RESEARCH JOURNAL OF UNIVERSITY OF ISFAHAN "SCIENCE"
Year:2001 | Volume:15 | Issue:1-2|Papers Count:14

The results in this study indicated that, the age of intrusive masses in the study area has been modified and probably could be considered as late Mesozoic.These masses are mainly granite, granodiorite, monzogranite, tonalite, monzonite, quartzmonzonite and quartzsyenite which have been intruded into the metamorphosed formations as small and big masses. According to diagram of Alk against silicate and triangular AFM diagram, the granitic masses in the area are sub alkaline and Calc-alkaline and the syenites and monzonites are alkaline types. According to multi cationic R1-R2 diagram and AFM diagram, the Golpaygan granitoides are mostly in POG range or after orogenic and a few of these are in CCG range or continental collision range, Diagram of Nb against Y and diagram of Rb that, the granitoides are within WPG range or intraplate Limit.

The metabasic rocks of north and north-west of khoy are metamorphosed in greenschist to upper amphibolite facies.Geothemobarometry studies on the base of microprobe analysis have shown that the metamorphism temperature is between 450 to 700°c and the metamorphism pressure is between 5 to 7.5 k. bars. Whole rock analyses of metabasics and their projections in different petrological and tectonomagmatic diagrams suggested that the parent magma was mainly arc - type & abyssal type tholeiite. These Rocks shows slightly calc-alkaline affinity.In the base on association of tholeiitic basalts with calc-alkaline basalts the primary tectonomagmatic settings of North kohy metabasic rocks may be an island arc environment.

One of the characteristics of Elika Formation in Ghoznavi section, is the presence of abundant vermiculate fossils trace in lower part that is regarded as calacareous vermiculate.The study on trace fossils in Ghoznavi section indicate the non variety of their ichnogenus, and as saxh it includes merely the different ichnospecies of ichnogenus, paleophycus, planolites, Rhizocorallium. These ichnogenus have no facies limits and are observed in different sedimentary environments. The bioturbation in Ghoznavi section in addition to to open marine environment is also observed in sediment that bear abundant lagoonal faunistic assembelage. According to thin section and microfacies study and its correlation with Wilson standard microfacies (wilson, 1975) most of the microfacies that bear micrite matrix have bioturbation. All these ichnogenus belong to cruziana fades.

The Alvand plutonic comlex is intruded to NW part of Sanandaj-Sirjan plutonometamorphic belt during Middle to Upper Cretaceous time. Basic, intermediate and acid magmas were intruded respectively.Regional metamorphism of region was occurred during Cretaceous and then intrusion of plutonic bodies was formed metamorphic auroele around them.In the east of Alvand, contact metamorphism superimposes regional metamorphism. This contact metamorphism is progressive on lower grade metamorphic rocks (phyllites and micaschists ) and retrogressive on high grade rocks (high grade schists and migmatites).Migmatites of metamorphic auroele are stromatic and in situ, and they are not injection complex. The intrusion of the plutonic bodies have been syn- to post-regional metamorphism feature (prophyoid granites are anatexites and intruded to upper levels afterpeak of metamorphism). Plutonism had caused contact metamorphism (up to hornblend hornfels facies) and deformation in metamorphic rocks.Refering to metamorphic reactions, maximum temprature in the contact of porphyroid granites is about to 530-550 C which is insufficient for migmatization in eastern Alvand. Migmatites have been dragged with granitic diapir to upper levels.The intense metamorphic zone is located in eastern contact of porphyroid granites but does not show any zonation around plutonic bodies because granitic plutons are not cause of dynamothernal metamorphism but result of that. Major thermal cause of dynamo thermal metamorphism and anatexis were extensive gabbro sheets which intruded to middle crust.

