Geopersia
Volume:11 Issue: 2, Summer-Autumn 2021

As a complementary work to the first part of the non-Euclidean distance measures in the spatial data decision analysis for mineral potential mapping (MPM), three families of squared L2, Shannon and combination are examined in this research to evaluate the performance of fifteen distances in geospatial data integration. The TOPSIS method as a well-known outranking method in the multi-criteria decision making (MCDM) problem was utilized in the MPM, where its distance kernel was substituted by these new families to investigate the efficiency of different distances in final preparation of the synthesized indicator layers. For consistency with the previous work (i.e. distance measures in spatial data decision analysis), the North Narbaghi porphyry copper deposit in the Saveh, Iran, was revisited as a deposit-scale prospecting zone. The ultimate goal was to prioritize the favorable zones for borehole drilling. The geospatial datasets were derived from a multi-disciplinary survey comprising of geological, geochemical and geophysical criteria. It is indicated that some distances could partially promote the performance of the mineral potential maps in comparison to the traditional Euclidian-based TOPSIS outranking method in the studied case, which is of considerable importance that deserves more investigation in the future.

Stratigraphic section of Margala Hill Limestone exposed in the Khaira Gali road section of the Hazara Basin, northwestern Himalayas has been measured, logged and sampled. The 96m thick section of Margala Hill limestone mainly consists of medium to thick bedded nodular limestone with intercalations of shale. This high resolution petrographic study of the formation has been done with an integrated approach of sedimentology, paleoecology and biostratigraphy and it mainly shows wackstone to packstone carbonate texture with different assemblages of Larger Benthonic Foraminifera e.g. (Assilina spinosa, Nummulites globulus, Ranikothalia sindensis, Nummulites mamillatus, Assilina subspinosa, Nummulites atacicus, Assilina granulosa, Operculina patalensis, Assilina laminosa, Ranikothalia nuttalli, Lockhartia conditi, Ranikothalia sahni, Lockhartia tipperi, Discocyclina dispansa, Discocyclina ranikotensis and Quinqueloculina), Bivalves and green algae. Five types of microfacies have been interpreted on the basis of carbonate texture and skeletal grains observed in thin sections. These microfacies include Rotaliids-milliolids mud-wackstone, Algal- bioclastic packstosne, Nummulitic wack-packstone, Assilinids wack-packstone and Discocyclina- Ranikothalia wack-packstone microfacies. The presence of these assemblages draws the conclusion that the deposition was occurred in closing Neo-Tethys on an inner to middle shelf environment at the northern extremity of the Indian Plate. Based on age diagnostic Foraminiferal assemblages, Ypresian, Early Eocene age has been designated to the Margala Hill Limestone.

The research is based on the numerical study of late Cenozoic compressional events of NW Himalayas, Pakistan. The study area lies in Potwar Basin and southern Hazara Basin bounded by north dipping Salt Range Thrust (SRT) and Panjal Thrust (PT) in south and north respectively. Four major thrusts i.e. Panjal Thrust (PT), Nathia Gali Thrust (NGT), Main Boundary Thrust (MBT) and Salt Range Thrust (SRT) are considered as major discontinuities in the study area. The main objective is to observe maximum principle stress (σ1) rotation along major discontinuities and to calculate total deformation. For this purpose, 2D finite element method (FEM) technique has been adopted and Ansys Workbench 19.2 is used, which provides the facility to simulate stress along major thrusts. Material properties i.e. density (2.5 - 2.75), Young’s Modulus (70GPa, 100GPa) and Poisson’s ratio (0.25) are used to calculate the possible results. Pressure (60MPa) is applied from north and remaining sides of geometry kept fixed. The results obtained show that the direction of maximum principle stress (σ1) is N-S but also rotates at discontinuities at different angles. At some segments along of major thrusts σ1 rotates 40-45 degree and at some points it becomes parallel to the fault plane. These rotations of σ1 are due to the change in material properties and fault angles. Strike slip movement has also been found along some segments of major thrusts.

