Petrology
Marziyeh Abazari; Seyyed Saeid Mohammadi; Malihe Nakhaei
Abstract
Abbas Abad area is located in the northeast of Sarbisheh, in the northern part of Sistan suture zone and southern Khorasan province. In this area, Tertiary volcanic rocks with the composition of intermediate to acid, including basaltic andesite, andesite, and dacite are exposed. Constructive minerals ...
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Abbas Abad area is located in the northeast of Sarbisheh, in the northern part of Sistan suture zone and southern Khorasan province. In this area, Tertiary volcanic rocks with the composition of intermediate to acid, including basaltic andesite, andesite, and dacite are exposed. Constructive minerals of basaltic andesite include of plagioclase, pyroxene and olivine and in andesite consist of plagioclase, hornblende and pyroxene, and in dacite are plagioclase, quartz, biotite and hornblende. The studied rocks have medium to high-K calc-alkaline nature. Most samples show enrichment in LILEs (K, Rb, Sr, Cs) (except Ba) relative to HFSEs (Y, P, Ti, Ta, Nb), which indicates the relation of these rocks to subduction zone and active continental margin. The relatively low (La/Yb)N (7.67 to 13.48) and Dy/Yb (<2) in Abbas Abad lavas indicate that partial melting of mantle occurred in transitional zone of spinel-garnet lherzolite. Based on the concentration of trace elements such as Ce, Yb and Sm, magma originated from a depth of about 95 to 105 kilometers.
Petrology
Maryam Kouchi; Malihe Nakhaei
Abstract
In northeast of Sarbisheh city, southern Khorasan, outcrops of lava rocks are exist that from view of geological subdivisions, located in eastern part of Lut block. Lithologic composition of studied collections consist of andesite (pyroxene andesite, andesite, trachy andesite), dacite and rhyolite. The ...
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In northeast of Sarbisheh city, southern Khorasan, outcrops of lava rocks are exist that from view of geological subdivisions, located in eastern part of Lut block. Lithologic composition of studied collections consist of andesite (pyroxene andesite, andesite, trachy andesite), dacite and rhyolite. The main texture of these rocks are porphyry with microlitic-glass groundmass, glomeroporphyritic, poikilitic and vesicular. The mineral constituents of andesitic rocks are plagioclase, pyroxene and amphibole with small quantities of biotite and sanidine and in rhyolite and dacite include of quartz, sanidine, plagioclase, amphibole and biotite. Disequilibrium textures such as chemical zoning, sieve texture, rounded and gulf shape margins in phenocrysts of these rocks are observed. Geochemical study results show that these lavas belong to high to medium-K calc alkaline series. Enrichment in LREE and LILE, depletion in HREE and HFSE with negative anomaly of Ti, Nb and P in these rocks indicated active continental margin volcanic arc magmatism. Based on tectonic discrimination diagrams, also support the relation of Zoolesk area lavas with subduction zone and active continental margin. Low ratio of Dy/Yb(<2) in studied lavas, indicated spinel lherzolite mantle source for magma.
B. Shahsavari Alavijeh; N. Rashidnejad Omran; J. Ghalamghash
Abstract
The Nodoushan intrusive complex is a part of Cenozoic plutonism, which located in the central part of the Urumieh–Dokhtar Magmatic Belt (UDMB). This complex consists of four main intrusives, including diorite, granite-granodiorite, diorite porphyry and granodiorite. Mafic microgranular enclaves ...
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The Nodoushan intrusive complex is a part of Cenozoic plutonism, which located in the central part of the Urumieh–Dokhtar Magmatic Belt (UDMB). This complex consists of four main intrusives, including diorite, granite-granodiorite, diorite porphyry and granodiorite. Mafic microgranular enclaves (MMEs) are abundant in the diorite porphyry and granodioritic intrusives and also in some parts of Granitegranodiorite intrusives, which consist of diorite, monzodiorite and rarely gabbro -diorite. According to geochemical data, the Nodoushan intrusive complex is metalominous to moderately peraluminous, I-type and shows medium to high potassium calc-alkaline affinity. Geochemical investigations show that contamination and mafic-felsic magma mixing played significant role in the evolution and petrogenesis of the mentioned intrusions magmas and formation of MMEs. Using U-Pb zircon dating method, the obtained magma crystallization ages are about 30 Ma for the dioritic and granite-granodiorite intrusives, 24 Ma for the diorite porphyry and 25 Ma for the granodioritic intrusives. In addition, the age for part of the granite-granodiorite unit that is located in the northeast corner of the region, at the north of the Nain-Dehshir fault (NDF) and the western part of the Central Iranian Microcontinent (CIM), was determined 40 Ma. The geochemical evidences suggest that the studied intrusions magmas were derived from partial melting of continental crust caused by the mantle melts in an active continental margin. It seems that the melting of rocks with combination of metabasalt and metagraywacke in the lower crust in balance with the residual consisting of clinopyroxene, amphibole and to a lesser extent plagioclase; have the greatest harmony with geochemical characteristics of the studied intrusions.
S.Z Hosseini
Abstract
The Eocene mafic lava flows of Sarcheshmehare cropped out in the southwest of Rafsanjan area at the central part of the Urmia – Dokhtar magmatic belt. The rocks are basalt, basaltic andesite and andesite in composition and consist of clinopyroxene + plagioclase ± olivine ± hornblende phenocrysts. ...
