Exploration and Mining
Shahram Ghasemi; Mashalah Khamehchiyan; Mohammad Reza Nikudel; Ahmad Zalooli
Abstract
Joints and cracks are an integral part of rock structures. When load applied to these structures, growth, and interaction of the cracks lead them to failure. This aspect is particularly crucial in cyclic loading because failure occurs at stress levels lower than the yield point due to the fatigue process. ...
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Joints and cracks are an integral part of rock structures. When load applied to these structures, growth, and interaction of the cracks lead them to failure. This aspect is particularly crucial in cyclic loading because failure occurs at stress levels lower than the yield point due to the fatigue process. This research aims to study the growth and interaction of the cracks in the fatigue process by the fluorescence thin section method. At first, different stages of fatigue for granite rock were determined, then samples loaded up to each stage. Later, the physical, mechanical, and crack properties of the samples were investigated. The results show that physical and mechanical properties declined by increasing the number of cycles. During the first stage of fatigue, crack initiated at a high rate, and in the second stage, the increasing rate descended, and energy mostly consumed to increase the length of the cracks. In the last staged, which is the failure stage, the rate of crack initiation increases again and forms a complicated network of cracks, which leads the sample to failure. Among the constituent minerals, feldspar exhibits the highest crack density, and biotite shows the lowest density of the cracks.
Economic Geology
Maryam Honarmand; Ghasem Nabatian; Mahtab Aflaki; Mohammad Ebrahimi
Abstract
Geology, geochronology and tectonic setting of the Moghanlou mylonite gneiss and granite bodies, west of Zanjan Abstract The Moghanlou mylonite gneiss and granite assemblage is located in the west of Zanjan forming a part of the magmatic-metamorphic association in the Takab area. The Moghanlou assemblage ...
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Geology, geochronology and tectonic setting of the Moghanlou mylonite gneiss and granite bodies, west of Zanjan Abstract The Moghanlou mylonite gneiss and granite assemblage is located in the west of Zanjan forming a part of the magmatic-metamorphic association in the Takab area. The Moghanlou assemblage comprises of leucogranite and biotite granite intrusions which have surrounded the gneiss body. The zircon U-Pb dating shows the ages of 563±6.5 Ma for the mylonite gneiss, 576±13 Ma for the biotite granite and 559±6 Ma for the leucogranite intrusions. Moreover, the samples from the Moghanlou assemblage display high-K calc-alkaline and slightly peraluminous affinities, except those from the leucogranite which are low potassium samples due to the sodic alteration and albitization of the K-feldspars. The trace element patterns suggest LILE and LREE enrichment and HFSE and HREE depletion as well negative anomaly of Nb, Ta and Ti. In general, the geochemical features of the Moghanlou intrusions are comparable with the melts formed from crustal partial melting in magmatic arc environment. The Moghanlou assemblage is analogues to other Late Neoproterozoic-Early Cambrian igneous and metamorphic associations in Iran and Turkey which are related to the igneous activity along the Cadomian magmatic arc, in north of Gondwana supercontinent.
P Didar; N Nezafati; M.H Emami; A Solgi
Abstract
In the south of Mashhad city, situated in the Khorasan-eRazaviProvince, NE Iran, there are a number of granitic intrusive bodies intersected by several pegmatite veins. These granitic bodies are of orogenic (collisional), peraluminous, S- type and host the pegmatites in an area of 40km2. This paper presents ...
