منصور وثوقی عابدینی

The study area, situated 50 km north of Ghaemshahr, structurally belongs to the Central Alborz tectonic zone. The volcanic rocks of the area, including basalt, andesite, trachyandesite, and dolerite are the products of fractional crystallization and some contamination processes. Clinopyroxene, olivine, and plagioclase are the main minerals of these rocks. Porphyritic to mega-porphyritic texture with microlithic, glomeroporphyritic, and amygdaloidal matrix are observed in these rocks. Plagioclase, hornblende, and pyroxene can be considered the main mineral phases of these rocks. The rocks are enriched in LIL and LREE elements and depleted in HFS elements. The ratios of trace elements and rare earth elements in the studied region indicate that the basalts were formed by melting a garnet bearing peridotite at great depths and pressures. Negative Ce anomaly, Nb negative anomaly, Pb positive anomaly the role of continental lithosphere in contaminating the magmatic sources of volcanic rock in the study area. The Pb/Ce ratio similar to ocean island basalt (OIB) sources, induces OIB sources, the asthenospheric mantle, in the initial formation of basaltic magma. it can be concluded that the volcanic rocks of the area have formed in an intra-plate environment in an extensional regime.

In the north of Jirandeh and east of Lushan, which are located in the mountains south of the central Alborz, a series of volcanic rocks are unconformablly located on the Middle Eocene limestone. These rocks have alkaline affinity of different types of lamprophyre and are studied for the first time from the petrology point of view. The texture of these rocks is porphyric to microporphic with microlithic matrix. The phenocrysts and microphenocrysts of the collected samples are generally olivine, alkaline pyroxenes and biotite, which are located in olivine, pyroxene, plagioclase, amphibole, very fine nepheline crystals, apatite and metal ores groundmass. Geochemical studies of these rocks indicate that these rocks are alkaline lamprophyres and the magma is the result of partial melting of an asthenospheric mantle source similar to OIB. They are classified in garnet lherzolite facies and were emplaced in an intercontinental rift tectonic environment.

Takab-Mahneshan's metallogenic area is essential in gold mineralization, and it is a part of the northern Urmia-Dokhtar magmatic belt. The northern Urmia-Dokhtar has two distinctive features. It contains the Precambrian basement, and the young Mio-Pliocene magmatism rocks overlie its Precambrian basement. Precambrian basement has two different compositions, oceanic and continental crusts (gneiss, granite, mica-schist, greenschist, amphibolite, serpentinite, marble). The Young rocks are composed of hyaloclastite, acidic tuff, andesitic-basaltic, acidic to intermediate intrusions (diorite, granite), limestone, and marl of Qom formation. We categorized the Young rocks into four phases based on their age and positions. The mutual effect of the basement and young magmatism --in the latest phase --creates hydrothermal solutions in the form of a heat engine. The heat engine has caused rotation and variety, increasing mineralization in the area. As a result, there are mines, deposits, gold indications, and some associated gold elements, including Tuzlar, Bayche Bagh, Baghcheh at Mahneshan area, Zarshuran, Agh-darreh, and Ay-Qalesi in Takab. The Tuzlar and Baghcheh deposits with gold mineralization are in a Silicic-argillic zone, including pyrite, gold-bearing silica, argillic and ferrous hydroxides minerals. The Ay-Qalesi polymetallic deposits often contain zinc and lead. The Zarshuran and Agh-darreh deposits are the gold types that the first one has a variety of mineralization of sulfides and sulfosalts. The second one has simple gold mineralization, and finally, the Bayche Bagh deposit with polymetallic type includes chalcopyrite, pyrite, rutile, arsenopyrite, sphalerite, bornite, smaltite, chloanthite, azurite, and malachite minerals.

