Economic Geology
Pooya Seyed Salehi Naeini; Saeid alirezaei
Abstract
The Kharestan-Bidester area, northwest of the Taftan volcano, is covered by a series of Plio-Quaternary lava flows and pyroclastic materials. The area is marked by extensive silicic and argillic alterations. The silicic zones, distinguished by vuggy texture, are bordered by advanced-intermediate argillic ...
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The Kharestan-Bidester area, northwest of the Taftan volcano, is covered by a series of Plio-Quaternary lava flows and pyroclastic materials. The area is marked by extensive silicic and argillic alterations. The silicic zones, distinguished by vuggy texture, are bordered by advanced-intermediate argillic alterations. They occur as linear features across faults and fractures, as well as massive bodies of variable sizes, and are comparable, at regional scale, to lithocaps developed in the upper parts of the porphyry systems. The silicic-argillic zones are mineralized with gold at variable grades. Gold occurs mostly as submicroscopic particles of electrum and native gold. Pyrite, variably oxidized at surface and shallow levels, is the main metallic mineral, associated with trace sulfosalts, tetrahedrite and enargite. Minor malachite staining locally occurs in the ore zones. The geologic setting, hydrothermal alteration, ore mineralogy and texture/structure allow the Kharestan-Bidester to be compared with high-sulfidation epithermal systems.
K. Nezhadafzali; R. Lak; M. Ghoreshi
Abstract
Mud volcano is a natural and spectacular phenomenon that usually appear in form of a dome but some are found as a basin. Mud volcanoes comprise a mixture of water, gas and mud. They are found in most parts of the world, particularly in the Alps and Himalayas belts. In Iran, most of the mud volcanoes ...
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Mud volcano is a natural and spectacular phenomenon that usually appear in form of a dome but some are found as a basin. Mud volcanoes comprise a mixture of water, gas and mud. They are found in most parts of the world, particularly in the Alps and Himalayas belts. In Iran, most of the mud volcanoes appear in coastal plains of the Caspian and Oman Seas. Mud volcanoes are known as indicators of oil and gas resources, and they are used to predict the existence of oil and gas reservoirs in Earth subsurface. The Napag mud volcano, as the largest and most active one in Iran, is located on the northern coast of the Oman Sea and is an interesting natural occurrence in the country. It is associated with a 39-m-high cone-shaped hill and several active and inactive vents. Mud eruption with different rates occurs usually every 3-5 minutes, and flows out from the western disrupted side of the edifice downslope toward the surrounding plain. In this research, a sediment sample was taken from the mud-flow during the field work, then analyses was analyzed for major, accessory and trace elements using ICP-OES machine in the laboratory. In addition, an analysis of the grain size of the sediment sample was carried out and the data were processed by the SPSS software. Results show that the sediment particles are of clay and silt in size. Al and Fe elements constitute 89.8 and 4.4 % of the sediment, and their high frequency is related to the high percentage of clay in the sediment. The evolution of the Napag mud volcano was investigated in three different stages: (1) Explosive, (2) Effusive (fast eruption with high rate), (3) Extrusive (slow and gradual eruption of material with high viscosity).
M Abdetedal; Z.H Shomali; M.R Gheitanchi
Abstract
The Makran zone in southeastern Iran and southern Pakistan is the result of subduction of oceanic crust of the Arabian Plate under the Eurasian Plate. From seismic behavior point of view, there is a distinct segmentation between the western and eastern parts of the subduction zone. The western part of ...
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The Makran zone in southeastern Iran and southern Pakistan is the result of subduction of oceanic crust of the Arabian Plate under the Eurasian Plate. From seismic behavior point of view, there is a distinct segmentation between the western and eastern parts of the subduction zone. The western part of the Makran has an abnormally very low level of deep seismicity with lack of recorded great earthquakes, while the eastern part has experienced many great earthquakes. Another difference between the western and eastern parts of the Makran region is that the distance between the Quaternary volcanic arc and fore-arc setting is larger in the east than in the west. Understanding the nature of unusual behaviors of the Makran subduction zone has long been one of the biggest challenges in seismotectonic investigations of this region. The present study aims at producing high-resolution love-wave velocity structure maps of the crust and the upper mantle in the Makran subduction zone using ambient seismic noise. To achieve this purpose, a large dataset has been provided to produce tomographic maps. Empirical Green’s functions were obtained from cross-correlations of broad-band seismic noise records at different stations inside and outside the region. Love-wave velocity dispersion curves were then extracted from the ambient noise, and finally converted into a 2D group velocity image (or tomography map) for crustal and upper mantle structures of the region.
