Crustal structure in the central Tethys realm
Authors: Teknik Vahid , Thybo Hans , Artemieva Irina , Ghods Abdolreza 
Published: March 2022

&lt;p&gt;The central Tethys realm including Anatolia, Caucasus and Iran is one of the most&lt;br&gt;complex geodynamic settings within the Alpine-Himalayan belt. To investigate the&lt;br&gt;tectonics of this region, we estimate the depth to magnetic basement (DMB) as a&lt;br&gt;proxy for the shape of sedimentary basins, and average crustal magnetic&lt;br&gt;susceptibility (ACMS) by applying the fractal spectral method to aeromagnetic data.&lt;br&gt;Magnetic data is sensitive to the presence of iron-rich minerals in oceanic fragments&lt;br&gt;and mafic intrusions hidden beneath sedimentary sequences or overprinted by&lt;br&gt;younger tectono-magmatic events. Furthermore, a seismically constrained 2D&lt;br&gt;density-susceptibility model along Zagros is developed to study the depth extent of&lt;br&gt;the tectonic structure.&lt;br&gt;Comparison of DMB and ACMS demonstrates that the structural complexity&lt;br&gt;increases from the Iranian plateau into Anatolia.&lt;br&gt;Strong ACMS show lineaments coincides with known occurrences of Magmatic-&lt;br&gt;Ophiolite Arcs (MOA) and weak ACMS zones coincide with known sedimentary&lt;br&gt;basins in the study region, including Zagros. Based on strong ACMS anomalies, we&lt;br&gt;identify hitherto unknown MOAs below the sedimentary cover in eastern Iran and in&lt;br&gt;the SE part of Urima-Dokhtar Magmatic Arc (UDMA). Our results allow for&lt;br&gt;estimation of the dip of the related paleo-subduction zones. Known magmatic arcs&lt;br&gt;(Pontides and Urima-Dokhtar) have high-intensity heterogeneous ACMS. We&lt;br&gt;identify a 450 km-long buried (DMB &amp;gt;6 km) magmatic arc or trapped oceanic crust&lt;br&gt;along the western margin of the Kir&amp;#351;eh&amp;#305;r massif in Anatolia from a strong ACMS&lt;br&gt;anomaly. We identify large, partially buried magmatic bodies in the Caucasus LIP at&lt;br&gt;the Transcaucasus and Lesser Caucasus and in NW Iran. Strong ACMS anomalies&lt;br&gt;coincides with tectonic boundaries and major faults within the Iranian plateau while&lt;br&gt;the ACMA signal is generally weak in Anatolia. The Cyprus subduction zone has a&lt;/p&gt;&lt;p&gt;strong magnetic signature which extends ca. 500 km into the Arabian plate to the&lt;br&gt;south of the Bitlis suture.&lt;br&gt;We derive a 2D crustal-scale density-susceptibility model of the NW Iranian plateau&lt;br&gt;along a 500 km long seismic profile across major tectonic provinces of Iran from the&lt;br&gt;Arabian plate to the South Caspian Basin (SCB). A seismic P-wave receiver function&lt;br&gt;section is used to constrain major crustal boundaries in the density model. We&lt;br&gt;demonstrate that the Main Zagros Reverse Fault (MZRF), between the Arabian and&lt;br&gt;the overriding Central Iran crust, dips at ~13&amp;#176; angle to the NE and extends to a depth&lt;br&gt;of ~40 km. The trace of MZRF suggests ~150 km underthrusting of the Arabian plate&lt;br&gt;beneath Central Iran. We identify a new crustal-scale suture beneath the Tarom&lt;br&gt;valley separating the South Caspian Basin crust from Central Iran. High density lower&lt;br&gt;crust beneath Alborz and Zagros may be related to partial eclogitization of crustal&lt;br&gt;roots at depths deeper than ~40 km.&lt;/p&gt;