Contribution of ultramafic rocks in central Sanandaj-Sirjan zone to the characterizing of physio-chemical condition during initiation of subduction
In the central part of the Sanandaj-Sirjan zone, there is an ultramafic rock exposure (hornblendite and pyroxenite) adjacent to Molataleb felsic complex completely located between Azna and Aligoodarz towns. The ultramafic rocks are actually cumulates derived from boninitic magma. During Upper Triass...
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| Format: | Article |
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University of Isfahan
2018-01-01
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| Series: | پترولوژی |
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| Online Access: | http://ijp.ui.ac.ir/article_22393_1786404167b8075c17f8fc85e9bc121a.pdf |
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| author | Amir Esna-Ashari Fatemeh Sarjoughian |
| author_facet | Amir Esna-Ashari Fatemeh Sarjoughian |
| author_sort | Amir Esna-Ashari |
| collection | DOAJ |
| description | In the central part of the Sanandaj-Sirjan zone, there is an ultramafic rock exposure (hornblendite and pyroxenite) adjacent to Molataleb felsic complex completely located between Azna and Aligoodarz towns. The ultramafic rocks are actually cumulates derived from boninitic magma. During Upper Triassic-Lower Jurassic time the boninitic magma has been originated from mantle wedge as the result of initiation of Neo-Tethys subduction. Later, when subduction was proceeding, the felsic rocks crystallized in Middle Jurassic. Major elements composition of olivine, pyroxene, amphibole and minor plagioclase from the ultramafic rocks reveals crystallization from a sub-alkaline to calc-alkaline magma in a subduction zone setting. Primary minerals have chemical characteristics typical of those derived from a magma with low oxygen fugacity. Different methods for minerals thermobarometry indicate that amphiboles crystallized in relatively low temperature (880°C) but crystallization condition of other minerals corresponds to higher temperatures (1000-1200°c). They were crystallized at pressure condition equal to 5.85 kbar corresponding to the depth of ~17 km. It is not common that a mantle wedge at the depth of ~17 km to be affected by such high thermal gradient during the normal subduction process. Asthenospheric flow around the subducting slab edge during subduction initiation can explain high thermal gradient prevailed the infant mantle wedge. This mechanism corresponds to the boninitic nature of the ultramafic rocks. |
| first_indexed | 2024-03-12T09:41:47Z |
| format | Article |
| id | doaj.art-24b65e882221451984b46164be792d30 |
| institution | Directory Open Access Journal |
| issn | 2228-5210 2322-2182 |
| language | fas |
| last_indexed | 2024-03-12T09:41:47Z |
| publishDate | 2018-01-01 |
| publisher | University of Isfahan |
| record_format | Article |
| series | پترولوژی |
| spelling | doaj.art-24b65e882221451984b46164be792d302023-09-02T13:07:46ZfasUniversity of Isfahanپترولوژی2228-52102322-21822018-01-01832456610.22108/ijp.2017.100430.022393Contribution of ultramafic rocks in central Sanandaj-Sirjan zone to the characterizing of physio-chemical condition during initiation of subductionAmir Esna-Ashari0Fatemeh Sarjoughian1Department of Geology, Payame Noor University, 19395-3697 Tehran, I. R. of IranDepartment of Earth Sciences, Faculty of Sciences, University of Kurdistan, Sanandaj, IranIn the central part of the Sanandaj-Sirjan zone, there is an ultramafic rock exposure (hornblendite and pyroxenite) adjacent to Molataleb felsic complex completely located between Azna and Aligoodarz towns. The ultramafic rocks are actually cumulates derived from boninitic magma. During Upper Triassic-Lower Jurassic time the boninitic magma has been originated from mantle wedge as the result of initiation of Neo-Tethys subduction. Later, when subduction was proceeding, the felsic rocks crystallized in Middle Jurassic. Major elements composition of olivine, pyroxene, amphibole and minor plagioclase from the ultramafic rocks reveals crystallization from a sub-alkaline to calc-alkaline magma in a subduction zone setting. Primary minerals have chemical characteristics typical of those derived from a magma with low oxygen fugacity. Different methods for minerals thermobarometry indicate that amphiboles crystallized in relatively low temperature (880°C) but crystallization condition of other minerals corresponds to higher temperatures (1000-1200°c). They were crystallized at pressure condition equal to 5.85 kbar corresponding to the depth of ~17 km. It is not common that a mantle wedge at the depth of ~17 km to be affected by such high thermal gradient during the normal subduction process. Asthenospheric flow around the subducting slab edge during subduction initiation can explain high thermal gradient prevailed the infant mantle wedge. This mechanism corresponds to the boninitic nature of the ultramafic rocks.http://ijp.ui.ac.ir/article_22393_1786404167b8075c17f8fc85e9bc121a.pdfultramaficboniniteThermobarometryinitiation of subductionSanandaj-Sirjan zone |
| spellingShingle | Amir Esna-Ashari Fatemeh Sarjoughian Contribution of ultramafic rocks in central Sanandaj-Sirjan zone to the characterizing of physio-chemical condition during initiation of subduction پترولوژی ultramafic boninite Thermobarometry initiation of subduction Sanandaj-Sirjan zone |
| title | Contribution of ultramafic rocks in central Sanandaj-Sirjan zone to the characterizing of physio-chemical condition during initiation of subduction |
| title_full | Contribution of ultramafic rocks in central Sanandaj-Sirjan zone to the characterizing of physio-chemical condition during initiation of subduction |
| title_fullStr | Contribution of ultramafic rocks in central Sanandaj-Sirjan zone to the characterizing of physio-chemical condition during initiation of subduction |
| title_full_unstemmed | Contribution of ultramafic rocks in central Sanandaj-Sirjan zone to the characterizing of physio-chemical condition during initiation of subduction |
| title_short | Contribution of ultramafic rocks in central Sanandaj-Sirjan zone to the characterizing of physio-chemical condition during initiation of subduction |
| title_sort | contribution of ultramafic rocks in central sanandaj sirjan zone to the characterizing of physio chemical condition during initiation of subduction |
| topic | ultramafic boninite Thermobarometry initiation of subduction Sanandaj-Sirjan zone |
| url | http://ijp.ui.ac.ir/article_22393_1786404167b8075c17f8fc85e9bc121a.pdf |
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