias, Peneroplis)miliolid packstone-grainstone, Bioclast corallinacea miliolid packstone, Miliolid grainstone, Intraclast bioclast packstone, Bioclast wackestone-packstone and quartz mudstone.Paleoenvironment reconstruction based on the occurrence of foraminifera, related to microfacies and environmental factors (light, depth and water energy) reflects that deposition of the Upper Asmari Formation (Burdigalian) was in a carbonate ramp platform.

Zarin ductile shear zone in north Ardakan with N-S orientation and arc geometry concaving to the west contains parts of Zann granite and Paleozoic metamorphic rocks that were deformed to mylonites and ultramylonites.This shear zone is the same as the grater dextral strike-slip ductile shear zone to the east (Kashmar-Kerman shear zone), that is the tectonic boundary of Yazd block to the west and Tabas block to the east in the central micro-plate of Iran. The major boundary faults of the tectonic blocks in the central micro-plate of Iran change their N-S trend (Nayband fault) to arc shape to the west (Kashmar-Kerman shear zone) and the arc form is continued to the west in Zarin shear zone. All these fault systems are strike-slip with dextral sense of shear.Fabric evidences in Zarin shear zone indicate that possibly it was originally in NS direction and gradually was changed to arc form.

Dalli mineralized area is located in Markazi province, about 200 km SW of Tehran within the Urumieh- Dokhtar Magmatic Arc. This mineralized area is hosted by andesite to dacite rocks that intruded into the volcanic rocks dominantly in andesitic composition and pyroclastics in miocene-pliocene age. In this area, igneous rocks have porphyritic texture and are composed mainly of biotite, amphibole, plagioclase, and quartz with variable amount of opaque minerals including dominantly pyrite, chalcopyrite and magnetite and secondary minerals such as epidote, calcite, chlorite, sericite. Geological and geochemical investigations show that mineralization in this area is of gold - rich porphyry Copper type. The content of Cu and Au is high wich is more than 0.75w% and about 1.2 ppm respectively. The mineralization is associated by felsic porphyritic igneous rocks and hydrothermal alteration such as potassic (secondary biotite, magnetite, and secondary k-feldspar), phyllic (sericite, quartz, and pyrite) and propylitic (calcite, chlorite, epidote...).The content of magnetite and stockworks of quartz - magnetite is high. These evidences can prove that Dalli mineralized area is a porphyry copper system.