Hassan Abad Region is located 180 kilomteres to the northeast of Esfahan along Uremia – Dokhtar Magmatic Belt. Most outcrops in this region belong to Eocene volcanic activity with rhyolite and tuff composition. The rhyolites consist of quartz, plagioclase, alkali feldspar minerals and glass fragments. The tuffs are of crystaline, vitric and ignimbrite typecropping out as interconnected domes along the great fault of Qom – Zofreh with a northern – southern trend. According to geochemical studies and diagrams, the constituent magma of the respective rocks with rholitic composition is classified in calc-alkaline series, and based on spider diagrams of the samples in the studied area, originates from partial melting of custral rocks. Discordant trends of Uremia – Dokhtar Belt and reverse faults as well as regional dykes according to Rieldel model imply that most volcanic and volcanoclastic rocks are subject to simple shear stress in the shear – compressional system (Bargowhar and Marbin – Rangan faults and Kachumesghal – Ganyan fault).

This region is located 330kmfar from north of Tehran in Gilan province. According to tectono-sedimentary classification of Iran (Nabavi, 1977), this region is located in Alborz-Azarbaijan zone. The area of understudied region in Gilan province is 450 km2 that is located in south and west part of Amlash city. In this region the upper part is formed of an Ophiolite set that its uplifting time is upper Cretaceous. Constitutive rocks of this part are rocks of old ocean crust and totally consist of carbonate cretaceous sedimentary rocks, pillow basalts (include basalt, basaltic andesite, andesite and trachyte terms), delorite and gabbro dikes. Totally it can be concluded that petrologic and geochemical studies in southern of Amlash indicate a magmatic event in various tectonic environments in a way that each rift environments, active continental and intra-plate margins are acceptable for some of the samples. In the other hand, there are evidences that show magmatic differentiation and crust pollution happened in understudied rocks. Therefore, clear and detailed interpretation about tectonic environment of these magmatic events is not possible.

The area of study is located 120 Km north-east of Shahrood city. In terms of structure and geological classification, this area is located in the northern part of central Iran zone. Granitoids of Troud ranging from monzonite to granite. The main minerals of granitoids are quartz, plagioclase, and orthose. The accessory minerals are biotite, hornblende, sphene, and opaque minerals. Various textures of granular, graphic and prethite are observed in these rocks. Based on various diagrams of major and trace elements, this rock is I-type arc calk-alkaline, Meta to para-aluminous with continental origin form at subduction zone. All these characteristics, combined with low Al2O3/(FeO + MgO + TiO2) and (Na2O + K2O)/(FeO + MgO + TiO2) ratios and high Mg# values, suggest an origin through dehydration melting of alkaline mafic of lower crustal source rocks.

This paper elucidates the compositional studies on clinopyroxene, plagioclase of basalts to andesitic rocks of Torud area to understand the geotectonic and geothermobarometry conditions. Early Eocene-Oligocene calc-alkaline volcanic rocks are exposed around Torud in the Central Iranian zone. Volcanic rocks consist of basaltic, andesite basalt, Tracyandesite, and andesite. Minerals in the volcanic rocks exhibit degrees of disequilibrium features. Plagioclase as dominant mineral in these rocks generally displays oscillatory zoning. Mineral chemistry studies show that clinopyroxenes in the volcanic rocks are diopside, augite and plotted in medium pressure field. The clinopyroxene composition yields the crystallization temperatures 900°C - 1000°C. The mineral composition indicates that these rocks are formed in a tensional environment.

There are metabasite exposures inside ophiolitic belt of northwest Sabzevar that metamorphosed under high pressure granulite facies. On the basis of mineralogical paragenesis, reactional textures between different mineralogical assemblages, textural and mineralogical relations between inclusion and porphyroblast and stability fields of different mineralogical assemblages, five stages of evolution of metamorphism is distinguished. These stages consist of prograde metamorphic stage (M1), peak metamorphic stage (M2), garnet kelyphitisation as the formation of Pl+Am symplectite and corona (M3), partial or quite replacement of garnet by Am+Chl+Ep assemblage (M4) and the occurrence of Prh-Zl veins. The thermobarometric data of these stages represent a clock-wise P-T path. This path is consistent with the collision of the Iranian micro-continent with the Alborz block and later erosion and uplifting.

P>The ophiolitic melange of the Sabzevar Range (northern Iran) is a remnant of the Mesozoic oceanic basins on the northern margin of the Neotethys that were consumed during the Arabia-Eurasia convergence history. Occurrence of km-scale, dismembered mafic HP granulitic slices is reported in this study. Granulites record an episode of amphibole-dehydratation melting and felsic (tonalite/throndhjemite) melt segregation at c. 1.1 GPa and 800 degrees C. In situ U(-Th)-Pb geochronology of zircon and titanite grains hosted in melt segregations points to an Early Cretaceous (Albian) age for the metamorphic climax. Results of this study (i) impose reconsideration of the current palaeotectonic models of the Neothetyan convergent margin during the Early Cretaceous and (ii) argue that punctuated events of subduction of short-lived back-arc oceanic basins accompanied the long-lasting history of the Neotethyan subduction in the region.