University of Isfahan Petrological Journal 2228-5210 12 2 2021 08 23 Devonian basaltic magmatism of Central Alborz: An evidence for Paleo- Tethys rifting Devonian basaltic magmatism of Central Alborz: An evidence for Paleo- Tethys rifting 23 42 25573 10.22108/ijp.2021.126782.1215 FA Amir Ali Tabbakh Shabani Department of Geochemistry, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran Morteza Delavari Kooshan Department of Geochemistry, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran Zahra Abdoli Arbat Department of Geochemistry, Faculty of Earth Sciences, Kharazmi University, Tehran, Iran Journal Article 2021 01 03 In the north east of Tehran province and in the Central Alborz zone, a thick basaltic horizon occurs at the boundary of Jeiroud and Mobarak Formations near the Jeiroud village and Darbandsar and Garmabdar areas, indicating a nonconformity boundary of Devonian- Carboniferous in this region. The rock horizon comprises basalt, trachybasalt and trachyandesite representing dominantly porphyry texture and diabase as feeding dike with ophitic and subophitic textures; all displaying alkaline sodic nature. Both Chondrite- normalized rare earth element (REE) patterns enriched in LREE with respect to HREE and normalized to primitive mantle spider diagram are similar to those of oceanic island basalts (OIB). The studied samples plot in within plate basaltic field in the tectonic discrimination diagrams of basalts. Trace element and some major element contents show low degree partial melting (< 10%) of a deep (90- 110 km) garnet- bearing mantle source. As the basaltic samples of Garmabdar area geochemically show intra- plate tectonomagmatic setting it seems that during the late Devonian (and earlier times), Alborz has been as a passive continental margin in the southern border of Paleo- Tethys and its magmatism was more probably affected by extensional tectonism or mantle plume activity related to earlier stages of Neo- Tethys ocean development. <br />  <br />  <br />  In the north east of Tehran province and in the Central Alborz zone, a thick basaltic horizon occurs at the boundary of Jeiroud and Mobarak Formations near the Jeiroud village and Darbandsar and Garmabdar areas, indicating a nonconformity boundary of Devonian- Carboniferous in this region. The rock horizon comprises basalt, trachybasalt and trachyandesite representing dominantly porphyry texture and diabase as feeding dike with ophitic and subophitic textures; all displaying alkaline sodic nature. Both Chondrite- normalized rare earth element (REE) patterns enriched in LREE with respect to HREE and normalized to primitive mantle spider diagram are similar to those of oceanic island basalts (OIB). The studied samples plot in within plate basaltic field in the tectonic discrimination diagrams of basalts. Trace element and some major element contents show low degree partial melting (< 10%) of a deep (90- 110 km) garnet- bearing mantle source. As the basaltic samples of Garmabdar area geochemically show intra- plate tectonomagmatic setting it seems that during the late Devonian (and earlier times), Alborz has been as a passive continental margin in the southern border of Paleo- Tethys and its magmatism was more probably affected by extensional tectonism or mantle plume activity related to earlier stages of Neo- Tethys ocean development. <br />  <br />  <br />  https://ijp.ui.ac.ir/article_25573_d5c16bce8a4b363d4999ad2e644f2b71.pdf