M. Maanijou; I. Rasa; D. Lentz
Abstract
Chehelkureh copper deposit is located in Kuh-e-Lunka area, 120 km NW of Zahedan (SE of Iran). The host rocks of mineralization are intercalated Eocene turbiditic greywackes, siltstones, and shales (flysch). They are folded with N-S trend and the eastern limb of this fold has ...
Read More
Chehelkureh copper deposit is located in Kuh-e-Lunka area, 120 km NW of Zahedan (SE of Iran). The host rocks of mineralization are intercalated Eocene turbiditic greywackes, siltstones, and shales (flysch). They are folded with N-S trend and the eastern limb of this fold has been drag folded. Several stocks and dykes of granodiorite to quartz monzodiorite and granite compositions intruded the turbidites, converting them locally to hornfels. These intrusions are oriented parallel to the major NW-SE fault set. The Chehelkureh ore field comprises numerous irregular lenses and veins. The ore field extends for 1500m in N23°W direction, and is displaced by late brittle faults striking roughly E-W. The fault and fracture filling ores include quartz, dolomite, ankerite, siderite, calcite, and lesser amounts of pyrrhotite, arsenopyrite, pyrite, chalcopyrite, sphalerite, galena, Se-rich galena, marcasite, molybdenite, ilmenite, and rutile. Assay data from 39 drill holes show high contents of base metals, with an average of 1.48% Cu, 1.77% Zn, 0.85% Pb (4.1% Cu+Zn+Pb), and silver (average 22 ppm in 45 samples). The ores are not so enriched in gold (0.14 ppm on average in 45 samples).
A composite sample of least-altered greywackes and shales (host rocks) is used for comparison with mineralized samples. Mass-balance calculations were carried out to quantify chemical changes resulting from different alteration episodes. With the low solubility and low variance of Al (Al2O3) in moderately altered sedimentary country rocks compared with many other immobile trace components, Al2O3 is used as an immobile component for mass-balance calculations. There is a net mass increase in Fe2O3T, and MgO and a net mass decrease in Na2O, CaO, K2O, and SiO2 with chloritization. Carbonatization shows Fe2O3T, and MgO enrichment and SiO2 and Na2O depletion, implying that ankerite, siderite and dolomite are predominant phases. SiO2 is enriched in silicified samples and depleted in other alteration types. There is no mass change in Cu, Pb and Zn with kaolinization, but these elements are enriched in other alteration types. Hg is enriched in all alteration types except kaolinization, which may even show a slight depletion. Samples from gossan with silicification showed an increase in SiO2, Fe2O3T, Cu, Pb, Hg, and Zn and a decrease in MgO, Na2O, CaO, and K2O. Some trace and major elements have high variance in different alterations and are more complicated to interpret, such as P2O5, MnO, Ni, Co, and Rb.
The REE contents of the composite host rock sample are enriched in the LREE relative to the HREE and moderately depleted in Eu and Ho. As a whole, samples with kaolinization and carbonatization (ankerite and siderite) have been enriched in REE contents and other wallrock alteration, including chloritization, dolomitization, kaolinization, minor sericitization, and silicification, are depleted in REE. SEM-EDS evidence indicates that enrichment of REE-bearing phosphates, such as monazite, occurred with carbonatization and kaolinization assemblages.
Z. Sadeghi; H. Mehdizadeh; M. Sadeghian
Abstract
Kuh- Shah granitoidic pluton is located in the NE part of 1:100000 geological map of Baft. Lithological composition of this pluton includes Alkali- feldspar granite, granite, granodiorite, quartzdiorite, diorite and gabbro. This pluton has been intruded in volcaniclastics ...
Read More
Kuh- Shah granitoidic pluton is located in the NE part of 1:100000 geological map of Baft. Lithological composition of this pluton includes Alkali- feldspar granite, granite, granodiorite, quartzdiorite, diorite and gabbro. This pluton has been intruded in volcaniclastics of Eocene age. On the variation diagrams the trends of major and trace elements of studied samples indicate the continuity of lithological compositional range of this pluton and they have been from differentiation of a basic (basaltic) magma. From the genetic classification point of view the studied granitoidic pluton is from I type granite and it belongs to magnetite series. Based on the geochemical features Kuh-Shah granitoidic pluton is metaluminous with high and medium potassic calc-alkaline nature. High amounts of LILE and low amount of HFSE on the spider diagrams show that the parental magma of these rocks have been enriched from trace elements and incompatible elements. Based on the tectonic setting discrimination diagrams, this pluton is belong to VAG type and therefore it has been resulted from subduction of neotethys oceanic crust beneath the central Iran continental crust.