Tarom mountains are located at the southwestern end of the Alborz mountain range with an approximate northwest-southeast direction. Tashvir region is a part of the northern margin of the Tarom mountains. Most igneous rocks in this area include basalt, andesitic basalt, and interlayers of tuff. Enrichment of LIL elements with positive anomalies of Ce, P, Sm, and depletion of Nb, Ta, Zr, Hf, and Th, elements and also K2O/Na2O and Ba/Rb ratios in the rock samples of Tashvir area, indicate magma contamination with the lower crust. The evidence of crustal contamination and the ratio of Nb/Y and Zr/Y in the samples indicate that the basalts of the Tashvir region belong to the source of the plume. Alkaline, shoshonitic, and peraluminous nature, REE enrichment (i. e. Ba, Rb, and Sr), low titanium content, origin, and depth of magma indicate they're belonging to the rift environment. In this study, in addition to determining the characteristics of igneous rocks in the Tashvir area, the results of several previous studies are plotted on the map of the Tarom mountains. Accordingly, the tectonic setting of the Tarom range is divided into two parallel sub-regions with magmatic arc and rift-type eruptions, which expansion of this rift zone has stopped before it evolve as a back-arc basin.

The Oligo-Miocene intrusive masses of northern Sarduieh are located in the Urumieh-Dokhtar zone and the lithology is composed of granitoids include quartzdiorite, tonalite, granodiorite, granite and granophyre. Mineral chemistery studies showed that the amphibole minerals in diorite and granodiorites are calcic in composition and range from actinolite to magnesio-hornblende.  Geochemical and mineralogical results revealed that these bodies have been generated in the lower part of the lower crust at a temperature of 700 to 750 °C, with an oxygen fugacity of -13.57 to -15.76 and a low pressure of 1 to 3 kb. These amphiboles are subduction-related and in accordance to the tectono-magmatic features seen in these massifs, they show characteristics of subduction and active continental margin environments.

The leucocratic granite emplaced as small masses and dykes in the Alvand batholith. The leucocratic granite consists of tourmaline alkali granite, biotite alkali granite, arfvedsonite alkali granite, rutil alkali granite, and biotite- muscovite granites with alkaline and peraluminous affinities. They show enrichments of LREEs relative to HREEs and LILE relative to HFSE with negative anomalies in Nb, Ta and Ti, in normalized trace element diagrams. The leucocratic granite of the Alvand batholith resemble A-type and can be further classified in two of A and A' types granite. The trace elements content of A-type is much higher than A'-type granite. Based on geochemical data, it seems that A- and A'-type granites were generated from partial melting of mantle source. As mantle magma ascends, fractionate and empalce into the crust, A-type leucocratic are formed with minimal contamination and A'-type leucocratic with significant contaminant with continent crust are formed. Field and geochronology data suggest that the leucocratic granite were generated in the late Jurassic, which is contemporaneous with the subduction of the Neo-Tethys oceanic crust beneath the central Iran. It seems that the leucocratic granites were emplaced during a local extensional phase as dykes and small bodies in the Alvand batholith.

From prospective of morphology, At first glance costal geomorphology is chaotic, intricate and complex. Geometrically fractal, estuaries have an internal order, and this order is so precise that the slightest irregularity can be obtained at any scale. In this study, fractal dimension in north of Persian Gulf shore for marine estuaries (Mouse’s estuary within the borders of Iran and Abd Allah’s estuary common border Kuwait and Iraq) and River meandering (Arvand roud River and Dalaki River in Iran North of Persian gulf) calculated by box-counting method. We used Arc GIS software and Landsat 8 of satellite image May 2016. In following, we make 10 partition scales from 100 KM to 100 M in each estuary and river of images. Our goal in this research is to investigate the pattern of order in the geometric geomorphological form of costal estuaries and Rivers meandering in the north of the Persian Gulf from a fractal point of view and its relationship to processes (geology, climate, hydraulic, etc.). Results show irregularity and disarrays in Mouse’s estuary by unit dimension fractal 1.5 to compare with Abd Allah’s estuary in Kuwait and Iraq by unit dimension fractal 0.67. Dimension fractal Arvand Roud River and Dalaki River are 0.53 and 0.46 respectively. In general, in this study, it can be concluded that geomorphological phenomena of fractal, the marine estuaries in the north of the Persian Gulf (especially Musa estuary) have entered the stage of turbulent edge. Also, on the 100-meter scale, fractal dimension of the Arvand Roud River is more turbulence than the Dalaki River. Geomorphological phenomena of estuaries and meanders at a scale of 100 meters are turbulent which shows the effectiveness of coastal and marine processes such as: tidal, marine waves, water erosion and loose sediments in estuaries and meanders in North of Persian gulf costal.