Study area, as an intermountain basin, is well developed parallel to the southwestern boundary of the Urumieh Dokhtar magmatic assemblage and northeastern margin of the Zagros orogenic belt in central Iran to the southeast of Isfahan city. It is surrounded by mountains, which are composed of Eocene volcanic rocks in the east and northeast, Jurassic and Cretaceous sedimentary rocks to south and west. Land surface ranges with a maximum height of 3330 m above the sea level in the northern mountains and a minmum of 1470 m in the gavkhoni playa Lake. The most important sedimentary environments of this area are Gavkhoni playa Lake, Varzane aeolian sand fills, alluvial and lacustrine deposits.The Vazaneh continental aeolian sand field is located to the west of the Gavkhoni playa lake and covers an area of approximately 140 km2. the height and volume of the aeolian sands in the northern part of the aeolian sands is more than in the southern part. The various important form of aeolian sand dune including sief, barchan, barchaniod, atar, dikaka, and sand sheet consist of interdune, overbank and sabkha are present in this aeolian sand field. Mineralogical investigations suggestthat the first major source of the Varzaneh aeolian sand field belongs to sedimentary rocks located in the south, southwest and northwest of this landform. The second major one belongs to igneous rocks exposed in the east and the northeast of the aeolian sand field and the third one (minor source) belongs to metamorphic rocks exposed mostly at the beginning of the drainage basin. According to abundant aeolian sands in the north, mineralogical composition variation, dominant wind direction, and special forms of some sand dunes the most concentration of water-laid sediment, deposited by Zayandehrud river in the north of the aeolian sands, is as the main origin of the aeolian sands.  

One of the most important late Visean -Early Sepukhovian rugosan corals are Actinocyathus florifromis. This taxon being as compound, cerioid, with relief axial cullumella, wide dissepimentarium called lonsdaleoid occupies 113 of the internal space of coralite. This speciment is reported for the first time in limestone - shale succession, an equivalent to the Sardar formation in the Ozbakkuh mountains in central Iran. Actinocyathus accompanied with other genus such as Siphonodendron, Lithostrotion, Orienastraea, Syringopora, has formed a great number of patch reefs at this formation. Actinocyathus in the Visean and Serpukhovian stages having been cosmopolitan and has developed in shallow water carbonate and clastic-carbonate platforms in Asia, Europe and North America. A florifromis species having been evolved from Lonsdaleia (that are fasciculate rugosa) determine RC8 zone and base of V3c in Belgium indicating Late Visean age for this part of succession.

In order to determine the microfacies and sedimentary environment of the Ilam formation, one stratigraphic column in SW of Semirom (Landaran Anticline) was sampled and studied. Sediments of the Ham formation in the area are dominantly of limestone and marly limestones. Study of petrography indicates that carbonate sediments of the Ilam formation can be divided into 8 groups of carbonate microfacies. Microscopic studies and field obserbations show that the carbonate microfacies form in four sub - sedimentary environments, including: Open marine, Barrier, Lagoon and Tidal Flat. The absence of build-up, slump and turbbidite currents indicate that the carbonate platform of the Ilam formation is a homoclinal ramp. presence of rudist debries indicates a protozoan assemblage and suggests a tropical condition for deposition of the carbonate sediments.

Sediments of the Permian in zaladu section (East Central zone of Iran) are dominantly of sandstone and shale in the lower part and carbonate rocks in the middle and upper parts. The thickness of the sediments increases from north to south. Study of petrography indicates that carbonate sediments of the Lower Permian can be divided into several groups of carbonate microfacies. Microscopic studies and field observations show that the carbonate mirofacies form in four sub-sedimentary environments, including: tidal flat, lagoon, bar and open marine. The absence of build-up, Slump and turbidite currents indicate that the carbonate platform of the Lower Permian is a homoclinal ramp. Clastic sediments (sandstone and shale) are also observed at the base of succession. Type of sandstones, sedimentary structures, lateral continuity of beds and a gradual replacement of carbonate facies (upward), probably show a coastal or transitional sedimentation. Increasing water depth in the Lower Permian caused a decline in clastic input and an establishment of carbonate deposition. The sedimentation ended by decreasing water depth and exposure of sediments. An Eros ional surface is also present.