The oil shale is a prodigious immature kerogen-rich resource, which represent an outstanding potential of oil generation through thermochemical processing at ~350-530°C depending on kerogen peculiarities. Kinetic investigation is one of the fundamental approaches for quantifying and evaluation of this process. The main aim of this study is thermal and kinetic investigation on the Garau oil shale (Early Cretaceous) from Lorestan province of Iran using TGA-DTG analysis (Thermogravimetry Analysis; TGA and Differential Thermogravimetry Analysis; DTG) under three constant 5, 10, 15 °C/min heating rate from 20°C up to 900 °C. The FTIR (Fourier transform infrared spectroscopy) analysis was used to evaluate the evolved gases during thermochemical decomposition of the Garau oil shale. The results show the combustion process of the representative sample from the Garau oil shale involves two main peaks of mass loss, which reveal two main reaction regions. The first reaction region is originated from organic matter (bitumen & kerogen) decomposition and the second reaction region is occurred as the result of calcite thermal breaking down. According to the average activation energy calculated for the organic matter decomposition (~183 kJ/mol), the Garau oil shale corresponds to medium-fast reaction rate kerogens, in consistent with IIS-kerogen reaction rate (144-218 KJ/mol).

Sedimentary successions in the eastern part of the Zagros Fold-Thrust Belt were episodically influenced by halokinetic events. The positive and negative accommodation spaces created by salt-induced uplifting and downbuilding processes caused variable sedimentation rates followed by stratal geometry variations and forming the halokinetic sequences. The Handun passive salt diapir, located in the north of the Bandar Abbas area is one of the best examples in which the evolution of the salt diapir could be analysed by the halokinetic sequences. These sequences are studied in four outcrop sections in the core of Handun anticline within the uppermost part of the Cretaceous to Lower Cenozoic successions (Tarbur Formation to Guri Member of the Mishan Formation). The succession flanking of salt diapir displays various halokinetic sequences with hook and wedge types growth strata. These geometries are mainly developed in the Paleocene-Eocene Pabdeh and Jahrum Formations. The Middle-Upper Eocene Jahrum Formation shows the maximum facies, geometry, and thickness variations and is truncated by a regional unconformity at the Eocene-Oligocene boundary. This stratigraphic unit is also interrupted by an allochthonous salt sheet as a result of lateral extrusion of the Hormuz salt. In addition, withdrawal and uplifting of the salt diapir caused strong lateral changes in accommodation spaces and sedimentation rates during this time interval. These variations could be documented by hook geometries in the halokinetic sequences around the Handun salt diapir. During the Oligocene to Lower Miocene times, in the Razak Formation and lower parts of the Guri Member, hook types growth strata can be observed in the N flank of the Handun salt diapir, while in other flanks, geometries of the sequence/growth strata become wedge-shaped more tabular far from the salt diapir. Based on these variations three halokinetic phases have been recognised which include nine halokinetic sequences showing the temporal and spatial effects of the halokinesis on the sedimentation systems.

This work aims to compare the 3D geophysical inversion models of electrical resistivity and chargeability with the 3D geostatistical-based models interpolated from 2D inversion of electrical data. The Takht-e-Gonbad Cu deposit situated in the central domain of Iran is chosen to find out the spatial correlation of the porphyry-type ore deposition with the electrical properties. Assuming an ordinary kriging algorithm, the inverted 2D electrical models were interpolated in 3D domain to provide insights about the geometry of Cu-bearing mineralization. Higher values of electrical resistivity and chargeability corresponded to the anomalous zones of Cu mineralization through a fractal analysis of concentration-number (C-N) model derived from exploratory drillings. Surveyed geophysical data were also inverted directly in 3D electrical models to compare them with the geostatistical models, showing that the 3D inversion could much better preserve the geometry of the Cu occurrences, and their classified fractal models were much in close association to each other. The correlation coefficients between the 3D electrical models and the Cu concentration were higher than the geostatistical models, and there is clearly information in the inversion result that is not being captured in the geostatistical interpolation. The significance of this study lies in improvement of the performance of 3D inversion methodology over 3D geostatisitcal interpolation.

