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
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
mohsen chekani moghadam; Zahra Tahmasbi; Ahmad Ahmadi-khalaji
Abstract
Study area located on N to NW of Rabor city in Kerman province that belong to Uromieh-Dokhtar Magmatic Belt (UDMB). Most of rock lithology in this area including diorite, granodiorite and granite which have been exposed in volcanic sequences. Based on geochemical studies all of rocks in this area classified ...
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Study area located on N to NW of Rabor city in Kerman province that belong to Uromieh-Dokhtar Magmatic Belt (UDMB). Most of rock lithology in this area including diorite, granodiorite and granite which have been exposed in volcanic sequences. Based on geochemical studies all of rocks in this area classified in two groups: (1) some igneous rocks show adakitic affinity with high SiO2 (61.49–66.78 wt. %), Al2O3 (15.72–17.74 wt. %), Sr (374–602 ppm), Sr/Y (34–53), (La/Yb) N (8.35–16.88) and low Y values. (2) another rock group that distinguished in study area including various granitiods rocks with typical calc-alkaline characteristics that distinct from adakitic types such as: SiO2 (63.07–72.32 wt. %), lower Sr/Y (3.8–13.2) ratio and higher Y (21.7–31.6 ppm) and Yb (2.29–3.26 ppm) contents, and the lowest Sr (119–297 ppm) and (La/Yb)N (3.02–11.13) values relative to adakitic groups, with distinctly negative Eu [(Eu/Eu*)N= (ave. 0.49)] anomalies.The adakitic rocks most probably originated from thickened mafic lower crust (garnet amphibolite) with garnet+ rutile ± plagioclase as residual minerals in the source corresponding to depths of >50 km, and calc-alkaline rocks were probably generated in shallow depth than adakitic groups in mid-lower crust (dominant amphibolite) correlating to depths of