Corals and brachiopods have the most frequency numbers of the Devonian fossils in Kerman. Two coral reefs of Hares and Greik sections exposed at east and west of Hojedk synclinal in Kerman province. Spinatrypina has the most faunas of brachipods within the coral reefs in the study area. Biometrical studies indicate that all samples of Spinatrypinas related to one genus that was named before. A high correlation exists between the numbers of individual spinatrypina and corals.There is a good relationship between Spinatrypina, Disphyllum and Tamnopora. It seems that reef environment was favorable for the living of Spinatrypina.

The studied area comprises of regional metamorphic rocks, as basement. These rocks have intruded by Borojerd intrusive pluton with contact metamorphism haloes. Biotic isograde was discriminated the contact metamorphism halo from low-grade regional metamorphism.Contact metamorphism halo from margin toward the pluton includes these rocks: graphitic schist, cordierit-schist, andalasite-cordierite - schist, andalosite-cordierite-hornfels, sillimanite- andalasite - cordierite - hornfels and sillimanite- k- feldspar- hornfels. Grade of contact metamorphism in halo comprises albite - epidote hornfels & pyroxene hornfels. This halo corresponds with le. Sub - facies that introduced by Pattisan & Tracy (1991).

In southern margin of Central Alborz near Garmsar City many of Tertiary salt diapirs are outcropped. Only in the western part of this city many of igneous rocks with calcareous caprocks can be seen. Some evidence has indicated that, these rocks in late Eocene-early Oligocene during the deposition of evaporate sediment were erupted. Petrography studies of these rocks indicate that, they are tholeiitic basalt, olivine basalt, andesit basalt, diabas and alkali basalt. Based on geochemical analysis, magmatic source of these rocks were alkali-potassic to sub-alkali, These rocks in some diagrams mainly located in basalt, basaltic andesit, trachy andesit basalt, trachy basaltic and basanit regions. The concentration variations of main elements in igneous rocks versus show that during mamatic differentiation a new magma with moremafic composition was mixed with this magma. The abundant concentration of rare and trace elements in these basalts and interplates alkali basalt (continental basalt and oceanic island basalt) have the best correlation. Based on triangulate diagrams for different tectonic environment, these basalts were also well correlated worth within plate basalts.Comparison of spider diagrams of within plate basalts and oceanic basalt and these basalts indicated that, these basalts like within plate basalts we enriched geochemistry of rocks and composition situation of these rocks show the presence of crustal contamination and indicates that, the within plate basalts, in this area were intercontinental basalt which were produced by refitting.

Miduk porphyry Copper Deposit is located in the north of shahr-e-Babak Town in Kerman and at the view point of geology is situated in Urima-Dokhtar volcanic belt.Copper mineralization is inside the porphyry granitoid has penetrated inside the ocean volcanic rocks. According to amount of weathering effect in this deposit, three geologic mining zone is distinct able. from the surface to depth, there are: Leached zone, super gene zone and hypo gene zone. Hypogene zone was studied at the point of oreperology. Pyrite and I chalcopyrite are in disseminated and veinlet form are the most important primitive sulfide minerals in the hypogene zone. The results show that a grandiorite and ca1x-Alklin body; 1- Type, Magnetite group; of miduk is placed in a volcanic environment out the water. This placement has been done in destructive tectonic regime setting of subduction continental margin. At the point of global and genetic comparison, This deposit is the same of porphyry copper deposits in the continental margin of cordilleran belt in America (Andian Type) and is comparable with lowell and guilbert model (1974). The porphyry copper deposits like Miduk in Urmia-Dokhtar belt may have been generated because of subduction and here agter partial melting of tethys oceanic crust beneath the Central Iran continental crust.

In this research we had studied had studied Dalichai formation (Middle Jurassic) at Kuh-e-sharaf (Eastern Alborz) in detail. This transgressive sequence (Dalichai formation) with 285 meters in thickness folleowes with distinct disconformity on the clastic rocks of the shemsjak formation.It contains a rich fauna of ammonites and rangs from late bajocian to late callovian.