Late Cretaceous time interval as a turning point in the Zagros history is characterised by the obduction of oceanic sedimentary cover of the Neotethys over the NE-tilted Arabian Platform. This event was associated with tectono-sedimentary loading and creating a foreland basin along the NE margin of the Arabian plate resulting in huge thickness and facies variations. For stepping the events and showing the foreland basin evolution during the Maastrichtian time, a SW-NE trending regional transect of several outcrop and well sections is constructed and interpreted in a high resolution sequence stratigraphic framework (six depositional sequences). In general, three phases of foreland basin evolution could be determined along the transect: tilting and backstepping of the platform, foredeep basin development and SW prograding of the subsiding platform during the Santonian, Campanian and Maastrichtian sequences respectively. The Tarbur Formation with shallow water carbonates is the main lithostratigraphic unit of the Maastrichtian, which laterally grades to the pelagic marls of the Gurpi Formation to the SW and onlaps onto the obducted radiolarite and ophiolitic complex to the NE Fars area. Temporal and spatial developments of platform carbonates of the Tarbur Formation and its equivalent basinal marls of the upper part of the Gurpi Formations is an indication to show how foreland basin migrated during this time interval. The Maastrichtian succession deposited from tidal flat to basinal environments. Initiation and re-activation of the basement faults are one of the most important controlling factors in accommodation spaces which overprinted locally by the holokinetic movements.

The ultrasonic pulse velocity including P-wave (Vp) and S-wave (Vs) velocity and elastic constants including the elastic modulus (E) and Poisson’s ratio (ν) are among most important parameters for estimating the strength and deformability properties of rocks. The specimen diameter size is one of the main factors that influence Vp, Vs, E and ν. This study presents the influence of specimen diameter size on the Vp, Vs, E and ν of sandstones. Moreover, we have investigated the accuracy of porosity (n) for estimating the Vp, Vs, E and ν at different diameters size. For this purpose, 10 sandstone samples were collected and core specimens with a diameters size of 24, 40, 54, 68, and 80 mm were prepared. Then, density (ρ), n, Vp, Vs, E and ν of sandstones were determined. It is concluded that the specimen diameter size has a significant influence Vp, Vs, E and ν. Moreover, the results showed that n is in good accuracy for estimating the Vp, Vs and E, while there are no meaningful correlations between ν with n.

Mesozoic limestones with Cretaceous and Jurassic age are widely seen in the Guilan province, north ofIran. Regarding the climate of this area, the development of limestone with a high percent of CaCO3(rather than 80%) and karst morphology development was investigated to evaluate the effect of freezingthawing (F-T) cycles concerning the karst development. In this way, the physical and mechanicalproperties of the four lithology units (Kl1, Kl2, Km2, and Jkl) were assessed before and after F-T cyclesto study the weathering effects. The survey of the petrography of rocks shows that the samples weregrainstone and packstone type, according to Donham classification. The highest deterioration occurredin sample Kl2 after 60 F-T cycles. The physical and mechanical properties of rock samples such as ɣ(unit weight), wa (water absorption), Pv (P-wave velocity), and UCS (uniaxial compressive strength) forboth dry and saturated conditions, and after 60 cycles of freezing-thawing (F-T) were attained. Thesoftening coefficient (K1) and freezing coefficient (K2) of samples were calculated using the UCSvalues. The F-T cycles caused significant losses in the UCS values. The measured Vp during the F-Tcycles provided a suitable tool for calculating the damage value and decayed constant (λ). This studyshowed that the F-T test is capable of creating microcrack and fractures within the rock as the initialfactors for increasing the contact surface in the dissolution process. The increase in Dn (damagevariable), porosity, water absorption, and decrease of Vp after 60 F-T cycles confirm this result. Also,the increase in tangent Young’s modulus and decrease in strain show that the samples were brittle after60 F-T periods. Therefore, it is concluded that the freezing and softening coefficient and Vp are effectivetools for assessing the rock damage during F-T periods.

