N. Sarhaddi; A. Ahmadi; Z. Firoozkoohi; M. Jami
Abstract
The Lakhshak granodiorite body with Oligo-Miocene age crops out in flysch sediments of northwest of Zahedan. This body has been intruded by dykes with variable color indices ranging from mesocratic to melanocratic, and NE-SW trend. Based on field observations, , melanocratic dykes have cut mesocratic ...
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The Lakhshak granodiorite body with Oligo-Miocene age crops out in flysch sediments of northwest of Zahedan. This body has been intruded by dykes with variable color indices ranging from mesocratic to melanocratic, and NE-SW trend. Based on field observations, , melanocratic dykes have cut mesocratic dykes in some parts.This indicates that mesocratic dykes are younger than the melanocratic types. Different thickness (2 to 12m) of dykes shows the effect of tectonic activities and magama injection into structural joints, and the formation of dykes during tectonic activity. In terms of lithology, the Lakhshak body is composed of granodiorite, dacitic mesocratic dykes and melanocratic dykes of microdioritic and andesitic types. The granodiorite body and the two types of dykes are of I type nature, and are calc-alkaline, high-K calc-alkaline and metaluminous. Based on the geochemical characteristics, dykes and granodiorite show enrichment in LILE, LREE such as Ba, Cs, Rb, Eu and Pb, and depletion in HFSE, HREE such as Nb, Ti and Ta, which are related to index characteristics of the volcanic arc setting of an active continental margin. Pb positive anomaly may demonstrate continental crust assimilation by magma associated with mantle metasomatism. Based on field observation and petrogenesis, the Lakhshak granodiorite and mesocratic-melanocratic dykes originated from magmatic activity of subducted oceanic crust (Sistan plate) beneath the continental plate (Afghan block). The parental magma of the Lakhshak granitoid was originated from melts resulted from amphibolite melting, and dykes are the late derivative of magma recrystallization granodiorite.
B. Hosseini; A. R. Ahmadi; M. Ghanbari Dolatabadi
Abstract
A suite of dykes at the north of Mashad –Ardehal which intruded into the Eocene volcanic and sedimentary rocks represents part of Tertiary volcanism in middle part of the Urumieh-Dokhtar magmatic belt. The rocks are cogenetic and are mainly basaltic andesite, andesite and trachy andesite ...
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A suite of dykes at the north of Mashad –Ardehal which intruded into the Eocene volcanic and sedimentary rocks represents part of Tertiary volcanism in middle part of the Urumieh-Dokhtar magmatic belt. The rocks are cogenetic and are mainly basaltic andesite, andesite and trachy andesite in composition and belong to tholeiitic and medium-K calc alkaline series. Chondrite-normalized REE patterns exhibit moderate enrichment in LREE relative to MREE. Enrichment in LILE and depletion in HFSE relative to REE on multi-element diagrams is similar to subduction related magmatic rocks. From the geochemical point of view, these rocks demonstrate intermediate characteristics of active continental margins and island arcs settings. Geochemical evidences and also association of the magmatic rocks with green tuffite and other shallow marine sedimentary rocks suggest that the rocks generated in an extensional continental (ensialic) back-arc basin.
A. Ansari; S. J. Sheikh Zakariaee; S. Dargahi; M. Arvin
Abstract
The Chargonbad batholith is located close to Sirjan and southeast of Urumieh-Dokhtar magmatic zone . This batholith is acidic to intermediate in composition and intruded into the Eocene volcanic rocks. The main volume of these rocks consisted of granodiorite and monzogranite, but it also consists of ...
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The Chargonbad batholith is located close to Sirjan and southeast of Urumieh-Dokhtar magmatic zone . This batholith is acidic to intermediate in composition and intruded into the Eocene volcanic rocks. The main volume of these rocks consisted of granodiorite and monzogranite, but it also consists of quartzdiorite, tonalite and syenogranite. Their contacts are gradational. They have allotrimorphic granular texture with subordinate porphyritic texture. Their enclaves consist of xenoliths enclaves, microgranular mafic enclaves (diorite to quartzdiorite in composition) and autolith enclaves(tonalite, granodiorite and monzogranite in composition).The Chargonbad batholith rocks are also cut by different types of dykes which are mainly consisted of dykes and veins of pegmatitic stage, microgranular dykes (andesite and andesite basaltic in composition) and microgranular dykes that are similar to mafic enclaves. Evidenc show that the samples represent properties of I-type granitoids. Chargonbad granitoid has magnesium nature and shows cordellarian granites features. Based on the tectonomagmatic environment diagrams, all samples from the Chahargonbad plot in the island arc setting of a subduction zone and show active continental margin setting characteristics .
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.