M Afarin; M Boomeri; A Mahboubi; M Gorgij; M.A Hamzeh
Abstract
In this study, geochemical and sedimentological assessment was carried out on mudstone and sandstone deposits of Eastern coasts of Chabahar. Fifty samples were taken from five sectione of Tiss, Ramin, Lipar, Gorankesh and Garindar estuary and subjected to grain size analysis and chemical analysis ...
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In this study, geochemical and sedimentological assessment was carried out on mudstone and sandstone deposits of Eastern coasts of Chabahar. Fifty samples were taken from five sectione of Tiss, Ramin, Lipar, Gorankesh and Garindar estuary and subjected to grain size analysis and chemical analysis using XRF and ICP AES methods. Positive sorting and skewness (with the frequency of fine grain particles) of samples indicate deposition in a low energy environment. Plotting geochemical data of major elements from Late Miocene- Pleistocene age 10 mudstone and sandstone samples in east coasts of Chabahar in Makran zone, on siliciclastic rocks classification diagrams, showed that the sandstones are wacky and Mudstones are shale. The mean calculated chemical indexes of alteration (CIA) and weathering (CIW) for siliciclastic sediments, confirm low level weathering of source rocks of this sediments. The average index of combinational variety (ICV) for the studied sediments was 1.57, which indicates that these deposits have a moderate chemical maturity and are derived from the first cycle of sediments. Distribution pattern of rare earth elements on spider diagrams shows the enrichment of light rare earth elements (LRRE) relative to heavy rare earth elements (HRRE) in the rocks. High ratios of LILE/HFSE and LRRE/HRRE in the rock samples and similarity of their chemical composition with subduction zone facies, indicates that siliciclastics of Chabahar coasts have formed in a subduction zone. The diagrams of tectonic setting associated with patterns of multivariate charts also shows that the studied rocks have been developed in an active continental margin.
A.R Shaker Ardakani; S Dargahi; H Amirpour
Abstract
The Ghaleh-Ganj dioritic- quartzdioritic massifs, Post early Eocene in age, located on the west side of the Makran Accretionary Prism and the Jazmurian Depression and the east side of the Jiroft fault, are part of the intrusives in the Ganj Complex, which itself is a part of the Jazmurian Ophiolitic ...
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The Ghaleh-Ganj dioritic- quartzdioritic massifs, Post early Eocene in age, located on the west side of the Makran Accretionary Prism and the Jazmurian Depression and the east side of the Jiroft fault, are part of the intrusives in the Ganj Complex, which itself is a part of the Jazmurian Ophiolitic Belt or the Inner Makran. The diorite- quartzdiorites are intruded into the Lower- Middle Eocene Bidak sedimentary units, which show spheroidal weathering and onion- skin erosion. The presence of feldspar, biotite and secondary minerals (such as clay minerals, secondary biotite and Fe oxides) in the study massifs played an important role in the occurrence of these features. Mineralogically the intrusives consist of plagioclase, clinopyroxene, amphibole, Biotite and opaques. Based on mineral chemistry studies, the plagioclases, oligoclase to labradorite in composition, show evidences of disequilibrium textures (e.g. sieve texture and oscillatory zoning). The clinopyroxenes are augite in composition and belonging to a tholeiitic magmatic series. Referring to linear relation between Ti and AlIV in clinopyroxenes, they seem to be formed in a pressure less than 5 kbs at a depth of less than 15 kilometers. Amphiboles are magnesiohornblende with tendency to actinolite in composition. Based on Zr/TiO2 versus Nb/Y and SiO2 versus Nb/Y diagrams, the intrusives plot in the fields of diorite- quartzdiorite and sub-alkaline, respectively. Their low Nb/Y ratio (0.14-0.16) also point out to their sub-alkaline (tholeiitic) nature. The intrusives are metaluminous and I-type, which referring to HFS and REE element contents, they belong to one group. The absence of a distinct Eu anomaly suggests the insignificance of plagioclase fractionation or oxidation state of the magma. The trace element discrimination diagrams together with chondrite-normalized rare earth element patterns show that the Ghaleh Ganj diorite- quartzdiorites formed in the Maturity Stage of a supra-subduction zone.
