Economic Geology
Sahar Tarabi; Mohamad Hashem Emami; Sourosh Modaberi; Seyed Jamal Shaykh Zakariaee
Abstract
Momen-abad area, in the southeast of Birjand and the northeast of Sarbisheh, is located in the Sistan-Zemestan zone. Based on the field studies, petrography, geochemical (XRF) and X-ray diffraction (XRD) in two volcanic sequences, the alteration conditions in the area have been investigated. According ...
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Momen-abad area, in the southeast of Birjand and the northeast of Sarbisheh, is located in the Sistan-Zemestan zone. Based on the field studies, petrography, geochemical (XRF) and X-ray diffraction (XRD) in two volcanic sequences, the alteration conditions in the area have been investigated. According to mineralogy and chemical studies, bentonites are sodium-calcium and heterogeneous. Mineralogy findings indicate that smectite minerals, cristobalite and quartz, alkaline feldspars (albite and anorthite and sanidine), gypsum, calcite, hematite, holandite, klinoptiolite, kaolinite, ileite, and halite minerals form bentonites. In the first sequence, the effects of argillic and iron oxide alterations and in the second sequence, the effects of alteration of argillic, carbonate, chlorite, calcite, albite, silicification and iron oxide are found. Altered units which are related to the second sequence in four layers include Rhyolytic perlites of the vein, masses, lenses; white bentonites and green; Rhyodacite and dacite with the effects of alteration of devitrification, and the alteration of perlite to bentonite, advanced argillic and silicification. In addition, the composition textures of lava-pyroclastic, devitrification and the alteration of perlite to bentonite due to diagenetic alteration are found out. Glass argillization and feldspars in volcanic units, and the alteration of plagioclase to albite + sericit, biotite to chlorite, stone to quartz, calcite, zeolite and chlorite in perlites, iron oxide veins and red unit are found out in the sequences. Moreover, the change color of bentonite in the region related to alteration hydrothermal, and the presence of fluids and iron-magnesium-rich solutions are obvious in these sequences.
F Jalili; F Hadavi; B Rahimi; A.R Khazaei
Abstract
In this research, biostratigraphy of a stratigraphic section in the east Afzalabad section in Lut Block (part of flyschoid basin in East Iran) were investigated based on calcareous nannofossils. Nineteen genera and 52 species of calcareous nannofossils were identified based on which the studied ...
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In this research, biostratigraphy of a stratigraphic section in the east Afzalabad section in Lut Block (part of flyschoid basin in East Iran) were investigated based on calcareous nannofossils. Nineteen genera and 52 species of calcareous nannofossils were identified based on which the studied sequence confirm with NN8- NN10 biozones of Martini (1971) indicating a middle Miocene to late Miocene age.
KH Kavyani Sadr; M.M Khatib; M.H Zarrinkoub
Abstract
Cheshmeh Khouri is an area which mainly comprises a zone of parallel, en-echelon faults along which metallic and non-metallic mineralization is observed. Structural controllers are important factors in the formation of the structural elements of the area such as dykes, faults, joints, folds, and particularly ...
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Cheshmeh Khouri is an area which mainly comprises a zone of parallel, en-echelon faults along which metallic and non-metallic mineralization is observed. Structural controllers are important factors in the formation of the structural elements of the area such as dykes, faults, joints, folds, and particularly mineral veins. Three types of dykes are observed: E-W trending wedge-shaped dikes, NW-SE trending folded dikes, and ring dikes, which are all kinematically controlled by structural movements of the area. A regional sinistral shear-compression (transpression) regime across the fault sets of the area has given rise to a large-scale counterclockwise rotation of andesitic blocks, developing a bookshelf structure over the area. Rotation of these blocks has provided open spaces for injection of ore-bearing hydrothermal solutions, which caused widespread alterations. Block rotation has also caused formation of dextral shear zones along the faults, which eventually controlled mineralization through the joint and minor fracture networks associated with these shear zones. Formation of mineral veins affected by the dextral shear zones of the bookshelf structure in the area, and defining the structural complexities and sequential elements as well as mineralization phase led to present a laboratory model which showed a good consistency with the results derived from others studies.
A Rashidi; M.M Khatib; M.R Heyhat; S.M Moussavi
Abstract
In KamarhajiMountain, NW Birjand there are geological structures such as: duplex, pop-Up, triangle zone, flower structures, folding, etc. The duplexes in KamarhajiMountain have E-W trend. They are parallel to the Shekarab fault system. The Shekarab fault is a reverse fault with sinistral component located ...
