Crustal structure in the central Tethys realm

The central Tethys realm including Anatolia, Caucasus and Iran is one of the most
complex geodynamic settings within the Alpine-Himalayan belt. To investigate the
tectonics of this region, we estimate the depth to magnetic basement (DMB) as a
proxy for the shape of sedimentary basins, and average crustal magnetic
susceptibility (ACMS) by applying the fractal spectral method to aeromagnetic data.
Magnetic data is sensitive to the presence of iron-rich minerals in oceanic fragments
and mafic intrusions hidden beneath sedimentary sequences or overprinted by
younger tectono-magmatic events. Furthermore, a seismically constrained 2D
density-susceptibility model along Zagros is developed to study the depth extent of
the tectonic structure.
Comparison of DMB and ACMS demonstrates that the structural complexity
increases from the Iranian plateau into Anatolia.
Strong ACMS show lineaments coincides with known occurrences of Magmatic-
Ophiolite Arcs (MOA) and weak ACMS zones coincide with known sedimentary
basins in the study region, including Zagros. Based on strong ACMS anomalies, we
identify hitherto unknown MOAs below the sedimentary cover in eastern Iran and in
the SE part of Urima-Dokhtar Magmatic Arc (UDMA). Our results allow for
estimation of the dip of the related paleo-subduction zones. Known magmatic arcs
(Pontides and Urima-Dokhtar) have high-intensity heterogeneous ACMS. We
identify a 450 km-long buried (DMB >6 km) magmatic arc or trapped oceanic crust
along the western margin of the Kirşehır massif in Anatolia from a strong ACMS
anomaly. We identify large, partially buried magmatic bodies in the Caucasus LIP at
the Transcaucasus and Lesser Caucasus and in NW Iran. Strong ACMS anomalies
coincides with tectonic boundaries and major faults within the Iranian plateau while
the ACMA signal is generally weak in Anatolia. The Cyprus subduction zone has a

strong magnetic signature which extends ca. 500 km into the Arabian plate to the
south of the Bitlis suture.
We derive a 2D crustal-scale density-susceptibility model of the NW Iranian plateau
along a 500 km long seismic profile across major tectonic provinces of Iran from the
Arabian plate to the South Caspian Basin (SCB). A seismic P-wave receiver function
section is used to constrain major crustal boundaries in the density model. We
demonstrate that the Main Zagros Reverse Fault (MZRF), between the Arabian and
the overriding Central Iran crust, dips at ~13° angle to the NE and extends to a depth
of ~40 km. The trace of MZRF suggests ~150 km underthrusting of the Arabian plate
beneath Central Iran. We identify a new crustal-scale suture beneath the Tarom
valley separating the South Caspian Basin crust from Central Iran. High density lower
crust beneath Alborz and Zagros may be related to partial eclogitization of crustal
roots at depths deeper than ~40 km.