Petroleum geology
Nasim Maleki Sadeghi; Ahmad Ahmadi-khalaji; Reza Zarei Sahamieh; Zahra Tahmasbi
Abstract
The study area is a part of Zagros Folded zone and located in the Lorestan sedimentary basin. In this regard, three areas with high bitumen potential were selected, which include the northern area of Kuhdasht, northeast of Poldokhtar and southeast of Sepiddasht. In the study areas, bitumens are exposed ...
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The study area is a part of Zagros Folded zone and located in the Lorestan sedimentary basin. In this regard, three areas with high bitumen potential were selected, which include the northern area of Kuhdasht, northeast of Poldokhtar and southeast of Sepiddasht. In the study areas, bitumens are exposed as veins between the fractures and as interlayers with host rock that the thickness of these veins is between 10 cm to more than 1.5 meters. Field studies showed that the studied bitumens have developed in the shales of Amiran Formation. Based on the results of organic geochemistry, 80.10 to 93.60% of the extractable saturated compounds are in the category of asphalts and have a very good quality in terms of thermal maturity (maturity of organic matter). The studied samples are formed in a reducing to slightly reducing sedimentary environment. Drawing the diagram of C34/C35 Homohopane vs. C29/C30 Hopane for the studied bitumens showed that the generating rocks of the studied samples are carbonate and detrital in nature. This can be explained by the lithology of bituminous formations such as Ilam and Gurpi formations in the study areas. The triangular diagram of regular streams (m/z = 217) for the studied bitumens showed that the source of organic compounds of the studied bitumens is mostly marine with a small amount of entry from dry environments. Severe depletion of the carbon isotope (average -28.83 per mill) indicates organic origin and biomass in these samples. On the other hand, sulfur compounds with depletion (-12.16 per mill) indicate formation in a reduced to semi-regenerated sedimentary environment and oxygen isotope data (+15.03 per mill) indicate the formation of organic matter of sedimentary origin.
Petrology
Nasim Askari; reza Zarei Sahamieh; Jafar Omrani; Mohamad Heshem Emami; C., Vaccaro; J. F. Santos
Abstract
Zarrin Mafic dikes, which outcrop in the Western Yazd block, Central Iran, trending NW–SE, emplaced into the Zarrin granitoid. They are sub-alkaline gabbro; characterized by intergranular and mylonitic foliated texture. Geochemical data reveal the Zarrin mafic dikes are from the partial melting ...
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Zarrin Mafic dikes, which outcrop in the Western Yazd block, Central Iran, trending NW–SE, emplaced into the Zarrin granitoid. They are sub-alkaline gabbro; characterized by intergranular and mylonitic foliated texture. Geochemical data reveal the Zarrin mafic dikes are from the partial melting lithospheric mantle, a spinel-peridotitic source. Furthermore, they are characterized by 87Sr/86Sr ratio of (0.7044-0.7028) and 144Nd/143Nd ratio of (0.5123- 0.5122), that consistent with the derivation from a lithospheric mantle. Their primitive mantle normalized trace elemental patterns display enrichment in LILEs compared to HFSEs, and positive Rb, Ba, and U but negative Ta, Nb, Th, and Zr anomalies, carrying characteristics subduction-related magmatism and metasomatism by subduction-related fluids. The petrogenesis of the Zarrin mafic dikes are related to melting of the lithospheric mantle, and upwelling asthenospheric mantle in the extensional basin which was associated with the subduction.
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
M. Amiri; A. Ahmadi Khalaji; Z. Tahmasbi; R. Zarei Sahamieh; H. Zamanian
Abstract
The intrusive bodies of Almogholagh Batholith, in western Iran are emplaced into the Sanandaj–Sirjan magmatic-metamorphic zone and comprise three main groups: (1) gabbro-diorite, (2) quartz syenite, and (3) quartz monzonite, which crop out in most of the area. The quartz syenite and quartz monzonite ...
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The intrusive bodies of Almogholagh Batholith, in western Iran are emplaced into the Sanandaj–Sirjan magmatic-metamorphic zone and comprise three main groups: (1) gabbro-diorite, (2) quartz syenite, and (3) quartz monzonite, which crop out in most of the area. The quartz syenite and quartz monzonite rocks, having characteristics such as metaluminous, generally ferroan, alkalic to alkali-calcic types, high content of Na2O+K2O, Zr, Ce, Ga, Y, Nb, Ta, REE, and depletion in Eu, Sr and Ti, show the features of borderline between A1 and A2-type granitoids with more A1-type affinity. On the basis of the results of the various diagrams, the gabbroic-dioritic rocks show between A1 and I-type granitoids nature with more I-type affinity. Distinctive peak patterns in spider diagrams accompanied by (La/Yb)CN values of 2.4 to 6.1 and Ba/La ratio >3 indicate magmatic activity in a volcanic arc environment, and the characteristics (Ba/Rb)CN<1, (Ba/Th)CN 143Nd/144Nd > 0.512638, εtNd >0, εtSr >0, high content of Nb, Ta and very high content of Zr (589 ppm) indicate that there was a subsidiary subduction after the initial collision for a long time and the magmas of Amogholagh batholiths were originated from mantle wedge, overlying the subduction zone or from mantle components around fragments resulting from delamination between continental crust and mantle lithosphere, demonstrating the involvement of subduction zone fluids, high flux of mantle-derived halogen-rich volatiles, and contamination within the crust during the petrogenesis of intrusions.