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In KamarhajiMountain, NW Birjand there are geological structures such as: duplex, pop-Up, triangle zone, flower structures, folding, etc. The duplexes in KamarhajiMountain have E-W trend. They are parallel to the Shekarab fault system. The Shekarab fault is a reverse fault with sinistral component located in the southern of the area; it is considered as one of the terminal branches of the Nehbandan fault. Based on the Geometric-Kinematic analysis, duplexes are of the horsetail structure type, which are set from the side view on each other. There are flower structures in the direction perpendicular to the horsetail structures, caused that the central layers of the duplex structures have the maximum height. Usually in the orogenic regions, the antithetic thrusts with motion opposite to the main thrust are observed. These thrusts are called back thrusts. The hanging wall blocks of two faults, thrust and its back thrust is called pop-Up structure. In addition, in some regions back thrust and new thrust created triangle zone. In duplexes of this Region, ramps have strike slip mechanism with Thrust component. The existing flats are non-horizontal and most of them have thrust mechanism with strike slip component. Due to the mechanism of flat, transfer direction is westward, and since the younger ramps are formed on the hanging wall of previous ramp (In other words, younger orientation is toward the hinterland) the formation of duplexes follows the break-back model. Since the physical model shows a better understanding of the formation model and the relationship between the structures, we have used of the experimental model. The results of experiments show a strong relationship between the geometry of the flat and the geometry of the structures of the area. Based on the paleostress studies and different trends of shortening of structures such as folding, duplexes, two deformational stages were identified. In the first stage, position of strain λ3 axis according to analysis of the conjugate joints, tension joints, and axial surface of folding is N42, 00, N40, 07, and is N38, 14 respectively. The amount of shortening in this stage of deformation is 41.46 %. Position of strain λ3 axis in the second stage of deformation according to analysis of the conjugate joints, tension joints, and E-W trend of thrusts is N83, 02, N84, 00, and N90E respectively. In this stage, strike– slip faults have been further developed. The shortening in this stage of deformation is 20.30 % and the amount of slip along the flats is 2640 meters. According to the geometric-kinematic analysis duplexes formed in the second stage of deformation, which was progressive.
M Abdi; M.H Karimpour; M.H Zarinkoob
Abstract
The main purpose of this study is processing of raw data by factor analysis method and having interpretation and integration them by geological, alteration and mineralization data. The distinctiveness of third factor of factor analysis for Au, Mo and W and the coincidence of third factor anomalies by ...
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The main purpose of this study is processing of raw data by factor analysis method and having interpretation and integration them by geological, alteration and mineralization data. The distinctiveness of third factor of factor analysis for Au, Mo and W and the coincidence of third factor anomalies by gold, high primary sulfide bearing area, secondary iron oxide and sericitic and silicic alterationrevealed that the third factor of factor analysis is the agent of mineralization in the study area. The suitable tectonic setting, shallow depth intrusiveswithintermediate composition, calc-alkalineand oxidant magmatism, anomaly of gold and disseminated mineralization in thehost rock and sulfide veinlet accompanied byabundant secondary iron oxide providedproperconditions for porphyry and epithermal type gold mineralization in the study area.
R. Monazzami bagherzadeh; H. Mirnejad; P. Eshback; M. H. Karimpour
Abstract
Listvenites or ophiocarbonates are considered important for exploration of precious and base metlas particularly Au, Ag, Cu, As and Hg. These rocks, which crop-out dominantly in ophiolite-mélange zones and in the vicinity of main faults and shear zones, have formed as the result of hydrous ...
