Abstract Lithospheric thinning and crustal extension have shaped the Alpine orogen in western Anatolia since the late Oligocene, resulting in the denudation of one of Earth’s largest metamorphic core complexes, the Menderes Massif. We review locations and characteristics of geothermal fields and of Miocene mineral deposits in the context of crustal structure and geodynamic processes. Thermal spring locations show a close spatial association with active fault zones; the largest geothermal areas are located in the widest graben and at fault intersections, but show little relation to volcanic activity. During the first stage of tectonic denudation in the Miocene, epithermal, porphyry-type gold and structurally controlled base-metal deposits formed synchronously with K-rich volcanic and plutonic complexes in the northern Menderes Massif. Depositional environments favoured the formation of lignite, sedimentary uranium and borate deposits. Throughout this phase of extension in a hot continental setting, secondary porosity caused by brittle faulting of metamorphic basement rocks provided the key pathways for fluids and magmas. Although the Menderes Massif has remained in a similar position relative to active plate boundaries from the Miocene to the present, three significant changes in subcontinental mantle dynamics affected the nature of hydrothermal flow. First, the partial removal of lithospheric mantle changed the primary source component of magmatic rocks and metals from metasomatized lithosphere mantle to asthenospheric mantle. Secondly, surface uplift and progressive crustal extension led to segmentation of the Miocene land surface along NNE–SSW- and east–west-orientated fault zones, which changed the overall structural control on crustal permeability. Finally, hydrothermal flow changed from locally magmatic driven, to focused flow of topographically and thermally driven fluids in the crust, with high background heat flow caused by regional upwelling of the asthenosphere. The Menderes Massif is a continental tectonic domain that has experienced rapid thinning of lithospheric mantle and crustal extension in an overall convergent plate tectonic setting. The tectonic and geodynamic framework for evolving hydrothermal activity in western Anatolia may be applicable to other ore-forming systems in hot, extending continental crust in Earth’s history. Supplementary material: Supplement 1: Compilation of 124 thermal spring temperature measurements from Akkuş et al. (2005); Supplement 2: Compilation of 127 geothermal well temperature measurements from Akkuş et al. (2005) is available at https://doi.org/10.6084/m9.figshare.c.3803935

Abstract In this field-trip guide we explore the tectonics of Samos and the Menderes Massif, two fascinating areas within the eastern Mediterranean section of the Tethyan orogen. We include detailed outcrop descriptions, maps, and diagrams to explore along-strike variations in the Hellenide-Anatolide orogen, including the architecture of the Early Tertiary Alpine nappe stack and its strong Miocene extensional overprint. The suggested itinerary is based on the 2010 Geological Society of America Field Forum “Significance of Along-Strike Variations for the 3-D Architecture of Oro-gens: The Hellenides and Anatolides in the Eastern Mediterranean.” We start the outcrop descriptions with Day 1 in Samos, where, untypically for the N-S–stretched Aegean region, Miocene extension is E–W. We describe a section in western Samos, where the Cycladic Blueschist Unit is in contact with the underlying External Hel-lenides along a large-scale thrust, reactivated as a Miocene top-east extensional shear zone. The focus of Day 2 is on high-pressure assemblages in northern Samos. The following three days explore the Anatolide Belt in western Turkey where the Mend-eres nappes—also known as the Menderes Massif—form the tectonic footwall below the Cycladic Blueschist Unit. The outcrops in western Anatolia include the Cycladic Blueschist Unit in the area around Selçuk (Day 3) and sections across the Bozdağ and Aydm Mountains including the Kuzey and Güney detachment faults and the Cycladic Menderes Thrust (Days 4 and 5). Outcrops on Day 6 showcase structures along the southern margin of the Menderes Massif in the Milas–Selimiye area.

Abstract Samos is not one of the typical Aegean “turtle-back–shaped core-complex type” islands like Ios or Mykonos, for example. The general structure of Samos is dominated by steep faults, and the overall architecture of the islands is best described as a horst. The topography of Samos is rugged and dominated by the sheer cliffs of 1433-m-high Mount Kerkis in the western part of the island (Fig.7). The geology of Samos consists of a number of metamorphosed nappes, one non-metamorphosed nappe, and a Miocene graben. The island offers a look at an exceptionally complete nappe stack of the Central Hellenides, ranging from the high-pressure–metamorphosed Basal Unit (as part of the External Hel-lenides), all the way up to the ophiolitic Selçuk Nappe and the non-metamorphosed Cycladic Ophiolite Nappe. This field guide is concerned with the two structurally lowest units, the Basal Unit and the overlying Cycladic Blueschist Unit, as well as the Tertiary sediments.

Abstract The Menderes Massif is a complex geological terrane. Despite much research progress in the past ten years, there are still substantial unresolved issues regarding its tectonic and meta-morphic history. Although we would like to outline some key controversies here, we recommend the review section in Bozkurt and Oberhänsli’s 2001 editorial article (Bozkurt and Oberhänsli, 2001) and van Hinsbergen et al. (2010) for an attempt to reconcile local structure with geodynamics. The pre-Miocene tectonics of the Menderes Massif have been interpreted in terms of a large-scale recumbent fold (Okay, 2001; Gessner et al., 2002), a series of nappes stacked during south-directed thrusting (Ring et al., 1999a; Gessner et al., 2001c), and a series of north-directed thrusts that subsequently collapsed either in a bivergent fashion (Hetzel et al., 1998) or through top-to-south extension (Bozkurt and Park, 1994; Bozkurt, 2007). The key controversies are focused on which structures are related to the kinematics of early Tertiary Alpine crustal shortening, which ones are related to late Tertiary crustal extension, and how this fits with the observed large-scale architecture of the massif. Whereas the role of Miocene to Pliocene normal fault systems bounding the Gediz and Büyük Menderes Grabens

Abstract This field-trip guide explores the tectonics of Samos and the Menderes Massif, two fascinating areas within the eastern Mediterranean section of the Tethyan orogen. The guide includes detailed outcrop descriptions, maps, and diagrams to explore along-strike variations in the Hellenide-Anatolide orogen, including the architecture of the Early Tertiary Alpine nappe stack and its strong Miocene extensional overprint. The suggested itinerary is based on the 2010 Geological Society of America Field Forum: “Significance of Along-Strike Variations for the 3-D Architecture of Orogens: The Hellenides and Anatolides in the Eastern Mediterranean.” The outcrop descriptions begin with Day 1 in Samos, where, atypically for the N-S stretched Aegean region, Miocene extension is E-W. The focus of Day 2 is on high-pressure assemblages in northern Samos. The following three days explore the Anatolide Belt in western Turkey, where the Menderes nappes—also known as the Menderes Massif—form the tectonic footwall below the Cycladic Blueschist Unit.