Petrology
Morteza Delavari; Khadijeh Ghorbani; Amir Ali Tabbakh Shabani
Abstract
The Urmieh- Dokhtar magmatic belt (UDMB) lying parallel to the Zagros suture zone is resulted from the subduction of Neotethyan oceanic lithosphere beneath the southern margin of Eurasia. The studied volcanic rocks of the Razan- Avaj area are part of UDMB magmatism. These rocks are composed of olivine-basalts, ...
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The Urmieh- Dokhtar magmatic belt (UDMB) lying parallel to the Zagros suture zone is resulted from the subduction of Neotethyan oceanic lithosphere beneath the southern margin of Eurasia. The studied volcanic rocks of the Razan- Avaj area are part of UDMB magmatism. These rocks are composed of olivine-basalts, basalts and occasional trachyandesites with alkaline nature. The interlayered stratigraphic relationships of volcanic horizons with sediments of Qom Formation implies Oligo-Miocene age. Major and trace element contents of volcanics and chemical modeling are indicative of significant role of olivine + clinopyroxene + plagioclase fractional crystallization (35-45%) in melt compositional trend. Bulk rock chemistry of theses rocks displays LREE/HREE enrichment and lack of HFSE negative anomaly similar to oceanic island basalts (OIB). It seems that after Eocene magmatic flare-up with obvious magmatic arc signatures in UDMB, during the Oligo-Miocene the origin of magmas has shifted to a deeper asthenospheric mantle. Probably, after the initial stages of the Arabian-Eurasian plate collision in the Late Eocene-Early Oligocene and the slab roll-back, an upwelling asthenospheric mantle is injected into the mantle wedge and is weakly affected by the subduction material, which is the source of Oligo-Miocene melts.
Economic Geology
Morteza Delavari; Amir Ali Tabakh Shabani; Samaneh Ghanbari
Abstract
The Oligocene dacitic volcanic rocks display widespread exposures in south of Julfa (eastern Azerbaijan). They generally show porphyritic to hyalo-porphyritic textures with major minerals of plagioclase, amphibole, quartz and biotite. Electron probe micro analyzer (EPMA) data indicates oscillatory zoning ...
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The Oligocene dacitic volcanic rocks display widespread exposures in south of Julfa (eastern Azerbaijan). They generally show porphyritic to hyalo-porphyritic textures with major minerals of plagioclase, amphibole, quartz and biotite. Electron probe micro analyzer (EPMA) data indicates oscillatory zoning and chemical variation of amphiboles (pargasite and edenite). The plagioclase crystals are, chemically, andesine (An= 29-51%) which mostly display oscillatory zoning. Based on geobarometric calculations, plagioclase displays pressures of 5 to 8 kb and amphiboles demonstrate different pressure ranges of 1.5 to 3 and 5 to 9 kb. Moreover, geothermometric calculations of plagioclase and amphibole provide temperatures of 1020-1050 and 850-900 °C, respectively. On the basis of geobarometric results, crystallization and growth of the minerals took place in magmatic chambers of different levels. Some of the amphiboles nucleated in lower continental crust and subsequently grown during magma ascent in middle crust whereas some others crystallized in the upper continental crust. Therefore, existence of minerals of different levels inside the studied rocks could be related to magma mixing in shallow magma chambers.
Petrology
Fahollah Mossavvari; Reza Zarei Sahamieh; Adel Saki; Amirali Tabakh Shabani; Ahmad Ahmadi-khalaji
Abstract
The metamamorphic rocks of Sanandaj-Sirjan Zone (SSZ) in the west part of Hamedan at CheshmehGhassaban village were intruded by olivine gabbro- gabbro at the middle Jurassic. The rocks consist of olivine, clinopyroxene, plagioclase, phologopite, brown amphibole and biotite and belong to alkaline series, ...
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The metamamorphic rocks of Sanandaj-Sirjan Zone (SSZ) in the west part of Hamedan at CheshmehGhassaban village were intruded by olivine gabbro- gabbro at the middle Jurassic. The rocks consist of olivine, clinopyroxene, plagioclase, phologopite, brown amphibole and biotite and belong to alkaline series, derived from partial melting in the stability field of a garnet peridotite. Moreover,LREE enrichment in chondrite normalized REE pattern, and relatively high ratios ofLaN/YbN (6.65-11.25)، Nb/Yb(22-22.38),Th/Nb(0.07-0.16) and Nb/Y (>1)indicate that the rocks originatedfrom an ocean island basalt like (OIB-like) sublithospheric mantle source and juxtaposed with and intruded into continental crust. With respect to geodynamic model of SSZ in the Alvand area in the middle Jurassic, ascribed to the subduction of the Neo-Tethys oceanic crust below the SSZ, the "Ridge-Trench" subduction model is proposed for thes egabbros. Based on this model, the subduction of the active spreading center of the Neo-Tethys oceanic crust produceda slab window in the subducted oceanic lithosphere, allowing infiltration of astenospheric hot OIB-like melt into SSZ. In addition, the development of a very substantial volume of S-type granitoid rocks in the Alvand granitoid complex of Hamedan region can be attributed to the melting of the metapilitic rocks due to ridge subduction events
Geological Environment and Engineering
Abbas Fallah; Soroush Modabberi; Alireza Sayyareh; amir ali Tabakh shabani
Abstract
For study the effects of traffic and urban pollution on heavy metals concentration, 40 soil samples were collected in green areas of Karaj city with different uses and 5 samples as geochemical background were collected from unpolluted areas and margins of the city. The samples after preparation were ...
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For study the effects of traffic and urban pollution on heavy metals concentration, 40 soil samples were collected in green areas of Karaj city with different uses and 5 samples as geochemical background were collected from unpolluted areas and margins of the city. The samples after preparation were analyzed by ICP-OES method. Statistical data were analyzed by SPSS (version 21) software. Relation of elements and pollution indexes determined for noticeable elements in karaj city. The Statistical analysis indicate that the distribution of metal such as: Cd,Cr,Cu,Ni and Zn in soil of Karaj city are similar to each other and often in the central part of Karaj city( Jahanshaher garden , Family park) Compared to other regions is more. Heavy metals in farmland soil are lower than other lands (garden, park). These findings are matching with the results reported by other researchers (from other regions of world). As, S and Zn have different distribution than other listed heavy metals. The Mean value of Zn, P, Ni, Cu, Cr, Co and Cd in the central part of Karaj city is more than other regions. PI value in the Karaj city soil for various heavy metals are respectively as: As>S>P>Zn>Pb>Cu>Ni, Cr>Cd The heavy metals pollution index for Karaj is 1.75, which is one of the moderate pollution soils.