The knowledge of geomorphology, which is based on the knowledge of forms (phenomena) and processes (forces), is quite complex, altering and difficult to predict. Costal and rivers are controlled by hydraulics, wind, tectonic, physical, chemical, geological, etc. Also Due to the large role of parameters in them, they usually show unknown and chaotic behavior processes. Fractal geometry provides a mathematical model for some of the more complex shapes and components in nature, such as beaches, hills, tree bark, clouds, and so on. The fractal dimension is a useful feature for examining the texture of components, classified shapes, and graphical analysis in some disciplines. Every phenomenon in the world has order. Although there may be irregularities, there is an order at the heart of each irregularity that can be accessed with special tools and methods and find the pattern and order in it. Self-similarity is one of the essential attributes of fractal in nature that may be quantified by fractal dimension. Our goal in this research is to investigate the pattern of order in the geometric geomorphological form of costal estuaries and Rivers meandering in the north of the Persian Gulf from a fractal point of view and its relationship to processes (geology, marine, geomorphology, etc.).

In this study, in order to achieve the fractal dimension of coastal and River tributaries in the northern part of the Persian Gulf, the Landsat satellite image of May 8, 2016 was used. Arc GIS software was used to create Husdoroff networks. Also the Fishnet option was used to create square networks or houses on the area. The following relationship was used to obtain the fractal dimension of the geomorphological phenomena of River and sea estuaries in the Persian Gulf: Nn=C/(R_n^D ) Nn= is the number of variables available for a phenomenon, C= is the constant coefficient, Rn= is the dimension of a special linear coefficient, and D= is the fractal dimension.

Khowr Mousa These results indicate the presence of three stages of foreground, threshold and threshold stage. The threshold and anomaly stages start from scales of 20 and 1.5 * 1, respectively, with a fractional fraction of 0.65 and 0.46. The total fractal regression for all three comprehensive backgrounds, thresholds, and anomalies is about 1.5. Also Khowr Mousa is 24% bigger than Khowr Abdullah. Khowr Abdullah Khor Abdullah is located in Kuwait and Iraq. According to Abdullah, the threshold and anomaly communities on scales 5 and 1.5 * 1 begin with a fractional fraction of 0.76 and 0.43, respectively. The total fractal for the whole population includes, foreground, threshold and anomaly of about 0.677. Dalaki River At the Dalaki River, the Astana and Anomaly communities begin at scales of 5 and 1.5 * 1 with a fractional fraction of 0.41 and 0.6, respectively. The overall fractal dimension of the Dalaki River is 0.46. Arvand Roud River The Arvand River has three main communities or stages, the anomaly of which is very small, and the background community and its threshold are endurance. The overall fractal dimension of the Arvand River is 0.5305.

The study's findings show that Mousa's marine estuary with a total fractal size of 1.5 is more disturbing than Abdullah's marine estuary with a fractal size of 0.67, which could indicate that Abdullah's marine estuary is younger than Musa's estuary. Conclusion this study shows that the estuaries north of the Persian Gulf are controlled by the operation of water power processes such as tidal, waves and sediment erosion and Tectonic forces have no role in creating and controlling estuaries directly. In general, Khor Mousa tends to be more chaotic than Khor Abdullah and Arvand roud River meanders desire to be more chaotic than Dalaki River from point of wives fractal dimension. Geometrically fractal, rivers controlled by costal and marine process and erosion sediment.

