Economic Geology
Fatemeh Esmaeili; Fardin mousivand; Mahmoud Sadeghian; Seyed Mehran Heidari
Abstract
Miandasht copper deposit is located in 110 km east of Shahrood, 24km north west of Abbasabad, and in the Cenozoic volcanic belt of north of Central Iran zone. The major rock units of the study area have Eocene age and include submarine flows (andesite, basalt, and trachyandesit), pyroclastic (tuff breccia ...
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Miandasht copper deposit is located in 110 km east of Shahrood, 24km north west of Abbasabad, and in the Cenozoic volcanic belt of north of Central Iran zone. The major rock units of the study area have Eocene age and include submarine flows (andesite, basalt, and trachyandesit), pyroclastic (tuff breccia and agglomerate) and sedimentary complex (Nomullitic limestone, tuffacous limestone, shale, sandstone and conglomerate). Mineralization in the Miandasht copper deposit occurred as parallel to layering of the host rocks (tuff breccia and agglomerate), and also along with cross- cutting faults of the host rocks in form of stratabound and epigenetic ores. The main ore textures include vein- veinlets, open space filling, disseminated and replacement. The Ores contain primary pyrite, chalcopyrite, chalcocite, bornit, and secondary covellite, chalcocite, malachite, hematite and limonite. The most important wall rock alterations accompanied with mineralization are carbonatic- silicic, sericitic, argillic, and chloritic, and that the amound of carbonatization and silicification increases with closing to mineralization zones. According to geochemical studies, tectonic setting of the deposit was extensional environment formed in a continental margin volcanic arc. Based on essential characteristics of the copper mineralization such as tectonic setting, host rocks, mineralogy, and type of alterations, the Miandasht copper deposit shows many similarities with Manto- type deposits, dominantly formed during orogeny, folding and faulting of the host sequence. It should be mentiond that some charachteristic features of the Miandasht copper deposit including development of argillic alteration, and lack of extensive zeolitic alteration, distinguishes it from other copper deposits in the region including Abbasabad deposit.
Petrology
Habibollah Ghasemi; Mahbubeh Arabzadeh Baniasadi; mojtaba rostami hosuri
Abstract
The Abbasabad Eocene volcano-sedimentary belt in the east of Shahrood includes of basaltic-andesitic rocks and related pyroclastics along with interlayers of sedimentary rocks. The volcanic rocks include olivine basalt, trachybasalt, trachy andesybasalt, trachyandesite and andesite with various textures ...
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The Abbasabad Eocene volcano-sedimentary belt in the east of Shahrood includes of basaltic-andesitic rocks and related pyroclastics along with interlayers of sedimentary rocks. The volcanic rocks include olivine basalt, trachybasalt, trachy andesybasalt, trachyandesite and andesite with various textures such as hyallomicrolitic porphyry, microlitic porphyry, glomeroporphyry, trachytic and sieve textures. The main minerals of the rocks are clinopyroxene and feldspar. Pyroxene composition ranges from diopside to augite and feldspar composition is in the ranges of orthoclase and oligoclase to bytownite. The 87Sr/86Sr(Initial) and 143Nd/144Nd(Initial) ratios of these rocks, taking into account the age of 40 Ma for them, range from 0.7042 to 0.7047 and 0.5127 to 0.5130 respectively. Also, the values of ԐNd(0) and ԐNd(t=40Ma) of them range between 2.67 to 7.72 and 3.8 to 8.8, respectively, indicate an enriched mantle source for them. Whole rock, isotopic and clinopyroxene chemistry indicate arc-related calc-alkaline-alkaline nature and basaltic composition of the parental magma originated from partial melting of an enriched OIB source in an extensional intra-arc setting. Geothermobarometry calculations on clinopyroxene indicate a temperature range of 1100-1150 Cº and pressures of 2-13 kb for crystallization of the magma.
S. Shekari; M. Sadeghian; M. Zhai; H. Ghasemi; Y. Zou
Abstract
Metamorphic - igneous Shotor-Kuh complex is located in the 80 km of SE Shahrood and in the northern edge of the central Iran structural zone. This complex includes a wide lithological composition range such as metapelite (micaschists and gneisses), metapsammites, metabasites (amphibolite and garnet amphibolite), ...
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Metamorphic - igneous Shotor-Kuh complex is located in the 80 km of SE Shahrood and in the northern edge of the central Iran structural zone. This complex includes a wide lithological composition range such as metapelite (micaschists and gneisses), metapsammites, metabasites (amphibolite and garnet amphibolite), metacarbonate (limestone and dolomitic marbles) and metrhyolites. Protolith of metabasites have been basaltic lavas, diabasic swarm dikes and small scale gabbro-dioritic intrusions. With respect to abundance and importance of metamorphosed basaltic intercalations and diabasic swarm dikes in comparison to the other basic rocks, this article specially advocated to investigation of their evolution. Based on the field evidence and petrography, increasing the degree of metamorphism of metabasites resulted in producing of amphibole schist, amphibolite, garnet amphibolite and eventually amphibolitic migmatites. Thermobarometery based on the chemical analysis of garnet, amphibole and plagioclase of the metabasites indicates that the thermal range of 602-711 °C and 9-11 Kbar pressure for their formation, stop of exchange and final equilibrium, which accommodate with P-T condition of amphibolite and upper amphibolites facies. From the geochemical points of view, the magmas forming of these metabasites have tholeitic to calc-alkaline nature. These magmas originated from the subcontinental lithospheric mantel source. Submarine basaltic lava flows and diabasic swarm dikes originated during extensional tectonic regimes which affected Late Neoproterozoic Iranian Gondwanan terrains. These extensional tectonic regimes are associated with producing of intracontinental sea to oceanic basins (riffitic or back arc). The mentioned basins closed in a short time and lead to generate tectonic melange or accretionary prisms on the continental crust. Based on the U- Pb age dating of the Zircons extracted from these metasbasites, these metamorphism event occurred in the interval time of 526-577 Million years (corresponds to the late Neoproterozoic and Cadomian orogeny in the Iranian Gondwanan landforms).
