Magmatism in the southeastern Anatolian orogenic belt: transition from arc to post-collisional setting in an evolving orogen

Abstract

Late Cretaceous to Middle Eocene calc-alkaline to alkaline magmatic rocks emplaced within the southeastern Anatolian orogenic belt, the most extensive magmatic belt in Turkey, result from the complex collision between the Afro-Arabian and Eurasian plates and the subduction of the southern and northern Neotethyan oceanic basins beneath the Eurasian continental margin during the Alpine–Himalayan orogeny. In a transect in east-central Turkey extending from Baskil (Elazig) to Divrigi (Sivas) to the north, and from Copler (Erzincan) to Horozkoy (Nigde) to the SW, these magmatic rocks vary in time, spatial distribution, and composition. 40Ar/39Ar ages supplemented by a few U–Pb ages geochronology from major plutons demonstrate a general younging of magmatism in the transect from c. 83 Ma in the south (Baskil) to c. 69 Ma in the north (Divrigi-Keban), followed by a c. 44 Ma scattered magmatic complex now found along a NE trending arcuate belt between Copler and Horoz. In general, trace element and rare earth element (REE) geochemistry in the magmatic rocks suggest two main sources for the melts: (1) a mantle-wedge and subducted oceanic lithosphere producing arc-type magma; and (2) metasomatized lithospheric mantle modified by subduction producing magmatic rocks with more metasomatized mantle and within plate signatures. The combination of geochemical and geochronological data presented herein provides a basis to reconstruct the temporal and spatial transition from subduction-related to post-collision and to late-orogenic magmatism in the eastern Mediterranean region. Subduction-related magmatism is rooted to closure of the Neo-Tethyan Ocean whereas post-collision and late orogenic-within plate-related magmatism is driven by the collision of a northern promontory of the SE Anatolian orogenic belt with northerly derived ophiolitic rocks. The magmatic transition occurs regionally in northerly to northwesterly trending belts in the southeastern Anatolian orogenic belt. The magmatism exhibit a clear shift from deep seated arc-type to late-orogenic from south (Baskil) to more deeply eroded mid-crustal plutons at the north (Divrigi), then to magmatism related to incipient slab-rupture from northeast (Copler, Kabatas, Bizmisen-Calti) to SW (Karamadazi and Horoz). The age progression follows a south-to-north geochemical trend of decreasing crustal input into mantle-derived magmas, and is explained as a consequence of slab roll-back after the collision/obduction of northerly ophiolites followed by slab steepening and incipient rupture leading to transtensional block faulting and subsidence, and thus to the preservation of near-surface magmatic products along a NE trending belt.

Geochemistry of Hydrothermal Alteration Associated with Cenozoic Intrusion-Hosted Cu-Pb-Zn Mineralization at Tavşanlı Area, Kütahya, NW Turkey

“…Based on the values of the changes (gain and loss) of mass and volume, each alteration zone has different major/trace additions and depletions calculated by the GEOISO-Windows™ program assuming Al, Ti, and Zr are immobile elements or their mobility was not significant during the alteration processes. 2 , and LOI with significant amounts of S, Cu, Zn, and Pb. Based on these data, the zonal arrangement of zones 1, 2, and 3 gives the impression of non-systematic distribution of alterations around the ore vein in the center from silicic-carbonate alterations +/á lbitization to phyllic-argillic alterations with increased base metals (Cu-Pb-Zn) from Cu, Cu-Pb, to Cu-Pb-Zn in zones 1, 2, and 3, respectively.…”

“…This mineralization is also related to the Oligocene-Miocene/Pliocene calc-alkaline magmatic activity during post-collision continent-continent setting and includes Pb-Zn, Sb, As, and Au-Cu deposits [1]. Kuşcu et al [2] reported four different varieties of mineral deposits occurring in the western TEMB: (1) low and high…”

“…It represents the largest regionally exposed NNE-trending pluton, covering ~400 km 2 , and it syn-tectonically intrudes into the northern Menderes Massif (foliated metagranites, gneissic granites, and microgranites) and Tavșanlı zone (blueschist/ultramafic belt) [7] (Figure 1a,b). Its granitic rocks occur in different textural varieties, ranging from microgranites chilled along the peripheral contact with Menderes Massif into a coarser holocrystalline character moving inward [8].…”

“…The mineralization associated with the Eğrigöz granitoids includes Fe skarn deposits [10,11], where they are distributed along the border of this intrusion and within other metamorphic rocks at the Çatak and Küreci area in the north, and the Kalkan and Karaağıl skarn in the south. [2,12]. (b) Area around Eğrigöz granitoids at the northern Menderes core complex (MCC) [13,14].…”

“…(b) Area around Eğrigöz granitoids at the northern Menderes core complex (MCC) [13,14]. [2,12]; (b) Area around Egrigöz granitoids at the northern Menderes core complex (MCC) [13,14].…”