This area has been located in a scene ETM No. 164-37 and ASTER linear band prediction satellite image No. AST-L1A:002:ASTL1A 0108220733380109011021. Such measured images in different band combinations will be used for extracting of geological structures and types of alterations (iron oxide, Argillite and Carbonate) and for detecting different stones and minerals of the ground, a spectrum range of 1.5 to 2.5 μ is very important.This range includes short to average IR range covering six linear band predictions (SWTR bands). On the other side, to use spectral reflectance curves of such minerals in USGSENVI spectral library for spectral analysis, it is necessary to resample the curves to the spectral range of ASTER. Linear Band Prediction methods, LS-Fit, Matched Filtering and BandRATIO used of ASTER images for all Minerals and iron alterations and for iron oxides there were also used visual interpretations and ETM images were used in band combination of RGB:531. Considering the petrological and geological situation of studied area (Scale 1:25000 of Kamoo), the type of Alteration and its index minerals detailed as below; Alteration of iron (Gotit, Hematit and Jarosit and Limotit), alteration of Argilic (Kaolinite, Motmorilonit, Ilite and Haloysite) and carbonate (Calcite and Dolomite) have been considered. Alterations present in remote sensing studies are in conformity with field and results obtained fromtypes of analysis conducted.

Sabalan volcano is located in the northwest part of Iran and 25km south of Meshkinshahr in the west Alborz-Azerbaijan structural zone. The rocks forming the Sabalan and its eastern and northern slopes are covered with significant amounts of white-gray pyroclastic deposits, which is indicating a very intense explosive activity at the last stage of this huge volcano activity. After conducting field studies and analyzing the results obtained using the mathematical calculations, a Plinian eruption was detected, and the extrapolated volume of the latest pyroclastic fall eruption was estimated 3.24 km3, and the eruption of Sabalan rated a VEI of 5. Also, due to the shape of the isopach curve, the role of wind in dispersing these deposits is from the west to the east. Also based on geochemical data, the Sabalan’s ignimbrite was rhyodacitic with calc-alkaline signatures and the high ratios of Ba/Nb>28 and Ba/Ta>450 are consistent with subduction related zone.

The 1/100000 geological map of Sarchah area in southern Khorasan province lies at 59˚,30′ to 60˚east longitude and 33˚to 33˚,30′ north latitude. The plain is covered by a wide spectrum of volcanic rocks with a compositional diversity from basic to acidic. In this research he parental melt's nature and evolutions via isotopic studies and measurements were studied t. Isotopic correlation plots of 143Nd/144Nd versus 87Sr/86Sr (Zindler and Hart, 1986) showed that extrusive igneous rocks found in this area were originated from those parts of mantle affected by subducted lithospheric slab or metasomatized by crustal substances. As a result, it is necessary to consider the role of parameters such as crustal mingling in dasitic-rhyolitic rocks formation Rhyolitic rocks are significantly affected by crustal materials. These rocks are characterized by higher levels of 87Sr/86Sr and lower levels of 143Nd/1444Nd.

The Bazman volcano is located in the Makran Magmatic Arc. The pyroclastic rocks and lava with rhyodacitic to basaltic composition and calc-alkaline affinities erupted from the central and lateral craters of this volcano during the Quaternary period. The primitive mantle normalized Multi-elements diagrams show a relatively high abundance of LIL relative to HFS incompatible elements with negative anomalies of Nb and Ti. Their chondrite–normalized REE patterns are slightly enriched in LREE relative to HREE with negative Eu anomalies. These geochemical features suggest that the volcanic rocks of bazman formed in a subduction setting by partial melting of metasomatized mantle. On the base of La/Yb vs Dy/Yb and La/Sm vs Sm/Yb diagrams the sources of the magmas is phlogopite-spinel-lherzolite or/and phlogopite-garnet- lherzolite.

The study area is part of Alborz-Azarbaijan zone exposed in NW Meshginshahr. The volcanic rocks, Eocene in age, include tephritic phonolite and phonolithic Tephrite. They have phenocrysts of clinopyroxene, analcime, plagioclase and alkali feldspar and set in the same minerals in the matrix. Microprobe analyses on polished thin sections were performed by using an electron microprobe analyzer for chemical analyses of the clinopyroxenes. Based on these results, it is concluded that all clinopyroxene phenocrysts are diopsidic in composition and have relatively high Mg-numbers (0.66-0.90), variable Al2O3 (3.39-8.38 wt %), low TiO2 (<2.02 wt %) and Na2O (0.36-1.5 wt %) contents and low AlVI/AlIV ratios (mostly <0.3), suggesting relatively low-pressure crystallization conditions of the magma in the storage region. Also it is revealed they formed at temperature of 1005-1080 ºC and pressure of 4-5.5 kbars. The geochemical studies of clinopyroxenes remarkes they have clinopyroxene characteristics of alkaline rocks related to volcanic arc. Existence of normal and reverse zoning in clinopyroxens deduces differentiation and magma mixing were effective factors on evolution of the area rocks.