S. S. Mohammadi; M. Vossoughi Abedini; M. Pourmoafi; M. H. Emami; M. M. Khatib
Abstract
Bibi Maryam Granitoid body with 5 km2 exposure area is located in the east Iranian ophiolite mélange belt in Sistan suture zone. This intrusive body consists of tonalite- quartzdiorite and granodiorite. The main mafic minerals are hornblende and biotite in quartzdiorite-tonalite. Existence of ...
Read More
Bibi Maryam Granitoid body with 5 km2 exposure area is located in the east Iranian ophiolite mélange belt in Sistan suture zone. This intrusive body consists of tonalite- quartzdiorite and granodiorite. The main mafic minerals are hornblende and biotite in quartzdiorite-tonalite. Existence of microdioritic enclave in tonalite and its absence in granodiorites is one of the main characteristics of the body. Perthitic and granophyric textures in granodiorites represent low water vapor pressure and relatively fast crystallization, respectively. Geochemical study of rock samples shows that the body is calc-alkaline and metaluminous to peraluminous. Trace element patterns in spider diagrams represent a trough for Nb and enrichment for K, Rb, Ba and Th that indicate contamination by crustal materials. Although Bibi Maryam intrusive body cuts the ultramafic rocks, it lacks petrographic and geochemical characteristics of oceanic plagiogranites. The geochemistry of the body is comparable with I-type granitoids and based on tectonic setting it can be classified as orogenic and VAG type.
A. Zamani; M. Agh-Atabai
Abstract
The 31 March, 2006 earthquake with Mw=6.1 destroyed villages in the Darb-e-Astaneh (Silakhor) region of the Lurestan province. The epicenteral area of this earthquake lies near the Main Recent Fault (MRF) and its right lateral mechanism indicates that it belongs to this fault zone. The main shock was ...
Read More
The 31 March, 2006 earthquake with Mw=6.1 destroyed villages in the Darb-e-Astaneh (Silakhor) region of the Lurestan province. The epicenteral area of this earthquake lies near the Main Recent Fault (MRF) and its right lateral mechanism indicates that it belongs to this fault zone. The main shock was followed by relatively large number of aftershocks. In this research, the aftershock sequence of this earthquake has been studied by measuring quantitative indices of coefficient of variations (CV), the exponent of the power spectral density function, and the generalized multifractal dimensions. The results reveal the presence of fractal structure in the temporal and spatial distribution of aftershock sequence. The multifractal behavior of the aftershock sequence indicates the clustering of the earthquake activity and the degree of the heterogeneity in the seismotectonic and geodynamic processes in the focal region. The results show that the multifractal dimensions of the aftershock sequence decreases and the multifractal dimensions of aftershock epicenters increases with time. It seems that these changes in the multifractal dimensions are related to the activity of secondary and sympathetic faults and changes in the tectonic stress regime of the region. The results also indicate that the multifractal method rather than monofractal approaches is a powerful tool for quantitative analysis of aftershock process's clustering behavior.
R. Shabanian; Kh. Khosrow Tehrani; I. Momeni
Abstract
Various stratigraphical sections of the Permian rocks in the northwest of Iran (Azerbaijan) shows that this sequence consists of Doroud, Ruteh, and Nesen formations in the southern flanks and Doroud, Surmaq , Julfa and Ali-Bashi formations in Zal and Illanlu sections.
The analysis and study of forminifera ...
Read More
Various stratigraphical sections of the Permian rocks in the northwest of Iran (Azerbaijan) shows that this sequence consists of Doroud, Ruteh, and Nesen formations in the southern flanks and Doroud, Surmaq , Julfa and Ali-Bashi formations in Zal and Illanlu sections.
The analysis and study of forminifera assemblages in the carbonate sequence of the area and the comparison of these microfossils with other parts of Iran and neighbouring countries indicate that the age of carbonate units is Kubergandian to Dorashamian in Zal and Illanlu areas and Kubergandian to Djulfian in others sections. Throughout the Azerbaijan, Lower Permian shows a great hiatus.
Field investigation, rock and microfacies studies show many progressive and regressive phases in the Permian sequence of Azerbaijan.
A. Kananian; M. Rezaei-Kahkhaei; D. Esmaeili
Abstract
The Lakhshak granitoid pluton which is located at 10 km northwest of Zahedan, has intruded into the Eocene flysch sediments with an elliptical shape and NW-SE direction. This pluton after emplacement has been cut by numerous dykes with NE-SW trend. These dykes comprised about ...
Read More
The Lakhshak granitoid pluton which is located at 10 km northwest of Zahedan, has intruded into the Eocene flysch sediments with an elliptical shape and NW-SE direction. This pluton after emplacement has been cut by numerous dykes with NE-SW trend. These dykes comprised about 20-30% of the Pluton with various compositions, ranging from granodiorite to monzodiorite in composition.