A Shaker Ardakani; M Arvin; B Oberhänsli
Abstract
The Lower Paleocene felsic plutonic rocks in the N- NE of Ghaleh-Ganj, are located on the western side of the Makran accretionary prism and the Jazmurian Depression and the east side of the Jiroft fault. They are parts of the intrusives in the Ganj complex, which itself is a part of the Jazmurian ophiolitic ...
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The Lower Paleocene felsic plutonic rocks in the N- NE of Ghaleh-Ganj, are located on the western side of the Makran accretionary prism and the Jazmurian Depression and the east side of the Jiroft fault. They are parts of the intrusives in the Ganj complex, which itself is a part of the Jazmurian ophiolitic belt or Inner Makran. Petrographically, the intrusives are quartz diorite, plagiogranite, tonalite, granodiorite, monzogranite and albite granite in composition with mainly equigranular to inequigranular textures and subordinate textures such as micrographic, granophyric, poikilitic and zoning. Mineralogically, the plutonic rocks consist of plagioclase, quartz, orthoclase, microcline, amphibole, biotite and opaques. The plagioclases show normal, reverse and oscillatory zoning and based on their mineral chemistry studies, are mainly albite to oligoclase in composition. Amphiboles are calcic type and magnesiohornblende in composition with affinity to actinolite. The geochemical studies show that the felsic plutonic rocks are trondhjemite to tonalite in composition and belonging to a sub-alkaline magmatic series with calc-alkaline nature, and have characteristics of peraluminous granitoids. Using trace element discrimination diagrams and ocean ridge granites-normalized multi-elements diagram clearly show that the Ganj felsic plutonic massifs are plotted in arc-related granites field with affinity towards ocean ridge granites field. These characteristics along with Nb-Ta negative anomalies are known as evidences for formation of Ganj felsic plutonic rocks in a supra-subduction zone environment.
M. E. Moslempour; M. Khalatbari-Jafari; T. Morishita; M. Ghaderi
Abstract
Mantle sequences exposed in west of Fannuj-Maskutan area comprise of lherzolite and porphyroclastic cpx-bearing harzburgite in the lower part and recrystallized fine-grained lherzolite with chromitite lenses in the upper parts of the sequence. Petrography studies and microprobe data show evidence ...
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Mantle sequences exposed in west of Fannuj-Maskutan area comprise of lherzolite and porphyroclastic cpx-bearing harzburgite in the lower part and recrystallized fine-grained lherzolite with chromitite lenses in the upper parts of the sequence. Petrography studies and microprobe data show evidence of melt/peridotite interactions, post-melting processes and subsolidus interactions associated with the appearance of two generations of deformed primary pyroxene-olivine and fine-grained pyroxene-olivine-amphibole neoblasts. Second generation of minerals formed as inclusion, interstitial and fine-grained. These two groups of minerals have different geochemical characteristics, i.e., the first group are comparable with abyssal peridotites and the second group are comparable to suprasubduction peridotites. Therefore, the chemical compositions of different generations of minerals show different petrogenesis for ultramafic rocks of the Fannuj-Maskutan ophiolitie complex. Interpretation of whole rock chemical data indicate that these rocks have a depleted MORB mantle source which underwent 5-15% partial melting. Rare earth element patterns normalized with chondrite standard values and compared with patterns of depleted MORB mantle (DMM), indicate enrichment in LREE/MREE ration and show U-shape patterns. Thus, the peridotites of the Fannuj-Maskutan ophiolitie have experienced multistage evolution and show characteristics of abyssal environment to suprasubduction zone. It might be said that transition from abyssal environment to suprasubduction has been affected by fluids derived from the subducted slab.