Heiran area is located in northwest of Ardabil and southwest of Caspian Sea. Field evidences indicate submarine volcanic activities in this area. The rocks in this area are of basaltic composition. The outcrops of pillow lavas, prisms, dykes and lava flows in different points are evidences showing the existence of oceanic crust in this area. Studies on other locations of southern margin of Caspian Sea as well as structural and petrological similarities between Heiran and these areas may confirm the fact that Heiran area is part of geo-suture of Caspian Sea southern margin. The submarine lavas in this area attributed to late Cretaceous-Eocene. With regard to petrographical characteristic, these rocks range from andesitic basalt to olivine basalt, and belong to alkaline series. The tectonomagmatic environment of these lavas is related to back arc basin. These magma originated from sub continental lithospheric mantle and formed in a supra subduction environment. During late Cretaceous-middle Paleogene, the closure of Sevan-Akera-Qaradagh led to the formation of marginal basin in the form of a back arc basin in the margin of Caspian Sea. The submarine lavas of Heiran likely originated from the volcanic activities in this marginal basin.

The studied granitoidic intrusion with about 50 km2 area is located in the SW of Kelardasht, one of the regions in Mazandaran Province. It is one of the pluton masses of the Central Alborz structural zone. The mass has an age between 56 ± 4 and 54 ± 4 million years (late Paleocene to early Eocene) and has intruded in the Mobarak and Shemshak formations. Petrologically it contains of two units of felsic (granite, qz-syenite, and qz-monzonite) and intermediate to mafic (monzonite to monzodiorite, diorite, and gabbro). The rocks of the first group especially granites and q-monzonites show many mineralogical and textural similarities and in which the evidences of magma mixing like rapakivi texture, poikilitic texture, acicular apatite, calcic plagioclase “spikes” in plagioclase, and micro granular mafic enclaves can be seen. These rocks have weak metaaluminous to peralumine nature (granite samples) and are richer in K2O+Na2O, K2O and the elements of Rb, Th, Hf than the second group. Due to the diagram related to REE, the rocks of this group have remarkable enrichment of LREE and related to the behavior of Y, Ba, Ce, and Zr in segregation process, they show the properties of low temperature I-type granites. In the second group, monzonite and monzodiorite rocks also show the evidences of alkaline metasomatism, associated with magma mixing textures including acicular apatite, septum biotites and anortite spikes in plagioclases. These rocks have meta alumine nature and show more richness in FeOT, MgO, CaO, bP2O5, TiO2, and the elements such as Sr, Ba, V, and Y than the first group; and also they show the properties of the high temperature I-type granites. Due to the geochemical evidences and the age of the mass, it can be categorized as post orogenic granite types, which have the properties between VAG and WPG. The isotopic investigation of 143Nd/ 144Nd revealed that only the granites of the region have can have enriched lithospheric source (negative εNd) and the other rocks have a depleted mantle source (positive εNd). According to the petrographical and geochemical evidences, magma mixing has played an important role in magma evolution, and therefore, the crust melting model by mantle-derived magma is suggested for the magma generation of the area.

