Petrological Journal - Articles List

Magmatism of northwest of Takestan: The product of asymmetric caldera collapse

Batool Nemati; Ali Asghar Sepahi Gerow; Abbas Asiababha

Volume 13, Issue 2 , August 2022, , Pages 65-90

https://doi.org/10.22108/ijp.2022.130237.1249

Abstract

One of the main products of caldera collapses is ignimbrite, and there is a direct relationship between the volume of ignimbrite and caldera dimensions. During caldera collapse, a large ... Read More One of the main products of caldera collapses is ignimbrite, and there is a direct relationship between the volume of ignimbrite and caldera dimensions. During caldera collapse, a large volume of magma is explosively discharged as products and pyroclastic flows (Druitt and Sparks, 1984). Lava domes and cones are placed along or inside the caldera rim structures after the collapse (Aguirre-Díaz, 1996). The studied area, in the northwest of Takestan, is a part of the Alborz and Western Alborz magmatic arcs, which consisting of some granitoid rocks, volcanic units, dacitic and rhyolitic domes as well as pyroclastic units. The presence of ignimbrite and dacitic and rhyolitic domes along with mafic volcanic rocks and intrusive rocks show the occurrence of the caldera in the region.In the Alborz and Urumieh-Dokhtar belts, extensive volcanic eruptions occurred in the Eocene. The studied area lies in the western Alborz zone. The first studies of stratigraphy and classification of the Paleogene volcanic and intrusive rocks in western Alborz are related to Taleghan and Qazvin regions (Annells et al., 1975). The dominant feature in the northwest of Takestan is pyroclastic deposits, lava flows, and intrusive and sub-volcanic rocks. Volcanic rocks and lava flows are placed on the tuffs with a more limited expansion. Sub-volcanic rocks are in the form of dacitic and rhyolitic domes and intrusive rocks intruded the tuffs.Method of studyIn this research, about 120 samples of different volcanic, intrusive, and pyroclastic rocks are gathered, then 56 thin sections were prepared and studied. To measure the main and rare elements, 29 suitable samples including 16 fresh samples of intrusive rocks and 13 volcanic samples were selected and analyzed using ICP-OES and ICP-MS at Zarazma Minerals Studies Laboratory in Tehran.PetrographyVolcanic rocks are rhyolite, dacite, andesite, trachyandesite, basaltic andesite, and basalt, with porphyry texture and a glassy or microlitic groundmass. Evidences such as the presence of ocelli quartz, plagioclases with sieve texture and the formation of a thin layer of fine pyroxenes at the edge of some pyroxenes show that the basaltic and basaltic andesitic rocks are contaminated with crustal compounds or mixed with crustal melts. The intrusive rocks are alkaline granite, granite, quartz monzonite, quartz monzodiorite, and monzodiorite, which often have a granular texture. The absence of muscovite and hypersolvus feldspars in alkaline granites and quartz monzonites confirms that these granites are anorogenic (Kleemann and Twist, 1989).Whole rocks chemistryBasic to felsic members are seen in both intrusive and volcanic groups. The range of SiO2 changes from 53.52-75.23% for intrusive rocks and 51.11-74.8% for volcanic rocks. MgO is 0.19-4.66% for intrusive rocks and 0.24-4.18% for volcanic rocks, and Al2O3 is 10.22 and 17.2% for intrusive rocks and 10.24 and 16.66% for volcanic rocks. According to Irvine and Baragar (1971) diagram, volcanic samples and most of the intrusive samples are sub-alkaline. In AFM ternary diagram, volcanic and intrusive samples have a calc-alkaline trend.Discussion PetrogenesisTrace elements variation diagrams show two groups with two separate trends in the volcanic rocks. The first group (rhyolites and some dacites) show the fractional crystallization trend, but the second group (andesite basalts and andesites and some dacites) demonstrate the partial melting trend. This phenomenon can also indicate the different origins of these rocks. Intrusive rocks are also divided into two groups with a parallel trend, which have a dominant trend of fractional crystallization trend, and probably these two groups also have different origins. The spider diagrams show that all the samples are enriched concerning the primary mantle. Some of the anomalies observed in these diagrams indicate that these rocks originated in subduction zone. Crustal contamination or extensive melting of crustal materials occurred in the region.Genetic classification of granitoids and tectonic settingDiscrimination diagrams show that the samples of monzodiorite and quartz monzonites are I-type and alkaline granites are A-type (subgroup A2). According to the tectonic setting diagrams, except for some alkaline granites, the other samples are in the field of volcanic arc setting rocks. Alkaline granites and rhyolites are related to the post-orogenic setting, quartz monzonitic samples are related to the late orogenic setting, and granites are located in the range between these two groups. The dacitic samples are located in the syn-collision to late orogeny environments. Acidic volcanic and intrusive samples are the melting results of amphibolites (some dacites and quartz monzonites) and some others are probably melting result of the metagraywakes (rhyolites, some dacites, and alkali granites).Basalt, basaltic andesite, and monzodiorite to monzogabbro, are product of mantle melting in the volcanic arc and rhyolite, dacite, alkali granite, and quartz monzonite, are the result of crustal melting.Caldera formationThe presence of ignimbrite units, dacitic and rhyolitic domes with a semi-circular arrangement in the east of the intrusive rocks, and co-ignimbrite breccias, reveal the possibility of caldera formation in the region. Considering the relatively less amount of ignimbrites, the dimensions of the formed caldera were probably small. The presence of dacitic and rhyolitic domes on one side of the intrusive rocks shows that the type of caldera is trap-door type.AcknowledgmentsWe would like to thank the research vice-chancellor of Bu-Ali Sina University for paying part of the expenses and the research vice-chancellor of Imam Khomeini International University (RA) for their cooperation in using the microscopic laboratory.