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Listvenites or ophiocarbonates are considered important for exploration of precious and base metlas particularly Au, Ag, Cu, As and Hg. These rocks, which crop-out dominantly in ophiolite-mélange zones and in the vicinity of main faults and shear zones, have formed as the result of hydrous and carbonic alteration of ultramafic rocks. Listvenites occur extensively in eastern Iran. Based on petrography, Hangaran listvenites are grouped into three major types: 1. Carbonatic listvenite (type I), 2. Silicic listvenite (type II), and 3. Sulfie-bearing silicic listvenite with brecciated texture (type III). Gold contents of listvenites is generally low and the highest concentration (290 ppb) has been found in type III. Studies of mineral concentrates from stream sediments reveal the presence of gold, pyrite, chalcopyrite, cinnabar and native copper. Gold grains reach to a maximum sizes of 80 microns, and they are often associated with pyrite. Electron microprobe analyses on several sulfides and carbonates in Hangaran listvenites show that sulfide minerals are mainly pyrite, marcasite, bravoite and to a lesser amount chalcopyrite, and that many pyrite grains have been altered to marcasite. Important carbonated minerals are magnesite and dolomite. The presence of obiquitous bravoite zonation that results from alternations in Ni content indicates periodic changes in the physicochemical conditions of the hyrdorthemal solution. Petrographic studies and paragenetic sequence of minerals show that magnesite and dolomite formed prior to the mineralization stage, which was then followed by the formation of sulfides (mainly pyrite). Studies on the oxygen and carbone isotopes in 3 dolomite samples (δ18OSMOW = 9.353- 9.982 ‰, δ13CPDB =1.57- 1.67 ‰ ) show that oxygen and carbone can originate from oceanic waters, and that dolomite has formed due to the circulation of this water in ultramafic rocks and their subsequent alteration. Considering the variation in marcasite-pyrite paris from Hangaran silicic listvenite (δ34SCDT value 5.7-7.9 ‰ ), it seems that sulfur has originated from granitic rocks in south of the study area. Taking into accout the extentive outcrops of serpentinized ultramafic rocks and granite in the region can considered the source of Au, Ag and base elements such as Cu, Pb, Zn, Hg, As, Sb in related to granite masses, and Cr, Ni, Ti and Fe in related to serpentinized ultramafic rocks. Fluid inclusion studies on mineralized quartz in Hangaran listvenites show that the hydrothermal fluid affecting the host rocks was low salinity and had a maximum temperature of 280ºC.
A. Shoale; E. Rastad; A. R. Babakhni
Abstract
Chah-Calap W (Cu-Zn) deposit is located in Lut Block. It is a part of Central Iran Paleozoic platform which has been subjected to late Cimmerian orogenic movements. Chah-Calap ore- bearing volcano-sedimentary sequence of upper Triassic-Jurassic age was metamorphosed to green ...
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Chah-Calap W (Cu-Zn) deposit is located in Lut Block. It is a part of Central Iran Paleozoic platform which has been subjected to late Cimmerian orogenic movements. Chah-Calap ore- bearing volcano-sedimentary sequence of upper Triassic-Jurassic age was metamorphosed to green schist-lower amphibolite facies. This sequence includes siliceous meta-pellite, lower meta-felsic tuff, meta-limestone with meta-chert interlayers, (main mineralized horizon occurred at the base of it) alternation of micritic and sparitic limestone, upper meta-felsic tuff and mylonitic rhyolite. In meta-limestone, 3 facies were recognized, in which the mineralization corresponds only to meta-chert bearing facies. No intrusive body outcrops in the study area. Two NW-SE and NE-SW trending fault systems can be observed in Chah-Calap mining region.
The stratiform mineralization with layering and lenticular geometry has 2 kilometer length. Based on these investigations, six mineralized horizons can be distinguished in Chah-Calap volcano-sedimentary rocks: siliceous meta-pellite (ore horizon I), lower meta-felsic tuff (ore horizon II), calc-silicate layers, bands and lenses occurring at the contact between meta-limestone and lower meta-felsic tuff (ore horizon III), at the middle of meta-limestone layer (ore horizon IV) and at the upper contact between meta-limestone and upper meta-felsic tuff (ore horizon V) and mylonitic rhyolite host rocks (ore horizon VI). Main mineralized horizon in Chah-Calap occurred at the base of meta-cherty limestone, at lower contact between meta-carbonate and lower meta-felsic tuff. Regionally metamorphosed chert-bearing parts of meta-limestone, forming calc-silicate horizon, composed mainly of sparitic calcite, tremolite, actinolite, diopside, hedenbergite and grassular-rich garnet. Ore assemblage includes: scheelite, chalcopyrite, sphalerite, pyrite, arsenopyrite, pyrrhotite, covelite, bornite, chalcocite, azurite/malachite and iron-oxide/hydroxides having massive, disseminated, laminated, breccia like and open space filling textures. Tungsten mineralization in Chah-Calap is considered to be of distal syn-sedimentary-syn-diagenetic type with exhalative origin. Diagenetic processes lead to primary concentration of mineralization which later experienced remobilization and re-concentration during regional metamorphism.