Field investigation and structural mapping of faults cut Mezozoic to Late Cenozoic (PlioceneQuaternary) rocks in Ziar area of Central Alborz have led to identification of the NW- and NE- trendingfault sets. Slickenlines, fault steps and riedel shear fractures are mainly applied as kinematic indicatorsfor analysis of the faults mechanisms. The NW-trending reverse faults with left-lateral strike-slipkinematics and positive flower structure geometry (such as Golezard Fault) is the first set. This set cutthrough all rock formations up to Plio-Quaternary are proposed to develop during the northeasternoblique transpression deformation governs the Alborz during the final collision of the Arabian- Eurasianplates in Late Cenozoic (Pliocene). The NE-trending strike-slip faults with normal kinematics that crosscut the Damavand Quaternary volcanic rocks as well as the first faults set are the youngest faults in theregion. This fault set development have attributed to the northwestern movement of the South Caspianblock in Quaternary, which led to an extension in Central Alborz. These young faults mapped for thefirst time in this work constrain the Late Cenozoic (Quaternary) faulting of Central Alborz zone, referredas a result of the range major faults reactivation, previously.

The systematic studies and taxonomic investigations carried out on the Early Miocene Gharamul Formation exposed in Gebel Abu Shaar El Qabili plateau, western side of the Gulf of Suez region, led to the recognition of twelve coralline algal species belonging mainly to five genera of three subfamilies (Mastrophoroideae, Lithophylloideae, and Melobesioideae) of Rhodophyta (Corallinaceae). The geniculate coralline algae are relatively scarce and represented by a single genus Corallina sp. The Mastophoroids (Neogonilithon and Spongites) and Lithophylloids (Lithophyllum) are more dominant coralline algal species and dominate the shallower coralline algal assemblages. On the other hand, Melobesioids (Mesophyllum and Lithothamnion) and sporolithales (Sporolithon) are the most abundant components and diverse in the deeper-water assemblages. The Gharamul Formation (Burdigalian) consists of a thick carbonateclastics succession. The lower part consists of a cyclic sequence of laminated, fossiliferous and argillaceous limestone intercalated with mudstone, and sandstones. It is documented that the clastic microfacies have good reservoir quality in the region due to the impacts of dissolution and fracturing diagenetic processes. The carbonate microfacies are impervious due to the effects of cementation, and micritization. The dominance of coralline algae and larger benthic foraminifera indicate deposition in the photic zone. Frequent oscillation of lower-energy (foraminiferal wackestones) with higher-energy (grain-supported grainstones, packstones and rudstone) suggest the likely incidence of cyclones/storms during the depositional time.

Sarchahan Formation (Silurian) consists of shale and sandstone interbeds in the studied well in the Persian Gulf. Sedimentological characteristic of this formation is presented here for the first time. Based on petrographic studies and wire line logs studies, five petrofacies and three facies associations were identified in the Sarchahan Formation. Variations in facies association in combination with palynological studies represent that deposition of the Sarchahan Formation took place in different subenvironments of a delta environment from prodelta to delta plain. The lower part of the formation is represented by a high amount of black shale and higher total organic carbon values which are the result of deposition in the deeper parts of the basin. Meanwhile, the upper part is composed of sandstone and red mudstone which are the result of deposition in the shallower part of delta environment. Cementation, compaction and dissolution are the main diagenetic features which affected the Sarchahan Formation. Silica and sericite cements are the most abundant cement types in quartzarenite and subarkose petrofacies the development of which resulted in porosity reduction. The comparison with the Arabian plate, the deposition took place in a southward deepening basin into which sediments were introduced from the northern parts. .