Petrography, geochemistry and Fractal analysis of Mafic Enclaves in the Alvand Plutonic to investigate magma mixing processes

Sara Shakiba; Ali Asghar Sepahi Gerow

Volume 12, Issue 2 , September 2021, , Pages 43-70

https://doi.org/10.22108/ijp.2021.122815.1175

Abstract

The Alvand plutonic complex is located in Sanandaj- Sirjan Zone in south and west of Hamedan. Petrographic studies indicate that this body is composed of mafic intrusive rocks, porphyry ... Read More

Geochemistry and petrogenesis of south Qorveh A-type granitoids (northwest of Sanandaj- Sirjan zone): An evidence for active continental margin tensional tectonic

Majid Shirmohammadi; Ali Asghar Sepahi Gerow; Mohammad Maanijou; Ashraf Tourkian

Volume 11, Issue 3 , December 2020, , Pages 85-110

https://doi.org/10.22108/ijp.2020.123500.1186

Abstract

The studied area (Galali- Varmaqan) located at the northern part of the Sanandaj- Sirjan zone, south of the Qorveh city. The granitic rocks are dominated by quartz, alkali- feldspar ... Read More

Mineral chemistry, geochemistry and petrology of Ay-Qaleh-si intrusive body (east of Takab, NW Iran).

Hamid GhoreishVandi; Ali Asghar Sepahi Gerow; Mohammad Maanijou

Volume 10, Issue 2 , September 2019, , Pages 1-28

https://doi.org/10.22108/ijp.2019.115738.1121

Abstract

The intrusive body of the Ay-Qaleh-Si is located between the West Azarbaijan and Kurdistan provinces at the intersection of the Urumieh–Dokhtar volcanic belt (UDVB) and the Sandaj-Sirjan ... Read More

Study of mineral chemistry, thermobarometry and petrogenesis of migmatitic rocks of Hamedan area

Ali Asghar Sepahi Gerow; Seyedeh Razieh Jafari; Mohssen Moazzen; Hossein Shahbazi

Volume 9, Issue 1 , June 2018, , Pages 165-190

https://doi.org/10.22108/ijp.2017.103130.1026

Abstract

In the Hamedan region, migmatitic rocks occur with various structures. In the Simin area (South Hamedan) stromatic and in the Darreh-Omar (Toyserkan) area ophtalmitic structures are ... Read More In the Hamedan region, migmatitic rocks occur with various structures. In the Simin area (South Hamedan) stromatic and in the Darreh-Omar (Toyserkan) area ophtalmitic structures are abundant. Migmatites have been developed in a poly-metamorphic region. At least one regional metamorphism and two contact metamorphism by mafic and felsic intrusions occurred in the area. It seems that in the Darreh-Omar area contact metamorphism of mafic body leading to migmatization, But in the Simin area previous regional metamorphism and development of shear zones followed by contact metamorphism by felsic body. Therefore, in some areas, such as the Simin area, the migmatization may have occurred in more than one stage. These are consistent with recent geochronological studies of the Alvand plutonic body and surrounding metamorphic rocks. Index minerals of metapelites such as garnet (almandine), biotite (siderophyllite), staurolite, andalusite, sillimanite, kyanite, fibrolite, cordierite, plagioclase (andesine) and spinel (hercynite) are existing in these rocks. Field geology, petrographic and geochemical evidences suggest that different generations of staurolite, biotite and cordierite exist in metamorphic rocks of different grades in the Hamadan area. These minerals sometimes have been formed by progressive reactions and some other times from retrogressive reactions. A number of these phases have been formed at the peak of metamorphism and some others in later time. Based on thermometric cation-exchange method of garnet-biotite pair, using different calibrations, the obtained temperature using first-generation of biotites is 655 °C and temperature range of 529 °C for second-generation biotites. Cordierite-garnet thermometry indicates a temperature of 637 °C for related migmatitic rocks. In barometry with GPBQ system, calculated pressure for first-generation biotite is estimated to be about 3.9 kbar and for the second-generation biotite around 3.6 kbar.