Quaternary volcanic rocks are widely developed in NW of Ahar, NW Iran. Based on geochemical data, these rocks mainly consist of alkali basalts, trachybasalts, basaltic trachyandesites and trachyandesites. The major- and trace-element chemistry indicates that the lavas are dominantly alkaline in character. The studied rocks display microlithic porphyritic texture with phenocrysts of olivine, clinopyroxene, and plagioclase ± amphibole ± biotite. Major and trace element abundances vary along continuous trends of increasing SiO2, Al2O3, K2O, Na2O, Ba and Rb decreasing CaO, Fe2O3 * and Cr with decreasing MgO.The volcanic rocks in this area are characterized by the LILE and LREE enrichments and negative HFSE anomalies. The Sr and Nd isotopic ratios vary from 0.704463 to 0.704921 and from 0.512649 to 0.512774, respectively. CaO/Al2O3 ratios versus MgO, La/Sm ratios versus Rb and Ba and Zr versus Th suggest that that fractional crystallization was a major process during the evolution of magmas. AFC modeling and isotopic data as well as microscopic evidence, clearly indicate that crustal contamination accompanied by the fractional crystallization played an important role in petrogenesis of the trachyandesites. Also, geochemical and isotopic compositions indicate that magma mixing was not essential process in the evolution of Ahar magmas. Alkali basaltswith high 143Nd/144Nd ratio, low 87Sr/86Sr ratio and high MgO, Ni and Cr contents indicate that they crystallized from relatively primitive magmas. REE modelling and Trace element ratios indicate that the alkali baslats were derived by small degrees (1-3%) of partial melting from the spinel lherzolite.

The Mirkuh Ali Mirza gold mineralization is located in north Sarab in the Western Alborz Azerbaijan structural zone. Mineralization was formed in the form of a vein occurring in Neogene dacitic and rhyodacitic tuff along a series of NW–SE trending fault; Mineralization associated with quartz-sericite-adularia-calcite and pyrite(<1%) assemblages is a typical of low sulfidation epithermal gold mineralization. The fluid inclusion data from quartz minerals indicate homogenization temperature of 161-260°C and salinities of 0.5 to 6.5 wt% NaCl equiv. The variation in gold grade in quartz vein is 270-3240 ppb. The highest gold content is in lattice and breccias quartz that can indicate direct relationship between boiling to gold deposition. The idea is supported by coexistence of vapor dominant and liquid-dominant fluid inclusions.

Dali porphyry copper-gold deposit is situated geologically incontact of the Urmieh-Dokhtar magmatic belt and the Sanandaj-Sirjan zone in central of Iran and for the first time this deposit was investigated with using the satellite image processing (TM). In this research, the Northern part of the Dali deposit has been investigated in order to recognize the potential copper and gold-bearing target areas. The survey layers include the lithologic units, alteration, geophysical and geochemical results, tectonics, and copper mineralization. As a accurate decision can have a considerable effect on exploration plans, so in this research efforts have been made to make use of new combination methods including index overlay method, fuzzy logic method, and the analytical hierarchy process. These three methods support and complement each other and have revealed highly potential copper and gold mineralization areas. Among these methods, Analytical hierarchy process is the best method for combining the exploration data in this area. The investigations (for instance field evidences of outcrops, mineralization and also sampling of 7 trenches) carried out in the study area confirm this matter. Based on achieved results, geological perspective in central of studied area is appropriate for continuing mining exploration, especially for subsurface exploration in future.

In northeast region of Birjand، two distinct groups of volcanic rocks are exposed. Paleogene andesitic، dacitic and rhyolitic rocks as the major formation and younger mogearites، andesitic basalts and basalts that have erupted in the paleogene intermediate to acidic extrusive rocks background with the main trend of northwest – southeast. Investigations show that these two lithological complexes are the results of two different petrogenetical phenomenas and they have different genetic and geochemical characteristics. Intermediate to acidic volcanic rocks belong to active continental margin calcoalkaline rocks and they have formed from differentiation of a primary andesitic magma that are affected from crustal contamination at least in its rhyolitic and dacitic terms. The major nature of basaltic volcanic rocks is alkaline and they belong to intraplate basalts with mantle magmatic source that has erupted to the surface through extensional systems as the right lateral fault zones revenue.

