Crustal structure in the central Tethys realm

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