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In the south of Mashhad city, situated in the Khorasan-eRazaviProvince, NE Iran, there are a number of granitic intrusive bodies intersected by several pegmatite veins. These granitic bodies are of orogenic (collisional), peraluminous, S- type and host the pegmatites in an area of 40km2. This paper presents the geological, geochemical, and mineralogical investigations on the pegmatite veins in order mainly to examine their economic value for lithium and lithium bearing minerals. For this purpose, the pegmatite veins of the area were first mapped and sampled. In this regard, more than 100 samples from the pegmatites and associated granites were taken and investigated using polarized microscopy, SEM, XRD, and ICP. According to the field observations and laboratory examinations, seven individual pegmatite facies were recognized, all of which of LCT (Li, Cs, Ta) type (based on Cerny-2005-classification). The studied pegmatites contain three main types of mica including muscovite, lepidolite, and biotite and host from 430 to 1150 ppm lithium. Beside lithium bearing mica, presence of some other minerals such as garnet (almandine-spessartite), tourmaline (schorl-dravite series and schorl-elbaite series), and apatite are of interest, especially because of their potential for hosting REEs. The average of A/CNK index for the pegmatites is 1.3 to 1.6, while the average of Mg/Li is 3.9 to 24.1. The average of lithium for the facies of "quartz + tourmaline ± muscovite" is 19.3ppm, while the average of Li for the facies of "quartz+ potassium feldspar + plagioclase + muscovite + lepidolite + biotite + tourmaline" is 177.2 ppm. The low Mg/Li ratio, the high content of lithium, and the mineralization of lepidolite introduce the pegmatites of Mashhad as a significant potential for lithium, what that is being introduced for the first time from these pegmatites.
J Ghalamghash; S. Houshmand Manavi; M. Vousoughi Abedini
Abstract
Oshnavieh Plutonic Complex (OPC), hosted within the northernmost part of the Sanandaj- Sirjan zone, allows distinguishing three suites including diorite, granite and alkalisyenite-alkaligranite (AS-AG). Dioritic rocks formed from partial melting of enriched lithospheric mantle sources on base of minerlogical ...
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Oshnavieh Plutonic Complex (OPC), hosted within the northernmost part of the Sanandaj- Sirjan zone, allows distinguishing three suites including diorite, granite and alkalisyenite-alkaligranite (AS-AG). Dioritic rocks formed from partial melting of enriched lithospheric mantle sources on base of minerlogical and geochemistry. The granite suite is S type that formed from partial melting of metapelitic-greywacke source. The peraluminous A-type granite of AS-AG suite are generated by partial melting of quartzo-feldspatic source at high temperatures. According to the negative Nb, Ta and Ti anomaly in spider diagrams, and tectonic discrimination diagram of Rb-(Y+Nb), the diorite suite formed in active continental margin (VAG) environment. According to the diorite’s formed environment and simultaneously formed granite in 100 M.a., OPC seems to have formed by northeastward subduction of Neo-tethyan oceanic crust under the Iranian continental crust. Following intrusion and setting of mafic magma into the crust, partial melting of pelitic-greywacke, resulted from heating by intrusion of the mafic magma, produced the granitic magma. After 20 Ma the AS-AG suite formed from melting of quartzo-feldspatic rocks of lower crust, probably by heating of mafic magma and/or in relaxation period of subduction and emplaced in the continental volcanic arc.
M. H. Kholghi; M. Vossoughi Abedini
Abstract
Safakhaneh batholith, situated at 47 km southwest of Shahin Dezh, northwest of Iran, is located in the central Iran structural zone intersecting the Cretaceous rocks. The absolute age of the batholith, determined for the first time by K – Ar method, has been calculated ...
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Safakhaneh batholith, situated at 47 km southwest of Shahin Dezh, northwest of Iran, is located in the central Iran structural zone intersecting the Cretaceous rocks. The absolute age of the batholith, determined for the first time by K – Ar method, has been calculated 69.535 Ma. showing upper Cretaceous – Paleocene epoch and Laramide tectonic orogeny. Geochemical investigations of the batholith show that the major part of the batholith is of mantle magma, in which magmatic changes of the crystalline differentiation and contaminations have occurred. The crystalline differentiation has caused the formation of different rock types of quartz monzonite, quartz monzodiorite, tonalite, granodiorite and monzogranite respectively. Primary magma of the rocks is of calc - alkaline and generally metaluminous. The specifications of batholith rocks can be compared with the I – Type Caledonian granites. From the tectonic point of view, the specifications of the batholith can be comparable with the volcanic arc granitoids (VAG).