Petrology and the effects of dynamic processes on the felsic rocks in the Darvazeh plutonic body (South Qorveh- Kurdistan)

Ashraf Torkian; Tahereh Molaei Yeganeh; Ali Asghar Sepahi Gerow

Volume 8, Issue 32 , March 2018, , Pages 105-126

https://doi.org/10.22108/ijp.2017.103624.1027

Abstract

The Darvazeh pluton is located in the south of Qorveh. Olivine gabbro, diorite, quartz monzonite and granite rocks are rock forming of this body, but this paper is focused on the leucocratic ... Read More

The study of morphology and formation mechanism for tourmaline nodules of aplites from Khaku area (Hamedan) with using fractal and three dimensional analysis

Ali Asghar Sepahi-Gerow; Sedigheh Salami; Mohammad Maanijou

Volume 8, Issue 29 , June 2017, , Pages 75-88

https://doi.org/10.22108/ijp.2017.21501

Abstract

In aplites of Khaku area, located in the east of the Alvand body, tourmaline noduleswith spherical and dendritic shapes are dispersed. Some of these nodules have light halothat is actually ... Read More

Petrology and geochemistry of Aliabad-Daman granitic body (Rashtkhar, Khorassan-Razavi)

Ali Asghar Sepahi Gerow; Mohammad Amin Shakouri; Ashraf Torkian; Sedigheh Salami

Volume 7, Issue 26 , July 2016, , Pages 79-98

https://doi.org/10.22108/ijp.2016.20843

Abstract

Aliabad-Daman granitoid body with NW-SE trend is located in northeastern of the Rashtkhar city (about 15 km) with an area of approximately 10 km2. This body with probably age of middle ... Read More

Petrology of gabbroic- dioritic intrusions in the Parishan Mountain (south of Qorveh), Kurdistan

Khadijeh Mohebbi; Ali Asghar Sepahi Gerow; Asharf Torkian

Volume 6, Issue 23 , October 2015, , Pages 27-44

Abstract

The gabbroic intrusion of the Parishan Mountain in the south of Qorveh (Kurdistan province) is located between the villages of Zarrineh to Tekyeh-bala and based on structural divisions, ... Read More

Mineralogy and geochemistry of granitoids and associated iron skarn of Takht (north of Kaboodar Ahang)

Mohammad Mostaghimi; Farhad Aliani; Mohammad Maanijou; Ali Asghar Sepahi Gerow; Somayeh Mansouri

Volume 6, Issue 21 , April 2015, , Pages 159-178

Abstract

In structural subdivision of Iran, the Takht area is located in the north of Uromieh-Dokhtar magmatic belt. According to field observations and mineralogical characteristics, the granitoids ... Read More

The study of petrogenesis, mineral chemistry and thermobarometry of contact metamorphic rocks from aureole of Alvand body, Hamedan

Nasrin Asadi; Ali Asghar Sepahi Gerow; Sedigheh Salami

Volume 5, Issue 19 , December 2014, , Pages 67-86

Abstract

There are various contact and regional metamorphic rocks, from low to high grade in contact of the Alvand plutonic body. These rocks have undergone regional dynamothermal metamorphism ... Read More

Petrography, mineral chemistry and geochemistry of granitoids of the Samen plutonic complex (SW Malayer, Hamedan)

Ahmad Ahmadi Khalaji; Farahnaz Sepahvand; Ali Asghar Sepahi Gerow; Sedigheh Salami

Volume 5, Issue 18 , November 2014, , Pages 77-92

Abstract

The Malayer plutonic complex is located in the northern Sanandaj-Sirjan zone of the western Iran. An intrusive body with granodioritic component known as the Samen granodiorite is in ... Read More

Timing of porphyroblasts growth and their relation to deformation stages in metamorphic rocks of the Hamedan area

Leyli Izadi Kian; Mohammad Mohajjel Kafshdouz; Seyed Ahmad Alavi; Ali Asghar Sepahi Garoo; Seyed Jafar Hoseini dust

Volume 4, Issue 13 , April 2013, , Pages 1-18

Abstract

Structural elements of four deformation stages have been recognized in the Hamedan schists. These deformation stages were synchronous with regional and contact metamorphism events. ... Read More

The study of minerals chemistry, thermobarometry and tectonic setting of plutonic rocks from Sarabi Tueyserkan area (Hamedan province)

Ali Asghar Sepahi Garoo; Kazem Borzoei; Seddigheh Salami

Volume 3, Issue 11 , December 2012, , Pages 39-58

Abstract

Sarabi area of Tueyserkan is located in Hamedan province which is a part of Sanandaj-Sirjan zone. Rocks of the area include igneous and metamorphic types in which the igneous rocks ... Read More

Petrology and geochemistry of the plutonic complexes of the Marivan area, Sanandaj-Sirjan zone

Ahmad Ranin; Ali Asghar Sepahi Garoo; Hossein Moin Vaziri; Farhad Aliani

Volume 1, Issue 2 , September 2010, , Pages 43-60

Abstract

The plutonic complexes of Marivan area, composed of two types of plutonic rocks of different genesis, are situated in the northwest of Sanandaj-Sirjan metamorphic belt. The stratigraphical ... Read More

Volume 13 (2022)

Volume 12 (2021)

Volume 11 (2020)

Volume 10 (2019)

Volume 9 (2018)

Volume 8 (2017)

Volume 7 (2016)

Volume 6 (2015)

Volume 5 (2014)

Volume 4 (2013)

Volume 3 (2012)

Volume 2 (2011)

Volume 1 (2010)

Author = Sepahi Gerow, Ali Asghar

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