Iranian Journal of Earth Sciences
Volume:11 Issue: 3, July 2019

The Fahliyan Formation of the Khami Group is the most important oil and gas reservoir in southwestern Iran. The formation attains a thickness of 435.5 m in the oil well X2 in Dorood oil field, Persian Gulf. It is represented mainly by thin-bedded limestones. This formation unconformably overlies the evaporate late Jurassic Hith Formation and conformably underlies the Gadvan Formation. Integrated palaeontological and sedimentological studies supported by an analysis of 150 thin-sections led to the identification of 21 benthic foraminiferal genera dominated by agglutinated forms with an additional 8 algal genera. Two foraminiferal biozones of Berriasian through Hauterivian age include the Pseudochrysalidina (Dokhania) arabica acme zone and Pseudocyclammina lituus- Coscinoconus assemblage zone, and an algal zone includes the Salpingoporella annulata range zone have been recognized. The correlation of the lower Cretaceous petroleum source rock in the Persian Gulf with regions from Tethyan Realm is limited by the lack of the analog formation that can be used for comparison. In this way, the foraminiferal zones are correlated with coeval zones in south and southwest of Iran.

Sedimentation in the dune fields of the Sistan Plain of Iran is the result of deposition of fine-grained sediment downstream of the Helmand River. Due to poor adhesion and low moisture content of soil particles, and the strong renowned Levar wind, dune fields mostly of Barchan and Nebkha types are created. This study aims to assess the physical, morphological and mineralogical characteristics of surface (S) and sub-surface (S-S) sediments and their genetic relationships with the aeolian sand surface. For this purpose, 48 S and S-S sand samples were prepared from Niatak Corridor (NC) east of Sistan and were analyzed to determine their physical and mineralogical properties by dry sieving, scanning electron microscopy (SEM) and optical microscopy methods. Results show that the physical characteristics of S and S-S sand particles, such as sorting, roundness, minimum elongation projection, Riley sphericity, morphoscopic and mineralogical characteristics, have no significant difference. The study of thin sections showed that all samples generally contain quartz, feldspar, calcite, gypsum and lithic components. This confirms that the source of S sand dunes is local and consists of the buried layers of sands in the close vicinity. Therefore, the Hamoun Lake are most likely not a source of regional sands. The local existence of Yardang also supports the conclusion of this research.

Regional exploration and identification of anomalies can be done by geochemical data resulted from stream sediments. In this paper, fractal methods of concentration-number and concentration-area were used for regional studies, and abnormalities of elements including gold, arsenic, bismuth and mercury were studied. Statistical processing of these elements took place with the help of 1063 samples of stream sediments in the Saqez 1:100,000 sheet (Kurdistan Province). The elements were analyzed in the laboratory of the Geological Survey and Mineral Exploration of Iran by ICP-OES method and Au element was analyzed by Emission Spectrograph method. According to the position of geology, existing structures and the dominant rock type, the comparison between the map prepared methods of concentration-number and concentration-area was conducted in Saqez sheet. In general, the results of the two methods showed that in the south, southwest, center and west of the region, the concentration of these elements is increased, and presence of ore promising areas is high in these areas. Concentration-number method showed a good overlap with concentration-area method; making extensive geochemical halos and encompassing known ores of Qolqoleh, Kervian and Qabghlojeh, it follows the expected process of mineralization in Sanandaj-Sirjan zone.

Mashhad Plain affects by a series of active faults in the northern margin of the Binalud and the southern margin of the Kopet-Dagh mountain ranges. The activity of these faults forms the morphology of the stepped bedrock of the Plain. In addition, the faults’ activities in the Quaternary period are the main effective parameters in thickness and texture of aquifer deposits in Mashhad Plain. In this regard, one of the active and important faults in Mashhad Plain is Tous fault, which runs from the northwest of Mashhad Plain into the city of Mashhad. The present research aims to analyze the effect of this fault on groundwater resources in the north of Mashhad Plain. For this purpose, ancient geoelectric studies and many well logs data are gathered, interpreted and by the combination of all of the geology information a new model for groundwater resource of the area proposed. The results of this study indicate that activities of Tous fault results to the uplifting of the Neogene Marly bedrock of Mashhad Plain, which such as a barrier prevents the flow of groundwater from the northern plain to the main aquifer of Mashhad Plain, and practically has divided the alluvial aquifer of Mashhad Plain into two parts. The maximum sediment thickness can be seen adjacent to the fault in the north of the Tous region and the tomb of Ferdowsi.

In the southeast of Iran (SE Bam), there is a collection of volcanic rocks with andesite, basalt and trachyandesite composition. The textures of these rocks are often porphyritic with microlithic, porphyric cavity, and sometimes glomeroporphyritic, sore throat trachytic. Main minerals include olivine, clinopyroxene, plagioclase and secondary minerals including opaque minerals, Iddingsite, secondary biotite, chlorite and calcite. The analysis of magma textures gives us valuable information about magmatic processes.   Micro textures in plagioclase of volcanic rocks in the region are divided into two groups: a) texture-linked to crystalline growth including: sieve texture, oscillatory zoning and degraded surfaces and b) Morphological textures such as glomerular crystals. Sieve texture and zoning in crystal represent processes such as magmatic mixing and abrupt reduction of pressure and, in general, unbalanced conditions in magmatic reservoirs. Based on electron microscope studies, plagioclase of igneous rocks of the region is within the boundaries of labradorite and bytownite.  

In the southeast of bam, there is a collection of volcanic rocks with andesite, basalt and trachy andesite composition. The texture of these rocks are often porphyritic with microlithic, porphyric cavity, and sometimes glomerulophorphuri, sore throat trachytic. Main minerals include Olivine, Clinopyroxene, Plagioclase and secondary minerals including opaque minerals, Iodenzyte, secondary Biotite, Chlorite and Calcite. Sieve texture and zoning in crystal represent processes such as magmatic mixing and abrupt reduction of pressure and, in general, unbalanced conditions in magmatic reservoirs.

Estimation of mineral resources and reserves with low values of error is essential in mineral exploration. The aim of this study is to estimate and model a vein type deposit using disjunctive kriging method. Disjunctive Kriging (DK) as an appropriate nonlinear estimation method has been used for estimation of Cu values. For estimation of Cu values and modeling of the distribution of Cu in Chelkureh, samples have been taken from 48 drill holes in Chelkureh, and the values of Cu have been analyzed. Resulting data from analyzing Cu values were converted to standard normal values using Hermite polynomials. Variography has been done in the Chelkureh deposit. After studying variograms in different directions, it was found out that the ore deposit has a mild anisotropy. The best-fitted variogram model was considered for disjunctive kriging estimation. The model consists of a pure nugget effect with 0.46 amplitude plus a spherical scheme with sill 1.20 and range 140 m. Consequently, a three-dimensional model of estimated value and error estimated value was provided by disjunctive kriging to divide the ore into an economic and uneconomic part. The models based on the estimate of the DK method in the study area exhibited an increasing trend of concentration from the center to North. Finally, validation between the disjunctive kriging carried out by using cross-validation. The result showed that the correlation of estimated values and real values was strong (63.4%).