The Lakhshak plutonic rocks are mainly metaluminous, calc-alkaline and belong to I type granites based on the P2O5 and Th content versus SiO2. Regarding TiO2 content these rocks resemble the continental margin granites. The MgO, Na2O, Ni, Cr content as well as Mg# and depletion in Y, these plutonic rocks are similar to the adakite, a rock type produced by partial melting of young oceanic crust. The low Ba/La content of the studied samples may suggest that subducted slab suffered dehydration prior to partial melting.
These rocks are enriched in LIL, LREE, however, they are depleted in HREE and Y. In addition, they show negative anomalies of Nb, Ta, P and Ti, and positive anomaly of Pb. The negative anomalies of Nb and Ta may indicate the effect of mantle wedge metasomatism by oceanic crust. The positive anomaly of Pb may demonstrate continental crust assimilation by magma associated with mantle metasomatism.
It seems that Lakshak pluton has been formed by subduction of Sistan young oceanic crust under the Afghan Block. Moreover, the low content of HREE and Y besides a decreased ratio of Yb versus SiO2, Y<15.13, Yb<1.2 and existence of amphibolite enxenoliths in these rocks may suggest partial melting of amphibolites. The latter is formed during the oceanic crust subduction in depth more than 35 km.
H. Ghasemi; E. Zabihi; A. Roshandel Kahoo; M. Zare
Abstract
Strong motion records from the 2002 Bam Earthquake are used to investigate the shape of attenuation function in several frequencies ranging between 0.8 to 18 Hz. Amplitude spectra of the records are inverted to find source scaling factor and attenuation parameters using Singular Value Decomposition ...
Read More
Strong motion records from the 2002 Bam Earthquake are used to investigate the shape of attenuation function in several frequencies ranging between 0.8 to 18 Hz. Amplitude spectra of the records are inverted to find source scaling factor and attenuation parameters using Singular Value Decomposition method (SVD). After correcting the obtained attenuation functions for geometrical spreading effect, the values of follow the frequency dependent relation, , which is in good agreement with similar results in other tectonically active regions in the world and could be served as a basic input parameter for future seismic hazard studies in the region of bam.
A. Akbarpour; A. Rasa; M. Mehrpartou
Abstract
The Masjeddaghi area is a part of Alborz-Azarbaijan Zone and located in the Jolfa 1:100000 geological map sheet. The oldest rock units cropped out widely in the south and northeast of the area belong to the Eocene flysch-type sediments. The other outcrops consist mainly of volcanic rock complex of andesites ...
Read More
The Masjeddaghi area is a part of Alborz-Azarbaijan Zone and located in the Jolfa 1:100000 geological map sheet. The oldest rock units cropped out widely in the south and northeast of the area belong to the Eocene flysch-type sediments. The other outcrops consist mainly of volcanic rock complex of andesites and trachyandesites affected by quartz monzonite intrusion and caused alteration of phyllic and carbonate phyllic type. The mineralization in volcanic complex is also accompanied by quartz and barite veins. The study of alterated zone around veins shows sericite, silicified, prophillitic, chloritic and alunite (jarosite) alterations. Investigation of alteration zones around mineralized veins shows epithermal gold ore in which alunitic alteration (jarocite) is the most important characteristics. The result of the study on alteration and extension of altered zones in the whole study area give rise to the probability of porphyry type copper deposit (potassic, phyllic, argillic and prophylitic alteration zone).
J. Ahmadian; M . H. Emami; M. R . Ghorbani; M . Murata
Abstract
Kal-e Kafi granitoid complex is a part of Central Iranian structural zone called Yazd block. This complex is composed of a wide spectrum of plutonic rocks ranging from gabbro to alkalike granite with age range of Upper Eocene-Lower Oligocene. Potassic granitoid shows geochemical ...
Read More
Kal-e Kafi granitoid complex is a part of Central Iranian structural zone called Yazd block. This complex is composed of a wide spectrum of plutonic rocks ranging from gabbro to alkalike granite with age range of Upper Eocene-Lower Oligocene. Potassic granitoid shows geochemical and mineralogical characteristics distinct from other plutonic rocks in the complex. The potassic granitoids are peralkaline and ferroan while other plutonic rocks in the complex are alkaline to calc-alkaline and magnesian. With respect to REE abundances and patterns, the potassic rocks of the complex are different from other Kal-e Kafi granitoids. Low REE abundances of the potassic granitoids indicate that the rocks could not be related to other plutonic bodies through magmatic differentiation. This would probably demonstrate that different petrogenetic processes were involved in petrogenesis of the potassic granitoids. The potassic granitoids are likely to be the consequence of crustal partial melting.