Dynamics of episodic Late Cretaceous–Cenozoic magmatism across Central to Eastern Anatolia: New insights from an extensive geochronology compilation

Abstract

We compiled geochronology data from 87 published studies within the Anatolia orogen (32.5°E-44°E) to investigate the spatial and temporal patterns of continental magmatism during the final stages of Neotethys Ocean closure. The number and diversity of studies compiled here collectively provide a thorough characterization of magmatism (>700 ages) in the Anatolia orogen since the Late Cretaceous (ca. 100 Ma). Our new compilation reveals that magmatism was episodic and occurred in three distinct magmatic episodes punctuated by two orogen-wide magmatic lulls. We used regional-scale insights into the timing, location, composition, and evolution of magmatism revealed by our compilation to evaluate the tectonic and geodynamic processes responsible for each widespread magmatic lull, and to test and refine existing geodynamic models for Anatolia. We interpret the first orogen-wide magmatic lull (ca. 72-58 Ma) to have been the result of Maastrichtian to Paleocene collision of the Kırşehir and Anatolide-Tauride blocks with the Pontides arc along the Izmir-Ankara-Erzincan suture zone and synchronous collision of the Bitlis-Pütürge massif with the southern-margin of the Anatolide-Tauride blocks along the Bitlis suture zone. Magmatic quiescence during the second magmatic lull (ca. 40-20 Ma) was variably related to terminal subduction and Arabia slab break off along the Bitlis suture zone in the east, and Cyprus slab flattening due to postcollisional southward retreat of the Cyprus trench in the west, each triggered by middle to late Eocene Arabia collision. Postcollisional Neogene-Quaternary magmatism was most likely caused by lithospheric delamination and slab tearing/rollback in the Eastern and Central Anatolia volcanic provinces, respectively.

Rapid Late Eocene Exhumation of the Sivas Basin (Central Anatolia) Driven by Initial Arabia‐Eurasia Collision

“…The MDA of 44.0 ± 0.7 Ma for this unit does not improve existing age constraints, which was deposited after the early Oligocene (~34–28 Ma) Selimiye Fm. The lack of late Eocene to early Miocene zircons in this sample is consistent with geochronologic evidence of a widespread magmatic lull from ~40–20 Ma across central and eastern Anatolia (Schleiffarth et al, ).…”

“…The DZ age distribution contains Late Cretaceous and middle Eocene age populations (Figure b). The consistency of these age populations with the timing of distinct magmatic episodes in the adjacent Pontides arc (Schleiffarth et al, ) suggests it was a major sediment source area for the northern Sivas Basin. We determined a MDA of 50.8 ± 0.4 Ma for the middle and upper parts of this unit.…”

“…This implies an exhumation rate of up to ~1.5–1.8 mm/yr, assuming a typical geothermal gradient of 25–30 °C/km. A widespread magmatic lull across central and eastern Anatolia from ~40 to 20 Ma (Schleiffarth et al, ) means that primary crystallization of apatite from magmatic sources was restricted during this time. Thus, rather than primary cooling and direct input from magmatic source areas, we interpret the abundance and consistency of late Eocene to early Oligocene AFT and AHe dates to reflect reset ages that record postdepositional, exhumation‐related cooling in the Sivas Basin.…”

“…All tectonic blocks south of the IAESZ, including Arabia, experienced southward obduction of suprasubduction zone ophiolites during the middle to Late Cretaceous (e.g., Parlak, ). Collision of the KB and ATB with the Pontides occurred during the Maastrichtian‐Paleocene (Kaymakci et al, ; Meijers et al, , ; Okay & Tüysüz, ; Parlak et al, ; Rice et al, ; Rolland et al, ; Yılmaz et al, ), coincident with a widespread magmatic lull along the southern Eurasian margin (Schleiffarth et al, ). The timing and kinematics of collision and closure of southern Neotethys are more controversial, as discussed in the previous section.…”

Magmatic Forcing of Cenozoic Climate?

“…Between~50 and~35 Ma there has been the demise of a highly productive magmatic arc/back-arc system across much of Iran and adjacent areas (e.g., Agard et al, 2011;Schleiffarth et al, 2018). This magmatism was a net source of atmospheric CO 2 .…”