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The Eocene mafic lava flows of Sarcheshmehare cropped out in the southwest of Rafsanjan area at the central part of the Urmia – Dokhtar magmatic belt. The rocks are basalt, basaltic andesite and andesite in composition and consist of clinopyroxene + plagioclase ± olivine ± hornblende phenocrysts. The geochemical characteristics show calc-alkaline nature for the lavas that are formed in an active continental margin tectonic environment. Low amounts of MgO, Cr and Ni in the Sarcheshmeh Eocene basaltic lavas points to the role of evolution in their parental magma. The MORB normalized multi-element patterns of the lava flows show enrichment in LILE (e.g. Sr, K, Rb and Ba) and depletion in HFSE (e.g. Ta, Nb and Ti). The Chondrite-normalized REE patterns show moderate enrichments in LREE with (La/Yb)n< 3 for all samples. The geochemical features such as (La/Yb)n
J Rasouli; M Ghorbani; V Ahadnejad
Abstract
Jebale-Barez granitoid complex is composed of intrusive bodyes included Mijan, Dareh hamzeh, Kerver and Hishin and is located In the southeastern province of Kerman on the lengths of the 57◦ 45 ' east to 58◦ 00' and Northern latitudes 28◦ 30' to 29◦ 00'.The petrologic composition ...
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Jebale-Barez granitoid complex is composed of intrusive bodyes included Mijan, Dareh hamzeh, Kerver and Hishin and is located In the southeastern province of Kerman on the lengths of the 57◦ 45 ' east to 58◦ 00' and Northern latitudes 28◦ 30' to 29◦ 00'.The petrologic composition in intrusive bodyes composed of granodiorite, quartzdiorite, granite and alkali-granite. The geochemical variation diagrams of major oxides, the continuous spectrum of rock compositions has been carried out which indicates the crystallization of magmatic differentiation and extensive appendices. The magma nature of these rocks is sub-alkaline-calc-alkaline, which in SiO2-K2O plot they fall into calc-alkaline series with high potassium. Field observations, petrographic and geochemical studies suggest that the rocks in this area have granitoides I type. Studying the geochemical diagrams of the rocks in the studied area indicates that these rocks have been formed in active continental margin tectononic setting. Most of the volcanic arc granites (VAG) are of "pre-collision" and "syn- collision" types. Three magmatic phases occurred in oligomiocene in this area. The first phase of magmatism in this area composed of the quartzdiorite and diorite that makes the main body of Jebale-Barez granitoid complex. Porphyry bodies will penetrate into the main body, after a short period of magmatic fractionation inside the nest of magma. Petrographic composition of the second phase is mainly diorite to tonalite. Oligo-Miocene magmatic final phase (Phase III) occurs in the region after a short time that the lithological composition of the granite to alkali granite. The third group of rocks in the study area from the main body mother came from magma fractionation. based on the location of Urmia-Dokhtar magmatic belt seems the rocks of this region there came to subducted oceanic crust Neotethyan beneath continental crust of central Iran.
S Ghaderi; E Rastad; N Rashidnejad-Omran; M Mohajjel
Abstract
Tungsten (Cu-Au-Zn) deposits and occurrences in Iran can be divided into two separate categories based on their genesis, tectonic setting, mineral paragenesis and related processes inherent in their formation. The first category contains deposits, which are located in metamorphosed Late Triassic-Middle ...
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Tungsten (Cu-Au-Zn) deposits and occurrences in Iran can be divided into two separate categories based on their genesis, tectonic setting, mineral paragenesis and related processes inherent in their formation. The first category contains deposits, which are located in metamorphosed Late Triassic-Middle Jurassic volcano-sedimentary sequences, and their distribution is indicated by layering. These deposits are located in a specific stratigraphic position and are concentrated in contact of volcanic units with carbonate rocks. The geodynamic setting of this category probably is intracontinental rifting. The second category contains deposits located in metamorphosed sedimentary rocks of the Shemshak group and Jurassic granitoids. These deposits have vein-veinlet geometry and their formation is controlled by faults, fractures and shear zones. The geodynamic setting of this category probably is active continental margins. The mineral paragenesis of the first group generally contains scheelite and Cu-Fe-Zn sulfides, whereas the paragenesis of the second group is wolframite, scheelite, chalcopyrite, arsenopyrite, with gold and specifically bismuth.
K. Kalantari; A. Kananian; A. Asiabanha; M. Eliassi
Abstract
Paleogene basic to intermediate lava flows of Central Alborz, in the northeast of Qazvin city (Zarjebostan), include trachy-andesite, basaltic trachy-andesite and basaltic andesite. These volcanic rocks are high-K calc-alkaline rocks. Based on the high LILE/HFSE and LREE/HREE ratios ...
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Paleogene basic to intermediate lava flows of Central Alborz, in the northeast of Qazvin city (Zarjebostan), include trachy-andesite, basaltic trachy-andesite and basaltic andesite. These volcanic rocks are high-K calc-alkaline rocks. Based on the high LILE/HFSE and LREE/HREE ratios and their similar composition to subduction volcanic rock suites; it seems that they have formed in a subduction zone. The subduction process has little effect on the concentration of Zr, Ta, Hf, Sm, Tb, Nd, Eu and Y elements, while it has strong influence on concentration of Th, U and La elements. Due to high Ba/La, Ba/Ta and La/Ta ratios and low TiO2 content of lavas, they could be attributed to magmatic arc setting. Th/Yb vs. Ta/Yb diagrams and association of study suite with extensive volume of acidic tuffs, indicate that these rocks have been formed in an active continental margin.