The Mirkuh Ali Mirza area is situated at north of Sarab, NW of Iran. The study area is located in in Meshkin Shahr 1:100000 geological sheets at western Alborz-Azerbaijan structural zone. The major exposed rocks in the area are the Eocene and Neogene volcanic and subvolcanic rocks which include rhyolitic and dacitic tuff with intermediate to basic rocks. Recent geochemical stream sediment (1:25000 scale) and litogeochemical surveys showed base and precious metals in the form of veins at the periphery of a porphyry copper deposit model. Occurrence of this mineralization can be a small part of a big hydrothermal fluids circulation that its effects were developed in large scale up to 10km2 to porphyry copper mineralization. The mineralization model follow as; porphyry copper in center, gold and other base metals in periphery, anomalous concentration of Ag, As, Sb, Pb and Zn in more distal relative to central body and Mn, Ba and Hg can be found at the outer part of the system.

Baba-Ali and Galali iron deposits in west of Hamedan are emplaced within the Songhor volcano-sedimentary sequence of Sanandaj-Sirjan geological-structural zone. Mineralography and SEM-EDAX analyses on magnetite iron ores at both deposits for better understanding of mineralogy and crystal-chemistry of the ores have shown some interesting results. Studies on concentrations of some trace elements such as V, Co, Ni, Cu, Cr, Ti, Au, PGE as well as S and P impurities in the ore indicate that only some of the primary pyrites have considerable concentrations of Pt. It seems that other generations of pyrite and magnetite are depleted in these trace elements. Late stage hydrothermal fluids that lead to mineralization of pyrite in calcite-quartz gangue veins, have also been impotant for gold mineralization and pyrite has actually acted as a favorable carrier for Au. Detection of abundant phlogopite and trace element concentration patterns at Galali iron ore have strengthened volcanogenic magnesian skarn hypothesis.

It has long been recognized that the TAS diagram is not robust in classifying altered volcanic rocks and proxies using more immobile elements have been developed for that purpose. Through recent years, researchers introduced new discrimination plot based on immobile Th – Co elements as proxies of K and SiO2 are very useful to classify metamorphosed and weathered rocks especially in volcanic arc successions. The application of different elements, especially Th and Co, in classification of the Cretaceous volcanic rocks in Saghez – Piranshahr area is examined here. Based on petrographic studies, these rocks are andesites and basaltic andesites. Also sub-volcanic and related pyroclastic rocks accompany them. Low grade metamorphism in green schist facies and weathering process are affected studied rocks. Secondary minerals, such as epidote, chlorite, tremolite, actinolite, prehnite, pumpellyite, sphene, iron oxides, calcite and quartz, observed and are products of low grade metamorphism and alteration. Microprobe analysis reveal that plagioclase composition became homogenized (albitization). Rare K-Feldspar crystals are formed within rock matrix. Cretaceous volcanic units in Saghez – Piranshahr area formed in a volcanic arc due to obvious negative Nb anomalies in spider diagrams normalized to MORB. Samples show scattered patterns by using ordinary classification methods which use main oxides or some trace elements, therefore their nature and type could not be clearly recognized. But, Th-Co diagram let us to classify them as calc-alkaline basalts, basaltic andesites and andesites. Therefore, Th and Co are efficient tools for recognition of magma nature and rock types in such metamorphosed and weathered rocks.

The area is located about 230 km of southwest of Tehran. Based of geological observations، the plutonic rocks in the area consist of Neogene (Miocene) alkaline gabbro، gabbrodiorite، locogabbro and diabase. The Oligo - Miocene calc-alkaline extrusive rocks are dacite - ryodacite، andesite trachyandesite، hornblendandesite، basaltic andesite and trachybasalt. Studing on isotopic analyses of Nd and Sr indicate that surveyed area were contaminated with crustal rocks of Sialic composition. In isotopy geochemical studies، The Andesite samples are plotted in the limit of BSE; however، it seems that mantling rocks besides being settled in crust (esp. the upper continental crust) have been contaminated with in. The combination of BSE towards enrichment، from the proportion of 87Sr/86Sr has shifted; a sample of rocks shows this position. Spider diagrams related to trace elements of plutonic samples which are used for identifying the tectonic setting show intrusives are in the extensive regime; while the lavas don’t have a steady trend and are similar to subduction zones. This shows that the intrusives of the the investigated area are different genesis from the southern volcanic rocks.