Petrology
M. Sadeghian; S. H. Hosseini; A. Hemmati; S. Shekari
Abstract
Granitoid plutons of SW Mayamey (60 Km east of Shahrood), located at the most northern margin of the central Iran structural zone, have granite composition (in general) and calk alkaline and peralouminous nature. In spite of coverage of these granitoids by Late Triassic – Early Jurassic sedimentary ...
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Granitoid plutons of SW Mayamey (60 Km east of Shahrood), located at the most northern margin of the central Iran structural zone, have granite composition (in general) and calk alkaline and peralouminous nature. In spite of coverage of these granitoids by Late Triassic – Early Jurassic sedimentary rocks, Late Neoproterozoic host gneiss are exposed in limited areas. These granitoids invaded by two series of the Late Neoproterozoic and middle Jurassic diabasic dikes. Although post – Liass, Pre- Dogger, younger than Jurassic and older than Cretaceous ages are considered for these granitoids, but for the first time U–Pb age dating on separated zircons indicates Late Neoproterozoic age (Late Ediacaran) (545±10 Ma) for them and they are a part of very ancient basement rocks of Iran. The studied rocks are similar Band -e-Hezar Chah, Sefid Sang, Delbar, Shotor Kuh, Reza Abad and Do Chah granitoids in age. Mayamey granitoids are resulted from partial melting of metapelites and metagraywackes, and they belong to S-type granioids. SW Mayamey granitoids were generated in a collisional tectonic setting in the Late Neoproterozoic, in relation to closing of intracontinental back arc basin and then metamorphism of the associated rocks from greenschist facies to amphibolite and rarely granulite facies, which finally companied with s-type granitization
F Yousefi; M Sadeghian; S Samyari; H Ghasemi
Abstract
In Ahmadabad Khartouran region located in 175 Km southeast of Shahrood, A significant number of adakitic domes crop out, which intruded into the Paleocene- Eocene volcanosedimentary rocks. Lithological compositions of these domes include andesite, trachyandesite, trachyandesite and dacite. Pyroxene (augite), ...
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In Ahmadabad Khartouran region located in 175 Km southeast of Shahrood, A significant number of adakitic domes crop out, which intruded into the Paleocene- Eocene volcanosedimentary rocks. Lithological compositions of these domes include andesite, trachyandesite, trachyandesite and dacite. Pyroxene (augite), green hornblende and plagioclase are typical mafic and felsic rock forming minerals. With respect to low HREE and high LREE along with other characteristic such as silica content (58.91- 63.41), Na2O more than 3%, Al2O3 more than16%, Yb less than 1.8 ppm, Y less than 18 ppm and K2O/Na2O ratio between .98- 2.3, these rocks can be classified as the high silica adakite. Enrichment of LREE relative to the HREE and depletion of Nb, Ti, and high concentration of Rb, Ba, K and Th, which imply crustal contamination of the mentioned adakitic domes. Enclaves with different size and composition have been seen in these domes which indicate contamination and magma mixing with continental crust. The evidence of petrographic and geochemical show that the magma forming of these rocks originated from melting of subducted metamorphosed Neotethys oceanic slab (Sabzevar – Darouneh branch) in P-T conditions of amphibolite facies.
R Ramazani Omali; N Hafezi Moghaddas; K Heidari
Abstract
Rock falls are the usual forms of slope instability in hill slopes. The high velocity and rapid occurrence are the main differences of rock fall and other rock instability. Therefore, the rock falls are among the most destructive mass movements and results in high loss of lives and heavy damage to the ...
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Rock falls are the usual forms of slope instability in hill slopes. The high velocity and rapid occurrence are the main differences of rock fall and other rock instability. Therefore, the rock falls are among the most destructive mass movements and results in high loss of lives and heavy damage to the structures, roads, residential area, farms and etc. In this research, rock fall in rocky slopes of the TepalMountain in northwest of Shahrood city was investigated. For this, the large scale geological map of area (scale of 1:10000) was produced and joint studies in 12 sections performed. Then, the slope instability was analyzed by two methods of stereographic (using Dips 5.103 software) and analytical method (by Swedge 4.078 and rock fall 4.039 softwares). The results show that all of the slopes are stable in static conditions and become instable in dynamic state. In critical states of huge raining and earthquake intense instability will be occurred and the big problems could be created for the down area of slopes. Based on the results of analytical and using the Arc GIS 9.3 rock fall hazard zonation map was produced. In addition, by overlaying of landslide hazard map and land use map, the area affected by rock falls was distinguished. The results of this study show that Salamaty road, Mazar Shohaday Gomnam and its access road, some part of AzadiPark, the tourism hotel, some of the residential area down of the Salamaty road and some parts of the AbsharPark are located in the hazard zones.
